IVC humming noise/rough & high idle (M20)

Post Fri Jun 30, 2006 10:35 pm

My M20's not run for a year (now resides in my marlin sportster kit car). I've been letting it run for a bit and warm up the last few days. Its always idled around 1000RPM since I originally bough the donor (111k on the clock). It seems pretty rough on idle but fine when you rev it a little. I cant take it on the road yet as the cars not quite done and not road legal.

Its has new:
BBTB
blue temp sensor
rotor arm / dizzy cap
timing belt
plugs & plug leads

The inlet manifold and ivc have been cleaned out.
The wiring between the injectors/temp has been cleaned out but im going to try soldering these tomorrow.

The exhaust is blowing a bit as its a tad rusty having spent a year round the side of my house - im getting a new exhaust made next week.

The IVC making quite a noticeable humming noise when you put the key in position 2 - is that normal? I've read up on a lot of posts with the solution being blue sensor, wiring or IVC. Im starting to think it may be the IVC.

Post Sat Jul 01, 2006 2:28 am

I think it does make a noise in pos 2 as i thought mine was knacked as was doing the same but someone on here said its meant to be like that

Have you cleaned it out? What like are the plugs?

Post Sat Jul 01, 2006 9:02 am

I'll take the plugs out and have a look, they are new ones. Yes I have cleaned the ICV out, however I'll take it off and give it another clean today.

Post Sat Jul 01, 2006 4:11 pm

Bottom of the plugs were black/carbon colour - a sign of over fueling I believe.

ICV is completely clean.

The plug connector for the temp sensors/injector rail have been replaced with round bullet pin connectors. The old one were in pretty bad shape.

I've also adjusted the valve/rocker clearances.

The engine is much quieter now, but the idle is now just under 1000 and it sill sounds a bit rough. I think a lot of may be to do with the old exhaust blowing around the manifold and top connection.

I'll be getting a new exhaust made next week so will see what its like then.

I may try a different blue sensor, the new one I got from motormec is not a bosch one.

Also how can i tell is the resitor mod has been made to the ECU? I'm think perhapse in always on cold start mode?

Post Sat Jul 01, 2006 10:31 pm

Whatever plug was worst it maybe a case of gunk in your injector, best give them a check too, try spraying some brake cleaner in them, can sometimes remove the worst debris

No idea about the resisitor mod though

Post Sat Jul 01, 2006 11:01 pm

Thanks for your help and tips

I've had a looking inside the ECU but the only evidence is that it used to have a different chip in there, no other work or dodgy solder joints.

I will pull the injectos out and a have a look, although I did give them a good clean with carb cleaner when I had the inlet manifold off. All the plugs seem pretty equally coloured.

I've bought some tesco super and put a bit of redex in there. The engine runs much better and picks up nicer but its not done anything to the idle.

Post Sat Jul 01, 2006 11:31 pm

http://www.pelicanparts.com/BMW/techart ... ooting.htm

Post Sat Jul 01, 2006 11:57 pm

Excellent, im going to go through that tomorrow. I need to order to bits anyway

Post Sun Jul 02, 2006 10:15 am

knackered AFM?

Post Sun Jul 02, 2006 6:02 pm

Mystery sort of solved. There was a giant leak by the break servo/brake master cylinder after plugging that up it runs sweet

Still idles at 1000rpm so I might swap out the hoses mentioned in the article above anyway.

It sounds like there may be a leak in the pipe that goes from the rocker cover to the intake but its really hard to tell with the rest of the engine noise.

On minus side my clutch master cylinder packed up after filling and bleading the system, that was the only thing stopping me from taking it to the end of the drive way and back!

I need to measure and check the afm, didnt have time for that though.