Guys

Just picked up a 1998 XJ8 3.2- it's a lovely car and was the right price with pretty much full service history and LPG conversion.

Driving it today, I notice only one significant problem. When the engine is at idle, or when slowing down to just before idle, the car seems to shudder. It doesn't stall, but just shakes a bit at idle-it's a really odd sensation.

It drives absolutely fine, smooth gearchanges and no stalling or warning lights.
It does the same on either LPG or petrol so I'm pretty sure it's not a fuelling issue.

Any ideas as to what the problem might be? It's not been serviced for over a year so I was going to do that as a matter of course.

Many thanks for your advice.

 

CEL? Codes?

 

Sorry-I'm new to all this. I assume you mean fault codes, which I intended to get checked after servicing, but what's CEL ?

Thanks.

 

Same as proper name - MIL.

Get an OBD tool - one with live data - and look at fuel trims as you may well have an air leak.

 

This kind of thing?
Car Scanner EOBD OBD2 OBDII Diagnostic Data Live Code Reader Check Engine Scan | eBay

 

Right. Just realised what you mean-no, no check engine light or any other warning lights visible. All normal whilst moving but rough idle. A friend has suggested it might be a coil failing-would this appear on a scan?
Thanks

 

Maybe. I'd stop guessing and look at live data. Very cheap to do.

 

Ok. Took it to a Jaguar independent garage today. He initially thought timing chains, but they are all very recent with metal tensioners. He did a compression test which shows three cylinders to be below par, two on one bank, one on the other. It is this that is producing the shaky idle. The car still drives fine so I've decided tpo put up with it until I decide whether it's worth a rebuild.....

 

My xj8 idles roughly. I am of the opinion that there is/are intake gasket leak(s).

 

Does anybody know what the torque values should be for intake manifold bolts?
Thanks.

 

Check fuel trims using OBD live data.

 

When I get that condition, it is usually a bad spark plug or wire leading to the plug. You should put an OBD reader on it to verify.

 

When i sprayed quick start at the intake gaskets, the rpms increased and that is the reason i think i have vacuum leaks at the intake

 

Hi ysgeye,

According to the Workshop Manual, the intake manifold-to-cylinder head bolts should be torqued to 21 Nm (16 ft. lbs.).

You can download the X308 Workshop Manual at the link below, courtesy of our member feloniousmonk. It's a very large file (66MB):

http://dl.dropbox.com/u/13224034/XJ-...Manual.pdf.zip


Cheers,

Don