94 Integra, stock LS engine poor idle/low RPM, [missing, runs like crap] only when hot out.

Cooler today and it ran fine.

Any ideas, FP good, ECT sensor tests good, no vac leaks and as mentioned it runs fine today, just like crap, [at low RPM] when hot out. 94

 

Have you checked the iat sensor? When was the last tune up?
Ignitor may be on its way out.

 

Just started happening,, [last three days, but not today] and as I said, pretty intermittent, [only when hot out out]

As soon as I have some time at the shop I will go over everything, been way too busy.

The car is well maintained, full tune up, fuel filter, plugs and fluids, valve lash 3 weeks ago, oil one week ago, [oil about every 2500mi since new], ICM is 4 years old, [not driven in winter for last 4-5 years], coil is MSD Blaster along with MSD cap/rotor/spark plug leads.

This car has been very good, considering it has been drag raced and autocrossed since new.

I have only had to replace the ICM, once, starter once and a blown heater hose, that's it, other then scheduled items, [timing and drive belts, brake pads and rotors and so on].

Up until now this car has run like a top, it burns no oil, never fails to start and still pulls strong.

I was kind of wondering when the shoe was going to drop, for years I have been hearing about all the problems others have had with their cars, [and helping where I could] I also do this for a living, [Dave Ward Auto Electric], the first time it happened, both Dave and I assumed spark plugs so I changed them out and that fixed it, then we got hot days on Sat. and Sun. and problem returns, did a quick test of ECT sensor this morning when I got to work, of course car is running fine, and sensor tests good.

I did not mention, on start up when cold, it also runs fine, it's not untill engine warms up, and it's hot out, that there is a problem.

I have searched and Googled figuring someone must have run into the same symtoms, nada, close but no banana.94

 

I've read that those can get hot and act funny. If I were you, I would re-install the OE distributor components and see what happens. Just a thought.

 

Hmmmmm could be the o2 sensor also might be on its way out. Stock ecu right?

 

Yes stock ECU and original O2 sensor, although temp at the O2 is so hot already I can't see a 5 degree hotter day having an effect on the O2, but then again stranger things have happened.

The blaster coil, maybe, easy enough to swap that out, again I has to be hot enough outside for the problem to occur, been cooler these last 2 days, so car is running fine. 94

 

Temp related made me think of the coil too. You could test the temp of the coil with a thermocouple and see if it coincides with the idle problem.

 

The iat sensor may be the problem as the temps rise the resistance goes down on the sensor maybe it has a dead spot. Its one of the easier sensors to check.

 

Probably a stuck o2 sensor... Unplug it(forces open loop) and drive around for a few days and see if the problem returns.

 

Did you fix this issue? Curious of the cause...