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RE: 535is Driveability Problems

Evan W Evans (de'juvu).. asks about 535 idles problems. Something I just
happen to know a bit about (a 2 year battle with BOHICA).

>Subject: 535is Driveability Problems
>
>I just installed a new Bosch idle control valve in my '88 535is (55K) hoping 
>to cure an annoying idle/driveability problem (it didn't help so I cleaned the
>old one up and reinstalled it, car runs the same maybe slightly better). 
>Symptoms: Idle tends to vascilate between 650-750rpm and the driver can
>perceive a slight shaking of the car due to the idle while at a stop. The car 
>stumbles slightly when cold and I think I'm hearing a slight backfire before 
>it's warmed up. I've also detected that it doesn't pull smoothly once I'm 
>around approx. 2700rpm. It feels like the car pulls....hits 2700rpm and
>begins to lose power then pulls through 3000rpm.....and loses a little torque 
>andthen begings pulling thru the rev range again. Granted this is such a 
>slight loss in power it's probably imperceptable to most, but I want to fix it 
>unless I find out that "they all do that." I've checked for vacumn leaks and 
>found none. I've installed new Bosch Platinum plugs and increased the gap as
>advised. What else am I missing? Also, any remedies for the "hard to shift into
>second gear when it's cold problem"? Any thoughts on installing a K&N air 
>filter or other mods i.e.,short shifter kit, chip, etc.?

Even, I won't go into the other item's you address, but THEY ALL DO THAT,
more or less. Things to do:

1. Throw out the Bosch Platinum plugs - they're basically not compatible
with this car. Spend about $4/each for the Silver ones that are ESPECIALLY
made for just this engine (check a BOSCH cross-reference book - guess what?
The only engine using these plugs is the big 6!).

2. Set them to 0.032" minimum gap. Even to 0.035-38" won't hurt, the
ignition system can easily handle it.

3. Install and TORQUE them in with no anti-seeze. 20 fl/lbs is about right.

4. Adjust valves to minimum of +0.002 over spec. +0.004 isn't even
noisy and will help even more.

5. Run mega-dose of techron full strength stuff (not the watered down
k-mart stuff) [mega-dose = 2 16oz can's in the last 1/4 tank. Run until
almost empty. Fill up. Change oil!!).

6. Run the piss out of it. It will like it.

Problems with the '86-88 big six engine idle is related to exceeding
(vastly) the EPA emmisions standards. The things run VERY lean at
idle (CO is almost unmeasureable at the tailpipe). None of them idle
great - but the above can make it tolerable - and not embarrassing
at a stop light (car rocking and rolling). The biggest change is made
by opening up the valve adjustment, followed by the correct plugs
and a wide gap. You'll notice as these open up with normal wear,
the car runs better and better - I'm often disappointed after I tune
BOHICA up, 'cause it runs WORSE - and end up resetting the new plugs
to the gap the ones that came out were at - and doing the valves again.
I'm currently running the valves at 0.014 +.001 - .000 - this seems to
work well, and with BOHICA gonna reach 100,000 miles TOMORROW - the
cam and lifters look JUST LIKE NEW - the car uses no oil, and the
compression is excellent, and very even. It won't hurt the engine
to run these wider - and will greatly improve the idle.

As a sidenote - for better performance - best bang for the buck,
with the smallest amount of work has been the DINAN chip. Gives
great midrange UMPHHHFF! (You actually get pushed back in the seat).
Check around - you can find them for as little as $125 discounted
by some Roundel advertisers. Takes about 20 minutes to install.

Best..


=======================================
Don Eilenberger ([email protected])
=======================================
  '79 R65 FrankenCycle - der Beemer
  '87 535i BOHICA      - der Bimmer
  '75 25' Hunter       - das Boot
=======================================
DOD#1177, BMW-CCA#104316, BMW-MOA#64000
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