Hello guys ,

I have an jaguar xjr v8 did some work to it chains and tensioners, thermo, pulley upgrade , oils and fiters , that kind of stuff . Now after all this the car ran great. Butt after 3a4 days it seems like it misfires / not run smooth this is only at 30 or 40 procent gas or higher sonds like the air fuel mix is not right but normal driving is no problem and the car sometimes does not want to start it crancks but it does not want to start . This is not only when cold or hot sometimes it start right up and sometimes not. I had a guy that read the codes from the car only thing that was in there was the park neutral switch but that one doesnt give me much trouble maybe ones in the 2months. Maybe someone knows what this could be?

 

Hello and welcome to the forum.

What year is your XJR?

If the tensioners were replaced and the car did not immediately run rough due to timing being off one or more teeth of the timing chain, you can eliminate that as a possible source of timing problems. Either the chain was put back in the correct position, or it was not, it will not change after a few days.

Which pulley upgrade did you do?

This may sound odd, but you might be experiencing fuel pump failure, as this is a common problem as one or both pumps start to fail.

If possible try checking your fuel pressure.

 

Were all the tensioners changed as well as all the chains?
You must swap everything out for the repair to last.
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It is very rare to have a chain fail. Why would changing the chains and primaries affect the life of the secondary tensioners?

 

Cam lock down or zip tie method of tensioner change?

Fuel pressure test a very effective first step.

 

Do you think the cams could have moved after 3-4 days?

The OP said "Now after all this the car ran great."

 

I have always been suspect of the way the exhaust cam and the chain sprocket is connected as there is no key or splines. Only a friction based connection. Keep waiting on a sign of slipping due to inadequate torque applied to the fastening bolt.

 

The xjr is from 97 and chains and tensioners are replaced and waterpump sparkplugs oil filters thermostat fuel filter and the car has now the upgrade upper sc pulley and lower pulley and inlet elbow and sc ports are cleaned flowd. I used cam and cracklocking tools for replacing the timing chain set so i dont think thats the problem as i said the car worked fine first days the things ive done are cleaning maf sensor , cleaning sparkplug coil connection , vacuum lines checked checked fault codes only 1 for the park sensor this is not the problem for now there is a vacuum leak sound comming from the throttle body and elbow area. But it sound like that but cant find it and with the engine running it is hard to tell it is a vacuum or other leak . The car is still driving good only when youre asking more of the car faster driving and hard acceleration it holds back and sounds like the fuel air mix is not right of misfire How can i test the fuelpressure ? And Thanks for all the replys

 

If you know you have a sound like a leak, then your first priority ought to be to fix that first. You might try spaying some carb cleaner in that area and listening for the rpm to rise, then you can confirm a vacuum leak and its location.

 

Ok good idea can this only be done with carb cleaner ? I have some disc brake cleaner or else i have to buy a can of carb cleaner not a problem but if discbrake cleaner works

 

It's really just a matter of using a flammable liquid. Some solvents might cause the engine to stall. I don't recall offhand what brake cleaner is, but suspect it might work.

 

Disc brake cleaner is nasty stuff, I would avoid it.

 

Ok guys today ive tryed thhe carb cleaner trick and could not find any leaks so i tought its a intake cleaner so cleaning the throttlebody again wont hurt so cleaned it with a shitload of the stuff and it was clean so it did not get any cleaner and put the intakepipe back and did go for a drive and the car was good and back the way it was for maybe 2min. So did the cleaner trick again allot of cleaner in the throttle body and drive car did drive good again so i think it is a fuel problem and will check the fuel pressure tomorrow hopefully

 

Do i have to do the fuelpressure check only at idile or also at other rpms ? To get a good picture of the pressure ? Thanks