1992 XJ6 Sovereign 4.0L Was Driving fine, next time using slow reaching drive speed (no power) when it reaches 50 mph engine drops to idle with no throttle speed goes down to 15 mph. If you shut off engine & restart you can slowly get back up to 50 mph and it does the ssame thing. No codes given. If in park or neutral the throttle works normal, either with foot peddle or by hand under hood ? ? ?

 

Hi

Re-post in the "XJ40" section for best results from those most familiar with your car. This section is for the previous generation XJ sedans

Cheers
DD

 

luckily we don't have to read codes, it's all "by ear". Unless the Series 3 has a secret code system in its F.I. computer