What spark plug do you guys recommend for my E53 4.8is?

[fishhouse4]

Originally Posted by StephenVA

Resolved?

If not.....Any codes?
At Idle take you hand and place it in front of the each exhaust tip. Which side is giving you the stumble?
Tip: Double check your plug gap on the NGK Iridium IX as it should be 0.044" and make sure all the small wire connectors are tight at the coil tops. Make sure the coil boot is on the plug not next to it in the hole.

There is always small chance of a bad new plug. Reasons: Poor handling anywhere in the distribution supply chain path and of course by the installer/DIYer. The manufacturing process quality control has approx .0001 to .001% failure rate. Most are installer errors sent back as defects. Seen one too many over the years.

Report back.

Still fighting this. Took it to a second shop yesterday with a certified BMW tech and he was stumped. Said he'd never seen anything like it as was "intrigued".

His initial intake smoke test did not find any vacuum leaks. Maybe I did a better job getting the valve cover on then I thought!

Have an appointment next week for further testing and diagnosing with him.

Problem is drivers side for sure. Vibrates worse on that side and white smoke out exhaust now on that side.

I pulled the new belt off this week hoping that was the issue. Does the same with main belt on or off...so struck out there as well.

In the meantime I'm going to do what you suggest. In fact, I have new plugs (the original NGK versions), new coils and new VANOS solenoids on the way. I will replace all of those in the meantime and cross my fingers one of those is the culprit. Will be sure to double check gap and all correctly.

It just doesn't feel like a typical misfire or stumble (and no engine codes)...so I was thinking it was something else. But at this point I'm willing to explore any option. Basically back tracking and replacing every affordable part that I touched during the initial work.

Stay tuned...

[fishhouse4]

Originally Posted by StephenVA

Resolved?

If not.....Any codes?
At Idle take you hand and place it in front of the each exhaust tip. Which side is giving you the stumble?
Tip: Double check your plug gap on the NGK Iridium IX as it should be 0.044" and make sure all the small wire connectors are tight at the coil tops. Make sure the coil boot is on the plug not next to it in the hole.

There is always small chance of a bad new plug. Reasons: Poor handling anywhere in the distribution supply chain path and of course by the installer/DIYer. The manufacturing process quality control has approx .0001 to .001% failure rate. Most are installer errors sent back as defects. Seen one too many over the years.

Report back.

My vibration and misfire-like issue FINALLY resolved today!!! Turned out not to have anything to do with plugs/coils/vanos/sensors etc after all.

Instead, just an embarrassing screw up by me during reassembly. More info on my full thread at https://xoutpost.com/1138858-post12.html