Biochem

I have re-built the q-jet with all new gaskets. I re-did the intake manifold gaskets. I have tried the spray test like 18 times. I still can't find a vacuum leak that would cause my idle to be as bad as it is!

It gets better when it warms up, but I still have to have the idle at 900 rpms. Any lower and it may stall when it surges. It is getting worse in the mornings now that it is getting cooler too. It's pissing me off!

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1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock... all the suspension stuff... 9-bolt posi disk is in... K&N filter... 93 octane...

I got the GO... I need the SHOW... Interior is next!

Jester

It really doesn't take much of a leak to mess things up, and they can be really hard to find. A good way to test is to richen up your idle and open (closed butterflies) your idle speed screws all the way. If it still runs...you know you have a leak somewhere. if it won't, them maybe you have a different problem.

Engineboy

Block off your brake booster hose. That won't show in a "spray" test.

"1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock... all the suspension stuff... 9-bolt posi disk is in... K&N filter... 93 octane"

Did this problem just start or have you had this problem since the motor swap??

Do you still have the EGR??



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ASE Mechanic/Machinist/Smog Tech

1999 NBM Trans Am, flowmaster,FRA,Pro Kit,BMR STB, polished calipers.
1986 Chevy 3/4 ton pick up,flowmasters,4.10s,
1981 corvette FOR SALE
1995 ZX6R,Yosh,D207s

GO #3

Biochem

It started after the swap... or at the very least became evident at that time. It almost feels like the engine is not balanced right or something. I am going to check the plugs some day soon, but I think it is carb-related.

I tightened the brake booster and replaced the hose, but I'll check again. YEs I do still have th EGR... NC is a land of Natzis when it comes to emmissions stuff (they look for it). I replaced it once, but wouldn't mind blocking it off until e-check time.

Disco Man

Even the very smallest of vacuum leaks can cause bad erratic performance from your Qjet. Since you rebuilt your carb with all new seals and are confident that there are not leaks around the carb, check all the hoses. After a carb rebuild, if there seems to be a vacuum leak, usually it is a hose that is the culprit. If you have the cash just replace all the hoses, it is a cheap insurance policy and it 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

One thing I forgot to add, check that EGR valve too. A bad EGR valve will also make your car idle rough and run the way you described.

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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

FastBroker

Intake gasket could be leaking into the lifter valley area, which would not show up in spray test. If this is happening, one or more of your plugs/plug threads will have a little oil on it/them. I'd pull the plugs and check them, also install an Air/Fuel meter to see if you are really lean...

Biochem

Fast- That was what I had thought, but when I replcaed the intake gastkets again, it still is there.

I replaced all the rubber hoses, but will double check the connections.

FastBroker

I suppose it could still be there even though you replaced the gaskets... The following could cause this:

intake is warped from bad torquing
Head intake surfaces warped/dirty/mismachined
heads milled a lot and intake now misaligned
intake gasket misaligning upon installation
Cylinder blowby that is excessive, as on a new/rebuilt engine