rough idle after head gasket job *SOLVED*

[benniku]

Hello everyone,
So after 2 months I finally finished the head gasket job on my 94 850 turbo. I fired it up last night and it all went smooth aside from all the smoke from the cleaning agents. That all wore off, bit the idle is still rough/lumpy
The car has great power (not pushing it to hard until after it breaks in) and is super smooth above 1000 rpm. The tach needle I does not jump around like it usually does with a vacuum leak, so I am kind of at a loss. A 325 memory failure code came up, but I am pretty sure this is because the ecm was disconnected for so long.

So how long should I wait/drive to allow the ecm to remap before looking at other stuff. And what should I look at?

[jblackburn]

2-3 days is what mine usually takes to figure out its idle. ~50 miles or so.

I'd start with looking at air hoses and such. Make sure there are no leaks at the intake manifold gasket.

[benniku]

Sounds good. Ill give it a good starting fluid spay down tonight.

[benniku]

I checked all the vacuum lines and sprayed everything with starting fluid and no change. I have been seeing posts on the forum about crank position sensors, but I can't see how mine would work fine before the head gasket work and not after. I would actually say that the idle is not so much rough as it is uneven. When I put my hand in front of the tail pipe I can feel the consistent pressure of the exhaust for a couple revs and then a little hiccup, then smooth, and a couple more hiccups.

[erikv11]

Did you do anything to the ignition system? If new plugs, what brand?

[benniku]

I used the same plugs and wires. Plugs were standard bosch oem replacements from IPD. The cap and rotor were replaced not too long ago as well. I guess it could be the coil, but I think that would effect the performanceover the entire rmp range. I pulled the cables on the battery to do an ecm reset
Ill post the results

[erikv11]

OK, I was just looking for ideas.

Maybe it truly is coincidence and not due to the head gasket job; if it is only at idle then it could be the IAC needs a cleaning. Do the throttle body too if it hasn't been cleaned recently.

[benniku]

I cleaned the throttle during the head gaske, so ill try the IAC. I noticed some arc marks on the outside of the coil too.

[benniku]

SOLVED! I cleaned the IAC with carb cleaner and tested the resistance between the pins and everything looked fine. I IAC was not gunked and moved freely, so I didn't expect much. I installed the IAC and fired the beast up...no change. I decided to run over the vacuum lines since I was getting an "ERG system leak" code. I found that I had switched the hoses on the ERG Vacuum Regulator. I flipped them around and fired it up. Now it's purring like a brand new engine! Thanks everyone for your help!