jumpy revs on idle and deccelaration??

[Rich540]

I have a 97' BMW 318ti about three weeks ago i suspected there may be a headgasket leak so I put some cooling system sealant in the coolant. The next day i made a short journey and then when I next started the car it was idling up and down between 900 and 1300 revs, then when I pulled away the car seemed like it was misfiring. Now its not as bad but the car is a little jumpy at low revs and when I let off the accelerator to slow down.

I have driven the car about 1500 miles in the last three weeks and the headgasket seems fine and the is no leak, but I just have this jumpy problem. My friend has checked the spark plugs which are nearly new and the HT leads which are fine, he also tested the coolant steam to see if there is a leak in the head and that was ok as well.

Im so confused, please help!

Thanks Rich.

[Boogiesox]

I had the same problem. Mine would "bounce" (400 to 800 RPM) after disengaging the clutch when the engine was warm. I had a hole in my intake boot probably for the longest time and didn't notice it until I replaced a leaky coolant hose. Replaced the boot and it made all the difference. Got rid of a mysterious whistling noise as well (Air rushing through gap). My best guess would be vacuum system. :dunno: