Cold start problem, high idle 91 300E 4matic
 

Just looking for some ideas on what could be causing cold start problems and a high idle speed on a 1991 300E

Over the past 2 weeks cold starting has become more difficult, the normal 1 turn of the engine is now 7-8, usually requiring a second crank to get it to catch. Once started you can turn off and it will start first time no problem.

The second problem is a high idle even when warm of about 1,000 - 1,200 rpm.

I am wondering whether they are linked, perhaps to the Idle Control Valve which is dead or needs cleaning out. I was also wondering if the OVP relay may give these symptons if it had gone.

Any thoughts appreciated.

I'd begin with the OVP relay. Cold start enrichment is a function of the CIS-E which is powered by the OVP. The idle valve is supplied current by the OVP relay as well. THe idle valve when unpowered will default to a larger cross section causing the high idle. When replacing the relay be sure to clean any corrosion from the connector and make sure the female pin sockets are tight.

Speaking from experience, I would remove ALL linkage including pivot points and lubricate. The speeds you indicate are not within the ranges of electronic control, but within the ranges of binding linkage.

I'll check the OVP, is it as simple as checking for 12 volts at the ICV connection, and if I get zero voltage then it is more than likely the OVP relay.

Thanks

Justin