Hi Folks,
Car starts and warms up fine - smooth at 1100 rpm. After warm-up, lumpy idle does not stall. Can drop to 500 rpm then pick back up to 800. Not rhythmical, constantly random. Where should I start looking?

 

5.3 Litre V12 engine?

Or 4.2 litre 6-cylinder fuel injected?

Or...to go off in the weeds a bit....3.4 litre 6-cylinder on carburetors?

What you you done so far, if anything, to address the issue?

Cheers
DD

 

Doug, It's a 4.2L 6 cyl. - Fuel injected - Bought it last week and drove 500KM home without any concerns at all, but idle is poor. Have not touched anything yet.

 

Ok ! Now we're talkin'

The 'could be' list might get long. And, rather than a single hard fault, you might have a 'stack up' of deficiencies contributing to the condition.

But, you gotta start somewhere. As a jumping-off point, for the symptom you're describing, I'd begin by A) making sure the ducting between the air flow meter and the throttle body is intact and secure and B) cleaning the throttle body and making sure the throttle blade is set to the proper .002" gap.

Cheers
DD