Rough Idle on 2000 Bonneville (Misfire)

[indyracer]

Code indicates misfire on cyl 6. I have moved coils around to see if the problem follows the coil and it didn't. I am thinking of moving the fuel injector and see if it follows the injector.

I was thinking maybe a vacuum leak. I have been pouring over vacuum hoses hoping to see something. Nothing yet. I do wonder, if it is a vacuum leak, would the misfire always be on cyl 6? So far the misfire has always been on cyl 6.

I have had the upper and lower intake gaskets replaced so it is very possible a vacuum hose got damaged and I just haven't found it yet.

My main question is if there is an easy way to check vacuum?

Thanks,
Tony

[maxwedge]

I would think that this is a misfire issue, usually a vacuum leak would set another code. Keep looking fo a wire/plug/injector issue, especially if you can feel it at idle.

[HotZ28]

Originally Posted by indyracer

My main question is if there is an easy way to check vacuum

I use a propane torch (unlit) while the engine is running. Open the valve and direct the tip around all vacuum fittings & hoses. If rpms increase, you found a leak! Have you check the resistance on the #6 plug wire? Is it rubbing on the 02 sensor wire?

[03CavyMan]

A vacuum leak would probably throw a fuel trim lean code, I can't see it throwing a misfire code on one cylinder. Pull the plug out and see what it looks like, check the plug wire and make sure it's not rubbed through anywhere. Then put the wire onto the plug, ground it and roll the engine over and see if it's sparking. If you have spark then you've more than likely have a fuel issue like a clogged injector.

[indyracer]

I have changed plugs and wires when this all started. I will check the wire and plug again. I could have a bad wire. The wires are AC Delco and the plugs are not Bosch.

The car runs rough at idle, but as soon as you give it any gas it runs great. Although, when you get to about 70 MPH it starts to run like crap again. I can see that maybe a fuel injector could have a problem. Like maybe it isn't giving enough gas at idle or at higher speeds. What doesn't make sense is while cruising down the interstate at 70 MPH the rpms are in the same area or higher as accelerating from a stop and it runs fine during acceleration but not cruising at 70 MPH. Weird I say. Really confusing.

Tony