e36m42 jerks when cruising

[selespeed]

the engine will sometimes die when idling. but when i am cruising it, say below 4000 rpm it jerks wanting to die but then continues. i also experience this when idling, idles ok and then suddenly it wants to die drop in rpm and then goes up. occasionally dies.

it feels as if there is no current going to the sparks or something!

however, under hard acceleration, i can't feel this. what si wrong? anyone has had this strange problem?

selespeed

[DesktopDave]

Do you have any codes set? Could be a bunch of things...isolate it. How old are the spark plugs? Do they look OK? If one is different, how is the coil pack and coil drivers?

The E36 is infamous for ignition key problems, and related EWS problems with the ring antenna not picking up coded keys.

Could also be a weak signal from a dirty crank sensor, or possibly weak fuel flow from a dying FP relay, plugged filter or bad fuel pump.

[Warsteiner]

selespeed,

I had the exact same symptoms and found the connectors/wires on top of the fuel pump to be loose. Always thought it was the fuel pump when it was actually the electrical to the fuel pump. Replaced the whole unit with a new OEM unit and never had the symptoms again.

Just my .02

Cheers,
~Ralph

[selespeed]

Do you have any codes set? Could be a bunch of things...isolate it. How old are the spark plugs? Do they look OK? If one is different, how is the coil pack and coil drivers?

The E36 is infamous for ignition key problems, and related EWS problems with the ring antenna not picking up coded keys.

Could also be a weak signal from a dirty crank sensor, or possibly weak fuel flow from a dying FP relay, plugged filter or bad fuel pump.

thanks Dave;

i am just thinking it's probably due to those things you mentioned. but my car has no EWS. so this is ruled out.

1. about spark plugs. i used NGK BKR6EQUP since May 2014 and 53,000 km later today they're still great. I have had very good experience with NGK plugs and never had to change plugs even after 100K km. in my view probably the best since i started using these in my Alfa days and never had problems even after 140,000km. so this is quite unlikely.

2. coil packs and the wires maybe culprits. not enough current? i might try to test my spare paks. but for the wires, do you guys replace with new ones?

3.  Dirty crank sensor? not sure but i had a NEW one since 2013 during engine rebuild.

4. weak fuel flow due to dying FP relay. this is interesting. which relay is the one controlling this? this is easy swap

5. fuel filter since december 2013 and 68,000km -- how often should this be changed?

6. fuel pump is NEW since exactly 3 years ago.

7. 2 months ago, i checked the diagnostics and found engine error code. no idea what that means.  also didn't manage to take down the code details...

lately, the problem is a bit less. but last month it happened frequently. idles at around 900 and then suddenly it sputters and wants to die dropping to like 300 but managed to go steady. this repeats until it dies...

also lately i can feel it tends to jerk more at higher rpm than before

[selespeed]

selespeed,

I had the exact same symptoms and found the connectors/wires on top of the fuel pump to be loose. Always thought it was the fuel pump when it was actually the electrical to the fuel pump. Replaced the whole unit with a new OEM unit and never had the symptoms again.

Just my .02

Cheers,
~Ralph

Ralph;

what item did you replace? do you have the part # from bmwfans.info? would be nice to solve this once and for all.