Help - High Idle @ 1000 rpm - Cannot figure it out

[dfaudi]

I have had this high idle issue for a while (since december). Basically, my car idles high during warmup (like it should) then gradually goes back down to ~800rpm (like it should), but then it works back upto about 1000rpm and stays there.

It started with my throttle body getting sticky because of my water/meth injection getting into the throttle body plate pins i guess. So to fix the issue, I bought a used replacementand, and since, my idle holds around 1000-1200 rpm. I also get a P0507 "idle control regulation - upper limit exceeded" (something like that).

Things ive done to test the problem:
-I did a boost leak test at the turbo inlet and a test on the TIP and didnt hear anything.
-I checked teh TIP for any rips.
-datalogged the MAF readings - running at ~4-5 g/s which is too high. So im thinking it may not be a vac leak becuase the MAF is actually reading the extra air (and its not being introduced after the MAF). Or does the ecu compensate for a vaccuum leak by adjusting throttle which, in turn, gives higher maf readings?

Im running out of things to check.

Suggestions??

[a4_1.8t_01]

Probably have a vacuum leak. You need to use soapy water on everything around the intake manifold. You will not hear the leaks. I tried and didnt hear anything then found 4 leaks.

[dfaudi]

Were you getting higher idle too because of these leaks?

[DenverNoob]

prob not a leak issue honestly....

one little thing to check, and its kinda random (but I have seen this issue on a couple of cars) is the clutch pedal switch (similar to the brake pedal switch)....this tells the car when the clutch is/is not engaged and alters RPM on that basis.

also...another thought...look at the secondary air pump and associated systems...if for some reason that is not turning off after your warmup (at cold-start) that could also account for the higher than average MAF readings as well as the increased RPM.

nothing here indicates a vac leak, nor would that cause higher MAF readings or higher RPM.

[dfaudi]

The clutch pedal switch?....Ill have to check that for sure. The high idle has been around since after my clutch job in December. And i was under my dash disconnecting my steering shaft when R&R'ing that.

For the SAI system, i hear it turning on and off so i think its working right. However, do you know the strategy to check it for leaks, and checking if the combination valve behind the head, etc? On the bentely, the Pcode does recommend checking the system too, but dont know how to go about doing that. Would you recommend just blocking it off totally?

Thanks for the suggestions, ill have to try them out.

[dfaudi]

Probably have a vacuum leak. You need to use soapy water on everything around the intake manifold. You will not hear the leaks. I tried and didnt hear anything then found 4 leaks.

I tried the soapy water thing but wasnt successful. Am i trying to get the soapy water as foamy as possible?? Where did you find the leaks?

Also, i forgot to mention, that my breather valve (the one on the intake pips) is bad. I breathed through it in both directions and there was no resistance. so i took it out and plugged the intake pipe and left the metal pipe side just open. Dont others usually just put a breather filter on that?

[diagnosticator]

I have had this high idle issue for a while (since december). Basically, my car idles high during warmup (like it should) then gradually goes back down to ~800rpm (like it should), but then it works back upto about 1000rpm and stays there.

It started with my throttle body getting sticky because of my water/meth injection getting into the throttle body plate pins i guess. So to fix the issue, I bought a used replacementand, and since, my idle holds around 1000-1200 rpm. I also get a P0507 "idle control regulation - upper limit exceeded" (something like that).

Things ive done to test the problem:
-I did a boost leak test at the turbo inlet and a test on the TIP and didnt hear anything.
-I checked teh TIP for any rips.
-datalogged the MAF readings - running at ~4-5 g/s which is too high. So im thinking it may not be a vac leak becuase the MAF is actually reading the extra air (and its not being introduced after the MAF). Or does the ecu compensate for a vaccuum leak by adjusting throttle which, in turn, gives higher maf readings?

Im running out of things to check.

Suggestions??

The "Idle Control Regulation Upper Limit Exceeded" DTC, means the ECU can't regain control of the idle speed because the control action can't be increased any more. The fact that the cold startup idle speed is initially about normal, then control is lost, points to a bad or mal adapted throttle body. Have you performed the TB adaptation procedure? If you log the TB postition sensor output values, does the graph look OK at cold start? What about while/after driving with the TB warmed up?

[A4ringedONE8T]

Clean the TB (see my DIY) and then do a TB adaptation

[dfaudi]

Diagnosticator, what block is throttle body sensor voltage that i should log? Should i just do an idle log at cold start then one when warmed up?

A4ringedONE8T, i dont think its the throttle body being dirty. I remember when installing it it was fairly clean. However, i will give it a shot.

Thanks for the suggestions, will try them.

[dfaudi]

Could the SAI combination valve at the back of the head cause any issues? Do they go bad? Im going to check the gasket mating surface and make sure its sealed.

[diagnosticator]

Diagnosticator, what block is throttle body sensor voltage that i should log? Should i just do an idle log at cold start then one when warmed up?

Measuring block 062:
062,0,Electronic Throttle (Sensor Values)
062,1,Throttle Valve,Sensor 1 (G187)
062,2,Throttle Valve,Sensor 2 (G188)
062,3,Accel. Pedal Pos.,Sensor 1 (G79)
062,4,Accel. Pedal Pos.,Sensor 2 (G185)



You can see the values of the throttle valve angle cold, then later hot. And you can also log the sensor variations while driving for awhile. Afterwards, graphing the logged data would show if any weird glitches occur in the sensors or not, etc. The sensors may or may not show anything that helps find the cause for your problem, but the only way to know is to check the possible causes one at a time. There are other things that can give a clue also.

[diagnosticator]

Could the SAI combination valve at the back of the head cause any issues? Do they go bad? Im going to check the gasket mating surface and make sure its sealed.

The SAI, effects the exhaust gas oxygen concentration, and the cat converter during cold start ups. Therefore, it really cannot effect the engine as far as running charachteristics and qualities, because the SAI acts on, and effects only exhaust gasses, it can't effect the combustion process as would be required to influence the running qualities of the engine.
Regardless, it's possible for the SAI combination valve to malfunction in various ways, effecting cat efficiency during post cold-start warm up emissions more or less.

[dfaudi]

Diagnosticator,

Will do the logs. Thanks for giving detail on how to log this channel.

In regards to the SAI valve, are you saying theres no way there can be any leaks in the lines or the valve's gasket mating surface that would cause a leak in the system?

[diagnosticator]

Diagnosticator,

Will do the logs. Thanks for giving detail on how to log this channel.

In regards to the SAI valve, are you saying theres no way there can be any leaks in the lines or the valve's gasket mating surface that would cause a leak in the system?

The only part of the SAI system connected to the intake manifold, is the combination valve via the control vacuum hose, and vacuum switching solinoid valve. If that part of the SAI was leaking, it would be unmeasured air, so that is not likely involved with the problem.

I think the throttle body is wacky. Have you tried logging the TB sensors yet?

[dfaudi]

Yeah did the logs. I just gotta graph teh values. Im going to buy a throttle body tomorrow anyways...theyre cheap on car-parts.com ~$40.


Another few things i noticed when logging....
-when at idle (warm) my shows ~7 degrees AFTD
- Also, my cf's sometimes show 1.8 across all 4 cylinders (at idle,when warm)

I think its the tb like you said Diagnosticator.

[GTMRS4]

make sure its a DBW throttle body and not by cable. It seems your throttle body is about to die, I'm certain of it as this is the 1st stage that happend to mine. It will crawl up to 1500 over the next few days, and then it just wont start.

Change out your TB as fast as possible.

[dfaudi]

Update: Got a low miles throttle body and bolted it up and its the same problem but idle actually got a lot worse. It would go to 1200rpm then 1400rpm and was very unpredictable. Im sure the gasket mating surface was sealed and i also did a tb alignment. When I put the current throttle body back in, it went back to the usual 1K rpm idle.

Next task is to test the check valves. Hope this f'ing works cause i cant get my GTRS custom tune till i have this figured out.

[dfaudi]

Another Update:
Im still kinda having the problem. I have checked all the check valves and theyre good. I also replaced a torn boost/vac line that connects to the 3-way valve that sits between the brake booster line and the L-hose that connects to the manifold. the one i replaced was the connection that goes downwards.

Now the rpms are a little more stable around 900 (instead of 1000-1200). You guys think this could be an intake manifold gasket leak? I do hear some suction near the manifold but cannot determine if its just the sound coming from air passing the throttle body, as it normally should, or if it is a leak.

DenverNoob, i do still have to get under my dash and check that switch. Is the switch normally open or closed?

[dfaudi]

Could it be the electric vaccuum solenoid valves under the manifold? Hmm. Ill have to check those out. Any info on that would be appreciated.

[dfaudi]

DenverNoob,
I checked the clutch switches and no issues with them. I unplugged them...jumped them, and it made no idle difference.

Any other suggestions anyone?

[dfaudi]

Btw, i logged my timing at idle, im at 6-9 degrees AFTER Top dead center ATDC.

It seems to me like whatever is causing the issue is related to something that kicks in after the car warms up. Cause during initial start, it idles normally, then as it reaches operating temp, it idles at 1k.

[diagnosticator]

Btw, i logged my timing at idle, im at 6-9 degrees AFTER Top dead center ATDC.

It seems to me like whatever is causing the issue is related to something that kicks in after the car warms up. Cause during initial start, it idles normally, then as it reaches operating temp, it idles at 1k.

That sure sounds like a (variable) valve timing related clue to me. Intake cam timing changes a lot from cold start up to closed loop warm idle. Also note that in the normal condition, a cold 1.8T starts and runs at about ~1200-1300 rev/min for about 30 seconds then slows down to normal idle speed of about ~800 rev/min. after that initial fast idle period. Seems from your description, your A4 is doing the opposite, (?) Check everything monitoring engine coolant temp, and false signal voltage, or reduced signal values, into the ECU temp inputs. (possible short in the signal wires.) check for cam position sensor signal values. Confirm crank speed sensor valves etc. Are you sure the throttle valve is closing all the way? Have you performed a TB adaptation? Besides throttle valve opening angle, the Torque demand based E-Gas engine control scheme, will use ignition timing adjustment to control engine torque. If the throttle valve is stuck open a little bit, the ECU has only ignition timing retard to reduce idle torque but that is a limited range variable. It just occurred to me that maybe your ECU is entering Emergency Running Mode, used when the E-Gas electronic throttle is whacked. The emergency running mode idle speed is about 1000 rev/min fixed value to allow the car to move regardless of no E-Gas function. But then again, you are driving the car, right?

[diagnosticator]

Could it be the electric vaccuum solenoid valves under the manifold? Hmm. Ill have to check those out. Any info on that would be appreciated.

One solenoid opens the diverter valve when the ECU energizes the solenoid, the other opens the Secondary Air Injection Combination Valve for about a minute at cold start up. Except for the vacuum circuit, neither system affects air flow into the engine intake manifold.

[dfaudi]

Diagnosticator,
I should have been a little more clear, upon cold start, it runs normally (revs at 1200-1300rpm), but when its warm, it goes down to 800, then shortly after it works its way back up to 900-1000rpm and idles there. I dont think i have any cam or throttle body issues. I got a different throttle body and it did the same thing.

Diagnosticator, what about the pcv system?? Would this cause idle issues? i know theres a valve near the intake pipe (some right off the valve cover), and the dealer said theres another valve (a blow-by valve or something) that is under the intake manifold. (i think this valve releases teh excess oil back into the oil system...it seams to be plumbed to the oil filter housing) Any experience with this valve?

Or it may be something as simple as my 02 sensor slowly failing. I did run E85 for a bit a few months ago (70/30 E85/93 blends) and since E85 absorbs water, maybe the moisture has affected the sensor.

[diagnosticator]

Thanks for clarifying the situation. The PCV can possibly be involved, if allowing excess flow into the intake manifold. The crankcase pressure is regulated by the pressure/flow (out flow) balance between the "PCV" valve above the oil filter base casting, and the fresh air inflow regulator valve in the large hose at the rear of, and connected to the valve cover. Crankcase pressure should be negative 1" water column below ambient, at least, (or the most, per reference viewpoint) To evaluate if crankcase ventilation is possibly involved, try pinching the out flow hose above the oil filter closed, note any change in the idle speed.

[dfaudi]

Diagnosticator,
Will do. However, I did shoot compressed air into the hose that leads to the pcv valve (under manifold to oil system) and when i did, it held up and no effects of leakage. I will check again though.

Any thoughts on the 02 sensor?

Are there any logs that would give more clues?

[kohl44]

dude, if you haven't yet, please re-adapt your throttle. i've only heard one person tell you to do it and i have no idea if you did. your ecu has to re-learn your throttle everytime you change it, loose battery power, ect. even if your throttle, ecu, whatever is going bad, that should at least bring it in line for a short while.

[dfaudi]

dude, if you haven't yet, please re-adapt your throttle. i've only heard one person tell you to do it and i have no idea if you did. your ecu has to re-learn your throttle everytime you change it, loose battery power, ect. even if your throttle, ecu, whatever is going bad, that should at least bring it in line for a short while.

Thanks for the concern, but im way passed it being the tba.

[dfaudi]

Diagnosticator,

I did notice my PCV valve is stuck open. I can blow in/out through both ports. Could this be my idle issue.

Also, recently I have not been getting the "idle control regulation" code. However, my idle timing is 7-9 degrees AFTD, and my MAF readings are 4-5 g/s. Both of those figures dont seem right to me.
I cleaned my Maf with Maf cleaner, vaccuum tested all the vac lines (with a vac gun i jut bought). I ordered a new 02 sensor.

I would like to take logs of the throttle body but dont know what to look for. Can i send you the log file?

[aaaudiprotein]

Could that be MAF sensor?.
I got a bit the same problem with IDLE.
First off all, i'm running lean. At idle, it might go up to 1050rpms, then go down to 900. I've tried to clean the MAF sensor, it seemed like it helped a bit, but i still have this problem.

[diagnosticator]

Could that be MAF sensor?.
I got a bit the same problem with IDLE.
First off all, i'm running lean. At idle, it might go up to 1050rpms, then go down to 900. I've tried to clean the MAF sensor, it seemed like it helped a bit, but i still have this problem.

Those are symptoms of a vacuum leak.

[aaaudiprotein]

Sorry for the offtop. But what are the most common places of the leak?

[diagnosticator]

Sorry for the offtop. But what are the most common places of the leak?

The check valves, and the "L" hose are common causes, but a leak is possible in any of the various vacuum system hoses and hose connections that have a vacuum applied, mainly anything connected to the intake manifold after the throttle valve.

[87quattro5ks]

You people confuse me...my car is idling high for some odd reason and also starting really hard (have to use starting spray or gas when cold)

any ideas?

[diagnosticator]

You people confuse me...my car is idling high for some odd reason and also starting really hard (have to use starting spray or gas when cold)

any ideas?

First, have the engine ECU scannned for fault codes. Your symtom described is allmost always caused by a large false air leak. (downstream from the throttle valve.)

[dfaudi]

PROBLEM SOLVED!!!

First off, thanks for all your help. Especially to Diagnosticator for pointing me in the right direction.

problem:
To diagnose for leaks, I have used my compressor to force air everywhere to look for leaks with no luck…however, it occurred to me last night that I should look for vacuum leaks while the car is on. So with the car idling and upto temp (at 850-900 idle), I started pinching off vacuum line, one by one, until I found the source of the high idle issue.



I pinched off the line that is directed downwards, coming off that 3-way valve between the manifold and brake booster and the idle immediate dropped to normal 760-800rom!! I don’t know exactly what the culprit is, but I do know it is something related to the pcv valve (the one below the intake manifold) that directs the blow-by oil back into the oil filter housing. The motor was too hot for me to get in there comfortable.

Temporary fix till i get dealer parts. I disconnected that line, and plugged the 3-way valve.

Idle is solid now.

[busakiller]

bring this back from the dead... I'm having the same problem but I don't understand how a vac leak can cause the idle to speed up only when the car is warmed up.... When it's cold it idles fine.... I'm going to try to pinch hoses and see what happens....

[dfaudi]

i think it was the hose that wraps around the airbox...but checkem all. when i swithced over to my big turbo kit and ditched all the unnecessary vac lines the problem went away.

you do a boost leak test yet?

turboboostleaktesters.com