Hi,

If someone can help me, I would be forever grateful.

I have a 2004 xj6 3.0 v6 and ive been trying to figure out what has been causing hesitation and a backfire when the car it cold. After driving for about 15 or 20 minutes the problem disappears.

It idles perfectly but seems to occur when I accelerate from low speed or is under load, and gives the occasional backfire. The rev counter usually dances between 1800 and 2100.

I've changed the plugs, coils, fuel filter, air filter, throttle body and position sensor, MAF sensor and had the gearbox serviced and the small rubber valves in the gearbox mechanism replaced. The problem is still there.

Has anyone got any suggestions that I could try?

Thanks so much
Pat

 

Could be a intermittent misfiring coil. They can be checked or a marginal or failing fuel pump.

Start with checking the coils first. One or more could be misfiring under load/acceleration until the car warms up.

 

Hi Abonano,

Thanks a million for the reply. There are no codes or faults each time its plugged in but I took a chance and replaced the 6 coils two weeks ago in the hope it might be that. No luck unfortunately.

I'll definitely check the fuel pump, that could explain it.

Thanks for your help

 

Your scanner should be able to tell you the fuel pressure..

 

Unusual that there are no DTC with these symptoms. I would try to read the vehicle with the manufacturer's own OBD system IDS/SDD and also check the fuel trims.

If there are actually no DTC I would start with measering fuel pressure and search for false air.

Fritz