In park the car runs fine, but when I shift to OD the car idles really rough and cuts out, in Drive it idles rough but stays running, what could be causing this.

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'86 IROC
T-TOPS, TINTED WINDOWS, BRAKE LIGHT BLACKOUTS
GM GOODWRENCH 350
EDELBROCK TES HEADERS
FLOWMASTER
EDELBROCK 600CFM CARB.
KN AIRFILTER
UNDERDRIVE PULLEY
ACCEL HEI DISTRIBUTOR
2:73 GEARS

 

Mark,

Any DTCs (error codes)?

A good starting point is always verifying the TPS voltage, throttle minimum air position, and cleaning the IAC air passages.

If the engine is idling a little higher in park, you might have a vacuum leak or sticky IAC. Check all hoses, including the PCV system. Don't overlook the brake booster.

If the TPS/throttle adjustment/IAC cleaning doesn't solve the problem, report back with results and data, like idle RPM, vacuum, fuel pressure, timing, whatever you can get.

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Later,
Vader
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"I'm'a do Things My Way - It's My way or the Highway."
Adobe Acrobat Reader

 

I fixed the problem, it's actually pretty dumb. The guy who had the car before me installed a kickdown switch, this is why I think my OD doesn't work, well when the switch is off the car will cut out in OD, but not drive, well at least that is how I remember it, now it seems the switch has to be off for the car not to cut out.

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'86 IROC
T-TOPS, TINTED WINDOWS, BRAKE LIGHT BLACKOUTS
GM GOODWRENCH 350
EDELBROCK TES HEADERS
FLOWMASTER
EDELBROCK 600CFM CARB.
KN AIRFILTER
UNDERDRIVE PULLEY
ACCEL HEI DISTRIBUTOR
2:73 GEARS