MyE28.com

Hi All,

Sorry, Bently still not ordered. I'll do it today.

What is the spark plug gap for an e28 535i?

Craig,

It's also listed in your owners manual. I don't have either my Bentley or manual accessible right now.

0.7mm +/- 0.1 mm, or .027" +/- 0.004".

I gap 0.8mm

Awesome, thank you. I also don't have the owners manual :-(

Soon to come, I just got it's TRX boots off and into a nice set of 15" e34 mesh wheels, all in good time.

Thanks again,

Craig,

I like my plugs on the wide side of that spectrum. It seems to run better and idle smoother (as smooth as an M30 goes, which isn't too smooth). Also, the WR9LS plugs are the only plug you should use.

Steve likes the NGK ZGR5A plug for the M30 engine. You know the one S. Haygood. He has stated fewer bad plugs. Like any of us have had a bad Bosch WR9LS. But I believe him.

The plug gap should be set to .032. This is based on a tech session I went to in 1989 that went over the M30 and a basic tuneup. A&E Motorsports in NorCal presented the info and said as the previous poster said, smoother idle, better burn. The ignition system can easily handle this gap, making a bigger spark for better performance.

Just wanted to input my findings to reiterate the above post. I just put in NGK BPR5ES plugs on my 535is, gapped to .028 like the NGK site says. The car was misfiring like crazy. Found this thread and regapped them to .032 and now it runs like a dream. Thanks!

Any other feedback with wider spark plug gap? I have typically run .028 but am having a misfire near idle on an early 1979 m30 (m90) and haven't traced it to anything else after going through the ignition system, Fuel system and checking for vacuum leaks.

Maybe I should try the wider gap just because of this thread...

My other e28s, m30 and s38 never seemed to be bother by spark plug gap so it may just be wishful thinking on my part...

tschultz wrote: Jul 02, 2024 10:42 AM Any other feedback with wider spark plug gap? I have typically run .028 but am having a misfire near idle on an early 1979 m30 (m90) and haven't traced it to anything else after going through the ignition system, Fuel system and checking for vacuum leaks.

Maybe I should try the wider gap just because of this thread...

My other e28s, m30 and s38 never seemed to be bother by spark plug gap so it may just be wishful thinking on my part...

In my M30 and M10 I use 0.8 mm (.032) after read a UK post saying 0.7mm (.028) is "not good" for those engines.....both are running very well, smooth idle.

Maybe I've just been lucky, but I've found these cars, both Motronic and L jet with electronic ignition to be extremely forgiving on plugs, both Bosch coppers and NGKs. Now going back to ancient history, M30s with carbs and points/condneser ignition, they were hard on plugs.

On my '85, 535i I passed smog one time, comfortably, with 45K on NGK plugs.