Hi

I have a problem with my 2003 Jaguar X350 4.2 V8, when the engine is warm (so not warming up) the car surges between 1000rpm and 2200rpm the surging can be a swing of between 100rpm and 300rpm. I did think it might be the torque converter but the car doesn't do it when it is cold???? The issue starts as soon as the car in warm and in close loop mode, checking the throttle position using an ODBII interface I can see at idle the car is showing 2% throttle position and fluctuates slightly between 2 and 2.4%. Could this be a sign of the throttle pot failing and what are other peoples throttle pots % showing at idle???

Please help as I'm getting close to burning the car.

New parts so far:
Spark plugs and 8 new coils.
Knock sensors
Breather pipe replaced with Silicone at the plastic one was split.

Aaron.

 

Sure sounds like the warm up surge synonymous To the zf , have never heard of it post warm up .
I'd start with Any codes ? Then check all sensor parameters via obd2 . Including fuel trims ,
Then I'd try a hard reboot , and failing that a transmition adaption reset via ids/ssd. Then finaly a trans software update . That pretty much covers all baces
Hopefully the codes or fuel trims will set you strait .

 

Thanks for the reply will give it another look over. The only other thing I wondered was PCV Breather cap as when I disconnected the breather hose there was as lot of oil in the tube going to the throttle body??? I had sort of ruled out transmission as even if I put the car in the manual part of the J gate the car still does it, as the rev's climb past 2200rpm it seems less. So I could just drive everywhere at 90mph I guess???

 

I agree with Datsports. Start with the codes.

 

Surging 100-200 revs on transmission fluid warm-up is well known, but continuing when everything is nicely hot is not so common. It could be the torque converter, but I'm not an expert.

 

+1 on codes

Could be the TPS or TB motor but get the codes.

I am guessing but 2 to 2.4% seems a lot.

Oil in the PCV is usual.

 

Check codes, and fuel trims. When surging goes away at high rpms, could be vac leak. Also fuel trims are a large part of close loop system. Browse over my last thread "Only Po174 on SV8". I had a lot of surging caused by Bank 2 O2 sensor. Live data showed erratic surges only on bank 2 side. My surging on live data did not change with high RPM which ruled out vac leak. I did have the TB cleaned, ran better, but did not cure surging.

 

+1 look at trims

E.g. use an elm327 - fantastic value for money.

 

misspost

 

Any luck?
Updating this thread could help others who are having a similar issue...

 

I too have this issue and a rich running problem at the moment so it would be good to know what the fix was as well.