At wits end. What is going on here..

[deezil]

have a 2000 regal gs that has a rough surging, bogging idle when I first start it. It's bad enough it will die if it is in drive. I can rev it to 1200 rpm for a minute or so and then it settles down into a decent idle like there was never a issue.

Runs fine after that. If I kill it, it will do it again hot or cold. I can then rev it to 1200rpm for a minute and then it is fine again. It makes a huge sucking sound while it isbogging and surging. Huge sucking sound goes away once it gets to holding a steady rpm.
I have tried several mafs off running cars they all do the same thing.

Engine was replaced with a low Mile unit and has ran great since it was put in. A case learn was supposedly not done when they did this. It seemed to run fine since the swap. And these symptoms don'think seem to be case learn symptoms do they? It is not showing any codes. I have checked for vacuum leaks but do not see anything Or hear anything when sprayed around with carb spray

Any suggestions?

[bobc455]

I'd be looking for vacuum leaks.

Any error codes? How is your MPG? Engine temp?

[Fivefingerdeathpunch]

IAC could be a issue aswell.

[deezil]

I Sprayed around with carb cleaner but it never had any effect. It throws no codes even when it is chugging and puffing down to 300 rpm. Sounds like it has a huge cam.

Engine temp is fine once it evens out and I can actually drive it.

[deezil]

Changed idle air control valve tonight with a new one I had. And put new o rings on the injectors. Neither of those helped.

[wowitsfast]

did you make sure the new iac pin was out the same as the old one? as i understand it that can cause it to not work right

[deezil]

Yeah its the same . Even tried a known working one from a a friends Park Av before I bought the new one.

[Reptile]

Tried unplugging the MAF?

[deezil]

Yeah it doesn't change anything. I swapped it out with the one from the same friends Park ave ultra as well. Same rough idle until I raise the rpms for a little bit then it is ok.

[NebTurboST5]

I you let it idle long enough after the raising the idle dies it stay smooth or does the issue come back? Will autoparts store handheld show you ltft?

[99GT2dr]

Unplugging front 02 sensor make any difference?

[deezil]

When i Start it it runs ok for maybe half a minute. then it goes into the Bogging and surging. Like a rump rump rump... I Counteract it by raising the idle to 1200 or so for a minute and then i can let off the gas and it settles back to normal idle like nothing ever happened. I Can drive it with no issues then. If i Shut it off for say a hour i Have to go through it all over again.

Sorry had to type all that out holding my 2 year old.

[deezil]

Unplugging front 02 sensor make any difference?

Nope, does the same thing.

[99GT2dr]

Couple other easy/cheap things I'd recommend is pulling/cleaning the TB ($3 gasket) and checking the pcv valve. I've heard the egr can cause similar issues, but I always ditch mine so I don't have any first hand experience with one going bad.

[deezil]

Couple other easy/cheap things I'd recommend is pulling/cleaning the TB ($3 gasket) and checking the pcv valve. I've heard the egr can cause similar issues, but I always ditch mine so I don't have any first hand experience with one going bad.

It has the egr delete done on it and has run fine without it. Ill pull the tb and clean it. It's pretty clean though.

[Reptile]

Other than actually hooking a tuner up to it, I got nothing.
The start/running for half a minute thing says that it runs fine until it goes into closed loop.

So, yeah.

[NebTurboST5]

yeah but when he un plugs the up stream O2 that should also put it in open loop and it still does stupid **** then too...