Marc3.4V6

iTrader: (1)

A week ago it was very hot and in the last few days I started noticing my warm idle oil pressure after driving for 20 minutes or more was lower than usual at 20-25 psi, though still technically within spec, it never used to dip that low. Anyways as I am moving from a stop at a light I feel a very subtle engine cutout. Then I park and get a haircut and when I am going home it starts to stumble and misfire real bad like it's going to die, seemed to happen when stopping and starting or letting off the gas and back on. As far as I am aware there was no backfire from the exhaust but there was a lot of backfire from the front of the engine which I get occasionally. I pulled over and let it sit for a while before I decided to try to make it home. Again it felt somewhat ok, but I was scared so I put it in neutral and kept the revs up and then few seconds after moving from a stop it did it again only I powered through it and it didn't do it anymore on the way home (only 3-4 blocks). When doing this I noticed it sounded like a 6 cylinder. I also noticed, especially after getting it home that the fuel pump was unusually loud with the engine running and a higher pitched like it was working extra hard. I don't remember if I checked the fuel pressure that nigh , I was tired and upset, but I definitely checked it the following night and noted everything was within spec, except for a few measurements being about 2-3 psi lower than spec. I also noticed the pump was loud again. I checked it again a few nights ago with the gauge already on and let it run for 10 minutes and drove it to try to get the problem to happen again or see how fuel pressure would be affected but there was no change. Also this most recent test the fuel pump was unheard while running. I had to get out and go in the hatch to hear anything, nowhere near as loud as the previous times. I can hear it prime like normal, but not just barely when running, which I think is how it's supposed to be. It should be noted that there were probably 2-3 gallons of fuel in the tank. Hard to say exactly because the gauge doesn't work and I just fill it up by mileage.

The first time I learned the gauge was not trustworthy at all was about 1-2 years ago when I ran the car out of gas. Freeway services gave me a little gas and it would start for a few minutes then finally started and I went to a gas station near my house and filled it up, it started but then died pulling out of the gas station driveway. I thought for sure I killed the pump. My dad towed my home with a rope in his avalanche lol. Now I've had so much **** happen I'm having a really hard time remembering when what happened and when I replaced what. If I had known I would have kept a detailed record. I know that I replaced the fuel pump at some point but I don't know if it was before or after running out of gas. I should also that this happened once before but much worse it actually died and would start right up first try but not stay running for more than 10 seconds to 1 minute before dying. After waiting over an hour and getting it towed home, roughly 2 hours later I started it to show my dad and it ran fine and would not die, and never had that problem anymore. It was chalked up to air in the fuel line as I just had one that was leaking under the car repaired/replaced. So now I'm thinking clogged fuel filter or clogged pump sock filter, but why now when the running out of gas occurrence happened so long ago? And If I already replaced both after the running out of gas like I might have, what else should I look at?

P.S. I scanned it with my auto x ray and got no codes.

EDIT: I searched throuhg my thread history here and it looks like the running out of gas issue happened in 6/09 and I did replace the pump and inline filter, and shortly after the EGR and FPR. Then shortly after that headgaskets

Marc3.4V6

iTrader: (1)

Any ideas? Heatsoaked ICM maybe?

96SilverZ

iTrader: (2)

To me it sounds like a plug wire fell of or the opti/coil is going bad. When my icm went bad i only noticed a slight drop in mileage and a slightly higher idle and I got a code.

Marc3.4V6

iTrader: (1)

thanks silver. I drove it around the block after letting it run for 8-10 minutes and everything was fine. When I was checking it out he night of the incident, the idle surged slightly in park and I can hear the loud fuel pump surging along with it like one was causing the other. I'll check the wires.

96SilverZ

iTrader: (2)

Does it feel like there is a loss of power?

Marc3.4V6

iTrader: (1)

No not really, not even when it was happening, just stumble and miss/backfire and momentary engine cutout a few times when barely touching the gas from a stop. And also the lower than normal oil pressure.

96SilverZ

iTrader: (2)

If the plugs/wires are good then I would recommend using shoebox's site to test the coil/opti as one of them is probably the cause

Marc3.4V6

iTrader: (1)

pulled a plug, it was black and smelled of fuel. There was some coffee color to it, but it was surrounded by black including a slight buildup of black gunk.

Also checked fuel pressure one last time for drop off and it actually went up 2-3 psi from 37 to 40 after roughly 20 minutes. After 1 hour it was back down to 37.

So I'm running rich and fouling plugs that have 20 k miles on them since I changed them and nearly everything else (sensors, 02s, etc) after my headgasket failure at 12k miles. I have no clue where to start. If I change plugs they'll just foul again, and it'll take me all day just to do the passenger side with my shortys. A hotter plug seems like a band aid in my mild build. I'm leaning towards getting the oil consumption sorted and getting a dyno tune, maybe the mail order is too rich?

Marc3.4V6

iTrader: (1)

I'm posting this from hawaii while on vacation. I shouldn't be thinking of my car, but I am. I have no clue which direction to go in except to throw parts at it. I don't even know if the rich condition and slightly fouled plugs in itself caused the original issue. Even if I get say, new 02 sensors for $100 each, I won't know if it's fixed the problem and if my plugs will just foul again....Any suggestions?

Marc3.4V6

iTrader: (1)

It got dark on me too quick so so far all I ahve to report is the 02s in closed loop both jumped around between 100 or under to 800, except the left 02 only would get as high as 598. I don't know if that means anything. I think I'll have to break down and get a data cable and start data logging so smarter people can see all the numbers, because I have no idea what the learned idle steps and block values mean.

Also, on a test drive I got a SES light. "yes!!! Finally", I said. But it turned out to just be TPS too low. Likely unrelated, but I have had trouble with the crimping of sensor wires of the maf, tps and iat coming off and setting codes. I think I'm going to go through all of my crimped wires and solder them.

Marc3.4V6

iTrader: (1)

Fuel pressure result: 30 psi prime. 38 engine start. 42 w/ fpr vac line pulled. pump held pressure for a while after. I checked it a few days later and it's prime was higher like 35-37.

I hand wrote scanner results as I dont have an ALDL cable just yet, plan to get one from moates or somewhere. This was after I took off and inspected the tb and sensor wires, which appeared to be crimped very well so I didn't know what the problem was. I cleaned the tb and re-installed everything and there was no more TPS code. I'm, thinking that I adjusted it back to normal voltage while re-installing it.

Here are the results for closed loop.

map sensor 1.48-1.54
throttle sensor 0.74
barometric pressure 4.82
left 02 105-682
right 02 101-888
block learn cell 16
left block learn 134
right block learn 131
Left integrator 132
right integrator 129
left injector pulse 3.7-3.8 (after letting it run a while it went to 3.3)
injector pulse 3.6-3.8 (3.1 after running a while)
maf 8 gr/sec
idle air mtr pos 21 steps (24 warm)
learned idle pos 37 steps (24 warm
spark advance 27*
knock retard 0*
knock sensor 213 (150 warm)
EGR duty cycle was always 0%.

Now I don't know if any of that does you guys any good, you might be better off looking at a datamaster file or something huh? Well if yo see anything strange please let me know.