E36 2.5 won't idle properly

[V8mate]

I've got a '96 323i (2.5) which had the M50 inlet manifold swap carried out a couple of weeks back together with a big bore throttle body.

Took it out for a little run last weekend and when I got home it was having difficulties idling - the revs falling away to stall point and then snatching back up to c.1200 and then bobbing about in between etc.

I took a look at the inlet pipes and the the small pipe from the main throttle body boot and the small pipe which comes up to it from below both had some splitting/perishing.

Replaced the full tb boot and lower pipe today - started and idled fine - then took it for a short run (c.8m) and the problem returned on the way home. I could actually feel the revs fluctutating not only at standstill but even at low speeds - pulling away from lights etc - as I go up the first couple of gears I could sense the revs surging and retarding until the car was more mobile.

Any ideas?

[buggalugs]

If you hadn't just had the manifold swap done I'd say try running with the O2 disconnected to elimitate that. But since you have and the swap involves loads of home made pipes and connections under the manifold around the idle valve I'd go over those with a fine toothed comb instead

[Buzzkill]

Just out of interest, how much of a difference is there top end in your view and is the loss of urgency in the midrange noticeable?

[V8mate]

anonymous said:

[redacted]

It was Alpina's kit fitted by the man himself!

[4rephill]

Could be a pipe not sealed correctly after the manifold swap or one of the manifold seals not sealing fully (very unlikely though, knowing Alpina527's work!).
More likely either a duff Idle control valve, a faulty camshaft sensor or could be dirty/faulty MAF.

[phelix]

and the throttle pot

[0191mark]

I had a widely recognised identical issue on a Clio a couple of years ago, which was solved by thoroughly cleaning the throttle body which got contaminated because it was situated in the inlet manifold, and due to a design fault, oil leaked into and pooled in it.

Additionally, I replaced the inlet manifold gasket at the same time, so for very little outlay the problem was solved. Of course, Renault advised others that they needed new ECUs, looms, ignition packs etc. Hopefully it'll be an equally cheap fix.

[V8mate]

Thanks all.

Still not sure what was causing it, but a nip round to check every pipe, clip and lead seems to have sorted it