MichaelR

Hey, folks. My 85 auto has just developed a curious ailment. When moving slowly, say through a parking lot or in traffic, and just barely giving it any gas, when you let off the pedal the RPMs tend to go too low, maybe recover to ~700, but sometimes stalls. Normally this is with engine warm, not cold. When cold it tends to idle a little higher and doesn't drop as low. Doesn't happen when on the road at speed, only when creeping through a parking lot or stop and go traffic.

BTW, the idle is normally OK, around ~700, no significant variance. I've started checking wiring connections, cleaning grounds, etc. Then I noticed that when sitting in the garage at idle, if you barely press the pedal and try to bring it up to ~1000 RPM, it will hit 1000...then drop back to normal idle even though you are still holding the pedal. If you release the pedal too quickly...stall. If you release the pedal slowly the idle drops a little, recovers, drops a little more, recovers...until you've released the pedal completely, then idles fine.

My first thought was idle/WOT switch. I pulled the LH plug, put meter between contacts 3 and 5, got low ohms (less than 1 I believe), then barely hit the pedal, resistance jumps way up. So idle switch seems OK. I tried the same thing with WOT, using contacts 5 and 12...but got way high (in the K ohms) resistance for full travel of pedal, as if the switch never closed. Need to figure out why, but I don't think that is causing the idle issue.

What's the next best thing to check to solve the idle drop issue? I plan to finish the ground connection cleaning. But is this more likely a electrical issue or vacuum?

Any and all opinions appreciated! It's getting embarassing having to restart the car a couple of times before I get out of a parking lot!

Kevin in Atlanta

Perhaps it's the idle stablizer. It's under the manifold in between the throttle body and the MAF sensor.

Pull it out and clean it out with brake kleen or carb cleaner.

MichaelR

Good idea. On an 85, can that be removed without removing the manifold? Perhaps just remove the air cleaner box and access it from there?

Bernie

Me Too??????
My '85 AT has been suffering from that exact ailment since the day I bought it. After a couple of $200.00 test drives at Porsche endorsed service centers, I finally gave up trying to figure out what the hell it could be. I have heard the idle stabilizer story already and they said the stabilizer checked out. This appears to be something that is semi-common. Any help to this problem is going to help out more than one person on this list. Put your BTDT thinking caps on guys.

Kevin in Atlanta

Remove the air filter and MAF. Loosen the band clamp that holds the center intake to the throttle body along with the rubber gaskets up top. A hose also runs from the center intake to the idle stabilizer. You can disconnect it at the idle stabilizer. A single 10mm nut holds down the idle stablizer assembly. The idle stabilizer is held in place with a band clamp. I think just loosening the nut is easier than loosening the band clamp. Not rocket science.
Unplug it pull it out. At least that's how I remember it all. Then clean it and re-install.

Good luck

Kevin in Atlanta

I left out something important: You will have to remove the center intake after loosening it.

-K

John Struthers

Look-up idle stabilizer under archives here and on the Greg Nichols site. There is also a quick fix using spray cleaner, then WD 40.
I'm sure you have run A couple bottles of injector cleaner thru the system by now. If not I had good luck alternating between Injector Cleaner and Octane Booster over 6-8 tanks of gas.
Purchasing from Walmart takes the sting out of purchasing either as compared to an auto parts store.
Couple of other things...
My battery was constantly running on the LOW side, the word is that if it goes low enough the Computer/ECU reset to default mapping -Running rich- .
If you notice a similar stall/variable idle problem after disconnecting battery for whatever reason it could be a weak batt., or lame alt.
Don't have complete faith in your tach. a lot of folks report real low idles -ME TOO!- with idle running from low 500's on up.
You could bump up the idle which helps a lot, just don't have it racing in the high 700rpm plus range.
This could be an annual thing as well; clean all of your MAIN Grounds.
Is the problem worse at night with lights and stereo drawing even more juice?
Again, check the archives under idle or flappy valve.
HTH, Good luck.
John S. <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

MichaelR

I've searched the archives, and even emailed a couple of folks in similar situations...but all the info seemed to be for '87 and up. I've at least been able to find the idle stabilizer (it's hidden well!), but as far as I can tell, on the 85 the hose doesn't route out to the side where the "WD40 fix" posts referred to. As 86_5Tiberion suggests, the best thing is probably to remove and clean. I was hoping to not have to remove the intake, though. 86_5Tib, do you mean the center section of the intake manifold? Sounds extreme, but perhaps that's the only way to get there from here.

John...yep, a few bottles of injector cleaner so far. In fact, there's one in the tank now, about half through. I don't have a tester (yet) that will show RPMs, but at last inspection the shop showed it around 680-690, which is in spec for 85.

The problem now appears to be intermittent. Doesn't seem to depend on electrical, or a/c on. Couldn't reproduce it today...but there's always tomorrow. I'm still suspicious of the idle/WOT switch, even though it tested OK. the connecter is cracked up and held together by elec tape until I can replace it. Didn't get the chance to work on it last night as I was fixing a leaking coolant hose.

Thanks for the info and advice, guys.

Kevin in Atlanta

"86_5Tib, do you mean the center section of the intake manifold? Sounds extreme, but perhaps that's the only way to get there from here."

You need to be able to see in there through the gap left by the center intake. It's not as extreme as you would think. Loosen the long gaskets at each end of the center intake and push them in toward the center. You may want to remove the intake boxes, too. Between removing the center intake and the MAF you should be able to get very good access for you to get a 10mm wrench in there to remove it.

Just another way to 'bond' with your car.

MichaelR

Thanks for the advice, Tiberion. Your quick step-by-step got me in there. Now this is one more thing that I've BTDT.

Just as stated, removed the various parts, cleaned the idle stabilizer, replaced everything, runs OK. Not sure if the problem is fixed yet, since it didn't happen too often. Need to put in a little more driving time to be sure.

Got one other issue resolved while I was in there. Tested the throttle switch. Idle contact was fine, but I had tested WOT from the LH connector, and the switch wasn't closing with the pedal to the floor. Tested at throttle switch connector and it worked, but that was turning the throttle linkage by hand. Had some slack in the throttle cable, tightened it up, and now the WOT switch makes before the pedal hits the floor.

Little by little...

Jay Wellwood

AFAIK - the bottle of Techron in the tank will not improve the performance of a sticky idle stabilizer. This is due to the arrangement of the Injectors and the air flow path thru the system. For the 87+ models, the air comes into the throttle body, with a tap off of the air dome upstream of the butterfly. This flow path goes direwctly to the idle stabilizer, which inturn dumps the air flow into the drivers side intake plenum directly into the Intake. The air is then passed thru the applicable runners to the Intake Chambers in the heads. As the air passes into the Intake Chamber in the head, it passes by the Injector which charges the fuel based on the Ignition system.

Looking at the illustrations for the 85/86 4 cam models, it appears that the air flow thru the Idle Stablizer is similiar.

There are a few tests written up for the 87+ models, however not much written up for the pre 87 models.

I look a bit more this evening and see if there is a better way to 'wash' the Idle Stabilzer for the 85/86 models without disassembling the entier Intake (most likely Wally already has it written up).

Bernie

Has anyone had this type of problem on an '85 without it being the idle stabilizer?
I was told by two different shops that my mine checked out ok. I even told them to specifically check the stabilizer.
My stalling has reached the point where my wife doesn't want to drive the car anymore. Its a parking lot / crawling traffic problem only and the car has no problem when moving above crawl speeds. At low speed, when you press and release the accelerator, she goes to sleep <img src="graemlins/sleep.gif" border="0" alt="[sleep]" />
Time to reset <img src="graemlins/crying.gif" border="0" alt="[crying]" />
Any other things to look for would be greatly appreciated.

MichaelR

Bernie, I'm with you. I'm still getting the idle dropping sometimes, so I'm not convinced it had anything to do with the idle stabilizer being sticky. Someone else (not on the list) advised me to check the fuel pressure. Haven't gotten there yet, but plan to try.

Any other ideas?

Bernie

Hey Michael,

I have no choice but to track this down somehow. I am sure you feel the same. If you find out anything, please let me know.
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

John Struthers

Mike & Bernie,
Go to: <a href="http://nichols.nu/tips.htm" target="_blank">http://nichols.nu/tips.htm</a>
There are 2 related Idle flux problems other than the afore-mentioned idle stabilizer.
One has to do with your (S model, or, 85')Air Mass Sensor. A simple disconnect, if there is no change you have isolated the problem.
The other is a pin test outlined by Wally - buy him a brew if the post helps - which should further isolate the problem.
The Good news is that these puppies are readily available from the Big Three.
Now the bad news: 928 International prices
New AMS - 85' - 95' = $525.00
Used AMS - 85' - 95' = $300.00
ReBuilt Ams - 85' - 95' = $395.00
Check around, if you need it pick your poison but, I would go with the ReBuilt.
POST the Nichols Site to your favorites list and browse at your leisure. Lot's of good stuff there.
Buy him a brew, too! Or, maybe donate to the upkeep of his site.
Later, keep em'rolling.
John S. and PATTYCAKES <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />