I have an L98 in my Formula

Car when cold will idle rough and stumble when applying gas, when its warmed up - runs great (except for a surge) will Idle from 800-1100 ish back and forth.

Could this be a bad CTS?

I know these things can do some crazy stuff, I just want to know. The motor sat for a long time before I put it in, I don't know if the sensor is gumed up and not reading right?

Sound probable?

 

To me,it sounds like either a vacuum leak or problem with the IAC.

 

with TIMMYS89GTA sounds like the IAC needs cleaned.

 

Failed to mention, Brand new IAC and its been set properlly, new TPS, also adjusted, TB has been cleaned and decarboned aswell as plenum when I did motor swap.

 

Vehicle has custom tune done, #24 injectors, AFPR - 47PSI at idle.

Runs awesome, pulls hard as hell right to 5000RPM, but just surges at idle when warm, and is stumbley and hesitates when cold as if its flooding

 

a friend of mine had a similar problem,we ended finding a crack in the IAC housing (thus causing a vacuum leak).Hope this helps.

 

That would make sence Tim, I appricate the advice.

Where abouts was your crack. I will look at it on my lunch brake, and possible use some JB weld.

Was it on the circle portion where it threads in?

 

it was on the bottom,we replaced the plate that bolts to the TB.

 

Ill check that ill spray some wd40 under that plate and see if the idle changes.

 

Did you ever find the problem?

 

heheh, his crack was on the bottom....

I believe I'm having a similar problem so when i get off my crack i'll have a look once all tpi stuff is off and hopefully save myself some time and money on other parts.