pete-si

Hi,
My dad has a 1990 xr3i. It ticks over perfect, runs smooth on power, but maintaining a constant speed (eg 30mph 3rd gear) it judders. He changed plugs and leads and cleaned breather pipes.
Any suggestions.
Cheers

mgtkr1

part throttle fuelling issue?? maybe worth getting a rolling road op to have a look at the a/f. normally an ignition issue doesnt behave at all ie start up 1st time or nice idle. a missfire would point to an ignition related issue esp when under load. 3rd or 4th gear from low rpm's for example. but you mention it struggles to maintain a constant speed without juddering. maybe sounds daft but id look at the airfilter and work back. could be a blocked fuel filter even.

GVK.

Guessing EFI....the early EFI CVH cars were not the best......

Fuel pressure regulator on those is adjustable,there is an allen key screw in the regulator,sometimes hidden by a cap. try raising pressure (turn clockwise 1/4 turn or so)

fuel pressure regulator, top right in this pic.



Make sure no air leaks on the inlet.

pete-si

Thanks for the advice. Will pass it on to my old man and let you know.
Cheers again