Running out of ideas on what to check on this so here we go. I recently changed plugs and wires on my 04 as the last set had about 80k on them at least according to the records I have. I had to swap out a motor mount so figured it was a good time. I went with the factory recommended champions and NGK wires from rock auto. I also replaced the no name coils with Bosch OE units. A couple of days after this work I noticed a rough idle that is more pronounced when in gear.

Symptoms:
1. I can feel the misfire only at idle but not always. It happens more often when at operating temp.
2. I have no codes
3. I get a slight hesitation when giving it gas slowly up to around 1k rpms. Has that misfire seat if the pants feel.
4. No misfires at higher rpm
5. I can hear an slight RPm drop but the gauge is steady on the cluster.
6. the misses are random, like 1 mis then smooth idle for a few seconds then 2-3 misses in a row then smooth again, etc.

I have checked:
1. The tightness of the upper intake bolts (yes all of them)
2. Blocked off the SAI vacuum port and then the brake booster port to eliminate a vacuum issue with the plumbing.
3. Checked spark at a couple random cylinders.
4. Checked the gap on all spark plugs.
5. Checked a couple plugs are not fouled in anyway. The previous plugs though worn looked normal.
6. Borescoped each cylinder before install all
plugs. All looked normal.
7. Power brake test and no misfires under load up to 3k rpm.

Any help is much appreciated.

Rich

 

Are any of your HT leads arcing? Maybe try watching it idle when it’s fairly dark.

 

Good suggestion but just went down and checked in my pitch dark garage and no light show.

 

Maybe fresh gas with a can of injector cleaner (e.g. Techron).

 

Thanks, that was done a couple months back. I have filled up since this issue first started. Does anyone know what sort of real time data the D2 supports? Per cylinder misfire counter, injector data, power balance, etc??

 

Just to close this thread out, this was a multipart problem.

1. I was shipped the incorrect OE spark plugs from AB. This might have been a manufacturer problem, the boxes where for Champion 7070 but the plugs themselves where RC10 instead of RC11.

2. I had a suspected sticking or clogged injector which seemed to be resolved after a can of BG44k

3. The NGK ht wires I got form RockAuto are crap. I broke down and bought the OE set from AB. $300 for the set…ouch.

After a few trips around town and highway so far so good.

 

Thanks for the feedback.

Regarding scanning, the OBD can show which cylinder is misfiring.

 

I had a similar problem and cleaning my MAF sensor seemed to fix it. Be sure to use MAF sensor cleaner not electrical cleaner or anything else. Or replace the MAF sensor if cleaning it doesn't work.