Taking one last stab at killing my 3.1 hesitation

[toadson]

re

I thought I had this issue solved..... but its been a recurring issue. I would drop the tank, clean rust from under the pump, car would run fine for a while.... then repeat. Well, last time I dropped the tank there was almost no rust under the pump this time, so I broke down and bought a new Delphi for 90 bucks. The new pump didn't help at all, so now I am back to square one. The car runs terrible when the weather is cold, say 50* or colder, the car hesitates pretty severely until it warms up. It will stumble when it starts up in cold weather, and taking off from a dead stop takes a lot of slipping of the clutch. Shifting into 2nd is embarrassing as well, because the car nearly dies unless you slip the clutch a lot. The only thing I can think of anymore is the fuel pressure regulator, so I guess that will be the next stop.

[torq455]

I have been around a few 3.1's in different models and years along with owning one myself. They all did what you are describing and others are complaining about. Mine got worse when I added my 62mm TB especially when cold. I started playing with the idle adjustment screw. I ended up screwing it to open the blade as much as I could, then resetting the TPS so the ecm would read a different voltage but with 0% throttle. My IAC counts are very close to 0 steps when FULLY hot, in park and NO electrical loads. Hesitation is gone even in the cold weather!! It's wonderful! My 94Z has 150,000 miles now and finally lost that bog.

[toadson]

How did you reset the tps exactly? Im about willing to try anything anymore lol.

[SappySE107]

There is no idle set screw. That is the throttle stop. If you have to open that, you have too much carbon built up around your IAC, or your IAC isn't working normal. That or something else is telling the IAC not to open as much as it should. My 3.1 never had any issues in hot or cold weather (indiana or phoenix).

[gpse3400]

I think you should isolate the cylinder that is not firing by removing the plug wires one at a time. At least then you can verfiy if it is the whole engine failing or just a couple a cylinders.

[torq455]

There is no idle set screw. That is the throttle stop. If you have to open that, you have too much carbon built up around your IAC, or your IAC isn't working normal. That or something else is telling the IAC not to open as much as it should. My 3.1 never had any issues in hot or cold weather (indiana or phoenix).

i have a screw on my old TB and everything is clean. it just seems like it needs more or a faster enrichment for throttle tip in.

[torq455]

How did you reset the tps exactly? Im about willing to try anything anymore lol.

iirc, key off, unplug the tps, turn key on engine off, plug the tps back in. the pcm will read that voltage as 0%. that can be done on the newer cars too.

[Hell_raiser]

tps/map/plugs/wires/fuel/coils thats all i can think of

[Sh3aNz0r]

throw a big magnet on the bottom of the tank and run the tank low for a few days, putting in 5 dollars at a time, see if it runs better, may pick up some extra rust thats clogging, and i would make sure with all that free floating you had that there isint a clogged line now.