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Old 04-04-2000, 11:22 AM
Posts: n/a
Re: 81 300d

I'm going to check the compression in my cylinders this week. I've been told an rough
and missing idle may be due to loss of compr.
in one cylindr or more.

The car runs smooth as silk idling one time,
the next time it will be rough, so my question is this. If the problem is due to
low compression in a cylinder, why does it
idle irratically? What causes it to just
take 'spells' missing and idling rough? and be just smooth and can be the other?

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Old 04-04-2000, 03:27 PM
Registered User
Join Date: Jan 2000
Location: New Bedford, MA USA
Posts: 1,583
Nope, a crappy idle due to a bad cylinder doesn't come and go. I'd look at fuel filters, injectors and the like.

Jeff L
1987 300e
1989 300e
1987 BMW 325
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Old 04-04-2000, 04:12 PM
Posts: n/a
Thanks Jeff.

I thought that myself. I'm glad you help
confirm it. Think I will have the inject.
pump checked first. I did take out the
injectors and had them cleaned. They were
fine according to the man that tested them.
I also changed the fuel filters. It does
have a bad overgrowth of algae, but i woulnd't think that would affect performance.

Do you think it may be simple adjustment in
the pump (timing?) if that's the problem? I sure hope i won't find it needs rebuilt!
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Old 04-04-2000, 06:30 PM
Posts: n/a
I always preface my statements that are opinion, so here it goes, this is opinion, since I have not experienced algae. I will say that it is a fule contaminant, and that can not be good. Intermittant plugging etc could be part of your bad idle. If you have had maintenance done and they said you had algae and did not recommend anything, I would get a different mechainc

Here is what I would recommend, regardless of the cause of the idle problem, run a fuel conditioner for algae through the system, twice! When the second tank is just about gone, pull the fuel tank screen and change it, change both fuel filters, and then follow it up by using one more dose of Deisel Dr or equivalent and changing both fuel filters one more time. Filters are cheap, especially if you do this work yourself. Even if you pay a shop to do it, it is cheap compared to a clogged system. I would also recommend that when you change the filters that you actually look at the contents. You can do this for the engine bay filetes by shaking them into a glass kitchen mixing bowl and looking at the bottom! I always do this! Also, when you do the tank screen, use a large clean metal container, such as an old refridgerator drawer (enamled metal). You can easily see any dirt and or filter it through a paint filter. I do not recommend using any plastic, because it is hard to get clean and detect "new dirt".

The Partsshop sells the fuel additives!

Any experts care to share real life drama about algae?

87 300TDT
150,000 miles

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Old 04-04-2000, 09:16 PM
Posts: n/a
Thanks for your input Deezel. I think I will
post a topic just on algae and see what
responses I might get.

I havn't had a mechanic look at it yet
actually. Only thing mechanic has done
is clean my injectors.

I know it's full of algae because the pre
filter stops up in no time, with black
flakes. I'm sure this is algae. Even when
I put in a new filter and prime the fuel, more black flakes are sucked up into the new filter as I pump the primer.

I'll see if I can find some Diesel Dr.
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Old 04-06-2000, 01:40 PM
Join Date: Jun 1999
Location: Quezon City, Philippines
Posts: 79
Have you tried pulling down your fuel tank and cleaning it?

Also, try checking the fuel overflow valve on your injection pump. The relief valve spring could have failed.

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Old 04-06-2000, 05:17 PM
Posts: n/a
Jake, cleaning the tank is on the agenda.

Where is this overflow valve yout mention?
I'm suspecting it may be getting too much fuel injected, thus causing the rough idle and smoke. However, smoke is NOT black. Once I rev it up or go on down the road, it does just fine. Only gives problems on idle.
Also, the fuel odor is awful when it takes the spells.

Someone mentioned checking a valve (or something like that) on the back of the fuel pump, but as I understand it it only is on Turbo's. Mine is not a turbo. Thanks Jake, Phill

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