I am huge car talk fan and glad to find this forum to share/discuss about our cars.
We have owned a 95 Camry V6 for 20 years and it has always been reliable. However, several days ago, the car started to have its first engine performance issue. When we start the engine cold, there was rough idle/engine lope. If it was warmed up for about 5-10 minutes, the car was fine for the entire day. but during this rough idle, the car jerked slightly as well if i press on the gas.
Since the symptom began, I took it to local shop A and they replaced all the spark plugs, pcv valve and air filter which did not solve the rough idle/looping problem. The rough idle continued, and few days later, I was unable to start the engine though it cranks. (at least that’s what I think it does). Had it towed to shop B and they’ve replaced oil pump, which they thought to be the problem. I took it home, and the next morning I found myself unable to start the car. Now the car is back at the shop, and I just want to check here to see if anyone has any idea what may be the problem. Thank you!!
Have you tried starting the car while holding the accelerator pedal say halfway down?
If not, give this a shot and see what happens. If it does start then the issue may be a vacuum leak or Idle Air Control Valve problem; both of which can cause a rough idle and failure to start if the accelerator pedal is not depressed.
That’s what I’d consider first anyway. At least it’s free and easy to do.
Thank you, ok4450. I will give it a try. btw, I fail to mention in the earlier post that the catalytic converter was replaced a few months ago and I wonder if it’s possible that a fail perfect fit from the new cat could have caused a vacuum leak as you described since the weather is now a bit colder and the shrink in the part may play a role in these symptoms? Thank you!
Cat will not cause the problem. Oil pump is a total reach and a waste of your money. Did they replace the fuel pump? Vacuum leeks and fuel pump pressure would be a good idea besides the dirty iac.
Is there heavy dew or rain the previous night? If so spark plug wires or distributor cap could be at fault
It might be a problematic idle air control valve, or the wiring to it, or an air leak, possibly through a faulty idle-up valve. It could be other things, like clogged fuel injectors, but I’d check that first.
The first step is to test the idle speed per Toyota’s method for this engine.
If the idle speed is off, that can cause jerkiness, especially noticeable in slow speed driving, like in neighborhoods, going around corners etc. When you let your foot off the gas, the ECM will completely shut off the injectors (to save gas and less emissions), then when the speed gets too low the ECM will turn the injectors back on. A similar thing happens if you are coasting to slow down, and the injectors are off, but then you press on the gas. If the idle speed is set incorrectly, both transitions, which are supposed to be so smooth as to be barely noticeable, they can become very jerky and make the car difficult to drive.
I would suspect the engine temperature sensor - not the one for the temperature gauge but the one for the ECM. It may be running in the closed loop mode all the time which would make it hard to start when the engine is cold. It needs to be in the open loop mode until the engine is warmed up.
As for the oil pump, that’s about as bogus a diagnoses as I can think of.