hello all I recently bought a 98' xj8 4.0 as a spares repairs car

it is a running car but has its problems (mice under the inlet for starters)

it starts and idles fine but anything more than say 5% throttle and it will start missing or cutting fuel or something

so far ive checked coils and plugs, they seem to be working fine although plugs are a bit carbony

removed the throttle body and cleaned it all out including the sensors

changed a knock sensor as mice had eaten the wire

it came with a spare fuel pump in the boot so I think the previous owner has changed it

have had it plugged into the scanner but theres no codes after I replaced that knock sensor

any ideas about what to check next? will be getting a video of it tomorrow show the problem

 

Check the gap on the plugs, usually over gapped plugs create acceleration issues. I would clean the MAF with a MAF only cleaner and check for any vacuum leaks.
Here's a link for ya you'll find helpful....http://www.jagrepair.com/S-TypeTSB.htm

 

Also check the fuel pressure. Maybe the po decided not to change the pump because he couldn't get the fuel line off, or what about the fuel filter

 

going to check the fuel filter tomorrow and hopefully get the fuel pressure checked soon, was reading about it and its meant to be at 55psi although that may be for the supercharged version

will change the fuel pump for that other one I have and see if it makes a difference

 

gonna check plug gaps too, thanks highhorse the gap should be 1.3mm

 

Fuel pressure about 40 for NA engine.