s14 bad start idle then die... ????

[mugengsr]

my 97` 240 starting acting funny in the past few weeks and its getting worst ... when i start the car in the mornings (not realy cold or anything) the idle will go up and down up and down a few times then settle at 1000 rpm .. . and now when i started this morning it did the same thing it useualy does but it stalled when it went down on the idle a few times ... any ideas ??????

and yes i have searched just have not found anything on the later s14`s most of the problems like this was with the s13`s from what i have found ...

[SilviaJDM]

I used to have the same problems, at first I thought it was the starter, but then it stopped doing it.

[slc240sxse]

Does it die after you've let it warm up? After it has warmed up, does it idle at all?

[mugengsr]

nope after it idles up and down for a few times maybe two to four times it settles at like 1100 rpm then its stable and dont give me any more problems at all ..

[slc240sxse]

You might want to check your coolant temp sensor.

[HashiriyaS14]

For the record, I'm having the same problem.

My car hasn't ever stalled doing it, but at times (not cold outside at all, 75 degrees) I'll start the car, and the idle will drop to like 450-500rpm, like it's going to stall, and then go back to 1000rpm and idle like everything is fine.

So the coolant temp sensor would have something to do with this? Can someone explain to me why that would be the case? I like to have an idea of what I'm getting into in my head before I actually involve the car...lol.

[AmoebAssassin]

I agree on the coolant temp sensor. My s13 had the same problem as you two are describing. I checked everything important, EGR, plugs, injectors, IACV, etc. etc. However, i went to take apart the coolant temp sensor, and after just wiggling hte plug around the idle settled down perfectly at 700rpm, no balking, no stalling, no jumpy/hunting idle.

The reason that this happens is that an engine will inject more or less fuel (turning fuel compensations on and off) based on the temperature of the block. It gets this information via the coolant temp sensor and other accessory sensors. If your coolant temp sensor is sending info that is out of spec, the ECU will fall back on the intake air temp sensor, which is a FAR FAR FAR less accurate of engine temp than the coolant temp sensor. If the engine doesnt know which compensation setting to run at, you get plain crappy performance, poor fuel economy, stalling while decellerating in neutral, lumpy idle, and reluctance to rev.

I got lucky, my coolant temp sensor was still good, just the connectors had oxidized at their contact points. I didn't even have to dissasemble the plug, just a bit of movement in the connector scrubbed the contacts clean and solved my problem.

Take a multimeter to your coolant temp sensor when its cold and after it's run a bit. Compare the readings against the FSM spec values. It's nothing more than a thermocouple that delivers a resistance reading, so you can take multimeter readings when the car's off, so as to avoid being mangled by the close-by radiator fan.

If everything is in spec there, the next thing i'd do is let the engine run at idle with the air conditioner off. Pinch off the EGR vacuum line and see if the engine responds. If that checks out, unplug each injector on ONLY one cylinder at a time. The engine should stumble and shake more every time you unplug an injector. If this doesnt happen, or the effect is lesser on one of the cylinders, you could have fuel, spark, or compression woes on that cylinder. If this checks out, you need to take the IACV off the intake manifold and douse it in carb cleaner, reinstalling it with a new gasket. If this doesnt help, you're pretty SOL. Try a new ECU, or consult the FSM for more info and diagnostics.

[HashiriyaS14]

That's one helluva good answer you just gave me, sir.

Thanks.

[AmoebAssassin]

No problem, gotta spread around the knowhow, y'know?

Just let me remind you to do everything with respect to your idle with the AC OFF! If your AC is on, the ECU opens your IACV so the engine will idle from 1100 to 1300, this masks many idle problems.

[HashiriyaS14]

No problem, gotta spread around the knowhow, y'know?

Just let me remind you to do everything with respect to your idle with the AC OFF! If your AC is on, the ECU opens your IACV so the engine will idle from 1100 to 1300, this masks many idle problems.

Funny you should mention that. I was trying to get my AITS in order this weekend with 2BN_S13, and I asked him why my idle tends to change when I turn my headlights on and off. He answered that I should try it with the AC, I saw the result, and he gave me that same explanation.

Learning how stuff on your car works is fun