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Discussion Starter · #1 · (Edited)
Hello, Thank you for click this topic,

First I appreciation this forum, because I really need help for this issue,

My E30 already drove 5 years in my hand,

seems 2 years ago, My E30 first misfire on the highway,

in misfire condition, gas has no any response,

then I keep rolling, (no stepping clutch), Instrument cluster looks like no any thing happen,

when I keep the Vehicle rolling for the 10 -15 sec ago(70-80 KM) , have some chance to wake up Engine,

due to the misfire some times occur on week, some times occur on 2 month later, even 6 month not happen,

and usually also have shaking symptom, feels like engine stop and resume on 1 sec within,

cause the troubleshooting is very hard, Could suggest me next step? as follow is my guess,

1. Pulse sensor (2017.12.30 replace)
2. Coil
3. fuel pump(2017.7.24 replace)
4. DME

Misfire history
2021/01/11 misfire
2021/01/13 misfire x2
2021/01/20 shaking.misfire
2021/01/28 shaking.misfire x2
2021/04/15 misfire x2 full fuel
2021/05/04 misfire x4 low fuel
2021/05/06 misfire full fuel
2021/07/06 shaking x4
2021/07/15 shaking x multi
 

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D'oh, You Kids!
1984 633CSi, 1985 635CSi, 1985 325e, 1987 325is, 1993 325is, 1995 318is, 1995 M3, 2003 F150
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Welcome to Bimmerfest!

This is almost certainly an electrical issue, which points to relay failure. Try replacing the main relay. Relays can momentarily lose contact and then reestablish contact while driving.
As you already know, diagnosing an intermittent problem is very difficult precisely because it IS intermittent. Unfortunately you have to continue as you have been, replacing one thing at a time, but I would concentrate on the electrical system. Any other cause would not be "self-correcting" and cause a stumble that resolves itself while you drive.
 

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Discussion Starter · #3 ·
Welcome to Bimmerfest!

This is almost certainly an electrical issue, which points to relay failure. Try replacing the main relay. Relays can momentarily lose contact and then reestablish contact while driving.
As you already know, diagnosing an intermittent problem is very difficult precisely because it IS intermittent. Unfortunately you have to continue as you have been, replacing one thing at a time, but I would concentrate on the electrical system. Any other cause would not be "self-correcting" and cause a stumble that resolves itself while you drive.
Thanks for your reply, is helpful for me,
I every day driving this E30 close 40 kilometer, issus happen probability is mystery...., I like "self-correcting" to means this symptom, it's so proper,
I remember main relay already replace in the 2019, whatever, I will replace again,
but if replace main relay issue still, what is next replace parts, Could you suggest? Thanks!
 
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