Terrible idle

[dh86svo]

One days everything was fine and the next it wasn't. I just got the battery charged and tested because it was drained. So I started it idled fine warming up and drove good. Then I was letting it sit in the driveway after running it hard, and all of a sudden it started idling like it was missing. I pulled the plugs, checked to gap, and checked to see if maybe they were fouled but everything looked fine. Once you get the RPMs up, everything is fine. Runs down the road fine. Anyone have an idea of what I might need to check next? I have had the intake pipe off and the throttle body looks to be clean so I would think the IAC would be ok? I know I have a small vacuum leak somewhere that I need to find but I had the leak before this started happening. I did not change anything is the tune on the idle side of things. I am leaning toward a spark issue? AFRs seems to be the same other then when it misses it goes rich.

[Stinger]

Could be a blown headgasket. I'd pull all the plugs, hold the throttle wide open, and do a compression test.

[dh86svo]

Aug 24, 2020 12:46:56 GMT -5 Stinger said:

Could be a blown headgasket. I'd pull all the plugs, hold the throttle wide open, and do a compression test.

Lets hope this is not the case. Wouldn't the car run hot or maybe even smoke if there was a blown head gasket?

[Stinger]

There are many different ways for a headgasket to blow and they all have different symptoms. Last two I've had here locally did not steam at all and didn't run hot. Only sign was a slightly rougher idle for one and slightly rougher idle and small coolant leak on the ground for the other.