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R129 M119 engine rev surge and cut off?

SLBrighton

Active Member
Joined
Oct 27, 2020
Messages
79
Location
Brighton
Car
R129 SL500
Hi everyone, I hope all's well.

I have a 1997 SL500 R129 with the M119 engine

I've been having an intermittent problem with the car for a few months now.

On most journeys, the engine will occasionally die when I pull up to stationary, in traffic or at stop sign etc. This doesn't happen every time I stop, just maybe once or twice on a longer journey, sometimes not at all. It seems to be when the revs drop. It drives perfectly well and I have no issues at any speed.

I have noticed that there will occasionally be a sudden slight surge in revs, as if it is trying to correct itself. If I'm in gear, this will move the car forward! It then settles and often, this is a sign that it will soon die. When it does die, it's instant. Lights come on the dash and it's off, as if the ignition is switched. It always starts perfectly straight away afterwards and then may drive for many miles without an issue.

I had an independant specialist here in the UK check it over. They thought at first it might be the crank shaft sensor, so this was replaced, but it made no difference. They said they checked the loom and it looked fine. My understanding is that loom issues affected up to 1996 models. Is that correct? They check the fuel pump and no issues and there were zero fault codes showing for the car.

I have read a few other forum posts with similar symptoms and some say it could be the MAF, others the vacuum lines, others the ECU and others the engine loom, but as often is the case, they never post what corrected it.

I have contacted another specialist who knows these cars, but I wanted to see if anyone has had similar issues and found a solution.

Thanks, Ian
 
I'd be looking at the throttle body wiring.
 

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