My buddy just got one, when you accelerate easily, it is great. When you accelerate hard, around 3000-2500 rpm, it surges the whole time you hold your foot to the floor, when you let off, it drives great. We changed both fuel filters, and replaced the o rings on the ip because they were leaking. WE did two cans of diesel purge mainlined into IP. It still does it. Any ideas???

Could be a boost issue. Are your boost sensing lines clear? How about your waste gate valve, or maybe the alda. Just a thought :-)

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Dean

Can you define "surges" a bit better?

surging as in if you were sitting in a chair, and lunged your head forward, than quickly backward multiple times, that is how it feels.

What would be the frequency of said surging?

constantly, every second

So, would you say that the frequency is 60 cycles per minute?

That's quite slow........and doesn't correspond to anything in the engine when it's running at 2500 rpm.

Possibly a fuel delivery problem from the tank. How freely did fuel flow when changing out the primary filter? A clogged fuel strainer in the tank would be one of the less expensive problems that could happen. Hopefully it is nothing wrong with your injection pump.

Ken300D

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1982 300D at 351K miles
1984 300SD at 217K miles
1987 300D at 370K miles

A clogged strainer won't cause surging. It will prevent the engine from producing any power and will cause a loping and slow idle.........but.........not surging.

transmission perhaps.. I know when my transmission gets low on fluid it will do something like he describes when shifting from 1st to second. Thus requiring me to let off the go pedal for it to shift.. It only happened to me twice since I've had the car..

yes, 60 cycles per second. I ran the motor on 1/2 gallon of diesel purge to dispel any idea of fuel or tank trouble, it did the same. It does idle quiter now, though!! maybe clogging injector cause fuel delivery problem??????????????

Ok, now first you state that the frequency is "every second".

Then, when asked if the frequency is 60 cycles per minute, you respond with "60 cycles per second".

This would be "3600 cycles per minute" and match very closely to engine rpm.

So, what have you got...........if you know???

Diagnosis is impossible without good data..........so, don't guess.

sorry typo, 60 per minute

If you are sure about that data, we can rule out anything that's engine related..........which leaves a definite quandry.........

IIWM, I would switch fuel lines from in to out, or run off some fuel in a jug under the hood, just to be sure to rule out a tank delivery issue. My tank screen clogged really bad, and the symptom was more like "bogging" rather than surging--low power across the band with no real bucking. But what the heck, it's an easy thing to do.

I'd also get a boost guage and bypass the overboost switch (or whatever they call that thing) on the firewall.

Could a sticky wastegate or overboost solenoid cause "surging"?

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1998 E300D, 287k, barely broken in.