still looking for the answer

I have a 1995 3.1L (3100) when cold the engine hesitates under light throttle if you get into it you can clear is out. As is starts to warm up it goes away usually only happens once during warm up. If you let it sit and cool back down sometimes it does will do it again. Gave it plugs, wires, tps , fuel filter, t-stat. There are no codes present , and uses no antifreeze, but the temp gauge does fluctuate some. Goes up when you slow down and drops when you speed up only has a 7 - 10 degree change when I watched it on the scanner.

You mentioned you changed a few things. Did you consider having the throttle body cleaned, fuel injectors flushed, IAC cleaned? Just a thought.

I cleaned the IAC and ran some FI cleaner threw it

When you say you ran fuel injector cleaner through it, do you mean the kind you add to the gas tank or a professional cleaning where you block the fuel from the tank and run and IV type setup to the shrader valve? A professional injection flush and a throttle body clean are in order if you have not.

I have the same car with virtually the same symptoms. Problem seemed to start after a bad intake gasket dumped some antifreeze into the oil. Engine has been all flushed out but now we have the hesitation and temperature fluctuation. I've replaced plugs and thermostat, and am running fuel injector cleaner through the gas. Any ideas what I shold check next? I am thinking of having the electronics scanned for errors but would rather not pay any more than I have to. I'd love to hear of any suggestions, and I will post a solution if I get one.

Well, for one, spray out the throttle body air intake really well, and ensure the butterfly is free-moving, do the same with all external linkages and pawls, ensure they are free-moving.

Check the air filter!!!!!!!!

I just cleaned the living hell out of my IAC motor, IAC cavity, throttle body, and UIM. And it made a world of difference - the things were filthy as hell.

Wow, thanks for the quick replies! I just discovered these forums a couple weeks ago and they are great. :smile: I did clean out the throttle plate with WD-40 last night and remove a small amount of gunk. I also checked the air filter, which was OK. The car was still acting up, though, so I will get some carb cleaner and get in there deeper tonight.

One thing I noticed as I test drove it after the cleaning: the temperature guage seems to spike up right after it has a hesitation incident. The amount of spike seems proportional to how bad it stalls. At a stop sign last night it stalled 3-4 times and then when I got it moving again the temp shot up to 260. It goes back down soon after. Another weird symptom: when starting the car on a cold morning, the RPM's slowly increase over the course of a minute and stay high. If I shut the car off and start it back up the RPM's return to normal. Not sure if this helps troubleshooting but I figure I'd throw it out there.

Well, I've got an update, sort of. I took off the throttle assembly and cleaned it all out with Gumout Carb and Choke Cleaner, and took off the two electrical items attached to it and cleaned them out. I found some condensation inside what I think was the Throttle Position Sensor (inline with the butterfly valve), so I cleaned it out and put it back on, then ran the engine and sprayed a bunch of the cleaner through the intake. During the test drive afterwards, the car seemed to do much better, so I thought I had licked the problem. No go; the next day the hesitation started up again. I would still appreciate any insight on this problem, as I continue to troubleshoot.

I was reading back in your post about the car overheating after it had stalled. Have you had your catalytic converter looked at? A plugged cat can cause stalling or no starts and if it is plugged that bad it could also cause the heat problem as the exhaust has no where to go.

Thanks for the tip, swalt. I was just reading another post here (http://www.automotiveforums.com/vbulletin/showthread.php?t=246213) that mentions both the catalytic converter and the mass airflow sensor. Since I have no idea where the MAF is, I'll take the car by Midas tomorrow and let them take a looksee. I agree with you in thinking the temperature fluctuation is the key. It also tends to hesitate more going uphill, so I'm assuming something in the cat. is sliding backwards and plugging it up.

Mass Air Flow (MAF) sensor will be the unit contained inline of your air breather. Usually it goes Filter - MAF - and then throttle body. I remember reading somewhere about doing a "tap test" as one of the tests for the MAF. With the car idling, tap the MAF with a screwdriver and if the idle changes at all, the MAF is likely defective, but I think your problem is the Cat.

I'm posting this follow-up just in case someone else comes across the same problem. I bought the car by a garage for a diagnostic (as well as have a wheel bearing replaced). The mechanic said that the TPS was turning out a higher voltage than spec, and the IAC seemed stuck compared to what he was used to seeing. His suggestion was to replace the IAC first, then the TPS if necessary (a bad IAC could be causing the TPS voltage to be high). I did this, and the problems all went away once I replaced the TPS. I might have been able to save $32 by replacing the TPS first, but at this point I'm happy that it wasn't something real expensive!