misfiring 1987 325is

[1987325is]

I have a 325is and it has a bad misfire bettween 2500-5000rpm
and it also has a rough idle.

I have replaced
fuel filter,plugs

I have inspected the
wires
cap
button

in good shape

what is doing this?? At slow aceleration it does not misfire but
at WOT it flat out sucks
thanks for info
Eric

[craigieeb]

Hi mate, firstly, welcome to the zone

your problem could be an air leak? have a "good" look at the rubber intake hose that is between the throttle-body and your air flow meter, it could be split somewhere, if it is split it would cause the symptoms you have,

you can pick a new one up from bmw for around £12+vat

[1987325is]

thanks for the warm welcome,
also thanks for the advice, I looked at the air intake and all looks good??
anything else
thanks in advance
Eric

[Dunx]

When warm - do you notice a loss in power?

[Palazzo]

Had a similar problem on ours, under hard acceleration, would cut out, then start/cut out/start etc, like a really bad miss. Turned out the insulation had worn out on an ignition wire (somewhere in the front), would swing back, touch the block and short out, then car woud hesitate, wire would swing free and start again etc etc

[MONSPORT42]

Still sounds like an air leak. Check all the small pipes and connections around throttle body and the one to the rocker cover and give the ICV a good clean, too. And the air filter. On the mark 2, not sure about the mark 1, there's a connection block located under the inlet manifold which has connections for the injector circuit which is worth a once over and clean. The dust boot on mine came away and it got wet in there with rough idle and running the result.

[1987325is]

thanks everyone for your replies,
Ill check out everything on the intake to the TB
and Ill also check the wires.
if you can think of anything else please let me know.
Eric

[1987325is]

still no luck car runs horrible bettween 3500-4500 rpms
is it the ecu
it also has a erratic idel
thanks

[MONSPORT42]

Sounds like the misfire is only at the upper range now (lower revs got better?). If you're sure the air intake is sound then it's probably going to be fueling. It's possible the fuel pump is not supplying enough fuel under load. First sign is noise. They usually whine when on tick over when on the way out. I've had 2 go on my cars; on one the car cut out when taking hard right hand corners the other gave erratic revs. Could also be a dirty fuel filter which is easy and cheap to replace.
It might also be electrical but it would unusual to just have a fault in a given rev band as you describe. Likewise with the ECU. The only other thing I can think of is changing either the orange or blue temp sensor in the thermostat housing. One sensor tells the ECU how much fuel it needs for the given temp the other feeds the temp guage but I can't remember which one is which! Again it's still strange that it's only in that rev range.
Hope this helps.

[1987325is]

well I replaced the fuel filter last week and no change.
and the fuel pump does not make a whine or any noise that I can tell. soo I am stuck in a pickel. if anyone thinks of anything let me know please.
thanks

[craigieeb]

still no luck car runs horrible bettween 3500-4500 rpm

blocked/dirty injectors??

anyone

[Brianmoooore]

See no mention of checking the throttle position switch!