[v12-engine] ROUGH IDLE

V12-Engine
1

I HAVE A 1988 XJSC V-12. I CANNOT GET IT TO IDLE SMOOTHLY, ALTHOUGH
IT RUNS GREAT RIGHT UP TO 150 MPH. IT HAS 33,OOO MILES AND HAS BEEN
WELL CARED FOR. IT WAS ORIGINALLY CALIFORNIA CAR. COULD THIS
PROBLEM BE CAUSED BY ALL THE SMOG GEAR ON CALIFORNIA CARS.–
CLUNY
PASCO, WASHINGTON, United States
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

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2

CLUNY dcluny@msn.com writes:
<< I HAVE A 1988 XJSC V-12. I CANNOT GET IT TO IDLE SMOOTHLY, ALTHOUGH IT
RUNS GREAT RIGHT UP TO 150 MPH. IT HAS 33,OOO MILES AND HAS BEEN WELL CARED
FOR. IT WAS ORIGINALLY CALIFORNIA CAR. COULD THIS PROBLEM BE CAUSED BY ALL
THE SMOG GEAR ON CALIFORNIA CARS>>

It could be a number of things. I’d start by checking for vacuum leaks.
Perished hoses or leaky intake gaskets. If not that, perhaps a couple of
injectors are stuck or not flowing correctly. Is it missing or just rough?
Pull each plug lead, one at a time to see if any of the cylinders aren’t
firing.

John Testrake
St. Louis, USA
84XJ6,
76XJ12L

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3

I HAVE A 1988 XJSC V-12. I CANNOT GET IT TO IDLE SMOOTHLY, ALTHOUGH
IT RUNS GREAT RIGHT UP TO 150 MPH. IT HAS 33,OOO MILES AND HAS BEEN
WELL CARED FOR. IT WAS ORIGINALLY CALIFORNIA CAR. COULD THIS
PROBLEM BE CAUSED BY ALL THE SMOG GEAR ON CALIFORNIA CARS.

CLUNY

First things to check (in no particular order) are correct plugs properly
gapped at .025", plug wires, vacuum leaks, intake manifold gaskets, fuel
injector seals, loose injector connectors, plugged injectors and the like.
Smog equipment has nothing to do with it. How bad is the roughness and can
you determine if it is the left or right bank (check the exhaust pipes)?

John

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