Help!! I'm going to get hit by a semi truck!! Random stalling, stumbling idle

[macadamianut]

Update,

Decided to start a new thread as the old one is so long now it is time consuming to follow.

Car is stumbling (intermittently) at any rpm below 4000. Will run smooth for approx 1-2 seconds then hit a wall dropping rpm by 200 or so. Occasionally causes stalling when at cruise on highway or at stop lights.

SO, problem seems to only occur near idle circuit. Small throttle or zero throttle opening.

Important note: It is not "surging" up and down like a boat in the ocean. Runs smooth, then hiccups, then smooth again somewhat rhythmically. Condition lets out a deep, airy poof at the muffler when the stumble occurs. Misfire? Backfire? Vacuum leak? Failing sensor? I can't figure this out.

Had car at a local Subaru dealer twice who first replaced intake manifold gaskets first, and then the alternator second, (again.) Last time they suggested that I buy an entire new engine wiring harness based on the fact that the outer coating is cracked on one of the crank sensor wires. Whaaaa???

Decided to take this on myself now:
Have not removed manifold yet. Trying things a little at a time.

-Pulled intake snorkel and inspected. Sealed up any suspect intake leak. = no change
-Pulled and cleaned Throttle body, not very dirty BTW. = no change
-Pulled and cleaned By-Pass air valve, also not very dirty. = no change
-Replaced small diameter vacuum hoses on top of TB to metal tubes near TPS = no change
-Replaced vacuum line between what I believe is the fuel pressure regulator (just above EGR valve) and the intake manifold = no change

-DVOM test on By-pass air = good
-DVOM test on Mass air, both key-on, and engine running conditions, even tapped on it hard and wiggled wires = good.
-DVOM test on knock sensors = good
-DVOM test on injectors = good
-DVOM test on pass side coils = good. Although when I removed the boots, the part attached to the coils, (not the plugs) had little white lightning bolt streaks on the inside. Cleaned off and re-installed. Have not pulled the driver side yet.

Have sprayed starting fluid, propane, MAF cleaner on all suspect vac leak areas with no change in idle. Arrgghhh.

After reassembly, running engine in garage:
Idle would not fall below 900 rpm no matter how hot, no matter how many times the fans cycled, no matter how many times I revved it at the TB. Running Defroster kicked it up to 1100-1200 rpm. Have not road tested yet, I don't like the idea of getting hit if it stalls again.

Still hearing a strange clicking chatter (pretty loud) from under the manifold when throttle is blipped and is returning to idle. Almost like the IAC valve is chattering or a solenoid is freaking out. Only occurs UNTIL car is completely warm.

Hearing a hissing type of noise coming from area around power steering pump/reservoir. The assembly is leaking fluid from somewhere (likely from re-using the o-ring under the reservoir when the timing belt was changed by a tech recently). Could also be the bearing going out on the PS pump shaft. Hard to tell. OR this could be my vacuum leak somewhere around this area.

I still question a burnt catalytic converter or O2 sensor that is not throwing a code. I had a thought to take the car to a muffler shop and by-pass the cats and fab up heat shields, (there are no emissions checks in MI) to help rule them out.

Any help is greatly appreciated.

[TomsSVX]

I guess you are the one who Todd told me about... PM me your address and I will send out my loaner set of position sensors.. I have had intermittent sensor failures that would not result in error codes but similar drivability issues

As for the click, the EGR sol, IRIS sol. and evap sol. are all mounted under the manifold. If it is clicking and not throwing a code, it is working as it should be

Tom

[SoCal LS-L]

Originally Posted by TomsSVX

I guess you are the one who Todd told me about... PM me your address and I will send out my loaner set of position sensors.. I have had intermittent sensor failures that would not result in error codes but similar drivability issues

As for the click, the EGR sol, IRIS sol. and evap sol. are all mounted under the manifold. If it is clicking and not throwing a code, it is working as it should be

Tom

Yeah take Tom up on that, I didnt notice anywhere back in my quick skim over of your other posts about you switching these out.

Didnt you say you were running a different ECU too Mac? Did you try putting the stock one back in to see if anything changes?

[oab_au]

Originally Posted by macadamianut

Update,

-DVOM test on pass side coils = good. Although when I removed the boots, the part attached to the coils, (not the plugs) had little white lightning bolt streaks on the inside. Cleaned off and re-installed. Have not pulled the driver side yet.

Still hearing a strange clicking chatter (pretty loud) from under the manifold when throttle is blipped and is returning to idle. Almost like the IAC valve is chattering or a solenoid is freaking out. Only occurs UNTIL car is completely warm.

Hearing a hissing type of noise coming from area around power steering pump/reservoir. . OR this could be my vacuum leak somewhere around this area.


Any help is greatly appreciated.

Mac these points stand out. The coil boots had shorting tracks down them.
When you cleaned it off them, did you put any silicone spray or such on them.

I think you should make a 'garden hose stethoscope' and go hunting for the 'hissing' and the 'clicking.' Finding what these are, may point you in the right direction.

Harvey.

[macadamianut]

Tom,

Yes please!! Loaner sensors to isolate would be most helpful. PM sent with address. Thanks.

Chris/Harvey,

Modifications on car:
-ECU tune 1v5, octane switch NOT installed, no stock ECU to swap out
-Stebro muffler
-Perrin lightweight crank pulley
-One pair Hella 500 off-road lights
-Mudflaps - darn, I bet it is coming from the mudflaps

Another possibly important point of interest- Oil fillneck gasket, valve cover, or both are leaking on the driver's side near the battery. It has coated the cam pos. sensor area and will look tonight if it is causing problems with my coils on that side.

If anyone has an extra unmolested OBDI ECU they could loan for a try that would be most appreciated too.

I will re-pull all plugs and coils tonight and inspect the boots for more shorting. Little tiny white tracks of lightning bolts inside the boots last time. Will spray with silicone this time. May still pull off the manifold and inspect/clean all the bits underneath.

Thanks for hanging-in here with me, I can't tell you guys how much I have learned about my car and working on cars in general so far.

[Mike621]

Originally Posted by macadamianut

Tom,

Yes please!! Loaner sensors to isolate would be most helpful. PM sent with address. Thanks.

Chris/Harvey,

Modifications on car:
-ECU tune 1v5, octane switch NOT installed, no stock ECU to swap out
-Stebro muffler
-Perrin lightweight crank pulley
-One pair Hella 500 off-road lights
-Mudflaps - darn, I bet it is coming from the mudflaps

Another possibly important point of interest- Oil fillneck gasket, valve cover, or both are leaking on the driver's side near the battery. It has coated the cam pos. sensor area and will look tonight if it is causing problems with my coils on that side.

If anyone has an extra unmolested OBDI ECU they could loan for a try that would be most appreciated too.

I will re-pull all plugs and coils tonight and inspect the boots for more shorting. Little tiny white tracks of lightning bolts inside the boots last time. Will spray with silicone this time. May still pull off the manifold and inspect/clean all the bits underneath.

Thanks for hanging-in here with me, I can't tell you guys how much I have learned about my car and working on cars in general so far.

Mac,

If you are pulling your intake manifold, I HIGHLY recommend replacing the PCV Valve, PCV Hose (molded hose, available from the dealer for ~$15) , IRIS check valve, and associated small diameter vacuum lines (you can use universal vacuum tubing and cut it to fit).

Pulling the manifold presents an excellent opportunity to address all of these items, all which are very inexpensive, and a PITA to address when the manifold is on.

Just my $.02.

[macadamianut]

Mike,

I will be replacing all associated vac lines and PCV line under the manifold. My PCV, fuel filter, timing belt and spark plugs (bosch iridium/platinum) were changed about 3,000 miles ago. Replaced IRIS check valve last weekend. Also removed K&N, cleaned MAF and went back to OEM paper type.

Does anyone know the DVOM specs for the egr solenoid and IRIS stuff under the manifold? I don't remember seeing it in the manuals. My DVOM tests on the coils has just been that they are all equal resistance. Does anyone have the correct specs to check primary and secondary on the coils?

Thanks.

[1986nate]

Originally Posted by macadamianut

If anyone has an extra unmolested OBDI ECU they could loan for a try that would be most appreciated too.

I will have one on my way back from my trip on the 14th if you don't figure your problem out or get one in the meantime. Hopefully you get it all sorted by then though

[macadamianut]

A random thought. The IAC (not by-pass air or auxillary air) controls the idle/off idle mixture and is driven by a solenoid of sorts right?

If that valve were to get stuck, it would screw up my mixture and cause stumbling problems?

I hear that strange loud clicking coming from under the manifold, so is it possible that that valve is stuck and I am hearing the solenoid freaking out from not be able to move it?

Is it supposed to be open at idle or closed? When I remove it from the manifold tonight, is it supposed to be open or shut?

[TomsSVX]

yes/no. The IAC is a dual action motor voltage in to open and voltage in to close. The MAF is what calculates the airflow regarldess of this. So if the ECU sees the valve is stuck due to an uncontrollable idle it will use a fuel cut (very noticeable) to stall the engine speed down. If this were happening, you would def. know it and there would be a trouble code active for it

Tom

[macadamianut]

Finally located that strange clicking sound. There is a solenoid?? under the manifold on the "airbox" side on engine. It is mounted between the front and middle runner and has a black connector. I think it is the purge control solenoid. The strange clicking sound is evident at fast idle until engine is warm and will quit when car reaches operating temp. Does the clicking ( very rapid clicking, but does not change speed with engine speed ) mean that it is doing its job, or that it has failed and cannot open or close that valve?

Still hearing a loud hissing sound from behind PS reservoir under the manifold. (Or maybe these cars just have a very noisy PS system. I can't find another car to listen to.) Anyone in the Detroit area with an SVX?

I read on another non-svx subaru forum that the purge control being stuck can cause a big vacuum leak and can affect idle. Is this true?

Also after cleaning TB and by-pass air valve, the car will not run at 600 ish rpm. Falls to warm idle at 900 rpm / 1000 rpm with defrost on. Is the by-pass valve sticking or did I not set the valve right at disassembly? I scored the position of the magnetic elec. assm. before I took it off. Is it supposed to be 1/2 open when I put it back in?

If I "by-pass the by-pass" at warm idle, I can get the rpm to fall slightly to say 750 ish.

[TomsSVX]

Yes that is the purge solenoid. The vacuum source for that solenoid is easily accessible on the RH side of the TB (note RH is the pass side). If you cap the nipple and take the hose off and retest, it should be a clear indicator if this is your issue... And yes the PS has been known to be pretty noisy in these cars when they pull air at the O-ring on the tank

Tom

[macadamianut]

Well,

I did get the manifold off today. What a sh*(&%#&^#)y job. I think I used up a years' worth of profanity.

Replaced all brittle/falling off vacuum lines and managed to break the purge contol solenoid, something bad had to happen right? :clap: Broke the plastic nipple right off. So, I'll be buying another of those unless I can by-pass it. (Not that I am a proponent of destroying the environment, but if I can eliminate something from the already way too complex system, I'm all for it.) Does anyone remember when an engine was simply an unmolested, glorified air pump????

I am thinking of replacing the fuel pressure reg. as well now that it is off. I don't want to rebuild the car, but I need to know what else I should be replacing while the mani. is off? Where to buy genuine subaru parts for less?

I also:
-Pulled all coils/plugs which looked fine. Put dielectric grease inside of the boots after scratching out the little white lightning bolts off of the "airbox" side coil boots.
-Pulled both crank sensors and cam sensor, inspected and cleaned them
-Pulled knock sensors and did the same
-Pulled IAC (the huge butterfly valve in the middle of the manifold run by the diaphragm unit) cleaned and reinstalled. Held my finger in front while closing to confirm that the diaphragm was still good.
-Will still pull EGR valve to inspect clean and replace associated vacuum lines
-Put dielectric grease on all connectors
-Replaced coolant temp sensor with new one and pulled and cleaned sending unit above it.

Thanks for following and helping.
Mac

[TomsSVX]

If you don't have emissions inspections, just cap the nipple on the TB like I said before and leave the solenoid plugged in. They are expensive to replace and they break ALL the time.

Sounds like you are on a war path, don't let me stand in your way

Tom,

[macadamianut]

Tom,

Thanks for the tip. I will try that for now. Is there a hose at the other end I should be plugging as well?

I am still excited by the prospect of replacing sensors one at a time to rule out an intermittent problem sensor. Any chance you were able to send the loaners?

Thanks