Solved - Jerking/Kangarooing/Rough Running

Sun Apr 16, 2006 7:28 pm

Don't Motor without your Rotor...

The M20 325i hadn't been running well around town for a while. On cold start I had to hold second gear as it would jerk like crazy if I changed up to third too soon.

I had a big problem today with jerky running. The idle was fairly rough and I was going to clean the Idle Control Valve. Then I drove the bugger. At about 2000 revs the engine would jerk like mad.

Yesterday I had been driving like a getaway-driver for about 60 miles and noticed that at full throttle acceleration there was a slight hesitation at the higher rev range. Today the rough idle and jerking was so bad I supposed that I had broken something.

I read lots of theads (with titles similar to this thread) and there was lots of information about temperature sensors or air leaks etc but fortunately mine was a simpler fix (and Halfrauds even had the parts in stock!).

Firstly - and fearing the worst, I checked as best as I could, for air leaks by spraying WD40 around inlet manifold and air flow meter pipes but no clues became evident - such as a smoothing out, or picking up of the idle speed.

I had a feeling this was ignition related so I took off the distributer cap and was amazed to find my rotor arm in about sixty broken pieces and just a cord haning out of the end, with the pickup area completely destroyed. About the front third of the rotor arm was missing! Yet it still drove!

Well obviously I changed the rotor arm and distributer cap as this looked quite old and unhappy, and changed the plugs too. Now it runs as sweet as a nut.

I put those WR 78 Bosch Plugs in (even though they are only sold in sets of four in Halfords - so have two spare) and they seem ok. I only hope they do improve performance or fuel consumption to justify their cost. I am curious about these plugs so I will raise a question about them in another thread.

Hope this bit of information is useful to someone with a similar problem.
Many thanks to all those out there who participated in previous threads as this gave me a nice logical plan of attack and I fixed the car in no time.

Cheers
Toby

Sun Apr 16, 2006 11:02 pm

Glad you sorted it. Any kind of hesitation or jerkiness should lead to an inspection of the rotor and dizzy cap.
Faulty blue temp sensor causing overfuelling can be diagnosed by looking at the plugs. They will be black and sooty.

Fri Apr 21, 2006 10:34 am

Cheers Brian.
Yeah the plugs were slightly black - I suppose due to the fact that spark was poor and fuel was remaining unburnt. There is still a slight, almost unnoticable hesitation, so I'm drawn to changing the leads next which have been previously replaced by the last owner with non BMW ones.

Cost being a factor I will wait until the new plugs wear out and change the leads then.

Fri Apr 21, 2006 7:34 pm

My problem is now solved too! I put the standard chip back in and it's much better now. Infact, now it feels like the accelerator pedal has a light, middle and full throttle whereas with the chip it was near enough an off/on button.

I think I prefer the car standard and unmolested. Its still a powerfull car that can go when it needs to.

Fri Apr 21, 2006 10:57 pm

sibzilla wrote:My problem is now solved too! I put the standard chip back in and it's much better now. Infact, now it feels like the accelerator pedal has a light, middle and full throttle whereas with the chip it was near enough an off/on button.

I think I prefer the car standard and unmolested. Its still a powerfull car that can go when it needs to.

which chip did you have?

Sat Apr 22, 2006 9:53 am

No idea, it was an ebay 'fast road' offering. I don't know where the map originated, it's entirely possible that it was made by the seller?