Discussion:
Unstable idle at startup ?
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Axel Griese
2007-08-01 18:57:43 UTC
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My '86 with the 2.8 multipoint fuel injection is very unstable for about
the first 30 seconds or so after startup - The idle pendulums wildly
between almost stalling and 2000+ RPM. Then after anywhere from 30 seconds
to a minute or so, it settles down. During this instability, the exhaust
reeks of partially burned gas.

Only happens when I start the car after it has been sitting for at least 4
hours. No codes on the OBD-I.

I'm no "expert", but my own best guess is that I probably have one or more
fuel injectors and/or cold start valve that are leaking after I shut off,
and after 4 hours enough fuel has built up in the cylinder(s) to drive the
ECM wild when I start.

Is this a plausible theory ? Or is there something else I should consider
before I replace all the injectors and the cold start valve ?
Randy
2007-08-31 12:54:02 UTC
Permalink
On Aug 1, 2:57 pm, Axel Griese <axel-dot-griese-at-yahoo-dot-com>
Post by Axel Griese
My '86 with the 2.8 multipoint fuel injection is very unstable for about
the first 30 seconds or so after startup - The idle pendulums wildly
between almost stalling and 2000+ RPM. Then after anywhere from 30 seconds
to a minute or so, it settles down. During this instability, the exhaust
reeks of partially burned gas.
Only happens when I start the car after it has been sitting for at least 4
hours. No codes on the OBD-I.
I'm no "expert", but my own best guess is that I probably have one or more
fuel injectors and/or cold start valve that are leaking after I shut off,
and after 4 hours enough fuel has built up in the cylinder(s) to drive the
ECM wild when I start.
Is this a plausible theory ? Or is there something else I should consider
before I replace all the injectors and the cold start valve ?
More likely is the IAC, (Idle Air Control), on the throttle body.
Is the seal on the adjusting screw intact or removed?
You might also want to check the ground wires on your engine.

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