Re: Exhaust changes causes problems
 

Roger,

Its possible that the less restrictive exhaust may have caused the AFR to lean out somewhat. Can you get a scantool on it? The 4500rpm region is where you might expect Knock Retard to come in and the hesitation could be the ECM pulling timing out.
Just possibilities which need to be verified by a scan.

Re: Exhaust changes causes problems
 

I am new to all this, I will see if any of the z guys around me have a scantool that might be willing to help. I just ordered the Helms manual, so that shows you I am little behind.

Re: Exhaust changes causes problems
 

you might want to invest in a setof ngk irridiums. i switched to them and just love em

Re: Exhaust changes causes problems
 

Hypertech makes a fuel gauge with a hose long enough you can gently shut the hood on it and still see the gauge while you drive. Screw one end on the shrader valve (make sure it dont leak) and watch the gauge under load.

Re: Exhaust changes causes problems
 

Thanks for the info. Sounds like something I can pull off. Where is the best place to buy a Hypertech fuel gauge? I have looked on line and can't find one for a 91 corvette.

Re: Exhaust changes causes problems
 

I think I bought mine from Mid America Motororks, Im sure there are cheaper places some of the guys know of but thats where I got mine.

Re: Exhaust changes causes problems
 

lazy 02 sensor.
New free flow exhaust, 02's are not warming up as fast or staying cool.

Just a guess.:wink:

Re: Exhaust changes causes problems
 

Correct me if i'm wrong,we have heated O2's and they are on the OE CAT/manifolds.

Also to run lean with CATS on i don't think that would be unless bad pump filter or injectors.
Our Z's run a bit rich from the factory around 12.6-12.8 AFR
I don't really think his running that lean to cause it with just an exhaust install since he also kept the CATS
Look at Marc H's web site on this.

Heck i ported the heck out of my intake,heads,63mmTB,headers,B&B's
X-pipe no/CATS and still didn't need to adjust fuel.

Pete

Re: Exhaust changes causes problems
 

Something else I didn't think too much about was the last couple of times I was letting the car warm up, it died. This has never happened before, but I just thought it was the cooler weather. The thing is it died after about 3 minutes. Could this be fuel related rather than cooler weather related?

Re: Exhaust changes causes problems
 

Sounds like primary fuel pump problem. When cold started, both the primary & secondary fuel pumps operate until the coolant temp reaches 167F, then the secondary pump shuts off.

You need to run the fuel pressure check described above.