VDP 96 engine vibrates

My 96 VDP engine vibrates on idle every morning when it’s cold (700-900 RPM, not when RPM >1200). The issue goes away when it is warmed up). Any help?

Sounds like it is misfiring. Check the archives for info on failing coils.

Coils checked okay. Not a misfiring issue (no diagnosctic also)

Hmmh… I think you might be dismissing “misfiring” too quickly. By that I mean an intermittent cylinder failure to fire from either loss of spark , loss of comprewssion, or incorrect fuel mixture. Not much else can make an engine shake, then go away. if the coils are all OK, then the CKPS might be a good second try. I will ask you my normal question, “What are the STFT and LTFT up to when this is happening?”

Coils rebuilt, new spark plugs, fuel injector rebuilt, compression checked at jag dealer. They gave up.

Well… You might have mentioned some of that in your original post. So, CKPS, and LTFT?

Now I remember why I get frustrated bothering to offer to help…

BTW, You seem to have confidence in what the dealer told you. Did they mention putting a scope on the CKPS and telling if the vibration occurred on the same cylinder? Did they mention the fuel trim numbers? Did they put an accelerator on it and measure the frequency of the vibration and the phase relative to the crank position? Did they actually test the injector pulse leak down? If not, it sounds to me like they are stabbing in the dark.

Also, It would sure be neat to know how they “rebuilt” and “checked” the coils.

Good luck.