Stalling issue

[alex61089]

Hey guys whats up? i'm gonna describe this problem as on point as possible. I start my car, my RPMS go up to 2,000 ( i know normal ) then it drops down slowly, here and there ( almost every other day ) the RPMS will drop down to like 500, i can feel the car stumble and then it jumps up to 1500, then does it again and again. As for driving, the car feels like it is stuttering and i have hardly any power at all and i literally have to floor it to get somewhere. Once i stop ( say at a light) and foot is on the brake the rpms will drop down to about 200 then the battery light comes on but then it jumps up to normal. Sometimes the car just stalls out while foot is on brake and it turns right back on. No CEL, no nothing. No codes. So im clueless to what it could be.

Also, this might help too but when im braking sometimes the rpms will jump back and forth from 800 to 1200 over and over while braking until i come to a stop then it stops. I tried getting to the IAC Valve and i removed 2 bolts but i cant seem to get it out so if that could be the issue could someone please direct me to get it out?

On another noteREMAN MAFNew fuel filterNew Fuel PumpNew TPS and adjusted correctly (OEM)OEM Air FilterThrottle bodies have been cleaned, twice. as of todayNew Spark Plugs OEM

[J30inthe sun]

I tried getting to the IAC Valve and i removed 2 bolts but i cant seem to get it out so if that could be the issue could someone please direct me to get it out?

On my 97 J30 there are 4 bolts that hold it on, if that helps.

[GerryO]

I copied this into a word file a while ago. If you do some searching, you might be able to locate the original source of the article.

General:Erratic idle is one of the most common problems with our cars. This is caused by the number of engine components that are affecting it, such as: IAA (Idle Air Adjusting unit), Air Regulator, Throttle Bodies, Injectors, CAS, fuel delivery, vacuum piping...This article will cover the three components mentioned first.

IAA-unit:This unit consists mainly of two valves: FICD and AAC. The FICD valve compensates for RPM drop when AC compressor is activated. The symptoms of the FICD failing are idle drop and vibrations when switching on the air conditioner.

The AAC (Auxiliary Air Control) valve:Is controlled by the ECU (PWM-control) to set the idle speed to a pre-programmed level. The ECU switches the AAC on and off very fast and thereby is able obtain a gradual opening of the valve. The AAC opening ratio can be observed on a Techtom MDM-100. If the valve is completely closed at idle it could mean that the idle screw is not adjusted correctly (too much air enters through it) or there is a vacuum leak (could be dirty TB's not closing all the way).

Very often is the IAA unit (pic 1.) diagnosed faulty and replaced. Since it costs ~$200 it's worth to take the time and fix it yourself. Just as long as the solenoids are electrically intact there's not much that can go wrong with this unit.First off, check the solenoid resistance (don't forget to clean the connectors too).FICD => ~22 OhmAAC => ~10 OhmYou can also check the solenoid operation by applying 12V from the battery to its connectors (you should hear a click). If the resistance is far off then you really need a new IAA-unit, if not then read on...

Remove the IAA from the plenum. It's attached to it with 4 screws. There is also a gasket between the IAA and the plenum. I reused the old one since it wasn't broken.



Disassemble the solenoids as in picture 2. Check if the spring inside them is not broken.Now clean the solenoids and the IAA-unit casing with WD-40 or Brake Cleaner or similar.Reassemble and it's as good as new.



Air Regulator:The purpose of the air regulator is to raise the idle during engine warm-up by letting additional air to enter the intake.The symptoms of the air regulator going bad is either low unstable idle during warm up or constantly high idle.The regulator consists of a bimetal-activated shutter that closes after ~5 min of engine operation and cuts off the airflow.Note: It's normal that the shutter is only partially open at room temperature.

Check the resistance between the pins in the connector. It should be ~75 Ohm. If not good then replace the whole regulator.Another problem could be that the regulator is clogged, causing the shutter to stick.The air regulator is located on the rear of the plenum and is attached to it with 2 screws.There are 4 screws keeping the housing together. Remove them and clean the regulator internals (pic 3).


Modified by GerryO at 8:34 PM 5/10/2009

[yodawill2000]

Where is the IAA located on the engine ??

[GerryO]

Where is the IAA located on the engine ??

Bolted to driver's side rear corner of the plenum.

[yodawill2000]

Thanks !!!Should be able to get to that pretty easy.need to give it a good cleaning I'm sure.

[alex61089]

lol.. that looks like a pain in the a** to get to. But on another note. I was wondering... What if my voltage regulator is failing in the alternator? I know it regulates that proper amount of amount to supply the car with the proper amount to run but what if it shorts out here and there and fails to provide the minimum threshold of 13.1? My car was doing the same thing last night and i pulled the multimeter out and put it on the car battery while it was doing it. Whenever the idle was falling so did the voltage from the battery. i was going down to 11 volts with the car barely running.

Now i know some people will say oh well its because the cars dying out so should the battery voltage be decreased but my idea is. If the engine was shutting off because say of a clogged IAC valve the alternator should still provide the same amount of voltage until the engine dies out correct?

[alex61089]

eh never mind. i took it to strauss and the battery and alternator is good they said sigh...