Newbie 300 SE W126 OVP relay fault?

[Steve W]

Have done a search and seen a few tips, but just wondering if anyone could see if I'm on the right track.

I have a 1988 W126 300 SE, and when you start it from cold it's fine for about two minutes, then the idle starts to fluctuate. It will sit at about 1200 rpm for a short while, then runs up to 1500 - 1600 rpm or so, then drops right off, almost stalling, then will immediately run back up to 1500 rpm or so.

I have removed and cleaned the idle control valve, changed the air filter, plugs, oil etc, and still the same. Its bad enough now that I have stopped driving it, as you can feel it pulsing even when you are driving along and it is potentially dangerous, not to mention it can't be doing the gearbox much good trying to go into drive or reverse at 1500 rpm.

Anyway the posts here seem to possibly point to a faulty OVP relay. Does this seem plausible?

Thanks in advance for any assistance

 

[television]

Can you give me the engine first 6 numbers is it the 103.940 or 980

 

[shirubaby]

the OVP could be at fault. Sounds like it's intermittently working due to vibration and heat.

Here's something to try... remove the ovp and resolder all the contacts and see if that fixes it.

On my 500se the ovp is located behind the instrument cluster and you have to reach up from underneath to remove it.

Good luck
Shiru

 

[Steve W]

Can you give me the engine first 6 numbers is it the 103.940 or 980

Hi.

It is 103981

Cheers.

 

[Steve W]

the OVP could be at fault. Sounds like it's intermittently working due to vibration and heat.

Here's something to try... remove the ovp and resolder all the contacts and see if that fixes it.

On my 500se the ovp is located behind the instrument cluster and you have to reach up from underneath to remove it.

Good luck
Shiru

On mine it is up on the bulkhead next to the ECU, just along from the brake servo. My friend has a 1986 500SEC and his is in the same place. Nice and easy to get to.
Just hope it sorts the problem.

Cheers

 

[Steve W]

Oh well. Changed it for a new one and its pretty much the same. Only difference is it seems to constantly idle around 1500 rpm for 45 seconds or so, then drops off suddenly and almost stalls, then immediately back up to 1500 pm ish again.