Help please with a few new motor gremlins

[alanw6]

Hello all,

I just spent some time searching and didn't find anything to be a good match to the issue I'm experiencing with my newly installed combo (less than 20 miles so far).

Upon a completely cold start, the engine runs very poorly. It searches for idle, almost stalling but never actually shutting down. If you attempt to blip the throttle, a backfire in the intake or two may happen (usually just one smal pop, maybe two).

Here's the strange part: If I let it warm up for maybe 3 minutes, it idles and performs perfectly, with no issues and a rock-solid idle.

The car has been dyno tuned, where it put down 409hp and 423 tq. New combo is:

306 ci with JE pistons/Eagle H-beam rods/stock crank/TFS stage 1 cam
AFR 185 heads (larger chambers)
SCT BA-2400 MAF, UPR powerpipe, Vortech V-2 S-trim @ 8 psi, 70mm TB
FRPP shorties, Bassani X (cats) and Bassani catback
255 intank, T-rex inline, Aeromotive AFPR, 42 lb injectors, stock line and rails
MSD 6AL, etc.

Any ideas? I'm happy with the overall manners and power, but the cold start behavior seems like it needs some attention.

Let me know if you need specifics to answer, and I'll provide them.

Thanks in advance!

Alan

 

[Jaswir]

check out ur spark plugs... i had a problem popping noise that sounded like it came fromt the instake and turned out to be my spark plugs.... also check out ur MAF and TPS

 

[alanw6]

check out ur spark plugs... i had a problem popping noise that sounded like it came fromt the instake and turned out to be my spark plugs.... also check out ur MAF and TPS

Plugs look good. They were replaced on the dyno (from those used during initial startup and setting), and it was tuned immediately. The car was warmed up properly when tuned, so I bet it's in the tune (the cold start crankiness).

MAF is brand new, and reading correct voltage. I'll check TPS, but it was within range when locked down. If TPS was off, how would it explain the perfect manners after a short warmup?

I'm going to keep going through everything, checking up for anything out of the ordinary.

One theory I have working is possible adjustments to fuel delivery in the cold start strategy in the EEC-IV, due to the bigger injectors? Just a hunch, does it hold water with any of you?

thanks...