Rough idle and bouncing revs

[murphykidd]

Can't seem to find the problem to my rough idle, done everything I can think of , change plugs,leads,ignition pack, cleaned ICV, checked for vacuum leaks, and still no joy to solving the rough idle.. At it again today and the car now gets a fit of Reving up to 1100/1300 rpm when it's idling and sit there few a few secs and drop back down to about 700-80 again.. Anyone help me out here.? Patience is running thin at the moment all week trying to sort this idle and just seems to be gettin worse (318is)

[bugs]

a cheap quick check is to use both jump leads to earth engine from two different sources as a bad earth can spike voltage and increase and decrease revs lights ect check voltage with load applied during hunting revs and look at brightness of lights ..
extra fuel is required to make an engine rev more something is supplying extra fuel .
I have seen plenty of steel fuel shut off cables melted as they were the only earth left for the starter when the main chassis one corroded and visibly looked ok from the outside.
try removing the air filter and see does it suck any engine oil as it will rev a little with extra fuel/oil created by extra suction from a blocked filter .
any fuel /diesel shop should tell you fairly quickly . regards bugs

[shaunokeeffe]

interested in hearing cause of this. Trying cure 318is with rough idle, seems be driving ok though hitting limiter early. Ownervis getting it plugged in some evening to check knock sensor, crank sensor etc

[Venom]

interested in hearing cause of this. Trying cure 318is with rough idle, seems be driving ok though hitting limiter early. Ownervis getting it plugged in some evening to check knock sensor, crank sensor etc

Was it a conversion? Speed sensor on the diff if not.

[shaunokeeffe]

Replacement engine was fitted by past owner but was driving grand for her for past month

[shaunokeeffe]

[murphykidd]

I'm handing it over to another lad this week to have a fresh head look at it and see if he can find any answers to why it's doing this. I'm still thinking its vacuum leaks by the way it's acting.

[HealyC]

Check the crank case breather valve?

[murphykidd]

Just went out there had the car running, still as bad as ever but when I place my hand under the intake mani, where the hose off the intake boot goes, I can feel a bit of cold air blowing out so I'll have a shot a trying to seal that up but its blind really can't see a thing under there.

[The Scout]

Check the crank case breather valve?

+1 on the PCV valve.

Had this exact same problem on an M52 and a new PCV valve sorted it.

Easy to change on an M44 and other similar era 4 cylinder engines.

Common fail on M43 and M44, change the pipes going to and from it as well.

Be thankful it isn't an I6 as its an intake manifold off job to change one unless you have long arms and tiny hands.