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:
https://blazerforum.com/m_7118/mpage...PI/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...

 

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.

 

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...