HELP!

Post Sat Nov 30, 2013 5:09 pm

I have a 325i as a daily driver. Today I got in and started as normal...

Sounds like an american V8 and is very lumpy / rough at low revs...

Appreciate any help and advice.

Post Sat Nov 30, 2013 5:13 pm

quick check :

Spark plug leads
Air intake boot (Back of AFM to throttle)

Post Sat Nov 30, 2013 5:18 pm

Blowing exhaust/manifold?

Post Sat Nov 30, 2013 5:21 pm

Blown exhaust, or you've blown a spark plug out of the head (you wouldn't be the first).

Post Sat Nov 30, 2013 8:04 pm

willnz wrote:Does it run ok at higher revs?

Not as rough but not normal...?

Post Sat Nov 30, 2013 8:20 pm

plugs, leads and air intake boot all look ok.

Can't get to the exhaust or manifold easily so cannot see anything suspicious. Back box all seems ok but my exhaust does look like it could do with an upgrade.

Post Sun Dec 01, 2013 9:04 am

So it turns out that removing lead 5 makes no difference. Have a spare lead and that made no difference either. Now I just need to figure out how to get the spark plug out because it just aint budging!

Post Sun Dec 01, 2013 1:15 pm

Try applying PlusGas or similar releasing fluid, and undo it with the engine warm.

Post Sun Dec 01, 2013 4:59 pm

Speedtouch wrote:Try applying PlusGas or similar releasing fluid, and undo it with the engine warm.

Right, got the plug out and replaced it, but made no difference....

Post Sun Dec 01, 2013 5:15 pm

dizzy cap ???

Post Sun Dec 01, 2013 5:16 pm

Could it be the injector? Or low compression on that cylinder causing a miss or dizzy cap

Post Sun Dec 01, 2013 5:47 pm

Have you confirmed you're actually getting a spark on that cylinder, by placing the plug on the rocker cover then cranking?

If there's no spark, it's an ignition issue.

If there is a spark, it's a fuel or compression issue.

Post Sun Dec 01, 2013 8:59 pm

I guess it will be paying a visit to my mechanic tomorrow

Can't complain as it has given me faultless daily driving pleasure for 2 years

Post Sun Dec 01, 2013 9:25 pm

Years ago I had a misfire on a 320i. Bmw couldn't find the fault and it turned out to be "arcing" on the dizzy cap. You are looking for 'veins' on the inside surface(closest to the windscreen).

Post Mon Dec 02, 2013 3:12 pm

gromgsxr wrote:Could it be the injector? Or low compression on that cylinder causing a miss or dizzy cap

Ended up being the dizzy cap, massive crack across the top.

Typical, I have a spare one and it is the only thing I did not get a chance to check before sending it to my mechanic this morning on the way to work.

Anyway problem solved for cheap this time round. Although he recommends doing the exhaust in 3 months when it is MOT time as he reckons it is on its way out.

Thanks for all the help gents!