blownrunner

Hey everyone. 91'Z. Just went through the engine and refinished it to include the cam covers. Eliminated secondaries and installed Haibeck chip. Did B&B headers and exhaust. New injectors and pumps. Brand spanking new throttle body. Got it all back together seems to run fine after I had to do a reset on the IAC valve (kept stalling). Went through whole car and this was the last thing done. Start and idles 1100 RPM when cold and down to 700 or so when hot.

Have one issue: when coasting in neutral like exiting freeway ramp the engine will go from 800-1100 RPM and back every couple of seconds until the vehicle stops. Then it looks like it stays at about 700-800 steady, even with A/C kicking on and off.

I don't know if it did this before with the stock quiet exhaust but I notice it now because the B&B is louder. Marc also added the anti-backfire for the exhaust.

This normal? The VSS signal goes to the ECM so I bet the ECM is trying to adjust something to get a certain parameter in spec. Any ideas where to start?

Dominic Sorresso

The free wheel coast down surging is fairly typical particularly after increasing air flow. The rpm stabilizes once the car reaches a particular speed where the calibration calls for closed throttle spark advance, which stock is 16* and 5mph. A cammed motor presents more of a challenge but the effect can be mitigated or reduced through tuning.

blownrunner

Think it happened less when the A/C was off, Still getting the white smoke out the exhaust when flooring it from a stop. Hope it's just running a little rich. My Viper doesn't do that though.

When you say tuning and extra flow, maybe I should adjust the idle on the throttle body screw. I know the primary throttle plate isn't totally closed so I could start there. Nice to know this pretty normal.

Dominic Sorresso

By any chance did you remove and reinstall the injector housings?

blownrunner

Nope, not this time around.