2002 S80 2.9LSmall Jerk In Engine When In Idle

[divinedavis]

Now the check engine light is on. A hissing sound from the computer box. Can it be the Electronic Control Module?

[searay440]

Have you tried unplugging the MAF sensor? If the engine runs normal with it unplugged it's a good sign it's the MAF sensor. Just a thought.

[Oly_850]

Definitely get the codes read at your local auto parts store write them down and report back.

[divinedavis]

Fuel trim system too lean
Random multiple misfire
Cylinder 5 & 6 misfire

[divinedavis]

My car started to hiccup when I was driving it. I was going pretty fast because I was late for a dentist appointment.

[chrism]

You could try moving the #5 and #6 spark plugs to cylinders #1 and #2, and move the #5 and #6 coils to cylinders #3 and #4. Clear the codes and run the car and see what new codes pop up. If it's still showing misfires on #5 and #6, I'd start thinking about a leaking intake manifold gasket at those two cylinders.

You say it misses at idle for sure, but when driving does it miss worse at light throttle or heavy throttle?

[divinedavis]

Light throttle. Or when I'm just sitting there. I changed all the spark plugs already.

[chrism]

My experience has always been that a missing ignition (spark plug or coil) will be worse under heavy throttle and a bad vacuum leak (like the intake manifold gasket) will be worse at idle or light throttle. You could try swapping coils around to see if the fault code moves to another cylinder. If the code remains at cylinders 5/6 that reinforces the gasket theory. Some people will test for a bad intake gasket by taking a propane torch and cracking the valve open (no flame) and running the tip around the manifold/head interface while the car is idling. If the idle smooths out and/or increases a bit while you're doing that, chances are the propane gas is being drawn into the intake stream via a bad gasket. I've never triad this myself.

The reason I'm so adamant about a gasket leak is because if there was a vacuum leak somewhere else in a vacuum hose or whatever, it would likely affect ALL cylinders. You know, a leaking injector seal is another possibility, but suddenly on two cylinders at the same time??? Ehhhh, I don't don't know about that.