Car Runs Weird After Cam And PI Swap

[cMcKinney97-GT]

Ok here's the deal a few weeks ago i did the pi swap and put some Hitech stage II's in as well. She runs great from 2,000 rpm's and up but below that it shudders and hesitates like no other. And she won't idle when it gets warm but will when its cold? I've replaced the IAC valve checked for vaccum leaks and don't know what wrong? Could it be running to lean? Could it be that i just need to take it to the dyno? Any suggestions would be great cause i'm at a lose on what it could be??? Thanks

 

[scupking]

Doesn't mater what parts you replace trying to fix the problem. You need a dyno tune with any aftermarket cam or your car won't run right.

 

[cMcKinney97-GT]

Well i knew i was going to have to get it tuned i just didn't know if i was over looking something. The idling when it was cold but not when it warms up is throwing me off. When it warms up sometimes the shudder almost goes away completly but, not all of the time, there is just no consistancy in what it does and when it does it

 

[wmburns]

I can not emphize strongly enough about vacuum leaks. Even a tiny leak can cause issues. At low air flow rates, a vacuum leak will have more impact because as a percentage, the amount is more.

Clean the MAF!

Start by monitoring the TP MODE PID. Check to see that it says C/T (closed throttle) when the throttle is actually closed. Play with the throttle checking that the PID matches the throttle's state.

Next disconnect the IAC electrical connector. The idle RPM's should drop (or the motor die). Monitor the IAC duty percent to see if it changes in response to changing motor load (AC on/off). Report.

When cold, the PCM is going to have a slightly higher idle than when hot. Perhaps some improvement can be had by increasing the idle by a small amount.

This may not be a problem that can be fixed by swaping parts (dyno tune as others have suggested). A PI motor likes more timing than a Non-PI motor. Consider that a stock 97 PCM has a timing curve set up for an Non-PI motor. You now have a new head/cam combination that flows more air. Such cams are well known for affecting low end torque. Add to this an increase in CR (from the PI swap) the load tables may just be too far off.

 

[Rickyll7]

its not likely a fuel issue as your o2s will send feedback to the computer which will make the appropriate adjustmets if your not at wot.

I think its more likely that you have some fairly hot cams, and heads for how your pcm is tuned from factory and you need a tune to adjust timing and iac parameters.

 

[navarro98gt]

You need a tune.

 

[COramprat]

Friend had issues with Comp 270's until he got a tune. Likely you need the same.

 

[scupking]

As I said in my first post. You need a tune. I have the same cams as you and I would randomly stall until I got a dyno tune. Don't waste your money on replacing parts when you don't need to.

 

[cMcKinney97-GT]

Well thanks for the info i guess i'll be going to the dyno within the next few weeks