2G Strange misfire

[V8killerturbo4]

I’ve recently rebuilt my 1996 GSX engine, I have some weird problems that I can’t figure out.

When I start the car it starts with no problem idles at about 1000 perfectly. However if it sits at idle for a few minutes it start to misfire and has a very choppy idle, as soon as I drive away the misfire clears and it runs perfect again.

The only thing I changed about the rebuild as it was a stock rebuild was deleting the EGR and charcoal canister. One other issue I have has to due with vacuum, on a cold start everything is fine and it has a perfect vacuum of 20. When it’s started at temperature however it won’t read any vacuum until about 1 minute of idling/driving.

Other than these issues the car has been running amazing and as long as it doesn’t sit idling for too long it has no misfires or issues.

 

[steve]

The only thing I changed about the rebuild as it was a stock rebuild was deleting the EGR and charcoal canister. One other issue I have has to due with vacuum, on a cold start everything is fine and it has a perfect vacuum of 20. When it’s started at temperature however it won’t read any vacuum until about 1 minute of idling/driving.

Where do you have the gauge connected? If it's after the FPR Solenoid (between it and the FPR) it may not see vacuum for awhile on warm starts because of how the FPR Solenoid works.

 

[V8killerturbo4]

I’m honestly not sure but I do know it never had this issue before I rebuilt the engine.

 

[steve]

Well I'm betting you touched quite a bit in the process, so you think that might have changed something?

 

[V8killerturbo4]

Not sure, I’m gonna take some time today to figure some stuff out though. Thank you

 

[V8killerturbo4]

Thank you Steve! You were right about the placement of the boost line, I moved it to the throttle bottle and now it reads vacuum all the time!

 

[steve]

Great, now to the other problem.

What besides the MAFT Gen 2 are you using to tune?

 

[V8killerturbo4]

I’m not using anything to tune, the car is completely stock

 

[steve]

Sorry, only saw the 1G in your profile and it slipped my mind this was a 2G.

On a stock car idling at 1k is a sign of a problem, usually an air leak and since you deleting the EGR and charcoal canister in addition to rebuilding the engine I'd try Boost Leak Testing with soapy water and see if you find anything.