if check engine light is off , is there any point to self-diagnosis?

[vancouverbc]

My check engine light is off so i assume that the computer has found no malfunctions and there is no point to self-diagnosis ie mode 1 to mode 5. My 240sx stalls at red lights. trying to find out why.

[1991S13]

Do you know if you have a check engine light?

I've heard of people either pulling the bulb or painting it black so it doesn't look like it's on. That's always a possibility.

If you're stalling at red lights I would check out the MAF, AIV, etc - all the air/fuel stuff. Or try driving with your AC on, that might keep the idle up enough.

[vancouverbc]

thanks:) what should i disconnect to get the check engine light to come on?
Modified by vancouverbc at 8:18 PM 6/24/2005

[1991S13]

I've never tried to make the light come on...

Maybe if you unscrew the oxygen sensor and plug the bung up with a bolt then start the car? Might be as easy as unplugging a spark plug wire though.

[nab911]

Lol guys, turn the key to the on position, it should light up, if not bulb is blown. Thats a required part of the Emissions testing. If you turn the key on and that light doesnt come on, you fail.

[masticatingcow]

Does the car stall at EVERY red light? Does it idle rough ehen parked? I had a problem like that for a while... everything would be fine, idling great, revving freely and all, and then coming to a stop, the engine would sometimes sputter and stall.

Try this... while driving, rev the car up to about 3500+ RPMs. Then, throw it in neutral (assuming you have a 5-speed) and brake to a stop. It's important to brake for this test, no clutch help. If your car starts choking or stalls, you may have a bad alternator. It's worth checking, since even if you have a working CEL, you wouldn't see a code; the ECU won't throw a code for the alternator.

[nab911]

if its a 5 speed, seafoam it and check you idle air valve. If its automatic, does it have problems shifting?

[vancouverbc]

Thanks:) Yes, the check engine light comes on when ignition is on. LOL

I don't know what seafoam is but i will be spraying carb cleaner into air intake where the throttle is.

I have a 1991 240sx 5speed. It stalls once in awhile at stops signs or when i turn a corner with foot on clutch. I have new alternator and fuel pump.

I will be disabling the AIV valve(air injection valve or pair valve) per the nissan article:

zer...age=1

I will be testing ground of IAA(idle air adjustment valve) and cleaning.

[1991S13]

Lol guys, turn the key to the on position, it should light up, if not bulb is blown. Thats a required part of the Emissions testing. If you turn the key on and that light doesnt come on, you fail.

Wow, why didn't I think of that? lol. Yeah yeah, that's just the easy way out.

[Xxplosive959]

I'm having the same Idle problem. Try cleaning out ur Maf, temp sensor and clean up anything that looks dirty. Taking out the AIV was easy but I didnt help me. Just make sure all ur grounds are clean and every plug near ur coils and cap are on tight.

NAB911 I MUST HAVE LOOKED AT THAT CLIP OF THE GUY RUNNING OVER THE GIRL A MILLION TIMES, LOL, WHERE U FIND THAT, LOL

[nab911]

Lol if you are looking at it htat much, go post in my sig thread... its a poll of how long you looked at it

[vancouverbc]

to answer the thread title question: yes! the engine check light does not come on for all codes and there is a mode 2 test of air/gas mixture.(1991 240sx)

[nab911]

Can you elaborate on the mode 2? Will it give you a good diagnosis of air/fuel ratio?

[navysnail]

like stated before, check your MAF, CTS, O2 sensor, etc. a search will bring up the procedures for each.

when i first got my car, the maf connector was loose and the car would die whenever i made a turn with the clutch in (because the load from the pump).

[Japanese Steel]

I had problems wih my idle and stalling with my 93. No check engine light. I did the self-diagnosis anyway and got no codes. I brought the car to a friends shop, he hooked it up to his computer, sure enough it was the mafs. I can disconnect the mafs and run the car, still no CEL.

According to my FSM, the mafs should light the CEL. I changed the mafs, now she's purrin like a kitten and hasn't stalled since.

I don't think the ECM's in the older models are that advanced. At least in my case anyway.

[AmoebAssassin]

Check coolant temp sensor, my car had a rough idle and died decellerating in neutral unless the AC is on, I had no CEL on and the ecu threw no codes. Wiggled my coolant temp sensor a bit and the idle settled right at 700rpm and the car runs like a champ now.

Coolant temp sensor is the red two-wire plug on the engine side of the upper radiator hose. Take that connector apart and clean the contacts with rubbing alcohol. That was my problem, maybe it will be yours...and its pretty easy to do.

Also, check you plugs and injectors, it could be that they're old/gunked up if your car has serious mileage on it.