Quality of idle
05-24-2007, 12:36 PM
#1
Three Wheelin'
Thread Starter
Quality of idle
My car idles at about 850 rpm. Rock steady. However, when coming to a complete stop, the idle does not go immediately to 850 but GRADUALLY DROPS from about 1200 to 850 after about 20 seconds. My other 2 cars (Audi A4 and Acura CL) goes IMMEDIATELY to their normal idle when stopped. Is this normal for the 928 (brand new idle control valve was installed after manifold job)?
Just thinking.
Hessank
89 S4 Koenig
Just thinking.
Hessank
89 S4 Koenig
05-24-2007, 12:49 PM
#2
Under the Lift
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It shouldn't hang up like that. 850 is quite high, as well, for an S4 (or even a GT), although if this is from the dash tach, it may be inaccurate (although I've actually not seen this to be the case). Check that with an external tach. Do you hear the idle switch click when you move the throttle just slightly off-the idle stop?
You may have an air leak somewhere, although I would expect more symptoms. It is hard to get the breather lines fully seated in the boot under the MAF when rebuilding the intake. These lines can be viewed after removing the airbox and MAF. You might want to try some MAF cleaner spray, particularly if you happen to have something like a K&N filter installed (naughty). CRC makes a MAF cleaner, which is like brake cleaner minus the acetone, so it is safe around plastic. Do not use brake cleaner or carb cleaner. I have seen MAF cleaner correct some high idle issues.
Have you pulled the battery ground recently? You might try that to give the LH a chance to readapt the idle.
A session with a Spanner or Theo's 928 diagnostic program would probably be very helpful. Maybe there is a 928er in your areas who has one of them. If not, there are direct tests you can do on the LH and EZK plug pins to check the function of the idle switch, etc.
You may have an air leak somewhere, although I would expect more symptoms. It is hard to get the breather lines fully seated in the boot under the MAF when rebuilding the intake. These lines can be viewed after removing the airbox and MAF. You might want to try some MAF cleaner spray, particularly if you happen to have something like a K&N filter installed (naughty). CRC makes a MAF cleaner, which is like brake cleaner minus the acetone, so it is safe around plastic. Do not use brake cleaner or carb cleaner. I have seen MAF cleaner correct some high idle issues.
Have you pulled the battery ground recently? You might try that to give the LH a chance to readapt the idle.
A session with a Spanner or Theo's 928 diagnostic program would probably be very helpful. Maybe there is a 928er in your areas who has one of them. If not, there are direct tests you can do on the LH and EZK plug pins to check the function of the idle switch, etc.
05-24-2007, 01:27 PM
#3
Craic Head
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Hessank,
Mine does that too. I always thought it was normal (my idle is adjusted to 750 though) But it doesn't usually drop to right there, it will come down to 1100, then slowly drop down after I'm sitting at a light for a little while.
I think mine might be related to the pedal actually hanging up a little, I found that the circlip is missing and one of the white bushings is missing from the back of the pedal. It feels like it's coming all the way back up, but maybe it's just giving enough resistance that it's slow to come up. I need to get that circlip and put the other bushing back in, lube it up and see what happens.
I'll be following this thread, so please keep us posted.
Mine does that too. I always thought it was normal (my idle is adjusted to 750 though) But it doesn't usually drop to right there, it will come down to 1100, then slowly drop down after I'm sitting at a light for a little while.
I think mine might be related to the pedal actually hanging up a little, I found that the circlip is missing and one of the white bushings is missing from the back of the pedal. It feels like it's coming all the way back up, but maybe it's just giving enough resistance that it's slow to come up. I need to get that circlip and put the other bushing back in, lube it up and see what happens.
I'll be following this thread, so please keep us posted.
05-24-2007, 02:32 PM
#4
Rennlist Member
S4 idle speed is electronically stabilised to 675rpm under all conditions. So your car definitely has a problem.
Bill has highlighted a good plan of diagnostics. A diagnostic tester could save you a lots of wasted time and money....
Bill has highlighted a good plan of diagnostics. A diagnostic tester could save you a lots of wasted time and money....
05-24-2007, 02:45 PM
#5
Under the Lift
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Originally Posted by John Speake
A diagnostic tester could save you a lots of wasted time and money....
05-24-2007, 02:45 PM
#6
Inventor
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Originally Posted by NJSharkFan
I think mine might be related to the pedal actually hanging up a little...
Trending Topics
05-29-2007, 02:21 PM
#9
Three Wheelin'
Thread Starter
Sorry for the late response. I was away after I posted my problem. Thanks for all the advise. I have done everyone of them. So far this is what I found: The idle is actually 700 rpm with an external tach (so dash is reading 150 too high), I do hear the idle switch click, there is no hang up of the throttle mechanisms (accel, cables etc) due to the carpet, I've lubed the entire cable,& throttle parts, used a stetiscope and propane to cvhanse down any air leaks and none were found. Porken wrote that "there's a small roller which rides in the throttle cam slot (part of the throttle plate mechanism). It was not turning, which made the throttle action 'rough'". I am currently investigating this and trying to locate a can of the CRC MAF cleaner (in my neck of the woods) area as Bill suggested.
05-29-2007, 02:39 PM
#10
Drifting
When I push the clutch in to come to a stop, my idle usually drops down very low and then jumps back up to where it should be, like a dip to 400 and then back up to 800 or so. Maybe I can get on the Hammer down at SITM and flush something out.
06-01-2007, 08:43 PM
#12
Rennlist Member
I cleaned my MAF, checked, cleaned and lubricated my linkage, verified that the idle switch is clicking when I move the accelerator linkage and "discovered" that I had Autothority chips installed - I disconnected the battery while I was in the process of replacing the chips. My idle is still 900-1000 rpm. It's actually a bit higher after it warmed up than it is when I first start it.
The lag when I let off the accelerator seems to be gone, but still high idle. Is it possible that this is just a function of the Autothority chips?
Rod
The lag when I let off the accelerator seems to be gone, but still high idle. Is it possible that this is just a function of the Autothority chips?
Rod
Originally Posted by Bill Ball
It shouldn't hang up like that. 850 is quite high, as well, for an S4 (or even a GT), although if this is from the dash tach, it may be inaccurate (although I've actually not seen this to be the case). Check that with an external tach. Do you hear the idle switch click when you move the throttle just slightly off-the idle stop?
You may have an air leak somewhere, although I would expect more symptoms. It is hard to get the breather lines fully seated in the boot under the MAF when rebuilding the intake. These lines can be viewed after removing the airbox and MAF. You might want to try some MAF cleaner spray, particularly if you happen to have something like a K&N filter installed (naughty). CRC makes a MAF cleaner, which is like brake cleaner minus the acetone, so it is safe around plastic. Do not use brake cleaner or carb cleaner. I have seen MAF cleaner correct some high idle issues.
Have you pulled the battery ground recently? You might try that to give the LH a chance to readapt the idle.
A session with a Spanner or Theo's 928 diagnostic program would probably be very helpful. Maybe there is a 928er in your areas who has one of them. If not, there are direct tests you can do on the LH and EZK plug pins to check the function of the idle switch, e
tc.
You may have an air leak somewhere, although I would expect more symptoms. It is hard to get the breather lines fully seated in the boot under the MAF when rebuilding the intake. These lines can be viewed after removing the airbox and MAF. You might want to try some MAF cleaner spray, particularly if you happen to have something like a K&N filter installed (naughty). CRC makes a MAF cleaner, which is like brake cleaner minus the acetone, so it is safe around plastic. Do not use brake cleaner or carb cleaner. I have seen MAF cleaner correct some high idle issues.
Have you pulled the battery ground recently? You might try that to give the LH a chance to readapt the idle.
A session with a Spanner or Theo's 928 diagnostic program would probably be very helpful. Maybe there is a 928er in your areas who has one of them. If not, there are direct tests you can do on the LH and EZK plug pins to check the function of the idle switch, e
tc.
06-02-2007, 05:55 AM
#13
Rennlist Member
Hi Rod,
It sounds as though there is a problem with your car's idle control system. The ISV may be stuck in one position, or there may be another problem.
Try and get a diagnostic tester on it, go to the "Actuator test" menu, and select "idle control valve". The tester will cycle the ISV through its range, and you should hear it clicking regularly as it does so.
If it doesn't click then the valve is stuck, there's a bad connection, or a problem with the LH (which regulates that idle speed)
It sounds as though there is a problem with your car's idle control system. The ISV may be stuck in one position, or there may be another problem.
Try and get a diagnostic tester on it, go to the "Actuator test" menu, and select "idle control valve". The tester will cycle the ISV through its range, and you should hear it clicking regularly as it does so.
If it doesn't click then the valve is stuck, there's a bad connection, or a problem with the LH (which regulates that idle speed)
06-02-2007, 09:26 AM
#14
Rennlist Member
Originally Posted by John Speake
Hi Rod,
It sounds as though there is a problem with your car's idle control system. The ISV may be stuck in one position, or there may be another problem.
Try and get a diagnostic tester on it, go to the "Actuator test" menu, and select "idle control valve". The tester will cycle the ISV through its range, and you should hear it clicking regularly as it does so.
If it doesn't click then the valve is stuck, there's a bad connection, or a problem with the LH (which regulates that idle speed)
It sounds as though there is a problem with your car's idle control system. The ISV may be stuck in one position, or there may be another problem.
Try and get a diagnostic tester on it, go to the "Actuator test" menu, and select "idle control valve". The tester will cycle the ISV through its range, and you should hear it clicking regularly as it does so.
If it doesn't click then the valve is stuck, there's a bad connection, or a problem with the LH (which regulates that idle speed)
Hmmm, now there's the problem - a "diagnostic tester". Is/are there any techniques for evaluating this without the tester? Remember, I live in central Indiana; Land of the Free, Home of the Brave, but not much on diagnostic testers.
Actually I have a couple of "extra" ISV's I guess the simpliest alternative is to just switch it out and see what happens.
Thanks,
Rod
06-02-2007, 09:51 AM
#15
Rennlist Member
As well as borrowing a tester from a kind soul, you would also need to fit the later EPROMS in your LH and EZK ECUs for diagnostics. Your 87 cars don't have diagnostic chips, but the car is already wired with a diagnostic 12 way port, like the MY88.