High Idle

[RedRiderZR1]

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. :dancing

[bdw18_123]

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%20Web/services/throttle%20body.htm

[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.

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.

:cheers:
Tom

[gbmidyear66]

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]

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]

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?

[bdw18_123]

Not to hijack this thread, but RedRiderZR1 & zr1don, I notice you guys are down in SoCal. My buddy Pete (PLRX) is planning another C4 run down there on March 19. You guys should come!

Link here: http://www.zr1.net/forum/showthread.php?p=107647#post107647

[RedRiderZR1]

RedRiderZR1,

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

Don,
Yes I do have stock manifolds and cats.
As far as the numbers they keep lowering them.
15 mph and 25 mph reading and my numbers are..

15 MPH HC (ppm)max is 77, mine was 48
15 MPH CO% max is .50, mine was .47 (squeaked by there)
15 MPH NO (ppm)max is 541, mine was 322
25 MPH HC (ppm)max is 59, mine was 47
25 MPH CO% max is .59, mine was .09
25 MPH NO (ppm)max is 498, mine was 47

15 mph CO2 % measured was 14.10
15 mph O2 % measured was .18
25 mph CO2 % measured was 14.60
25 mph O2 % measured was .04

Gives you an idea of how much they lowered the numbers from last time. If you still have your sheet from last time. Dropped it quite a bit. Just swapped out plugs and new fluids before taking it in and new gas. Didn't pass by a clear margin as last time, but then the numbers were higher on the test last time. They like to keep dropping them.

Good luck on passing.

Greg

[RedRiderZR1]

Not to hijack this thread, but RedRiderZR1 & zr1don, I notice you guys are down in SoCal. My buddy Pete (PLRX) is planning another C4 run down there on March 19. You guys should come!

Link here: http://www.zr1.net/forum/showthread.php?p=107647#post107647

Already saw that post and I am planning on going. :cheers:

[Aurora40]

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).

[zr1don]

RedRiderZR1,
Thanks for the info, my stock cats were blown out two years ago and I replaced w/aftermarket headers and cats. I have been trying since last August to pass and haven't yet (despite numerous changes and tries). Was hoping you had a stock system to compare against, thanks again for the info. Apologize for hijacking your thread, hope you get your idle fixed.

[RedRiderZR1]

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.

[RedRiderZR1]

RedRiderZR1,
Thanks for the info, my stock cats were blown out two years ago and I replaced w/aftermarket headers and cats. I have been trying since last August to pass and haven't yet (despite numerous changes and tries). Was hoping you had a stock system to compare against, thanks again for the info. Apologize for hijacking your thread, hope you get your idle fixed.

No problem. From what i have read here lately, it seems people with the stock manifolds and cats have a better chance of getting them through. Most likely due to the cats being closer to the engine on the stock manifolds. Hope you get it passed soon.

Greg

[mike100]

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.