Hi,
I have a 1987 260E with 330K miles. Recently it is having acceleration problems, actually the problem has gardually become worse. The car idles fine but as soon as I depress the acceleration pedal, it becomes rough and the maximum rpm I can get is 2500. I looked at the air meter's plate and noticed that it was fluctuating when the acceleration pedal is depressed or blipped. So I checked the vaccum at idle at one of the vaccum ports on the intake manifold. The vaccum level is fluctuating between 3 and 5 mmHg. And as soon as the pedal is depressed, it goes to zero. This sounds very wrong, because based on the vaccum gauge's manual, the idle vaccum should be between 18 to 22 mmHg. The manual also indicates that this behavior (low vaccum at idle and diving to zero on accleleration) is consistent with a clog in the exhaust system or an overactive EGR. I dont think this car has an EGR so that leaves only one possibility, and that is a clogged exhaust system. The car has recently been burning oil at a quite high level, a quart every 800 miles which indicates problems with the valve seals as well as possibly valve guides. The compression test comes normal for all the cylinders. I have tried plugging all the vaccum ports (even the brake booster line was plugged) and the vaccum level remains the same so if there is a leak it is a pretty big one and I dont think that big a vaccum leak is present anywhere that I could see. Is So the questions are: 1. are there any other possibilities that can make the vaccum go so low ? 2. is there a way to search for the big vaccum leak ? 3. is there a way to check the exhaust system independantly ?
Thanks for your help,
Saumil

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Saumil S. Patel