[michla]

1989 XJ w/4.0.

What are typical symptoms of a troublesome EGR ? New one installed, I suspect a defective unit.

I remember something that it will start cold but hestitation until warmed up?
Midrange RPM is most affected.

[Curly5759]

An egr should only be open above idle, on a warm engine.
If it opens at idle/partly open= stall or very rough running
If it doesn't open = may cause pinging on acceleration, Nox emissions will increase.

Apply vacuum to the valve with the engine idling. If it stalls or is noticably rougher, then you know that it is 1) closed at idle and 2) the vacuum diaphram is ok.
Your PCM applys vacuum at the correct time by energizing the vacuum solenoid in the vacuum line. Check for vacuum at the valve at idle, there should be none. If you always have vacuum, then the solenoid is defective or there is a problem with the PCM

curly

[michla]

Thanks, Curly--that was great info !
Question: can that pinging, as if the EGV is never opening, be in the form of hesitation under heavy acceleration/high RPM??