DME detectives needed... Goofy idle problem

LeeH · 03-04-2002, 08:36 PM

My car has suddenly developed a problem idling. It started a few days ago. The engine was fully warmed up. As I pulled up to a stop light I noticed the car was still pulling even with no throttle input. I pushed in the clutch and the tach swung up to 3000 RPM.

I tapped the gas a few times and it fell down to around 1200, then around 850 where it usually sits. The same thing happened when I pulled onto my street... let of the gas and the car wanted to keep going holding 3000 RPM

Today I took it out and drove around until it was warmed up. Same type of behavior, but with an odd twist. I was coming down a hill and could tell it wanted to stay at 3000 RPM with no throttle. So, I put it in neutral and let it coast. The tach is at 3000 UNTIL I put the clutch in, and it drops to 850. I let the clutch out, and it jumps to 3000. In 850, out 3000. What's going on? The other twist... the speedo just started acting up. It sits on zero until I hit about 25 MPH the comes to life.

don911 · don911's Garage

Don't know about the idle problem. I would start with the simple things. Check the throttle return and make sure it's not sticking or the spring is weak. After that, maybe the idle position switch but that would be a guess. I'm sure the experts on the bb can help more.

As far as the speedo, it's common. Mine does that as well. Seems better after warm but it normally doesn't spring to life until after 20mph. I doubt that it's related to the idle.

good luck.

Victor · 03-05-2002, 12:59 AM

LeeH,

I have an '89 3.2 and about a year ago it did the same thing. Only when the engine was warm. It turned out to be the main temperature sensor, but they changed all sensors (I think there where five of them) because apparently they are known to fail when they turn ten years old. Sort of pre emptive maintenance.

Sorry for the lack of technical terms, I am one of those people who are too stupid to work on their own car.

The whole lot was about AU$500 or $250 real dollars.

Cheers, Victor

Joeaksa · 03-05-2002, 06:08 AM

Lee,

Where are you in Phoenix? I have an extra: DME computer with chip & DME Relay with me now.

Just had a cylinder head sensor go out and it caused lots of sputtering at idle and motor died from time to time and would not restart. Changed the sensor and it was the problem.

We can switch out the idle valve out of my car and troubleshoot yours this way as well. I am moving to Hiway 101 and Cave Creek area road tomorrow and will be glad to help you with this anytime after Wednesday night.

JoeA

602 418 5642 cell

dhamilto · dhamilto's Garage

Try disconnecting the oxygen sensor, assuming your car has one. This cured a similar problem for me.

83SC

LeeH · 03-05-2002, 02:52 PM

Joe,

Thanks for the offer! Of course I'm at the opposite end of the planet from you (Ahwatukee). I'm trying to decide how I feel about getting far from home in it right now.

At least the problem is pretty consistent. It starts in once it's fully warmed up. The car seems to run OK. It hasn't died on me(yet), just idling funny.

I talked to Stuttgart SW a while ago and they said it sounded like a bad idle speed motor. That's one of the few parts on this car that appears to have been replaced (just a bit cleaner looking than everything else). I think it may be time to invest in a Bentley manual!

LeeH · 03-05-2002, 03:55 PM

Additional info on this problem:

I went through the records and found the PO had the same problem 9 months/900 miles ago. He took it to a Porsche where the idle stablilizer was replaced (I thought it looked new).

Joeaksa · 03-05-2002, 04:16 PM

Lee,

Drive up here on the weekend or one evening and we can sway the idle stab valve off of my car with yours and see if its the problem. I also have a old Oxy sensor plug that we can ground out and confirm that the problem is not your oxy sensor if you like...

The idle valve takes 10 minutes to change and the oxy sensor plug (not the actual sensor, its a ***** to change) takes even less time. If you are supplying the beer I might be tempted to meet you halfway or ??

Joe

LeeH · 03-05-2002, 07:06 PM

Joe,

I'd love to take advantage of your stash of spare parts. My wife gets in tomorrow AM and leaves again very early Saturday morning. That means I'm available any time Wed, Thurs, Fri.

I drove the car around more today and am pretty comfortable that it'll make the trip... only seems to be a problem with the idle speed. My only issue driving way up there from way down here is that I don't want to get stuck in rush hour traffic. Let me know what your schedule looks like.

Lee

Joeaksa · 03-05-2002, 07:14 PM

Lee,

Call me on my cell phone tomorrow sometime and I will see how its going. Moving into the new place tomorrow and will be around all day.

Can work something out...

Joe

LeeH · 03-06-2002, 08:59 PM

Well, Joe was kind enough to take some time out of moving into his new house (You know you're a car guy when...) to swap the idle controller from his car to mine. That didn't solve the problem. Joe did notice one of my vaccuum hoses was loose. It's hard to say, but it may have improved a bit. The search goes on.

Any other suggestions would be appreciated.

Symptoms only begin when at fully warmed up:
3K RPm idle. Tapping the gas may (or may not) drop idle to 1200 or may return to normal. Sometimes pushing in the clutch will cause idle to return to normal. Upon releasing the clutch, idle goes back to 3K RPM.