If the car is under light throttle and a moderate load, say going up a slight hill, and in OD I will get a surge like the TC cannot make up it's mind.

I had installed new O2's and made some programming changes while I fixed the intake oil leak. On my first few test drives the car was great. The programming changes I made were idle, fan temps, removed knock retard and I increased the MAF tables by 10%(due to ported MAF). I stopped to get gas this morning and noticed that I had not retightened the gas cap from releasing the pressure in the tank. Never set the SES light either.

Now that I have gotten gas and tightened the gas cap to three clicks I am now getting the surge again.

WHY??

I though the system has to be capped on the filler end to work correctly. I am going out in a bit to grab a bite, I am going to loosen the gas cap so that it just stays on and see what happens.

Anyone with an explanation for this?

 

My car did that once. I kept loosening off the cap and driving, tightening , driving , eventually it went away. Hoping so eh?

 

Test drive complete -- NO SURGE

Ok I give up, do I have bad cap? Is the fuel pump getting weak? I guess I need to do run with the fuel pressure guage, the cap on tight and see what happens.

Anybody have any suggestions?