97 V6 Camry cylinder misfire problem - external temperature?

[jack_mai]

I owe a 1997 Toyota Camry (V6) manufactured in Japan 06/97. The car has +170K miles and generally runs very well.

In December, an engine maintenance light come on, and my trusted car mechanic diagnosed it as cylinder #2 misfiring. I start to add fuel additives to clean injectors, but the problem still persisted. As I drove the car I have noticed that t worked smoothly when it was cold (below 75 F) outside; as soon as external temperature went up the problem started. Finally I gave up and in March, after replacing the injector the engine worked smoothly again. (In addition we replaced plugs, wires, and fuel filter). Yet, when during warmer days the problem comes back, but now instead of cylinder #2 I have cylinder #3 misfiring. It continues misfiring in warmer days …

I am not a mechanic, but based on observations it is obvious that there is an impact of external temperature of air. I do not believe that replacing injector #3 will remedy the problem. Any suggestions how to fix it? A sensor problem ? Is there a temperature sensor?

Thanks for any comments

jack

[RIP]

Might be something here that will help: http://www.obdii.com/articles/Diagnosing_Misfires.html

A little more info : http://www.northwestmr2.com/incoming...Control/16.pdf

Ignition colis are known to fail with verying temperatures. Your engine has three coils each firing two cylinders. If cyl #2&3 are fired by the same coil, that may be worth looking into. You could try swapping the coils around and seeing if the misfire moves with the coil position. Go to the Factory Service Manuals thread at the top of the forum, open the manual for your year, and look for additional info. Welcome to the forum.

[jack_mai]

Dear RIP,

Thanks for a response and a very informative selection of references. I will have to study the reference in detail to form any opinion.

Originally Posted by RIP

Might be something here that will help: http://www.obdii.com/articles/Diagnosing_Misfires.html

A little more info : http://www.northwestmr2.com/incoming...Control/16.pdf

I willl try your suggestion:

Ignition colis are known to fail with verying temperatures. Your engine has three coils each firing two cylinders. If cyl #2&3 are fired by the same coil, that may be worth looking into. You could try swapping the coils around and seeing if the misfire moves with the coil position. Go to the Factory Service Manuals thread at the top of the forum, open the manual for your year, and look for additional info. Welcome to the forum.

So far, I can confirm that the cylinders have good pressure, engine does not burn oil or lose coolant, so the seals and gaskets seems to be in good shape.

To address the suggestions in the links above, I changed sparks, cables, and fuel filter - that means that electrical and fuel line are functional (and they indeed function at lower temperatures).

Once the car starts misfiring it is quite pronounced, I am not sure if OBDII captures and holds the first misfire or it shows the last detected - so I am assuming that only #3 is affected. The only possible culprits are fuel mix and coils - but how it affects coils at higher air (!) temperatures is hard to guess. ANy special sensor that controls the mix at individual cyclinder ?!

Thanks for the help, any additional comments?



Jack

[RIP]

Individual cylinder sensor? No. As you well know, the ECM determines airmix via sensors and sends it to the injectors. Unfortunately, a sensor or set of sensors determines air mix for all cylinders. Well at least without the book in front of me. Also I think codes are kept for a number of key cycles (#?) then dumped. You've got a good one here. I'll let you know if I come up with something. Maybe someone can jump in here and give you that magic bullet.