Thread: Surging on cold startup / down on power

Lately I've been having an issue where the car surges at idle when I start it for the first time in the morning. Idles down to where it almost dies, then jumps up to around 1200 RPM, then up and down for about 4 or 5 minutes til it warms up.

I can also tell its down on power while driving around. Not as quick off the line and kinda sluggish on the highway.

Also I've noticed a kinda motor vibration when stopped at a stop light or something. Just not as smooth as before.

Within the past year or so, I have replaced the MAF, fuel pump, fuel filter, air filter, and the plugs and wires were replaced about a year and a half ago.

Where should I be looking first to try and get this cleared up?

vac leak, bad o2, or bad egr

Originally Posted by 01GTP

I bet your upper plenum is cracked, when it is cold the gap is bigger, and when it warms up the crack seals.

Upper Plenum as in my supercharger?

Originally Posted by 01gpgt01

Surging idle is common in moded cars. Usually tune related.

It's not really modded that much...3.4 pulley, SLP intake and cat back, MSD wires and Autolite 104's

Bought a retuned PCM by DHP from the pfyc store March of '08

Problems just started recently within the last 2-3 weeks.