2001 ZTS Idle Issue

[s22225]

The idle when you start the car or even have it warm while still in park will seem fine for a moment and then will briefly drop 100 or so RPMs and then within a second be back to a normal idle. I have cleaned the IACV, MAF, replaced pcv hose, spark plugs swapped, replaced DPFE, cleaned TB as best as i could without removing anything more than the snorkel.

Any ideas? vacuum leak? tps? The problem is only present at idle.

Thanks.

[Sponsor]

[cyfocus01]

Have you tried with A/C on? If idle is better with A/C, IAC is working. easy starting point.

[s22225]

The idle seems ok with the AC on, but everytime I stop at a traffic light etc..the rpms will slightly dip for a second and the engine feels pretty rough and then it normals back out. The AC fan also seems to slow for a split second and resume in in sync with the engine roughness. I think maybe the radiator fan comes on each time the car is stopped at a light with the AC on and it's pulling electrical load which perhaps is doing something funny with the engine. The alternator is newly replaced last year and hasn't exhibited other issues.

Thanks.

[s22225]

I've also noticed a big drag on the engine with the AC on going uphill. Maybe the new alternator is not strong enough? or something with the connections?