fuel additives

[feunfer]

I'm told the M42 has a potential issue with deposits on the intake valves.  I own a 91 318is with 125K miles.  On cold start up, the engine does not idle perfectly , but once warm it's OK.

I'd like to try some fuel additives... I've used Techron in the past, but there are obviously others.  I'd just like to know if anyone else has had success and with which additive.

Thanks in advance.

[feunfer]

Pardon the lack of knowledge of this car.  I run an e28 535is DD... this is my son's and now mine since he's off to school.

The M42 is idling horribly.  After driven for awhile, it's better, but still not what I remember when we first purchased the car.  Had the car in the shop a few days ago... the throttle gasket was replaced as it was leaking. ICV was cleaned... I was told it was OK.  Spark plugs were also changed as they were due.  Drove the car tonight on highway for about 20 miles and while the car idled afterwards, it was not perfect.

Any comments appreciated.

thanks

[keflaman]

I'm not sure any M42 idles perfectly, so as long as it doesn't surge and die I'm usually happy.

I was speaking with an elderly gentleman a few months ago about this same problem with an M42 I had just installed. His recommendation was to perform an "Italian Tune-up...just run the piss out of it!"

Well, I never need much encouragement to do that and went straight away to carry out his advice (If you're a Porschephile, you probably know the name Weldon Scrogham).

I used a can of Sea Foam in the last tank simply because I had a couple cans sitting around, but I don't know exactly how effective it is. I've also read using a can of water and slowly feeding it into the throttle body using the vacuum port works just as well, just feed it in slowly so you don't hydrolock the engine.

[bmwman91]

I would bet that the bad idle is due to a vacuum leak, or multiple. There are tons of places that they can arise. Start snooping around and blowing into hoses to see if they can hold a little pressure.