sir lancelot

Hey y'all. I had my ignition coils replaced yesterday bc of a cylinder misfire. After i got them replaced, my car has been idling pretty rough. It will get as high as 1250 rpms, drop down quickly to like ~250rpms, and then shoot back up. It has just been fluctuating anywhere between that range.

Can any of yall help me out on this? Im thinking it was the dude who put the coils on

cliffyk

You had them ALL replaced because of "a misfire"?

Replacing the passenger side COPs requires that the air intake tube be removed, make sure it has been reinstalled correctly with the PCV and IAC feed tube properly inserted;

or,

it may be that the battery was disconnected by whomever did the work and the PCM needs to learn the new idle trims (though this does not generally create the profound variances you report);

or,

it may be that the battery was disconnected and the PCM is trying to learn the new idle trims with a sticking/sluggish IAC that was on it's way out anyway--the OEM IACs in our cars tend to act up/fail between 70 and 100k miles...

sir lancelot

Thanks for the reply man.

My apologies. I only had one coil replaced. So is there anything you recommend that I should check for? I did check the intake and everything looks good.

AuburnStang00

Sry to hijack..mine did the same things..i replaced my battery and its gotten better..just occassional slight dip not near as bad...how do you replace the IAC? is there a write up?

cliffyk

The IAC can be tested by unplugging it while the engine is hot and idling--the idle speed should drop and the engine may even stall. If it does not then the IAC is likely sticking or sluggish.

The electrical resistance between the two terminals should be 6.0 to 13.0Ω, the resistance between either terminal and the IAC body should be > 10kΩ.

Replacing it consists of:

1. Disconnecting the battery;
2. Unplugging the electrical connector;
3. Disconnecting the feed hose;
4. Removing the two machine screws that fasten it to the upper plenum;

4-3-2-1, in reverse, to install the new one, torque the screws to 89lb-in...

sir lancelot

I figured it out. There was a disconnected hose that i didn't catch the first time i looked for problems. Problem solved. She's idling real nice and smooth now. Thanks for your help cliffy.

cliffyk

Cool, more often than not intermittent problems are something simple/overlooked...