Slight cut out when on freeway

[xavier]

When driving on the freeway at about 100km my 323i seems to cut out for a split second. It then goes back to normal. Any idea where to start looking for the cause? Everything else is running fine.

[zaust]

When you say cut out. Engine dropped power or total loss of everything including electric (dme).

[Brianmoooore]

What does the rev. counter do during these incidents?

[gmf_uk]

sorry to hijack this thread, i had the same issues after a 3 hour journy south all was going well then on the way home about 2 hours in to the journey my car started missing, spluttering, rev counter seemed to be steady tho, was about -2 outside at this time, once i got home took the car for a drive during the next day all was fine, went out again last night and was missing again, any advice? Cheers

[Bristol_Jer]

My 320i did this on it's last journey before the lump got ripped out. It cut out a few times for a split second, accompanied by a small backfire, never bothered finding out what it was though!

[xavier]

The revs drop right down, but the radio lights etc stay on

[Speedtouch]

Could be all manner of things, but most likely a loose electrical connection somewhere.

Check the engine to body earth strap, and all connections to the ignition coil, and the distributor cap, rotor arm, HT leads (measure their resistance; it should be around 6,000 ohms) and spark plugs.

If it persists, try another ignition coil, then DME relay.

[redcar]

When was the Dizzy cap and rotor arm last replaced?

[Brianmoooore]

The revs drop right down, but the radio lights etc stay on

In that case it's an engine electrical fault. DME relay is a possible suspect, and is cheap and easy to change, and after that it could be a crank position sensor,or, more unlikely, the ECU itself.

[xavier]

Cap replaced one year ago, but the new rotor arm was not the correct height, so I just cleaned up the old one

[Speedtouch]

I would take a close look at the centrifugal rev limiter built into the rotor arm - perhaps the spring has stretched over the years. It can be safely removed, since the ECU has its own built-in rev limiter, which gives a far more progressive cut-out.

[xavier]

I don't think mine has the rev limiter. It is a 1984.

[Speedtouch]

A 1984 L-Jet car will have a centrifugal rev limiter built into the underside of the rotor arm; pull it off, and if you can see a spring-loaded mechanism then that is it.

It can be safely removed - as mentioned above, there is already one built into the ECU, so it is superfluous!