My car does not seem to stop wobbling, shaking and rough idling...

Changed 3 motor mounts first...still wobbled...
Measured fuel pressure...48psi...I got the fuel pump out and cleaned it, it had a lot of dirt and also cleaned the tank...checked fuel lines and one was clogged before the fuel filter...checked fuel pressure again an it is steady at 55psi...

Last week it died on me on a red light with less than 1/4 of a tank...poured around 2 gallons to check this...and the next day when it had less than 1/4 of a tank I saw that the low fuel light was lid and it died...turned back on instantly!!! Yesterday I took the fuel pump relay and it had corrosion, cleaned it an electrical cleaner and I am carefully checking this if it happens again...
Also did the following...
changed everything possible there is to my car and nothing has helped...rotor, cap, fuel filter, air filter, wires, plugs, cleaned egr, cleaned iac, cleaned throttle body, clenaned maf with electrical cleaner, etc, etc....

DO these symptoms and very rough idle and shaking have to do with a bad fuel pump?

Vacuum leaks?
I checked mine and found none...will prolly double check today and see...
Anyways I just ordered: 6 new ac delco plugs, new air temp sensor, new pcv and new vacuum tee...

Only things I can think of left to buy is:

-Throttle position sensor (rpm is steady at 550, it is not jumping up and down)
-both knock sensors
-all oxygen sensors
-map sensor

The IAC and complete throttle body got cleaned a month ago and the truck accelerates better but the jumping at idle is still there...I even cleaned the maf with electrical cleaner...the fuel pump is reading 55 psi steady...cranks neat...
I am about to sell the friggin truck...I am thinking that It may die on me on a hwy but its only rough at idle...

Also, I am getting some gas smell the past few days...

I know its long but the more info the better, I think...


I have 99 Blazer with:
-Custom y-pipe
-Flowtech Raptor Muffler
-Gutted cat
-MSD Blaster Coil
-K&N FIPK

ok, you stated that you checked your fuel pressure, but did you do a leak down test? This is to make sure that you don't have a leak in the fuel system. It is possible that the injector spyder under the upper plenum has developed a leak and is causing the rough idle. In the earlier CPI 4.3L engine, the FPR (fuel pressure regulator) would blow its diaphram and fill the crankcase with fuel. The later CSFI engines have a tendancy to leak in the same area but generally only need an o-ring kit to fix the problem. Rarely, the entire spyder will need to be replaced.

I would do a leak down test on the fuel system. If you see a drop in pressure, you've got a leak and 10 to 1 its on the injector housing under the plenum.

Good luck. Sucks that you probably replaced all of that stuff for naught...

Egr valve may be faulty check it out.

A truely faulty EGR on a 99 would throw a code.

The leaky fuel pressure regulator gave my Blazer the same symtoms. Fixed it with a new spider kit/pressure regulater/nut kit. Bought from an online Chevy dealer (through Ebay) for $308 and 2 hours' labor in my driveway. Fixed it right up, and no longer shakes at idle - and I got my mileage back up to just around 20MPG.

Here's a link to his post:
http://www.blazerforum.com/m_7118/mpage_1/key_CPI/tm.htm#7118

Also take a lookat your plugs. If the plugs on the passenger side of teh Blazer are carbon fouled, and the ones on the driver's side look fine, then suspect the pressure regulator (it sits over the passenger side of the intake manifold). When the leaking fuel gets deep enough to exit through the drain holes, thaen you'll smell it occasionally.

G'Luck! & Keep us up to date on the fix!
Rex S.

Here again, the '99 is a CSFI, not CPI. Problem still applies, but the FPR is located at the back of the upper intake plenum where it would effect cylinders 3,5, and 6 if I remember correctly from when I had my upper plenum off replacing o-rings.

I will check the fpr this weekend anyways to see if it is leaking...
Anyways I will receive by monday a new air temp. sensor, new delco plugs, new vacuum tee, new pcv...will change all this to see if it helps in any way...
All of this started after I changed the motor mounts, an abnormal vibration started...when I rechecked and rechecked if I did the job well, I took the car to two shops and said they were put well...no disconnected hose, everything OK...some have told me that the 4.3L's shake in idle, but c'mon, as if it gonna die on you at avery stop light??? please!!!

I have spent TOO much money with no clue on the solution...Probably $650 roughly adding all I've done...parts, labor, tranny fluid flush, etc...I am not including the performance parts such as MSD coil, mufflers, FIPK, etc...

ORIGINAL: swartlkk

A truely faulty EGR on a 99 would throw a code.


I cleaned the egr and put a new gasket...it was LOADED with carbon...idle got smoother by that time...BUT when I did this the car was not shaking like it is now! this was probably 3 months ago when I cleaned it...don't think it should be clogged again...

Well, it is possible for the exhaust supply tube to be coated up pretty good and if that has started to flake off, it is possible that rather large chunks could be getting to you EGR valve. I have gone as far as to get some steel pipe cleaners and really soak the crap out of the exhaust supply line then run the pipe cleaner through it to remove the gunk. Then a nice nozzled down shop vac to suck the line out and you're good to go.

ORIGINAL: swartlkk

Well, it is possible for the exhaust supply tube to be coated up pretty good and if that has started to flake off, it is possible that rather large chunks could be getting to you EGR valve. I have gone as far as to get some steel pipe cleaners and really soak the crap out of the exhaust supply line then run the pipe cleaner through it to remove the gunk. Then a nice nozzled down shop vac to suck the line out and you're good to go.


Alrighty then...let me ask some dumb questions now...
The exhaust supply tube is the one that holds the EGR?
I can use something like "Drano steel pipe unclogger" on this? Isn't this dangerous for the exhaust?
What do you mean by first "soak the ehaust supply line" and then run the pipe cleaner through it?

Your help has been great man...

By "soak the exhaust supply line", I mean to spray sensor safe carb cleaner into the port where the EGR valve mounts to, then use a pipe cleaner - a metal twisted core with either copper/steel/stainless steel wires wound into it.

Other types of pipe cleaners include those used for washing dishes which have plastic wires (or whiskers - however you look at it). Another name for them would be a bottle brush or cup brush, but the one that you will need should be some kind of metal for the wires. It also should be around a half inch in diameter. They come in various lengths, but I couldn't tell you where to buy them from. I grabbed one off the maintenance shelf at work.

You could clean both the ports in this manner. The reason why I suggest this is because, as the carbon builds up inside the EGR valve, it is also building up on the inside of the supply tube. It can get a pretty decent coating on inside there and eventually it will flake off.

Will do this today right after getting out of the office...last time I cleaned the EGR I only sprayed the valve NOT the port...it was clogged and the port seem very clogged also but I was afraid to spray some carb cleaner in there...
Thanks man,

Not a problem. If you have any more questions, please don't hessitate to ask!

Sweet Bravada btw...;)

I took my lunch break to do this...

Cleaned the EGR valve which was dirty and the port was a lot more dirtier...used carb cleaner on both sides, an old toothbrush and a pipe cleaner I got from work...

Took out each one of the plugs from the right side and compared them one by one to the left side...they seem all the same...non have carbon buildup...

Truck is still wobbling at idle...[:@]

Will count to 1,000 before my nerves get me...

ORIGINAL: lovetheblazer

I took my lunch break to do this...

Cleaned the EGR valve which was dirty and the port was a lot more dirtier...used carb cleaner on both sides, an old toothbrush and a pipe cleaner I got from work...

Took out each one of the plugs from the right side and compared them one by one to the left side...they seem all the same...non have carbon buildup...

Truck is still wobbling at idle...[:@]

Will count to 1,000 before my nerves get me...


Should I buy an o-ring kit for the fpr? Or should I buy a new fpr?
Maybe this is the solution to pain...:(

You really should do a fuel pressure leak down test first. Second, if the leak down test didn't really provide much information, would be to pull the upper plenum off and look for a cleaned off spot from the fuel dripping.

You should see a pressure drop over a period of time if the fpr or an o-ring is leaking.

The o-ring kit is available from your local GM dealer for about $28 out the door. Don't be worried if you have afew pieces left over. The kit fits both 6 & 8 cylinder engines, so there are extra o-rings for the injectors as well as extra plate for the underside of the spyder body.

I will find a shop to do this test...
Man, I drove the airport with my wife and she even noticed the huge bad ass gas smell inside the truck!!!Damn...she never notices anything, 'till now...
When the fpr leaks do you smell that much gas? Specially if I floor the gas pedal the smell in much more noticeable...when I took down the gas tank I triple checked for any leaks and there are none...what really is bothering me is the shaking seems to never stop and that if I have the fuel level between 1/4 an 1/2 it all of a sudden goes to low fuel and the truck sometimes dies...????

If you are still looking for metal brush to clean out the EGR supply line I would suggest a bore cleaning kit from either a Sporting Goods store that sells rifles/shotguns or a Gun Store. The cleaning kit comes with varying sizes of metal bore brushes to fit differing sizes of rifles or shotguns. The brushes are made of wire that would be strong enough to remove carbon after having been soaked with a carbon cleaner for more than 5 min.

I might also suggest something like Seafoam or a Top End Cleaner to soak the carbon with. Just follow the directions on the can for use and you should be good to go.

Also if you don't find any leaking fuel with the FPR you might have a carbon fouled poppet valve in the lower manifold... the GM dealers have a service bulletin about this rough idle and there are two options listed; the first is to use high pressure cleaning system to dislodge the carbon after using the GM Top End Cleaner. If that failed to fix the problem, if you were still under warranty to replace the "Spider" unit with a newer style "Spider" that replaces the poppet valves with true direct port fuel injectors. If the warranty has expired then you have the option of chosing to pay for the replacement of the Unit to repair the rough idle...but you have to take it to the dealer to have them attempt to repair the rough idle...could be costly.

I will take the truck today to do a high pressure fuel injector cleanup and have them check if the o-rings are leaking...I'll see if they let me peek at what they are doing to learn a bit more!
I cannot stand to drive my car since saturday due to the strong gas smell and way too rough idle...mpg is af it was a v12!!! it gave me 18 avg, now I am getting 11mpg prolly[:@]...
Will let you know if this works, thanks to all for your help...:)
Appreciate it...

Had to leave the truck at the shop today...they checked all fuel rails, fuel tank, throttle body, etc. They found no gas leaks...since it was almost 7pm, they told me that it is almost certain that the leak is at the fpr and that they'll check this today in the morning and change the o-ring if necessary, then they'll do the high pressure injector cleanup...

And your positive you don't have a vacuum leak?

I sprayed carb cleaner to all the vacuum lines with the truck at idle and it did not bog down or stalled even a bit...

Towel thrown...!
Here's the final diagnostic: Car is in OK condition...
This cannot be ok...they say that s-10's are shakers but, THAT MUCH?

They checked all vacuum lines, vacuum ball, vacuum tee, egr valve, throttle body, maf sensor, iac valve, map sensor, fpr, all fuel rails, fuel pressure, fp leak down test, checked for codes, checked all injectors and they are clean (maybe 'cause I pour one bottle of injector cleaner per month) , fuel filter, k&n fipk, air temp. sensor, pcv, motor mounts, checked tranny fluid, they even did a compression test!!! etc.
They found NOTHING!!!???
The only thing left to do is to hook the car to some machine that tests the amount of air/fuel mixture the car is doing...they will do this next week since their machine was out for maintenance...don't think this should be the problem because it is not smoking black or anything like that...
Yesterday I poured TWO bottles of Prestone SUV injector cleaner to see if helps out...

I love my truck because it is comfortable, has a smooth ride and it has power...I decided 1 year and 1/2 ago to buy it over the following vehicles: Toyota 4 Runner, Mitsubishi Montero Sport, Ford Explorer, Isuzu Rodeo...
The one I wanted the most was the Ford Explorer and the day I was about to buy a 00 model (with the dough in my pockets), I went to just check a couple of Blazers...I immediately was amazed how much smoother than the Explorer it was...I decided for the Blazer and cannot think that these cars shake so much!
I have thought about selling it due to this issue...but I love the truck!:(

Will spend the last $500 trying to remedy this issue...
Will buy the following:
-new fuel pump
-both knock sensors
-all 02 sensors
-new MSD spark plug wires

MSD is a waste of money. Just buy the Belden Premium wires from Napa. Lifetime warranty and damn good wires.

I don't think that the fuel pump has ANYTHING to do with this issue. Typically, a fuel pump works or it doesn't. They really don't have an in between.

O2 sensors possibly could, but unlikely. A bad O2 sensor (bad enough to screw with the idle quality) would be horrible under load (accelerating) and would definitely throw a code.

I guess the knock sensors could possibly be a problem, but a scan of the timing advance and knock sensor active count would verify if you are getting false knock, but again, this would magnify as load and rpm increased.

Have they checked out the harmonic balancer on the front of the crankshaft? Also, I am trying to think of a way to verify that the balance shaft is turning (driven by a gear off the cam shaft). Both of these can have an effect on your idle quality. Also, a cracked distributor housing can throw off your timing, but it should be apparent at higher rpms as well.

I would have to disagree on what you said about MSD...when I changed the stock coil to the MSD Blaster coil, the truck woke up...maybe the stock coil was going bad or something...but the truck was smoother when accelerating, hesitated a tad more with the stock coil...took out the msd and put back the stock coil and immediately felt the difference is the engine sound...don't think that I gained some hp but it is smoother and I am getting approx 1mpg more!

I am planning to buy an MSD 6A ignition and MSD plug wires because I have seen the results in some of my friends cars...you won't get more hp but you do get more mpg and acceleration is smoother, like it will not need more gas to get to high rpm's...

Regarding your question about the harmonic balancer...looks like they did not check that...
About the distributor housing...how can I check it?
About the 02 sensors and the knock sensors, you are right...in theory, it CANNOT harm the idle quality if not harming the overall rpm range...

Getting a bit desperate here...[:@]

My comment had to do with the wires. You aren't going to be pushing enough voltage, even with a blaster coil, to out 'flow' a set of factory wires. Now with a 7al box (don't know if you need to go that big), you might need a larger core wire. For that, I would buy a spool of MSD wire and cut to length, crip, and slap the boot on. Quality comes with practice, but you won't get a better wire for the price. Only down side is you have to buy a wire crimper and a spool of wire that you may use 10' of per job.

When it comes to wires, there are only 3 sources I would deal with. Belden, AC Delco, and MSD spool. I have seen many many quality issues with MSD premade wiresets. Things may have changed now, but a few years ago the wires were only warrantied for 6 months and would generally take a dump after 7.

Hey, I am thinking on the following noob stuff...

-Is it COMPLETELY necessary to use premium unleaded gas?
-How can I check if the spark plug wires are deffective? Maybe they are bad since I bought them new?
-I am running splitfire plugs...people have said many terrible stuff about them...rough idle, not enough spark, etc. maybe the gap is too small? but it is at .045!!! Maybe splitfires are not good in GM's??? They are about 1 year old only...

Are you running premium in your blazer? WHY??? 87 octane is all that is required.

You can check spark plug wires by misting water over them at night. If you get a light show, you've got a bad wire. Just take an old windex bottle (thoroughly rinsed out) and fill it up with tap water. Just mist it over the wires from the distributor to the plugs.

Pull a plug and have a look at it. If the center electrode looks worn down, replace them. If the gap measures loose, replace them. I can't exactly remember, but I could swear that I set mine at 0.055... I'll have to do some checking to find out what the correct gap is supposed to be. I might have my Bravada screwed up with my Bonneville.

I wouldn't put anything but a regular Double Platinum plug in the newer 4.3L. Just buy them from a reputable vendor (AC Delco, Champion, Bosch, etc.), but don't go for the +2 or +4 crap that's out there. It does absolutely NO better than the normal single electrode spark plug. Not to mention that you can't adjust the gap on those plugs at all. You need to check your gaps before installing your plugs. I pull all of my plugs about once a year on my Bravada and replace my plugs once a year on my Bonneville, but I'm only running regular copper plugs on the Bonneville due to their supperior performance with a blower.

I am running premium gas ever since I bought it...1 year 5 months...Is this bad for my engine?

Last week I got the plugs out and they all seem fine, no carbon in any of them and all had the same gap...what I'll do today is mist the wires with water withe the engine on to see what goes on...

The only place it will hurt is your pocket book. You can't gain enough performance out of the expensive stuff without the PCM being tuned for it to make it worth while. Basically, you won't gain enough mileage to cover the added cost. When I ran my test on my Bravada after I bought it and I only got ~1mpg better on premium than on 87. At between 20cents and 27cents difference between the two, it wasn't worth it. If you are worried about deposits in the cheaper stuff, just run a can of injector cleaner at each oil change. All you need!

ORIGINAL: swartlkk

Are you running premium in your blazer? WHY??? 87 octane is all that is required.

You can check spark plug wires by misting water over them at night. If you get a light show, you've got a bad wire. Just take an old windex bottle (thoroughly rinsed out) and fill it up with tap water. Just mist it over the wires from the distributor to the plugs.

Pull a plug and have a look at it. If the center electrode looks worn down, replace them. If the gap measures loose, replace them. I can't exactly remember, but I could swear that I set mine at 0.055... I'll have to do some checking to find out what the correct gap is supposed to be. I might have my Bravada screwed up with my Bonneville.

I wouldn't put anything but a regular Double Platinum plug in the newer 4.3L. Just buy them from a reputable vendor (AC Delco, Champion, Bosch, etc.), but don't go for the +2 or +4 crap that's out there. It does absolutely NO better than the normal single electrode spark plug. Not to mention that you can't adjust the gap on those plugs at all. You need to check your gaps before installing your plugs. I pull all of my plugs about once a year on my Bravada and replace my plugs once a year on my Bonneville, but I'm only running regular copper plugs on the Bonneville due to their supperior performance with a blower.


I believe that the plug gap for the Blazer should be factory .060 ...

Haynes says .045 and my engine bay says .045...some sites say .060...Who should we believe?

My sticker says 0.060 on my Bravada. Its my Bonneville that I have dropped down to 0.055 (from 0.060) to keep the blower from blowing out the spark on the colder plugs. I was mistaken.

I just put the regular cheap motocraft plugs in my 02 , are these plugs ok to use? or do i need to run the plattnum plugs ?

Regular copper plugs will only last for a shorter period of time...
Why does my Blazer ask for .045? Damn...

I went to the parking lot on my lunch break with a couple of guys that know a bit about mechanics to check the freaking shaking...
With the engine on...I checked all vacuum lines by spraying carb cleaner to them and the truck did not hesitate not one bit...
I opened the hood and told them about the shaking...
The engine seems to have a small miss in idle...if you accelerate it a bit and then let it go, it like bogs down...
They told me that the truck does have a miss...I have taken the truck to two shops now and they have not found anything...I thought, hey, it may be me...but all my friends that I tell them to check this they say that it has a small miss...
I will put tomorrow the new ac delco regular plugs and will buy new ac delco spark plug wires...
Maybe the wires have gone bad inside or maybe they are bad since new...maybe one of the splitfire plugs is bad inside 'cause outside they look clean...
Watta' headache....

ORIGINAL: swartlkk

My sticker says 0.060 on my Bravada. Its my Bonneville that I have dropped down to 0.055 (from 0.060) to keep the blower from blowing out the spark on the colder plugs. I was mistaken.

What would happen if my plugs are gapped at .045?

The copper plugs won't last as long. They will wear down the electrode much faster than the platinums. I run the coppers in my bonneville because for ~$1 per plug, they won't break the bank to replace them yearly (yes yearly) and they perform better than the platinums on a blower application.

Sorry... Didn't see your other 2 posts here before I replied.

Too close of a gap could definitely cause a miss. Basically, you aren't exposing enough of the spark to the cylinder gases and it doesn't ignite properly. I would try your plugs at 0.060 and see how things go. Also, the Belden premium wires found at Napa are just as good (quality wise) as the AC Delcos and they come with a lifetime warranty. I think I spent like $65 for the set when I did my plugs, wires, cap & rotor.

Another thing I have been reading about lately is the cam sensor trigger magnet (in the distributor) having a crack in it. I don't know how much validity I'm going to give to this right now seeing as how I haven't done my own research into it, but what I have read seems to suggest it could be at fault for some pretty weird problems.

Agreed...
Will put the ac delco plugs tomorrow gapped @.060 and then I can determine if I'll need new wires...the Belden wires are cheaper than the Delco's ($87) and cheaper than the MSD's ($92)...will definitely consider buying them if the ones I have are bad...
Do you feel any shaking in your truck at the steering wheel?


Will advise if shaking stops...
Thanks for your support...

It's me, AGAIN!
So I gapped the plugs @.060 and bought a new set of wires...the old ones seemed ok...
Damn, I hate taking out the plugs in my 4.3L, I believe cylinder #2 is the the one by the steering wheel? that one is hard...had to use a jack and all...
To keep the story short, it is now missing even more...now I can even feel it accelerating! double checked if all wires were hooked correctly and they are fine...
My engine sticker says the plugs should be gapped @.045, but I don't think that this should create SUCH a miss...it is only .015!!!

HELP!!!!!!!!!!!!!!!!!!!!:(

After hearing that, it sounds like a coil problem. If, when you increase the plug gap, the miss gets worse, it almost always leads to a bad coil. The reason being that the spark is weak enough that it has trouble jumping the gap. This will cause a cold spark of short duration and could quite easily cause the miss.

I just read back through the entire thread (pheww) and noticed that you are running and aftermarket performance coil. First thing I would try is to swap out that coil with either a new one or if you wanted to go real cheap, grab one from a junkyard. It's not the best practice to use junkyard ignition parts, but the price is right. I could get both the ICM and coil from my local pick-n-pull for $3 out the door. I guess it is also possible that something has screwed up in the cam position sensor (in the distributor). I have been hearing about this quite a bit lately, but it has all been conflicting information. I think that the cam position sensor is a hall-effect sensor that works against a reluctor ring (gaps in a ring that get sensed). Some things I have read say that the sensor reads a spinning magnet that is connected to the distributor shaft and that the magnet cracks causing the sensor to pickup an incorrect pulse.

I was tempted to grab a distributor from the junk yard to see exactly how it was assembled and what was inside it just for a frame of reference. I am thinking this is a problem on my Bravada as well. Every so often while driving down the road, I 'feel' a miss, but I get no indication of a miss when I scan it. Definitely weird.

The problem is that the truck is shaking like this for about 4 months or so...I changed to an MSD Blaster coil in december and noticed the same results with the stock coil regarding shaking and rough idle...
Do you think that I should buy a new distributor?

I am just about to buy a gallon of gas, pour it on top of the truck and ignite the **** outta of it...[:@][:@][:@][:@][:@]

I just noticed that cylinder#2 wire was not hooked up tight...shaking got a tad better but it is now as it was before I changed the plugs @.060 and the new wires...this means that the truck shakes with no matter what plug gap or plug wire I use!!! Just discovered the telephone![:@]

Well, that atleast means that your coil/ICM are good... Don't know what else to tell you. You could possibly grab a junkyard distributor and toss it in. The local pick-n-pull here even allows you to get your money back on parts bought there (they brand them when you checkout) if the part is defective. Alls it takes is your time to pull the part. It is very useful for trying out high $$$ parts.

I will take the car to a gm shop...EXPENSIVE...if they don't find a cure I WILL sell the car...
This shaking is pulling my %&#%&&^**,,.

Hey swartlkk...just noticed the following...
When the truck is cold, the shaking is not felt that much, I believe that it is just engine vibration, but when it starts to warm up it starts to shiver on stop lights...this happens if I have the truck in Drive...does this ring a bell to ya?
I changed the air temp sensor from the intake but this has nothing to do with my issue...after I gapped the new plugs @.060 and put in new wires...the truck feels somewhat smoother and takeoff is slightly better...
Thoughts?

What is the function of these parts in the engine?

EVAPORATOR EMISSION CANISTER CONTROL VALVE (what's the difference between this and the EGR? This seems to be for emissions also...Can it be cleaned?)

IDLER PULLEY (can this cause bad idle?)

I am pretty much guessing trying to figure out in any way possible how can I eliminate the shaking at idle on my truck...other than this, it runs like a champ...the other day I beat the &*%$ outta some guy in an Integra who said he'd whoop my ass...sorry for him...

EVAP control valve is a solenoid valve that controls the application of vacuum to the fuel tank/charcoal canister. I am not aware of any way to clean it, but it shouldn't cause any problems with your idle quality. If anything, this will cause a higher idle if stuck open. You can check the EVAP system, but if you aren't getting any codes, it isn't the problem.

The idler pulley is a pulley on the front of the motor that is basically just there to support the serpentine belt in its normal routing. This will in NO way affect your idle.

I don't condone street racing and neither does BF.com. Please keep racing on the track.

You're right about street racing...it was my second and last time doing this...just prolly a heat of the moment stuff...I have tried the blazer at a strip a couple of times and do not approve on street racing also...Last time when it was stock I ran 16.8s...will go someday to the strip to try with the mods I have done to see how much I pullin the 1/4...
I have put mods only 'cause I love the sound it has now and the added torque...


Regarding what I said about bad idle when hot, do you know what this could be?

I'll have to think on that for awhile and re-read this entire thread! I'm very busy with work at the moment, but should be able to get back to it later tonight.

My '00 is also gapped at .60.

As soon as I get out of the office I will check each one of the drivetrain mounts, just in case I misplaced one or something...just a thought...haven't pulled the rabbit outta the hat yet!

Guess what? Pulled the darn rabbit...!!!!!!!!!!!!!!!

Abnormal shaking @ idle is gone!!!!!!!!!!!!!!

I checked the passenger side and drivers side engine mounts and looked ok...did not trust my instincts and decided to take them out...I took all nuts from the passengers side mount and when I pushed the engine up with the jack and took the mount off, it strip itself in HALF!!!!!!!!!!!! Immediately went to a NAPA and got myself a new mount and hey, THE SHAKING IS GONE!!!!!!!!! I just feel normal engine vibration now...normal for the 4.3L....

Almost $1,500 later it was only a freaking mount!!!!!!!!!!!!!!!!!!!!!!!!!
Swart, thanks for all your help trying to solve this man...I've learned a couple of neat stuff with your help...appreciate it...

I just went through the same ordeal. Shaking badly at idle after warmup.

Turned out to be a bad O2 sensor!
Not sure if there is a bigger issue behind why this sensor went bad or not but I guess I'll see if it messes up again.

Not a problem. I could have sworn that I had read somewhere that you had replaced the mounts so I didn't even suggest that. Even though I should have, considering the quality of aftermarket parts lately. Glad you got it figured out and fixed. That's the main thing.

Anyway, glad I could atleast help you learn some things, even if none of it really was the problem. I can't believe that the shops didn't check the mounts! I would be so PISSED if that's all that it was. What did the mount cost you? $60? if that? Alot better than the cushy hydraulic front mount on my Bonneville. I'll be replacing that one for a poly mount of my own design/construction this summer. That hydraulic mount actually limits the transfer of torque to the front wheels off the line and will hinder a launch at the track (where I plan to be a few times this summer for a baseline before upgrades).

The first mount I put in was a MOOG...never will try that brand again...I was thinking of buying the lower ball joints of that brand, BUT no way...I don't even know the brand of the mount I put in now, BUT what the heck...the shaking is gone...when I put the MOOG passenger side engine mount that's when my problems started!!!I spent about two hours doing this, but it certainly was worth it!

I really don't know why Precision Tune Auto Care spent 2 days with the car and found nothing wrong with it...thank God they did not charged labor, otherwise I would've spent a buttload o' money...