Hope someone here can help me to scope out a problem with our 2001 Corolla S. Car has 135K miles and has given us little problem in the past.
A couple of months ago, we started getting a bit of a miss while it was idling - nothing much, acted like it needed new plugs. However, it also had developed a bit of a ping during freeway ramp acceleration.
I started doing work on the vehicle. Changed oxygen sensors (both upstream and downstream) with NGK (upstream) and Denso (downstream) units. Also installed new NGK platinum plugs at the same time.
After I did all this work, it not only had MORE of a miss, it had a hesitation starting from a dead stop particularly when "cold", along with a too low idle speed, again particularly when "cold".
Took car to Toyota independent mechanic that we've used several times. He cleaned the throttle body (do not know if he cleaned the MAF, though). Car acted quite a bit better after the MAF cleaning. He got it to duplicate the problems, but didn't have any ideas as to the solution since he said it was "inconsistent". (Yes, it IS inconsistent when warmed up). He suggested putting a bottle of Techron in it, which I did followed by filling it up with gas. The Techron didn't really change anything.
After researching the issue, I tried two more things - cleaned the PCV valve and the OCV filter. I cleaned these at separate times, and each time, the car got a little better. The only incident I had when cleaning the OCV filter was that I smashed it a bit on the metal part (but did not bend or break the plastic frame).
Any suggestions anyone? A family friend is suggesting that we have an "air leak" somewhere, perhaps an injector seal or a vacuum hose leaking. We're at our wits end on the car right now. Thanks.
John