Rough Idle 1988 300E w/ABS dashboard light
 

I have the notorious rough idle and stalling on my 88 300E. It runs fine with my foot on the gas but at idle it has problems. While it has a rough idle, it will only stall when the ABS dashboard light comes on or the battery light. both come on and off sproadically and/or intermittently.

Does this indicate anything specifically that might be causing a rough idle. I haven't checked my voltage regulator and the brakes work fine. Is this possibly electrical?

Thanks for your help!

Ken

Low voltage condition..possible causes are battery low, alt output low/regulator, or blown fuse on top of OVP


Do a search on OVP, as that would be a first check.

The rough idle is unlikely the same problem with the stalling.

The stalling will be your OVP though so start with that.

In general, ABS light on + rough idle = no power to the CIS-E and ABS ECUs, and Idle Control Valve.

All three are powered through the OVP relay. Check the fuse mounted right on it's top, and if OK then check the connections at the pins inside the OVP itself, as it is a well known problem that the connections develop hairline cracks over time. You just need to resolder them to correct the problem.

You can also try rocking the OVPR a bit in and out of the socket and see if the problem comes and goes. If it does, it's a sure sign that the internal connections are going intermittent.