mspiegle

The LH Jetronic has a map to govern fuel mixture when the MAF is disconnected/broken right? Can I use this feature to my advantage to see if i have a vacuum leak? Example, if I have a very erratic idle, and I disconnect the MAF, should the idle become a little more stabilized if i have a vacuum leak?

I'm having a starting issue that may or may not be related to a vacuum leak...

- When the car is cold and I try to start it, it will fire up right away, but then die.

- If I start it and give it gas for a couple seconds and let it idle on its own, the idle will bob up and down for about 10-15 seconds.

- If I start the car, and give it enough gas to idle around 1K rpm, it will idle VERY poorly (bob up and down more violently)

- If I start the car, then give it a little gas to hold it @ 2K RPMs for about 10-15 seconds, i can let off the gas slowly and it will idle on its own.

- For the first 15 minutes of driving the car, if i let the throttle shut too quickly, the car will just die.

- If I start the car, get it to the point where it idles, then disconnect the throttle switch, the car will start sputtering. Doing this would close the idle valve - right? (trying to test the idle valve)

This all started happening about 2-3 weeks ago. Before then, I was able to turn the key and the car would start and idle perfectly with no gas or user intervention. At first, the car would start and run, but have a bobbing idle for 15 seconds. It got worse and worse, and now this is where i'm at.

Any ideas?

Thanks in advance!

Garth S

Between the lines, it seems as if your car idles fine after warm-up. (?)
If that's the case, there's the possibility that the crud & varnish is building up on the rotating disc in the IAC - just enough so that the disc may move freely when warm as the 'glue' softens.
One of the simple cures is to spray an O2 sensor safe carb cleaner/WD-40/LP-S1/etc. down the inlet hose.
Ahhh - having passed out this gratuitious tidbit, it may be trash: I can't recall if the 86.5 has the same 'S4' IAC setup!

John Speake

""- If I start the car, get it to the point where it idles, then disconnect the throttle switch, the car will start sputtering. Doing this would close the idle valve - right? (trying to test the idle valve)""

wrong - the idle switch closes than the throttle is shut. this triggers the idle stabiliser loop in the LH ECU.

Does it take 15minutes for the engine water temp to get to normal ? You say that it idles OK then. If so, I would suggest you start with the Temp sensor 2.

Regards,

mspiegle

@Garth
I did spray WD40 inside of it once, strangely... i didn't have these problems before then.

@John Speake

You mean that when the throttle is shut, the idle switch closes the circuit in the LH and activates the idle stabilizer - right?

So, if I unplug the cable, it will open the circuit, and the idle stabilizer will no longer work, and my car will sputter. If my car sputters with the idle stabilizer off, that means it must have been working when it was "on".

Is my logic totally flawed?


thanks for your responses.

John Speake

"""""You mean that when the throttle is shut, the idle switch closes the circuit in the LH and activates the idle stabilizer - right?""""""
>>>>>>>
Right !
>>>>>>>>>>

So, if I unplug the cable, it will open the circuit, and the idle stabilizer will no longer work, and my car will sputter. If my car sputters with the idle stabilizer off, that means it must have been working when it was "on".

Is my logic totally flawed?
>>>>>>>>>>
No, you have it correct.


What about my question on warm up time ? Is the return to normal idle on the same time constant as the engine water temp warm up ?

mspiegle

Well, it only takes the car about 15-20 seconds to start idling normally. However, even if it is idling normally, sometimes the car might die when I come to a stop if the car isn't fully warmed up yet. When it is fully warmed up, it is rare that it will die, but it has happened a couple times.

John Speake

I would start looking for vacuum leaks first. It could be that the idle stabiliser can get within range only when hot.

There are other possibilities of course...............

How many miles on the car ?

mspiegle

Ok, as for the vacuum leaks, I used a whole can of starter fluid to search for the vac leak, but just couldn't find anything.

I'm actually starting to think its the idle control valve.... I'll see if I can get another one to test with.

Yes... there are many possibilities as this car shows about 175K on the clock (and the clock has been broken for 3 years...)

Question - I disconnected the power to the ICV while the car was running, and it didn't seem to make much difference, however disconnecting the throttle switch makes a noticeable difference. Is the ICV normally open and closes when on the throttle?

John Speake

I am not sure about the ICV, but my understanding is that it will stay in the position it is set to when power is removed.

The throttle switch has to be closed for the idle stabiliser loop to be activated.

It doesn't sound like a LH ECU problem. It could be a ICV problem. It could be a MAF problem.

MBMB

Where did you spray the WD40? Not down the MAF throat, I hope.

Lagavulin

It sounds to me it's running rich; have you altered the fuel system?

Maybe your fuel mapping got whacked out and needs a fresh start; have you tried resetting the computer by disconnecting the battery? It's best to do so after the car is already warmed up, otherwise while cold, it will run pretty rough as the computer starts it's learning phase.