Slight misfire

[mcbonio]

My 325i has a slight misfire, if you rev it slightly with your hand on the engine you can feel the engine popping or jerking slightly. 2-3 times a second. You can also hear it at the backbox..

What might be causing this?

[mcbonio]

Anyone??

[HairyScreech]

Is it a misfire or is it afterfiring in the exhaust from how rich these things can run?

[mcbonio]

This is what I'm trying to figure out, I can only describe it as a the engine blipping.... like this.

brrr. bub..brrrrrrrr.... bub bub... brrrr

[Speedtouch]

I'd first check the spark plugs are the correct type and properly gapped, then do a compression test.

[ETERNITY]

Afm?

[mcbonio]

Could be the sparkplugs, I replaced them in January with NGK ZGR5A plugs. They were cheap so I'm guessing a bit crap too?

[Speedtouch]

They should be fine, but it may be worth trying another set, just to rule out the possibility that one or more may be duff.

[mcbonio]

A few months back my blue coolant sensor was acting up making the car run rich. I changed it and it sorted it out, you think this period of rich running could of fouled the plugs?

[Speedtouch]

It would have cleared them by now, assuming you've used the car regularly since.

[mcbonio]

The engine has 108k miles, would an injector refurbish help?

[HairyScreech]

You need to diagnose the fault first, there is no way we can help until we know if its a lean condition, a rich condition or a spark issue.

[mcbonio]

I think its a rich condition as it smells a little rich when its running.

Its had all new spark plugs, dizzy cap and rotor arm and blue temp sensor.

[Brianmoooore]

The engine has 108k miles, would an injector refurbish help?

It's certainly overdue, but whether it would help with this particular problem is impossible to say.

[mcbonio]

So what could this problem be? Anyone have an inkling?

[Brianmoooore]

Start with the injectors, and take it from there. The £66 investment will soon pay back in fuel consumption.

[ETERNITY]

The engine has 108k miles, would an injector refurbish help?

It's certainly overdue, but whether it would help with this particular problem is impossible to say.

I have heard injectors being cleaned can help improve

Mpg
Drivalibility
Performance

Can it really make this sort of difference
Or is it just hyped up

Thanks

[capri_rob]

Its true but best combined with a freshly serviced engine or you're just blunting the effects of having the injectors cleaned by leaving tired/badly adjusted components elsewhere

[mcbonio]

Would a slipped timing belt caused these slight misfirings and rich running? Say if it had slipped a tooth?