1) Check resistance across coil pack for cyls 1-4. Defective coil could be causing you to lose spark, however I'd expect you to have trouble with #4 also.
2) Check compression on all 4 cyls (pull fuse for fuel inj before
doing this) -- if compression in 1 is normal and all are about the
same, probably not a valve/ring issue.
3) Injector on 1 may be clogged/defective.</span>
2) Sounds like possible vacuum leak...had any engine work done lately? Spray some throttle body cleaner around the intake manifold and the throttle body while the engine is running. If the rpms go even higher, you've found your leak.
3) Check/Replace ECTS -- Engine coolant temp sensor -- when they
fail, they often read way too cold and cause the fuel mix to be pushed
too rich -- increases idle. This is a $40 DIY that will resolve your
issue or rule out the ECTS as the cause (which for S cars is a critical
I found this on another forum and they said it took care of the problem. I would suggest checking for a vacuum leak at the intake manifold gasket. With engine idling, spray brake cleaner or throttle cleaner in the gasket area near cylinder #1. If a vacuum leak is the case, there should be a reaction depending on what you spray it with. For late 99 -02 SOHC 1.9s with P0301/P0507- check the intake manifold gasket at the number 1 runner.
I just sprayed some Throttle Body Cleaner at the #1 Cylinder Intake
Manifold and the engine stalled right away! No such effect on the
other cylinders... Carefully just spraying the Fuel Injectors didn't change engine
I tighten the manifold bolts but there was no change...
Looks like I will be changing the Intake Head Gasket this weekend.
I'll post the results.
Thank you Rory_W and derf.... looks like I saved a trip to dealer and a few hundred bucks.
Looks like the problem has been corrected. I replaced the Intake
Manifold Gasket last night and the idle came back to normal and the
trouble codes are gone. The old gasket was definitely damaged on
Cylinder #1, causing a large vacuum leak.
Thank you for the information.
BTW: The AC had stopped working as well and now it is running again, I
thought the two problems to be unrelated, but apparently they weren't.