I had posted in March that my 1991 Mercedes 420 SEL with a 1988 560 SEL motor was acting up while I was on vacation. David Poole was kind enough to take my phone calls and offer his valuable advice and was very helpful. Thanks David. The symptoms were that the car would start and then idle erratically with the rpms going from 750 to 1700 over and over and then stall.

Nothing helped and then, out of nowhere, the car just started to run normally. I was able to drive the car home (3 hours). I immediately brought it in to my mechanic (familiar with Mercedes but not a specialist). The car at first ran well (of course it did... It was in the shop) but then started acting up again.

My mechanic has since swapped all of the usual suspect modules: over protection, kickdown, rpm control relay located under passenger side floor mat. He has cleaned the throttle body and butterfly.

I had to travel quite a bit and the mechanic had a loss in his family and the car just ended up sitting until now. I would like to get the car running now. The current status is,the car starts up and runs normally for 5 minutes then the idle goes up to 1500 rpm for a few minutes then stalls. The mechanic has been asking around for advice and was told that the gasket under the intake manifold is the possible culprit. Any other ideas before he goes down that road?