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Old 02-02-2003, 03:38 PM
RKreutzer RKreutzer is offline
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Join Date: Sep 2002
Location: Kingsport, TN
Posts: 375
Fuel starvation or transmission flaring?

Hi everybody,
when I took my '87 420 today for lunch, I experienced the following:
1. Accelerating from a stoplight "briskly" in second, all is well until suddenly the car "jerks" 3 times as if it shifts up into 3rd but doesn't. I guess I took the foot from the gas and it shifts into 3rd.
2. I do it again a few stops later with an eye on the rpms and sure enough at 3500 rpm it jerks again.
3. Driving with less gas and letting the transmission shift at 2000 rpms or so everything is fine.

Now first I thought this is the "flaring" but the engine is not really revving up. Then I thought it felt like the car is not getting enough gas. After all, I installed the fuel pumps only 2 days ago and there might be a kink in one of those fuel lines.

So at home I put it in Neutral and rev the engine expecting it to cut out at 3,500 but it does not. It seems to rev easily above 4000. I didn't rev it much higher.

So what do you think,
fuel starvation or transmission problem?

Could a resticted flow cut the engine out like that at 3500 rpms while driving (i.e.over a longer period) but then rev in Neutral without problems?

Should I just rev it up to 6000 in Neutral for a longer time to really see? I thought you are not to rev an engine without load that much.

Your thoughts are much appreciated.
Reinhard Kreutzer
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