High Idle - ZR-1 Net Registry Forums

RedRiderZR1 · 02-11-2011

Took the car in for california smog check today. But before taking it in I used some Throttle Body cleaner on it. Now when I get the car up to 3k rpms it hangs there until I blip the throttle to bring it down. It's been doing it all day. Why would spraying some cleaner in there cause this?

Car usually hangs at 1.5k until I stop then it goes down to 750 rpm idle. Even when I blip the throttle it only goes down to 1.2k idle speed now. Is there some throttle body reset procedure I can try.

Oh yeah.. It did pass emissions.

bdw18_123 · 02-11-2011

There is some dark brownish stuff that the factory put around the throttle body bore right where the butterfly plate contacts when it is fully closed to help create a better seal. That stuff is called DAG. It's easily mistaken for dirt/oil. I don't think you can get it anymore and to my knowledge, no one has found a suitable substitute yet.

Since you used TB cleaner on it, you probably cleaned off the DAG and now the butterfly plates don't have that seal anymore.

Here is a link to a page on Marc Haibeck's site where he talks about the idle issues the LT5's TB can develop:

http://www.zr1specialist.com/HAT%20W...tle%20body.htm

tomtom72 · 02-11-2011

Usually T-body spray cleaner will not affect the DAG, or at least it isn't supposed to attack it. Carb cleaner will dissolve it though.

Did you stick something in the 2* blades to hold them open while spraying? Or did you disconn the T-cable and open the blades using the linkage? Or did you take out the IAC and spray thru that port to get the inside of the T-body?

Maybe if you pull the T-body and get her on a bench you might find that some of the DAG has been bunched up out of position and that is holding a blade off of the closed position. If the DAG is missing it is an air leak and that's the reason for the high idle, it's just like a vacuum leak.

Tom

gbmidyear66 · 02-11-2011

You could check and clean the IAC, but I agree with TomTom, it is probably a Vacuum leak.

If the vacumn pump cycles (more than every minute or so) when the ignition is on, engine not running - you have a vacuum leak.

RedRiderZR1 · 02-11-2011

Thanks for the help. Will have to look at it further. Was fine until I sprayed it with TB cleaner. Now I have to blip the throttle for it to drop.

zr1don · 02-11-2011

RedRiderZR1,

I am trying to pass CA smog w/90 ZR1. Do you have stock exhaust manifolds and cats? Can you post your emmissions #'s?

Aurora40 · 02-11-2011

Quote:

Originally Posted by tomtom72

Usually T-body spray cleaner will not affect the DAG, or at least it isn't supposed to attack it. Carb cleaner will dissolve it though.

I used TB cleaner and it did just what he is describing. At the time I didn't know anyone with a ZR-1, and had no idea how to fix it. Since a new TB was like a grand from GM, I put that grand towards a Haibeck ported plenum since the TB was also ported (thus solving the DAG issue).

RedRiderZR1 · 02-11-2011

Quote:

Originally Posted by Aurora40

I used TB cleaner and it did just what he is describing. At the time I didn't know anyone with a ZR-1, and had no idea how to fix it. Since a new TB was like a grand from GM, I put that grand towards a Haibeck ported plenum since the TB was also ported (thus solving the DAG issue).

Not great news there. I would of thought throttle body cleaner would be safe. Odd though, after I blip the throttle it goes back down. So it sounds as if it is hanging up until I blip the throttle. Well I will have to check it out. All good info. Thanks.

mike100 · 02-17-2011

my NOx was pretty high when I transferred from the previous owner's smog (the rest of the numbers were real low), but I think it was elevated combustion temps due to running lean. It had a large vacuum leak under the plenum which caused it idle at 1200 rpms all the time and would never slow down.

I may have wiped a little bit of the DAG off the lower half of my t.b., but it still idles below 1000 rpms now and slows down on the road when you let off the accelerator.

to test for a leak:

1) take off the inlet duct and air filter housing
2) clamp the vent hoses that come from the cam covers so they can't bypass air to the engine
3) get a real stiff box or notebook binder and block the front of the air horn when the engine is idling.

if it still runs at 700-800 rpm's, then it has a big air leak somewhere else...if it chokes it, then all the air is going through the throttle body and/or IAC valve. I don't see wiping away some of the DAG making it hang at 1500 rpms.

02-11-2011	#1
RedRiderZR1 Join Date: Jun 2005 Location: Orange County, California Posts: 75	High Idle Took the car in for california smog check today. But before taking it in I used some Throttle Body cleaner on it. Now when I get the car up to 3k rpms it hangs there until I blip the throttle to bring it down. It's been doing it all day. Why would spraying some cleaner in there cause this? Car usually hangs at 1.5k until I stop then it goes down to 750 rpm idle. Even when I blip the throttle it only goes down to 1.2k idle speed now. Is there some throttle body reset procedure I can try. Oh yeah.. It did pass emissions.

02-11-2011	#2
bdw18_123 Join Date: Apr 2009 Location: Prather, CA Posts: 804	Re: High Idle There is some dark brownish stuff that the factory put around the throttle body bore right where the butterfly plate contacts when it is fully closed to help create a better seal. That stuff is called DAG. It's easily mistaken for dirt/oil. I don't think you can get it anymore and to my knowledge, no one has found a suitable substitute yet. Since you used TB cleaner on it, you probably cleaned off the DAG and now the butterfly plates don't have that seal anymore. Here is a link to a page on Marc Haibeck's site where he talks about the idle issues the LT5's TB can develop: http://www.zr1specialist.com/HAT%20W...tle%20body.htm

02-11-2011	#3
tomtom72 Join Date: Dec 2004 Location: Jacksonville, FL USA Posts: 4,609	Re: High Idle Usually T-body spray cleaner will not affect the DAG, or at least it isn't supposed to attack it. Carb cleaner will dissolve it though. Did you stick something in the 2* blades to hold them open while spraying? Or did you disconn the T-cable and open the blades using the linkage? Or did you take out the IAC and spray thru that port to get the inside of the T-body? Maybe if you pull the T-body and get her on a bench you might find that some of the DAG has been bunched up out of position and that is holding a blade off of the closed position. If the DAG is missing it is an air leak and that's the reason for the high idle, it's just like a vacuum leak. Tom __________________ 1990 ZR-1, Black/grey, #2233, stock. ZR-1 Net Reg Founding Member #316 & NCM member

02-11-2011	#4
gbmidyear66 Join Date: Feb 2008 Location: Vancouver, BC Posts: 251	Re: High Idle You could check and clean the IAC, but I agree with TomTom, it is probably a Vacuum leak. If the vacumn pump cycles (more than every minute or so) when the ignition is on, engine not running - you have a vacuum leak.

02-11-2011	#5
RedRiderZR1 Join Date: Jun 2005 Location: Orange County, California Posts: 75	Re: High Idle Thanks for the help. Will have to look at it further. Was fine until I sprayed it with TB cleaner. Now I have to blip the throttle for it to drop.

02-11-2011	#6
zr1don Join Date: Jan 2006 Location: Temecula, CA Posts: 88	Re: High Idle RedRiderZR1, I am trying to pass CA smog w/90 ZR1. Do you have stock exhaust manifolds and cats? Can you post your emmissions #'s?

02-17-2011	#9
mike100 Join Date: Feb 2011 Location: San Marcos CA Posts: 1,786	Re: High Idle my NOx was pretty high when I transferred from the previous owner's smog (the rest of the numbers were real low), but I think it was elevated combustion temps due to running lean. It had a large vacuum leak under the plenum which caused it idle at 1200 rpms all the time and would never slow down. I may have wiped a little bit of the DAG off the lower half of my t.b., but it still idles below 1000 rpms now and slows down on the road when you let off the accelerator. to test for a leak: 1) take off the inlet duct and air filter housing 2) clamp the vent hoses that come from the cam covers so they can't bypass air to the engine 3) get a real stiff box or notebook binder and block the front of the air horn when the engine is idling. if it still runs at 700-800 rpm's, then it has a big air leak somewhere else...if it chokes it, then all the air is going through the throttle body and/or IAC valve. I don't see wiping away some of the DAG making it hang at 1500 rpms.