Poor engine performance
Posted: Fri Nov 09, 2007 5:52 pm
I have a 1998 4Ltr XJ8 Sovereign with 84,000 miles on the clock.
The car had been having a gradual reduction in performance. Noticeably, a reluctance to pick up with a hesitation on gentle pedal application (kick down OK), along with an increase in fuel consumption. It was the same in Sport, Manuel or Auto with the engine hot or cold. Although on a motorway at a steady 70mph the fuel consumption was still in the high 20's.
Earlier this year the water pump failed and the temp went off scale and I had to limp the car 12 miles home, in very short hops. The pump and thermostat were replaced by a local (non Jag) garage. The problem seemed to get worse after that.
I replaced all the Plugs, Air filter, and Fuel filter then substituted the MAF sensor, all with no effect.
Thinking it may be a Nikasil problem I spoke to the local JMD. They informed me there was still an outstanding Service Action on this car, which may solve the problem. Even though the car is nine years old and hasn’t got a full Jaguar service history, the Throttle body was replaced under warranty (normally £800 + Labour). Unfortunately this also had no effect on the problem.
Following advice from David Marks. A code reading came up with P0328 (Knock sensor 1 circuit high). On inspection of the sensors, the forward sensor had one of the connector sockets almost pulled out. This probably happened during the water pump replacement. I re-seated the socket and reconnected the connector. This gave a slight improvement.
Knowing the problems with the timing chain tensioners, I decided to have the uppers replaced. This was done by “XJK Jaguar” in Newcastle-under-Lyme for a very reasonable £350. During the replacement they found that the engine breather T-piece at the Throttle body was broken. With this replaced the cars back to full performance again.
This is my first ever post on a BB, so I hope you find this of interest and maybe a little help if your having similar problems.
Thanks again to David Marks and Gavin at XJK.
Chris Whear(Growler)
The car had been having a gradual reduction in performance. Noticeably, a reluctance to pick up with a hesitation on gentle pedal application (kick down OK), along with an increase in fuel consumption. It was the same in Sport, Manuel or Auto with the engine hot or cold. Although on a motorway at a steady 70mph the fuel consumption was still in the high 20's.
Earlier this year the water pump failed and the temp went off scale and I had to limp the car 12 miles home, in very short hops. The pump and thermostat were replaced by a local (non Jag) garage. The problem seemed to get worse after that.
I replaced all the Plugs, Air filter, and Fuel filter then substituted the MAF sensor, all with no effect.
Thinking it may be a Nikasil problem I spoke to the local JMD. They informed me there was still an outstanding Service Action on this car, which may solve the problem. Even though the car is nine years old and hasn’t got a full Jaguar service history, the Throttle body was replaced under warranty (normally £800 + Labour). Unfortunately this also had no effect on the problem.
Following advice from David Marks. A code reading came up with P0328 (Knock sensor 1 circuit high). On inspection of the sensors, the forward sensor had one of the connector sockets almost pulled out. This probably happened during the water pump replacement. I re-seated the socket and reconnected the connector. This gave a slight improvement.
Knowing the problems with the timing chain tensioners, I decided to have the uppers replaced. This was done by “XJK Jaguar” in Newcastle-under-Lyme for a very reasonable £350. During the replacement they found that the engine breather T-piece at the Throttle body was broken. With this replaced the cars back to full performance again.
This is my first ever post on a BB, so I hope you find this of interest and maybe a little help if your having similar problems.
Thanks again to David Marks and Gavin at XJK.
Chris Whear(Growler)