Hi I have a strange problem. My 5.3 starts fine from cold. but when left to warm itself it starts hunting as its getting warm. A quick blip of the throttle clears the problem. Any ideas?

 

Probably the AAV (Auxiliary Air Valve) sticking; lots of posts on here about it.

 

Ditto.

What Steve M. Said

 

Also the TPS is probably having a female moment, age related now, and the "blip" settles the wiper on the track.

The common V12 black goo in the throttle body inner bores needs cleaning, AGAIN.

AAV, of course.

Being 1989, is it Lucas or Marelli?? Some variables between the 2.

 

Thanks all. Will have a look when its back together. Just finishing welding at back end also had front suspension out and total rebuild new rad power steering pump plus other bits. Will look good again soon.