E28 M5 Cold running hesitation

["Todd Kenyon" <todd.kenyon@xxxxxxxxxx>]

Me and another guy seem to have identical problems with our E28 M5s. The cars
hesitate or drag for about the first 30sec - 1min when started cold. Then,
just as the temp guage rises out of the blue, the cars act as if someone flips
a switch: the car will suddenly accelerate say from 3000 to 4000+ rpms and
drive fine thereafter. Here are some other hints:

1 - My car at least seems to have a program in the computer that causes the
car to idle higher, at about 1100 rpm for about 30 secs when started cold, and
then it settles back to normal 700 rpm idle. If I wait for the idle to lower
before driving off, the car runs fine even tho it is still in blue on temp
guage.

2 - The car has no other driveabilty or idle problems. It is not the coolant
temp sensor, mine tests fine and the other guy replaced his, no change.

3 - it is not the thermo -time switch / cold start valve. The s38 engine
doesn't have 'em. I assume that the fast-idle mode replaces them.

4 - I do not have any detectable air leaks.

5. The problem seems to actually IMPROVE when it is very cold out (although I
have not absolutely proven this)

6. My car at least is chipped with a Jim C chip. Someone suggested it may be
the idle map in the chip??

Anyone care to take a stab?


Todd N. Kenyon 88 M5 82k

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