325i hesitant and almost undrivable when it gets un to temp

Post Mon Apr 20, 2015 10:08 pm

Hi all

I have a 325is and have had a few problems recently due to what I thought was a misfire. I have since replaced the spark plugs and leads, crank sensor (cable was damaged), blue coolant sensor and battery. The car starts first time and seems to runs well and revs ok. When I take it out on the road its abit lumpy to start with when accelerating and gets worse as it warms up to until after 1 mile it just hesitates and I cant increase the revs but if I pull away over 3000rpm and stay on the throttle and change through the gears it goes well. I am going to start to work through the Haynes manual testing with a multimeter to try and find the problem.

Just thought it was worth a try to see if anyone has any suggestions. Any help would be appreciated.

Thanks

Jonny

Post Mon Apr 20, 2015 10:12 pm

First thing that came into my head is an air leak, have you checked for split pipe work between afm and throttle body, engine breather pipe work and any vacuum hoses?

Post Mon Apr 20, 2015 10:42 pm

I have checked for split pipes only visually and added a couple a jubilee clips to tighten up some of the connections.

Post Mon Apr 20, 2015 11:43 pm

Post facelift car? Check the plug and socket under the inlet manifold, especially under the rubber boots, that connects the injector loom to the main engine loom.
It is common for the wires under this boot, especially the engine temp. sensor wire, to rot through. There was a TIS issued by BMW concerning this.

Post Tue Apr 21, 2015 7:46 am

I have a facelift car. I haver had the socket apart but not really had a good look at for corrosion. I shall check it tonight. If they are rotten is it a case replacing them or to make a repair?

Thanks

Post Tue Apr 21, 2015 9:43 am

Before you touch anything, you should perform the 'blue temp. sensor' procedure AT THE ECU PLUG, as (I hope) detailed in the wiki.
The plug and socket themselves are not usually the main problem. It's the wires under the lower boot that fail as a result of trapped water and electrolytic corrosion.
Repair varies from replacing the injector loom and engine loom completely, through splicing in repair sections, to removing the plug and socket completely, and splicing the ends together. A potential problem with the latter is that the corrosion tends to travel along the copper of the wires, under the insulation, making soldering difficult.
I wouldn't recommend cheap crimp terminals as a method of repair.