Stuart S

Sometimes my LG4 kicks down in the morning and other times it doesn't...every once in a while, the ide either goes ridiculously high or very low...changing the idle on the carb manulally is a quick fix, but it soon varies again...ideas?

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Stuart S
1987 Trans Am LB9/WS6
1986 Camaro IROC-Z
OEM Posterchild of the soon to be Infamous Long Island Crew

MRZ28HO

Is this a Holley, Q-jet ... ?

If it's a q-jet, are you allowing it to warm up (it should take ~2-3 minutes). Also, your choke could be improperly set. What keeps you idle high is the fast idle cam, located under the choke housing. Use a phillips screw driver and turn it in to increase idle, or turn it out to decrease idle. Fast idle should be at ~1500 rpms.

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George P. Lara
1994 Z28 LT1 T56
1984 Z28 High Output
Member: SCFB
Member: SC3GFB


[This message has been edited by MRZ28HO (edited September 11, 2000).]

Stuart S

LG4 - Q-jet..

I said I HAVE adjusted the idle screw...it doesn't matter...out of nowhere it just raises or drops for no apparent reason...most of the time, its fine...



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Stuart S
1987 Trans Am LB9/WS6
1986 Camaro IROC-Z
OEM Posterchild of the soon to be Infamous Long Island Crew

Ed Maher

I don't really understand the question. It seems as simple as a sticking fast idle cam to me. I get this from the sometimes it kicks down, sometimes it doesn't remark. If you mean the idle will mysteriously raise way up after having warmed up and kicked down, well, that would be weird. I'd still think it was the fats idle cam getting stuck on a low step, then the idle speed rises as the engine warms up.
If i'm way off base you'll have to explain better
...ed

MRZ28HO

I said Fast Idle cam not idle screw, that is totally different. The idle screw is on the driver's side where your linkage is, you meant the other one (fast idle set screw), I hope. Also if your choke is adjusted improperly this will cause the symptoms your are experiencing. Spray some Liquid Wrench on the choke linkage rods as Ed suggested also.

[This message has been edited by MRZ28HO (edited September 11, 2000).]

Stuart S

That's what it's doing...very infrequently, but it does...



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Stuart S
1987 Trans Am LB9/WS6
1986 Camaro IROC-Z
OEM Posterchild of the soon to be Infamous Long Island Crew

Drew305

Stuart,

Just to clarify, does the idle only climb on you, and you keep turning the adustment screw to successively lower settings? Or one day you will have to turn it down, and then later it will idle too low, and then you need to turn it back up?? Are you adjusting the idle screw, or the position of the anti-dieseling solenoid?

The only ideas I have right now is the possibility that the anti-dieseling solenoid is periodically getting power and causing the idle to raise, and then shorting out and causing it to drop back down. Or the possible sticking throttle linkage, but adjusting the screw shouldn't be even a temporary fix for that. Intermittant vacuum leak is a third possibility, possibly related to the HVAC control position, or Thermac flapper position?

Pretty much just grasping at straws here, sounds like a relatively elusive problem.

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Pimped-out '85 Z

Ed Maher

I still vote for a ticking fast idle cam. Like i said at the end of my post, if it got stuck on a low step, the idle speed would drop down after giving it some gas when it was a little warm. Probbaly to a normal level. Then, as the engine fully warmed up, the idle speed would rise back up. Depending on how it is set and where you expect it to idle this could be anywhere from 1000-1200 rpms, maybe a little higher.
Easy way to check this. Next time it does this, take off your air cleaner. Behind the choke housing there is a little trapezoidal tab. Push down on it. If your idle drops, your fast idle cam is sticking. if it was already at the bottom, a strange vacumm leak related to an emmisions system is where i'd look next. That's why i always gut all my non-essential stuff.
If it is sticking, i would NOT advocate using any liquid wrench on it. Oiling it will prolly make it worse as it will collect dirt and funk. Instead, clean it real good with carb cleaner. If it still does it you'll need to take the choke off and see what is making it hang up. Sometimes it's nothing, and just a simple disaasembly/reassembly will appease teh carb gods.
ed

Stuart S

Thanks guys...

Disco Man

Stu,
If it is not the fast idle cam, it will be your choke. A simple one notch clockwise turn on a qjet choke, may fix your problem.



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Disco Man

1982-83 Cross-Fire Trans Am Site: http://members.xoom.com/the305cfi/

1979 (L78/W72) 10th Anniversary Trans Am
1982 (LU5) Trans Am

Disco Man

Ed,
When the choke is faulty on a Qjet, the idle can be all over the place even when the car warms up. I had a qjet that would idle at 650 rpm one day the next day 1,200 rpm. Sometimes I would start the car and it would fast idle at 1,500 rpms and I could not kick the idle down until I turned on and off the engine and then it was fine. Other times I would start up the car and it would fast idle at 1,500 rpm and then it would drop after about 15 seconds to curb idle and then it would stall. It turned out to be the choke causing the problems. Sometimes re-adjusting the choke will fix the problem other times the choke is beyond adjustment and just needs to be replaced.


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Disco Man

1982-83 Cross-Fire Trans Am Site: http://members.xoom.com/the305cfi/

1979 (L78/W72) 10th Anniversary Trans Am
1982 (LU5) Trans Am

Ed Maher

I agree disco man, a bad choke coudl do the same thing, but it would still show up by testing the fast idle cam. If he pushed the fast idle cam down by hand then it kicked back up (after the engine was already warmed up) then it would be obvious the choke was not coming off. I didn't want to have to hold his hand through this entire process though, if he would have discovered this himself he might have learned something. Besides, in my expereince, once a choke goes, it is gone. Since this seems intermittent, it's not real likely. Not saying it couldn't happen, just that it wouldn't be my first guess. Either way it's a pretty easy diagnosis.
ed

Disco Man

Ed,
I agree with you 100% that is why I said "If it is not the fast idle cam, it will be your choke."


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Disco Man

1982-83 Cross-Fire Trans Am Site: http://members.xoom.com/the305cfi/

1979 (L78/W72) 10th Anniversary Trans Am
1982 (LU5) Trans Am

Disco Man

Ed,
One thing that I forgot to mention. You are right usually when the choke starts malfunctioning it is gone for good. However sometimes the tightening it by turning it clockwise will fix the problem. I have fixed a few by doing this, when others said the choke needed to be replaced.

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Disco Man

1982-83 Cross-Fire Trans Am Site: http://members.xoom.com/the305cfi/

1979 (L78/W72) 10th Anniversary Trans Am
1982 (LU5) Trans Am