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  #1  
Old 02-23-2001, 09:46 PM
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Join Date: Nov 1999
Location: Matthews, NC, USA
Posts: 133
My 84' 380SE has developed a sudden phenomena.

It has long since had a slight stumble when accelerating from a dead stop and sometimes its worse than others and sometimes it disappears completely. That I could live with.

However, just recently it has developed another infrequent anomolie. when it chooses to act up, the tach stops at approx. 1800 to 2000 rpm, you can hear the motor continue to rev up as you watch the speedometer climb (the climb is slower than it should be and the motor sounds like an old 440 Magnum with the valves floating out at the upper rpm range). The car doesn't seem to want to shift out of the gear either.

Once at highway speed, it cruises o'k. If you try to accelerate & by chance the tach does properly resume exceeding 2000 rpms, then there is a dead miss.

While it seems like the "old potato in the tail pipe syndrome", which lead me to think clogged CAT, I didn't think CATs could clog & then unclog. I checked the muffler output by hand while reving the engine and it is clearly moving plenty of hot air out the tailpipe.

At times it feels like the tranny is slipping, but I believe its really just a loss of horsepower due to the puffing miss.

while this next tidbit seems to be a red herring, I also note that in a sweeping right hand curve under power there is a squeal like a fan motor bearing or an alternator bearing. I have recently had the alternator rebuilt (for the third time) by a local electical motor repair shop. He is very reasonable and has historically provided good results. Is there a root cause to my repeated alternator bearing failures? Is the alternator or the tach causing some strange electrical anomolie.

I had a bad tach (electrical short?) in the 911 turbo which created similar but different results.

We plan to put the car on an engine analyzer tommarrow morning.

Do you have any suggestions as to what else I should check and how to check it. This car is a cream puff and having been in the family for some 15 years and 160,000 miles is part of the family.

any suggestions are welcome.

Dwight
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  #2  
Old 02-24-2001, 01:00 AM
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Driver, Mercedes-Benz
 
Join Date: Feb 2001
Location: Malaysia
Posts: 1,645
Its only a wild guess but I gather your injectors might need either a very good clean or to be replaced altogether. Then it might also do some good to check on those spark plugs and get an electronic-tuning done.

My colleagues' car had such symptoms as yours, and the above rectified it. We sent it to a tuning specialist where he tuned the engine, and also something down the driver's compartment supposedly for the fuel injector.

The next thing my colleague knew was that his MB performed better than ever.

I hope your problem will be sorted out soon.
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  #3  
Old 02-27-2001, 04:05 PM
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Join Date: Nov 1999
Location: Matthews, NC, USA
Posts: 133
Thanks for the response. In further checking, we found the #2 cylinder drops out at precisely 2000 RPM. We replaced the distributor cap, the plug wire, and the Plug then grounded the plug to the engine and miraculously watched while the plugged fired until the engine approached 1800 RPM at which time it began to fire intermittently, and then at 2000 RPM the plug just quit firing at all. As the engine revved above 2000 RPM, it began to fire intermittently, but the engine struggled to gain RPM. We also noted that while the engine clearly stumbled its way to what had to be 3000+ rpm, the tach never read above 2200 inside the car.

Frustrated and confused, we closed shop and stumpbled all the way home.

To my surprise, Monday morning I awoke and hesitantly decided to drive the car to work and then afterward go to the shop to investigate further. The car has not stumbled since and I cannot for the life of me tell why. Until the phenomena returns, I will continue to happily & yet,hesitantly motor on.

Thanks again

Dwight
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Old 02-27-2001, 10:41 PM
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Driver, Mercedes-Benz
 
Join Date: Feb 2001
Location: Malaysia
Posts: 1,645
You have a bright and intelligent car that knows how to rid itself of all problems ... good on ya mate!
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