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high idle-1978 280z


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hey im having a weird issue with my 280.

it will idle just fine, drive fine, but once i start winding down, slowing down and getting ready to stop and what not, the idle jumps up and sticks to like 1500-2000rpm, once i get back on it the idle drops back down and i am normal again. also, it will idle fine on start up, but once i hit the gas, it will stick at around 1200???

any clues anyone?

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I had a similar symptom on my Cutlass; turns out it was the Cruise Control Servo Linkage that was pinching the throttle linkage. It too would idle fine at an initial start up-but once you gave it some gas it would stick & you counldnt get the engine to kick down; it's idle was stuck at 1200rpm's.

 

Check your throttle linkage or R&R the throttle linkage/make sure it isnt binding. A week throttle return spring could cause similar symptoms.

 

Also had a 66 Cutlass once that had the exact opposite problem; initial idle was fine but once the engine warmed up it would die at idle. Turned out the carb.base plate gasket was defective & interferring w/incoming air. Once I put new plenum gasket on everything was fine.

 

Kevin,

(Yea,Still an Inliner)

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  • 3 weeks later...

Could also be the BCDD, i believe on that model it was used to decrease emissions during shifts, etc. I eventually just filled mine with body putty and drilled the correct diameter hole to get the correct adjustment with the idle screw. Mine leaked all the time, though. The BCDD is connected to the speedo, and any time your over 10 mph and let off the gas suddenly, it allows air to leak around the throttle blades to burn the fuel that is already in the system. worth checking out anyway...

 

Bill

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  • 1 month later...
Guest Anonymous

....your car HATES YOU!....have you done something to it that it didnt like?...did it want to go out on a date w/a mustang and you wouldnt let it go?.....just kidding....does your's have a "cold start" solenoid (valve or whatever)...? ..s

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