High idle ... what could it be? Not TPS.
10-22-2011, 11:39 PM
#1
Three Wheelin'
Thread Starter
High idle ... what could it be? Not TPS.
ALL HELP APPRECIATED FOR THIS ONGOING PROBLEM!!!
I have a 1986 944 turbo.
Idles at 1500 rpm when warm or cold. However, it will idle normally for about 30 seconds when then engine is started, then rise to 1500. I've changed the TPS twice and made sure it was correctly adjusted. I don't suppose it's a vacuum leak. Also, the idle is not rough. And the engine revs down normally after releasing the gas pedal...it doesn't come down slower than normal.
Here is a symptom: when the engine is really warmed up, the car will SOMETIMES rev from about 1100 to 1500, drop back to 1100, and do this over and over again by itself. I have heard others having this problem.
So, is it the idle control valve (ICV)???
Please help... Thanks rennlisters!
I have a 1986 944 turbo.
Idles at 1500 rpm when warm or cold. However, it will idle normally for about 30 seconds when then engine is started, then rise to 1500. I've changed the TPS twice and made sure it was correctly adjusted. I don't suppose it's a vacuum leak. Also, the idle is not rough. And the engine revs down normally after releasing the gas pedal...it doesn't come down slower than normal.
Here is a symptom: when the engine is really warmed up, the car will SOMETIMES rev from about 1100 to 1500, drop back to 1100, and do this over and over again by itself. I have heard others having this problem.
So, is it the idle control valve (ICV)???
Please help... Thanks rennlisters!
10-23-2011, 11:10 PM
#5
Three Wheelin'
Thread Starter
thank you....
and I'll just leave this here. http://sfbay.craigslist.org/nby/cto/2665179341.html
not my car but it looks like a good deal for a 951
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10-24-2011, 12:53 AM
#8
Three Wheelin'
Thread Starter
No but I am going to put in a used one as soon as I'm back home... I was just trying to gather information regarding my problem; I wanted to know whether the symptoms indicate that it's possibly the ISV. If it's not the ISV, I am dreading the possibility that it's a vacuum leak. But I'll also try the cruise control cable, as mentioned above.
10-24-2011, 11:47 PM
#9
Drifting
Don't worry about vacuum leaks They're easy to find. I've posted here before about my experience (someone else originated it) and it's basically: get a PVC cap (2" for the non-turbo) with a air hose fitting threaded into it and stuff it into the rubber boot prior to the throttle body and hose clamp it.
Apply 7 to 10 psi of air pressure and spray soapy water solution all over a cold engine (so you don't cook soap residue on the springenwerk) and any leaks will show up as bubbles. I found one under the intake runner where the temp sensor is and the other was the seals in the throttle body.
Apply 7 to 10 psi of air pressure and spray soapy water solution all over a cold engine (so you don't cook soap residue on the springenwerk) and any leaks will show up as bubbles. I found one under the intake runner where the temp sensor is and the other was the seals in the throttle body.
Last edited by mytrplseven; 11-19-2011 at 03:49 PM.
10-25-2011, 01:03 AM
#10
Three Wheelin'
Thread Starter
Don't worry about vacuum leaks They're easy to find. I've posted here before about my experience (someone else originated it) and it's basically: get a PVC cap (2" for the non-turbo) with a air hose fitting threaded into it and stuff it into the rubber boot prior to the throttle body and hose clamp it.
Apply 7 to 10 psi of air pressure and spray soapy water solution all over a cold engine (so you don't cook soap residue on the springenwerk) and any leaks will show up as bubbles. I found one under the intake runner where the temp sensor is and the other was the seals in the throttle body.
Apply 7 to 10 psi of air pressure and spray soapy water solution all over a cold engine (so you don't cook soap residue on the springenwerk) and any leaks will show up as bubbles. I found one under the intake runner where the temp sensor is and the other was the seals in the throttle body.
11-04-2011, 01:46 AM
#11
Three Wheelin'
Thread Starter
Okay, I was home last weekend so I tapped the ICV with the handle-end of a rake with the engine warm and idling at 1500 rpm. Nothing happened. I then knocked the ICV rather hard several times, but still nothing.
My next move was to disconnect the ICV with the engine off. So I disconnected it and turned on the engine. The idle was still at 1500 rpm and it began to "dance," meaning it would dip to 1000 then rise to about 1500, drop to 1000, and repeat. I turned off the engine and turned it back on. The "dancing" stopped but it was still idling at 1500 rpm.
Is the ICV NOT the problem...or is it? If it's not the ICV, I am gonna use mytrplseven's method to test for vac leaks.
Thanks again for your continued diagnostic assistance. I looove my 951!
My next move was to disconnect the ICV with the engine off. So I disconnected it and turned on the engine. The idle was still at 1500 rpm and it began to "dance," meaning it would dip to 1000 then rise to about 1500, drop to 1000, and repeat. I turned off the engine and turned it back on. The "dancing" stopped but it was still idling at 1500 rpm.
Is the ICV NOT the problem...or is it? If it's not the ICV, I am gonna use mytrplseven's method to test for vac leaks.
Thanks again for your continued diagnostic assistance. I looove my 951!
11-04-2011, 04:03 AM
#12
Three Wheelin'
Thread Starter
I'll be shamelessly bumping this tomorrow morning. 
I've searched all over the place but each problem seems to be a little different.
I've searched all over the place but each problem seems to be a little different.
11-04-2011, 11:17 AM
#13
Got Nothin'
Rennlist Member
Rennlist Member
Have you reset the idle to the correct setting of 900 ?
There is an air-bypass screw on the throttle body. You need to disable the ISV, and then set the idle.
Get the idle closer to spec, then update as to the engine's behavior.
There is an air-bypass screw on the throttle body. You need to disable the ISV, and then set the idle.
Get the idle closer to spec, then update as to the engine's behavior.
11-25-2011, 05:48 PM
#15
Three Wheelin'
Thread Starter
According to clark's garage, the idle spec for turbos is 800-880 RPM. I unplugged the ISV, and had to turn the idle screw ALL THE WAY in. At that point, idle was about 1000 or a little more and steady...the engine was at operating temperature. I then plugged the ISV back in and the idle settled to about 900 to 950. Not a bad place to have the idle, but why did I need to turn the screw all the way in?
Sure enough, as I went on a drive, I noticed the idle was increasing little by little. Turns out the screw was backing out! I put just a bit of medium strength thread locker on there. But why should I have needed to turn the screw all the way? Idle seems great now, but am I masking another symptom?
Thanks For The Continued Help!
my 951 loves it
Sure enough, as I went on a drive, I noticed the idle was increasing little by little. Turns out the screw was backing out! I put just a bit of medium strength thread locker on there. But why should I have needed to turn the screw all the way? Idle seems great now, but am I masking another symptom?
Thanks For The Continued Help!
my 951 loves it