Here's a strange one on a '96 E300D... I've had minor engine surging issues (+/- 100rpm) at low highway cruising speeds and low engine load for some time now, but as long as I stay out of the 'surge sweet spot' I'm OK. I've had the intake crossover pipe off and the intakes look pretty clean. The first resonance flap was pretty sticky because the vac line was off for presumably some time. I got it free and moving again. So I could live with all that.

Last weekend I drove 3 hours in heavy rain and the engine bucked and surged like a texas bronco. As soon as the engine load eased during ANY cruise speed, it would surge, flutter, run rough, however it can be described. Pressing the accelerator casued some hesitation but then it took off nice and smooth.

Monday morning, sunny and dry weather and the engine runs normal.

I had just recently replaced fuel & air filter in my attempts to track down the surge so I know they're clean.

Anyone have any suggestions???

Gersti,

I had my '80 300SD engine steam cleaned after a trip to AK. On the ride home from the cleaning the engine ran terrible. It was like a gasoline engine with a bad set of points if any of you guys can remember that.

Next day the engine ran perfect and has so ever since. I think it just dried out from the heat under the hood. Even though it is an older Diesel there are some electronic engine controls.

Thus I suspect your electronic engine controls are getting water in them which causes them to malfunction. Your engine has many times the electronic controls that mine has so it easy to understand how water could affect engine operation.

AH for the old days when the Diesels engines didn't know what an electron was.

P E H

I dunno if this is relevant, but after a carwash the other day, my 300D was smoking alot more than usual. The next day, it was right as rain...so to speak...

I had a Peugeot diesel that had no electronics, it was all mechanical (I used to disconnect the battery and leave it running) and I almost drowned it once. The engine was all wet, and partially submerged and ran fine. It started sputtering when it got water in the intake (bow wave), but the instant it was clear it was fine. It got me past several drowned gas 4x4's. The brakes were gone, the clutch got real pissed, and it took a little while to dry out the interior, but as long as the engine got a reasonably dry gulp of air it could care less.

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5 speed '91 190E 2.6 320,000 mi. (new car, fast, smooth as silk six, couldn't find any more Peugeots)
5 speed '85 Peugeot 505 2.5l Turbo Diesel 266,000 mi. (old car, fast for a diesel, had 2 others)
5 speed '01 Jetta V6 (new wifes car, pretty quick)
5 speed '85 Peugeot 505 2.2l Turbo Gas 197,000 mi. (wifes car, faster, sadly gone just short of 200k )
5 speed '83 Yamaha 750 Maxim 14,000 mi. (fastest)
0 speed 4' x 8' 1800 lb Harbor Freight utility trailer (only as fast as what's pulling it)

I clean my '85 300SD engine by blasting it with a cleaner and then pressure washing the hell out ot EVERYTHING. The motor never even misses a beat when I do this. By using this cleaning method is how I found out my intake was leaking.

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'85 300SD (formerly california emissions)
'08 Chevy Tahoe
'93 Ducati 900 SS
'79 Kawasaki KZ 650
'86 Kawasaki KX 250
'88 Kawasaki KDX200
'71 Hodaka Ace 100
'72 Triumph T100R

Sounds like wet electrics, possible a connector.

Are there any codes stored in the computer? Dealer or independent with OBDII (I think) scanner can check to see if the computer can tell you what went wrong.

Did you notice any significant corrosion on the resonance flap actuator that might get more 'sticky' when exposted to wet/dampness?

If you are brave, you could try misting various electrical connectors with water, then go for a drive while they're wet to see if it duplicates the problem. Intermittents, as you probably know, are darned difficult to diagnose, and impossible unless the computer remembers or the fault re-occurs.

Best regards,
Jim

Had the exact same problem last week during a heavy rain storm with my '95 E300 Diesel. Got home, looked at the Over-voltage relay and the fuse was blown. Replaced the fuse only to have it blow again. Looked at the wiring harness going to the over-voltage relay, in my case its behind the battery, and saw that all the wires were corroded, were shorting to each other and to ground.

Repaired the damaged wire harness section, replaced the fuse and all is back to normal. So, Check your over-voltage relay, its fuse, and the wire harness going to it.

Phil

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'95 E300 Diesel, 264,000 Miles. [Sold it]

I live in a rain forest my diesels love rain...............

William Rogers.............