On my 98 XJR, I have recently replaced timing chains, tensioners, guides etc. Shortly after, the car started to misfire at idle and occasionally stalls at idle. Seems to run great above 1000 RPM. My Jag dealer scanned it and said it registered a misfire on cylinder 1. I replaced the plug and swapped the coil pack with cylinder 2. The misfire still occurs. Upon scanning again, the message now points to Crankshaft/Camshaft syncronization. I have had the car in the dealer all day. They started out checking the sensors, then called to ask if It was OK to check my work to see if I had pre-tensioned the chains properly. I thought I had done it correctly, but not wanting to be too sure of myself gave the the go ahead. 3 hours later, reported back that I had done it correctly. Next test was the to run a sensor wave test. All seems to be fine there. They have kept the car overnight to run the wave test again, I think. The car starts fine, even after it stalls at idle. Although I understand the dealership is trying to resolve the issue, I hated spending several hundred dollars to end up with no answer. Does anyone have experience with such problems?

 

hate to ask an obvious question...what about the plugs....?

 

The dealer had the car all day again today. They do not seem to be able to pin down the problem. I will likely go and pick it up tonight or tomorrow.... most likely no better off than when I took it in. Their "service advisor", (not the tech) said the car was reportedly running great, so they thought perhaps there was an intermittent problem with one of the sensors. If the car is now miraculously running great, I will be happy, and may consider changing the sensors one at a time. My sense is that it is not actually running great, as it was only at idle that it ever acted up. When driving down the road, there is no sign of misfire or poor running at all. When stopping at a red light, rough idle is apparent. I am anxious to find out, but with second hand news, I am not too optimistic. The service advisor seemed to indicate that it was only a phantom error message they were ever chasing. I took it in due to the rough idle.

I though I should perhaps change all of the plugs, however the only message is the Crankshaft/ Camshaft sync problem. It is not displaying misfire anymore, although it is pretty obvious there is a misfire. The plugs have only got about 15,000 km on them. When the car is cold, it idles smoothly, but starts to misfire shortly after, as it begins to warm up.

Again, if anyone has exprienced similar symptoms, I would appreciate a response. After about $1000.00 and only knowing there is a check engine message,which I knew without spending the money, it is pretty frustrating. I am trying to steer myself clear from being angry at the dealer... but it is not easy. Apparently, rough idle is not all that simple to diagnose.

 

I assume that you have done all the MAFS, TB, part load breather stuff, including disconnecting/reconnecting the TB connectors. A little silicone grease on the connectors couldn't hurt.

 

Cleaned MAFS, TB, Breathers etc recently, but have not disconnected & reconnected TB connectors. Will give that a try.

Thanks

 

Mysteriously, the car has returned to smooth idle. Dealer could not explain, except that they thought the cmp sensor was throwing intermittant errors. I think they were chasing that... to the tune of $1004.00!!@@## No new parts were put on.
At least it is running properly, which is a relief, however the dealer warned the check engine light could show up again, since they could not pin down the error. I would have assumed replacing the sensor would have been simpler? ( Dealer has no parts and must fly them in !!##**)
Can anyone explain how the Crank & Camshaft sensors function together? Could a error in one sensor cause the car to run poorly, even though the valve timing was properly in sync with the crankshaft position?

Happier now ... but curious.