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2001 Corolla troubles

Okay, so I have a 2001 Corolla (auto trans, 186K miles) that I’m having problems with, and even more difficult is diagnosing what actually is wrong. All winter I had no problems whatsoever, only recently has the problem arose, I think only after I hit a large pothole and blew out a tire… but that may be irrelevant.

Anyways, the problem goes as follows: Say I’m at a stoplight, idling. When I push the pedal down to go, nothing seems to happen(it will kind of make a coughing sound), if I tap the pedal again, sometimes it’ll go, but occasionally it will stall…Keep in mind this doesn’t happen all the time, it’s pretty inconsistent. I’m not sure what it is, and the OBD II tells me I’m running rich so I’m currently running injector cleaner to see if it’s buildup on the injectors… It seems to help a little bit, but the problem still persists. Another thing me and a friend figured it could be is the throttle position sensor… Can anyone else shed some light on what this could be?

You will have to start with reading the codes for that check engine light and then starting to check all the systems that the codes refer to. When has been the last “tune-up” for the car?

The CEL codes say that the engine is running rich… That’s about all that it tells me there. The car was purchased from a dealer that said the previous owner had all the proper maintenance done and that it had mostly highway miles on it. So, I can’t really say when the last tune up was.

What DTC code is that which means “running rich”? A sticking idle air control valve (iacv) could be causing the problem of stumble at the stoplight. Spray the air passages to the iacv, and throttle bore and throttle plate, with Throttle Body Cleaner.


The code I get is a P0172 if that helps.

A faulty engine coolant temperature sensor (ects) will cause an engine to run rich.

OK, so it’s been a while but I acquired some throttle body cleaner. I’m not sure where the IAC valve is though, as I don’t have a Haynes manual for my car yet… Also, would I need to remove the TB to use this stuff? One more thing, should the vehicle be on or off for this procedure? Ok enough questions. One last thing i should mention is that the CEL turned off last night while I was driving… Not sure why, but I was thinking maybe the cooler air… maybe irrelevant but just thought I’d mention it. Thanks for the help so far and I’ll keep you all updated.

Please also check out your exhaust system., When you hit the pothole, you may have collapsed your muffler or exahaust pipe causing a severe restriction.

This article will help you clean the throttle body:
And, here’s an article, with pictures, on cleaning the idle air control valve:
Here are more instructions and pictures from Register there to see the page:

Hey, thanks for the links, these will help a lot. I did notice earlier that there was a bit of grime inside the throttle body, so I’ll grab an old toothbrush and get scrubbin’

MAF Sensor. You are getting P0172 and the hesitation on acceleration, aka no throttle response.

Do one thing at a time (the cleaning, first). You and your friend could be correct about the throttle position sensor (tps). You can KNOW with a simple check with an ohm meter. Follow the tps testing instructions (engine OFF), AND, check the tps ohms as you s-l-o-w-l-y move the throttle from idle to off-idle, and back to idle . The ohms shouldn’t jump around. If it does, replace the tps.