More updates...

Just to recap a bit...I recently brought the truck to another mechanic thinking I might be able to purchase some imperical knowledge. No such luck. But, he was able to tell me that cylinder 5 was more frequently misfiring than the others. With my scan tool, I was able to pick up P0304 and P1345 (Cylinder 4 misfire, and camshaft / crankshaft sensor correlation error). P0304 has shown up recently.

Last night I had a couple hours to spend in the garage.

So, the first thing I did was to pull plugs 4 and 5. They were both badly fouled, and smelled strongly of unburned fuel. Because some said the 4.3 is picky about plugs, and to help eliminate variables, I did replace all the plugs with the OEM ACDelco plugs (gapped to .060" - out of haynes manual).

I checked over the plug wires again, making sure that each wire was seated properly at the distributor and at the plug. I also checked again for any visable or audible arcing. Everything there checked out just fine.

I checked the rotor to see if it had been burned again. It was not. All looked good there. I also checked to be sure that the camshaft sensor was securely fastened. All looked good there.

I had read, inanother post, that the ignition module can exhibit degraded performance if it gets too warm. So, I cleaned the module, heat sink, and mounting plate, applied fresh heat transfer compound and reinstalled the module.

This is ALL I did...and things are MUCH worse now. I can't say for 100% sure that this is due to changing plugs, or cleaning the heat sink...or whatever. But, I drove the truck Saturday and it ran like crap. I worked on the truck Sunday, then took it for a test drive, and it ran like crap x 10.

It still starts and idles just fine, save rough idle...but it's always done that. But, now I have a hell of a time getting going. From a stop I spit and sputter and buck until I can get above 1800-2000 rpm.

Some other details that may or may not be important...

During the summer I tried a bottle of Chevron engine treatment. I tried this right after doing the list of things I originally posted with. This was the only time during this diagnostic journey that I saw improved performance, rather than degrading performance. But, because I did so many things at once, it's hard to tell which things were successful contributors to the improvement.

I mention this because I read elsewhere that combustion chamber deposits can create the types of symptoms I'm seeing. Thinking back, I wonder if I saw some improved performance because, albeit for a short time, I was able to get rid of some of the build up.

I alsonoticed, during last nights efforts, that I was low on coolant. As long as I've owned the truck I have had a moist spot at the front right "corner" of the intake manifold. It's been my understanding that this is seen on alot of these vehicles. It has apparently progressed to a drip. I have never seen white, sweet smelling exhaust, and I have never seen evidence of burned coolant on the plugs. I have never seen coolant in my oil, or oil in my coolant.

I don't know how or why low coolant level, due to a leak, could contribute to anything I'm seeing. But, at this stage, I'm reluctant to skip over any detail.

I will be changing plug wires as soon as I can...mostly for lack of any better identified task.

Any suggestions would be greatly appreciated.

Thanks!

Icarus

 

It definitely sounds like something is wrong with those plug wires... When you pulled the wires off of the plug, did you make sure to pull by the boot and not the plug? It is possible that you stretched the wire and broke the conductor.

One other thing that I have seen numerous times is boots pushing themselves off of the distributor. When you install the wires, try to slip a small philips screw driver (the really small one) into the boot as you slide it over the terminal on the distributor. This will allow the air to escape. This is especially evident when dielectric grease is used in the boots as it adds to the seal.

If wires do not cure the problem, then I would take your coil and ICM (ignition control module) in to your local Autozone or Advanced Auto and have them tested.

 

Will do. Thanks!

I'll post back with findings.

Icarus

 

Quick update...

I did change the spark plug wires last night, following swartlkks advice about using a small screwdriver to get the boots on the distributor cap and prevent them from coming off.

During the swapout, I closely inspected the insulation and terminals of each wire for any sign of trouble. None was found. I found no evidence of wear of any kind, arcing from the insulation, or long sparks at the terminals (burn marks).

I had also remembered that when I cleaned up the ignition module and heatsink, I noticed the mounting screws were a little rusty. I didn't think anything of it at the time. But, I recognized later that those screws provide ground to the mounting plate. So,I removed the module and heatsink again, cleaned the screws and mounting holes, and reinstalled the module.

None of this helped at all. It's just as bad as it was during the last couple of days.

I'll bring the module and coil to have it tests ASAP. Do I have to have those out of the vehicle for Autozone to test them?

Thanks all.

Icarus

 

More...

I stopped and talked to the guys at the parts store about testing the ignition module and coil. They said that they could test the module, out of the vehicle, but not to bother with testing the coil. According to them, the simple resistive test they would dodoes not produce a reliable good / bad verdict. True or not...

I pulled the module and had it tested. It tested good...3 times in a row. So, I put it back on.

Out of curiosity, I asked how much the coil was...in hopes of eliminating any other "cheap' variables. Since the coil was only $40 ish...I replaced it.

Now, after replacing the coil, I'm back to running like crap x 1 (rather than crap x 10). I'm pretty much right back to where I was before I changed plugs back to OEM, performance-wise.

For what it's worth, I also tested the IAT sensor to make sure it was reading proper temperature (verified).

So, the coil seemingly made a difference. I'm not violently bucking anymore...but I'm still doing plenty of spitting and sputtering.

No new codes yet.

Now...that I can think of...there's a relatively small list of things left that could be wrong (ie:things I haven't already tested or replaced). There's the camshaft sensor (which most say is unlikely), there's the crankshaft sensor (which most say is unlikely), there's the timing chain (which most say is unlikely)...and then there's the distributor. Some have said that the gear on the distributor could be worn, causing the trouble.

I should mention, for completeness, that the distributor has never been removed during my ownership(to my knowlege). So, the idea that base timing could be off seems strange to me. Maybe I'm missing something and someone can explain how base timing can change without the distributor or timing chain moving.

I also got to thinking...what of the knock sensor. If I understand, the knock sensor detects a misfire and communicates it to the computer. The computer adjusts by advancing / retarding timing. But...what happens if the knock sensor is detecting misfires that aren't actually happening? Can the knock sensor throw timing off??

Dunno.

I've literally spent a year, and about $2000 on trying to get this thing to stop running like a complete piece of garbage. Granted, I'm not very smart...but those worth thier salt have trouble too.

For what I'm spending in wasted fuel and repair parts per month...add a hundred or two...and I could have a brand new car. Almost there. GRRR.

If it weren't for the fact that the people I work for only pay me if I continue to show up for work...I'd just drive it 'till it dies.

Please...any last ditched suggestions?

Thanks,

Icarus

 

Please verify that your plug wires are going to the right plugs. Some of the dist caps have the plugs numbered on top of the cap.

Do oyu have gas in your oil?
If so your fuel pressure regulator may be leaking, or you may have a leaking spider hose.

 

Hanr3,

I agree misrouted plug wires are something to look for. When I replaced the wires I payed very careful attention to the cylinder numbering diagram, to the numbers on the distributor cap, and also verified that they matched. Last night when I replaced the coil, I checked them again. All is good there.

I'm certain I have gas in my oil, because I'm flooding the cylinders with unburned fuel all the time. The oil is due to be changed...that'd let me know for sure. The entire "multi-port spider assembly" was replaced less than a year ago. It contained a new FPR. This along with a new OEMfuel pump were a couple of the first things I did to try to eliminate rough running.

Before I changed the fuel pump and spider, I was seeing fuel pressure bleed off badly. If I put a fuel pressure gauge on the fuel rail and cycled the pump, I got an initial 60 psi...but the pressure bled down to 40 psi (or less) in less than one minute. After replacing fuel pump...same. After replacing spider (with new FPR)...same. I gave up on that.

I've got lots to learn...but this misfire stuff seems like a spark issue to me. No?

Icarus

 

S10 Blazer...one year later, and I don't even know how much money (over $2k)...you win.

I spoke to someone at the local chevy dealship about my issues, siting all I'd done so far. Swag prognosis is that either the distributor or the computer needs to be replaced. I didn't even ask how much...because it really doesn;t matter at this point.

I'm spending almost $200 a month on parts to keep this thing going. I give up.

I want to thank you all for your support and helpfulness. I likely got a year more out of this vehicle, because of the availability of this knowledge base, than I would have otherwise.

I broke down and bought another vehicle yesterday...I really didn't want a car payment. But, in a way...I had one all this time.

I'll check back from time to time. Maybe I would have come across something someone is asking questions about.

Thanks again.

Icarus

 

I SUre did/do appreciated you coming back with any updates you had!!

After over a year & $2000 of basicallywalking the same battleground as you, i too am hardly any better off. I am down to buying a new computer as a last option.The Blazerwould have been a much better SUV hadthe name 'Gremlin' been afixed to it's exterior.

 

I don't know if I'd say all that.

I bought the vehicle in 2003 (3 years old). It was a good vehicle for me for the first few years. It really only got to be problematic during the last year or so. But, man...how.

In reality it was fairly trouble free (at leat during my ownership) during the first 6-7 years of it's life...which is pretty damn good. It's alwaysbeen my belief that there was a reason why warantees and financing terms (for most auto manufacturers) hovered around 5 years. Every auto manufacturer has it's own reliability engineers, and these guys know the probability that a given widget is going to fail within a given amount of time. Of course, we don't want that to happen during warantee period.

So, in effect the coordinated failure of a bunch of stuff (around the 6-7 year mark) is completely by design...for most all vehicles. It is thier intended life span. To a significant degree, it's when a bunch of us cheap, or industrious do it yourselfers, or generally stubborn people try to fight these design characteristics that we get the feeling that the machine is a piece of crap.

There's an intellegent time to let a machine go, everything has a life cycle...and it's no ones fault but mine that I attempted to over extend that period, and was unsuccessful.

$.02