Rough idle, cylinder 4 may not be firing

[streetspirit7]

I've got a 97 240 with a KA24de engine. The car has a rough idle. With the car running I pulled each plug wire individually and noticed a drop in idle on all but #4. I did this same test with the MAF unplugged and noticed a drop on all four cylinders. I did a compression test and had between 170-180 on all four cylinders. Any guess as to what my problem might be?

[OutToWinPAHC]

Well check 4 for spark, if its there check for fuel.

[scotty-2-forty]

I've got a 97 240 with a KA24de engine. The car has a rough idle. With the car running I pulled each plug wire individually and noticed a drop in idle on all but #4. I did this same test with the MAF unplugged and noticed a drop on all four cylinders. I did a compression test and had between 170-180 on all four cylinders. Any guess as to what my problem might be?

Pull the injector plug from #4 while running and see idle changes. Pull the spark plug, inspect it and if in doubt replace it. Same for the wire. Good luck; keep us informed.

[EnjoiNismo]

Yes check spark, then check fuel.

Most likely a clogged injector, happens quite often.
Pull off injector #4 and swap then injector with another one from #1-#3 and see if the cylinder runs normal now. If so its your injector.

[streetspirit7]

Ok, I swapped the injector with another one I had lying around and that did not help. I swapped the plug and wire with the #3 cylinder that did not help. I took the plug out, grounded it and started the car, it sparked, so I have spark. Not really sure how to tell if the injector is working properly though. To make the problem even more weird, I hooked my multi meter to my plug wire to check RPMs. I was at around 780, then I pulled the injector plug and dropped to around 690, plug it back in and back up to 780. Then I pulled the plug wire out, there was no change in my idle. Does that make any sense to anyone?

[AZ89two4Tsx]

Check for a vacuum leak.

When I power washed my engine I knocked a few vacuum lines off and it completely screwed up the idle and gave the symptoms that you are having. Just make sure they're all hooked up and none are torn.

[streetspirit7]

Well, I think my problem is the gasket between the intake and the head. I can hear an air leak down in that area, so I sprayed some starter fluid right at the point where they connect. When I did this I heard it suck up the starter fluid and my idle went up. So I guess I need to take off the intake and replace that gasket.

[thomasjamal]

Well, I think my problem is the gasket between the intake and the head. I can hear an air leak down in that area, so I sprayed some starter fluid right at the point where they connect. When I did this I heard it suck up the starter fluid and my idle went up. So I guess I need to take off the intake and replace that gasket.

Well an intake manifold gasket will only run you $5, so I'd definitely say try it.