Ok, went to a friend of a friend's house to look at his 88 4- cyl-

The truck runs rough until it warms up, and makes a high- frequency 'spitting' noise back through the carb. It eventually settles out- until you goose the motor, and then it does it all again for maybe 5 minutes... and then settles down again.

He thought it was exhaust valves sticking, but it's not making much valve lash noise. He's replaced the VLA's with no change in symptoms. We checked the EGR- it seems to be closing, but when it's open, we get symptoms very close to the idle problem- but with a different noise!

My guess, after much yakking and not nearly enough beer, was that it's a couple of the little jet valves (or whatever those dumb <img src="/forums/images/graemlins/butwiggle.gif" alt="" /> things are. It's just too quiet for a main valve problem.

whaddya all think?

Toby