Hunting/surging idle at cold start and a hesitation

[jimtash]

Developed a problem that includes an idle that drops down to around 400 RPMs then goes back up from cold start. Also has a definite tip in hesitation as soon as it's given gas. Getting no codes and disconnecting various sensors doesn't improve anything. Also will backfire into the intake depending on how fast the throttle is applied.

Hooked up a vacuum gauge and it's a steady 15 in/hg which is low. Plugs are in good shape as are the wires. Distributor has been replaced and still no change. This has been steadily getting worse as it used to just hesitate but now the cold start idle is hunting.

[yellowrob]

Probably the TPS or vaf.

[Brizzy]

Cold start would make me think iac

[branscoset]

ahem..iacv...clean..or replace yolo

[jimtash]

Cold start would make me think iac

IAC cause throttle hesitation as well?

[Brizzy]

It can.

It changes your idle speed for all different kinds of situations. Like when turning at idle , ac, and cold starts

[jimtash]

Today it started and idled fine. Also noticed that the hotter the engine got, the better it ran. But it feels really low on power like it can't breathe.

[jimtash]

OK, I've come across a big vacuum leak at the throttle body and also the IAC. Took everything off and apart to clean it and now it's got a huge vacuum leak especially where the IAC attaches to the throttle body.

[yellowrob]

Did you change the gasket? You can use a little rtv.

[jimtash]

Didn't change the gasket and used RTV. Thing has a huge leak and when I took it apart, noticed dried coolant all over the gasket. Not just where coolant passes through.

It's a KL47 throttle body BTW. On a KLG4 intake.

[96prizobe]

still having issues? ever figure it out? I'm having a similar issue, thought it was iac but replaced and still same except mine is better when cold worse when warm and only under 3k rpm

[yellowrob]

How old is your vacuum?

[jimtash]

I got it running much better. Still has a slight hesitation though and the RPM's drop down when the AC is first switched on. Replaced the alternator belt along with the harmonic balancer because it was wobbly. Base timing was also adjusted because the old balancer was off.