steamroller
Full Access Member
Has the distributor gear been checked yet? Known issue for them to get knife edged and cause problems, alot of times it's just on 1 side of the gear.
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I did have a performance programmer that I used but I restored the factory programming after the tune-up didn't fix it.Unless something was disabled in your pcm codes would have been thrown for a malfunctioning oxygen sensor...
You are SO right, if you only knew how pissed I was that the dealer came back at me with cap, rotor and AC Delco plugs LOL but sunlitcomet was right, the plugs were fouled there was crossfire in the cap and they had to start somewhere...Seems to me you are treating symptoms here. The same parts are replaced over and over with the same results.
I agree, seems like this will ultimately point towards the origin of the problemThere are other failures that can contribute to running too rich. The comment about being intermittent at first is an important clue.
Can these be tested with an ohmmeter or something? If I can test them rather than the dealer it will no doubt be more cost effective.I would be looking towards things like the MAF (Mass Air Flow) sensor and the MAP (Manifold Air Pressure) sensor. Even the IAT (Intake Air Temp) sensor. Seems like you go into a failure that causes all 8 plugs to come out black. Oxygen sensors are a possibility, but they would seem to want to fail one at a time rather than all four at once.
Mileage is 145,771, the first mechanic said he tested them but I can't say for sure how much he moved the wires while he did itIf you have a lot of miles, could be wiring degradation, possible broken wire. Know it’s a pain to do, but checking wiring between these above mentioned sensors and the ECM, while moving the wires as much as possible might be a cheap test.
Lost me again there bub, I'm learning a LOT here on this forumAnd then there is the distant long shot of run-a-way, fuel pressure. The ECM has no way of knowing what the fuel pressure is.
Agreed, show me the way can I test these sensors with an ohmmeter or something or are they cheap enough that I should replace them just to rule them out?So before you order up a replacement engine, might want to do a little testing on these sensors.
I'm with you there sunlitcomet, I think the first mechanic, although he was limited, ruled out most of the "usual" problems.I am still racking my brain and tech info still but when the fuel spider was replaced the pressure regulator should have been eliminated as the culprit and I would believe that if there were frayed wires by now something would show up as an computer error. The computer is capable of a lot of detailed info. And without the software and interface to access it it will be that much more difficult.
You got it:Gulley could you possibly post all known codes you had pulled in case you missed any on previous posts as well as anything else that may seem weird with your truck even if it does not sound engine related?
---------- Post added at 07:53 AM ---------- Previous post was at 07:43 AM ----------
Including anything installed before it happened.
Agreed, can I do that myself with an ohmmeter?I guess from what I have read in this thread, it’s time to start thinking outside of the box....I’m suggesting mostly taking some test meter readings of the components are could affect mixture. MAF, MAP, IAT and a simple check of the fuel pressure to answer the that question.
Also the comment that this all started intermittently should be analyzed further.
Just sayin………………
Yup, can I do that myself with an ohmmeter?O2 sensors should be able to be backprobed to read voltage so doing that could help decide a fork in the road as far as the other sensors go.
SweetI just eliminated the pressure as a probibility because the old regulator went out with the old spider.
You lost me again sunlitcomet, what does "reoriented in axis only" mean? LOLI would eliminate any alarm/starter modules if running rough while truck is not moving or the if the modules are reoriented in axis only.
Wow, I think you may have just explained how to test those sensors but it went right over my head! I feel like a chicken in an Algebra classMaf, Map and Tps can be tracked to what is known as performane or range problems when they don't coincide.
The Iat and Engine coolant temp. (ECT) sensor does not have such a direct error code.
There is a code for insufficient coolant temperature for closed loop ops that would eliminate the ECT in my opinion as if was given feedback for a hot engine or a direct high or low stalled reading.
A malfunctioning Iat does not have a performance variable code but under obd2 can be diagnosed with the help of monitoring egr activity and feedback voltage.
So that is likely a candidate for backprobing based on that the others could report performance problems and up to now haven't.
As far as the inability to cut the pulse width I will for now side with rich bank codes indicating that for now.
I do believe that there is more then just"expected problems".
If you really get into the data and understand theories of operation of the components used and how they interact with other known givens you can extract unexpected problems not dreamed up as well.
I believe the answer is in the data I just can't see his data other than what he reports.
I hate the fact that I am broke right now and can't get the interface and software I want for my own truck right now. I can work on stuff like this for at least a full day or longer and forget to eat or sleep.
I will break for a moment.
Both if I understood the mechanics explanation, that's why he replaced it.Gully, do you know if if the cam correlation error showed before or after the crank sensor was replaced?
Don't know if the fuel pressure has been checked.Thanks Jonathan, great OBD2 info. I only do Tec3, so I can only guess.
I totally agree. It’s hard to diagnose a truck with a unknown history, that has gone through three sets of plugs and wires and distributor caps in a short time.
I understand the FPR's were changed with the injectors, but I would still check the fuel pressure just in case the return line is plugged down stream.
The error codes need some interpretation sometimes. Like a miss in certain cylinders does not exactly say, your wires are crossed, even though that is what was wrong.
I think the intermittent occurrence during the onset is still one of the big clues.
There is likely to be more than one component contributing to this mystery.
Can a loose timing chain or skipping a tooth cause late firing which would not totally burn the fuel, leaving the plugs fouled?
It would be nice to have a wide band sniff the tail pipe……………
The only unusual noises I've noticed are exhaust leaks and the typical GM fuel pump whining, doesn't sound like it's dying but it's definitely louder than my Lexus and Nissan fuel pumps, sounds just like the Caddy I owned last year. Hope that helps...ran out of room again, to be continued...That is why I was asking about when the cam/crank correlation problem showed. You can get false misfire codes after replacing the crank sensor. I am kind of leaning to a problem in the drivetrain. I would have thought Gulley would have picked up on a unusual noise from there by now.
Sorry for the late response guys, been sick with the flu and broke too. I was gonna take it to another mechanic or back to the dealer but I can't afford it right now so it's just sitting in my back yard driving me CRAZY! Hopefully we can figure this out so I don't have to spend what little money I can scrape up on another mechanicWell then, it looks like it’s time for Shane to step up and do some more testing and get back to us with the results…………….
Check that ECT sensor.
The ECT can throw a indirect fault code that a sufficient temperature could not be reach for closed loop ops. or direct one for a short or open circuit but he has not reported one yet.
Yup, had the first mechanic check that.Has the distributor gear been checked yet? Known issue for them to get knife edged and cause problems, alot of times it's just on 1 side of the gear.
Yup, I'll try to get some tomorrow....In case I missed it how are the plugs fouled. Oil? black sooty? colored deposits?
Can you post pics?
At this point I'm tempted to do it just to see if you can pull a rabbit out of your butt....what was the name of the one you recommended and how much do they cost?At this point it might be wise to save when you can for a good scanner that can do a memory dump to post readouts here. It would provide all the sensor data for analysis. I hate to see you keep spending on parts. I still have more details but enough for now
A pic is worth a thousand words, and I have a thousand questions......A home theater example: http://www.sunlitcomet.com/images/home/agoraquest.jpg I still use Minidisc, Laserdisc and super VHS.