86 760 wagon toubleshoot problem

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george farquharson - 06 Apr 2008 16:40 GMT

I have a 1986 760 turbo wagon. On cold startup the idle is rough and
lumpy; after driving 5 or 6 miles the idle smooths out somewhat. After the
engine is warm, if the car is left to idle in park for any length of time
the RPM will jump from the usual 1000 to 1500 without any reason. It
occured to me that the temp sensor may be the problem; does that seen
plausible.

Cheers...George

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James Sweet - 06 Apr 2008 19:43 GMT

>I have a 1986 760 turbo wagon. On cold startup the idle is rough and
>lumpy; after driving 5 or 6 miles the idle smooths out somewhat. After
[quoted text clipped - 4 lines]
>
> Cheers...George

Have you replaced the engine wiring harness yet? Those are notorious for
crumbling insulation and will cause all sorts of weird problems.

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george farquharson - 07 Apr 2008 04:24 GMT

The wiring harness has not been replaced; you're right the electronics are
dodgy. However the rough idle and RPM swing are very consistent suggesting
a more concrete problem.

>>I have a 1986 760 turbo wagon. On cold startup the idle is rough and
>>lumpy; after driving 5 or 6 miles the idle smooths out somewhat. After
[quoted text clipped - 7 lines]
> Have you replaced the engine wiring harness yet? Those are notorious for
> crumbling insulation and will cause all sorts of weird problems.

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James Sweet - 07 Apr 2008 04:35 GMT

> The wiring harness has not been replaced; you're right the electronics are
> dodgy. However the rough idle and RPM swing are very consistent
> suggesting a more concrete problem.

Replace or rebuild the engine harness first, trust me, get that out of the
way, the car will never be reliable until it's been done. I procrastinated
on mine and ended up rebuilding it on the street in the front of my house on
a cold wet January evening.

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