My Jaguar XJ8 had recently developed a fault when started from cold most of the time it runs rough and tries to stall. You have to rev the crap out of it to stop it stalling. Then it idles fine and drives ok but sometimes stutters slightly like it is getting a lack of fuel. When starting when it has been running it's ok.

 

Look at the fuel trims, both LTFTs & STFTs, for clues.

A small air leak would be plenty for what you suffer.

 

Yep: need to see the codes and review the LTFTs. Couple of thoughts, tho: clean the throttle plate and bore, mucked up, can cause bad idle at start and poor acceleration; clean the MAF sensor and check the prongs are not bent; check the air tube from the air cleaner to throttle; how old is the fuel filter? Plugs, too?

Final thought (for now): some times the temperature sensor will go bad and either fail to enrich the engine on start up or enrich it too much if it is warm out.

Always useful to know what year, model, and mileage -- put it in your signature.

 

It starts up fine now and does not run rough on startup. I cleared the ecu so maybe the ecu adjusted itself. There is a slight petrol smell coming from the exhaust. It also seems to be loosing water. I cannot see it leaking anywhere though. I have put k seal in it to see if that will stop the leak.

 

I don't know how many miles you have on that car but I think I have experienced a similar situation due to oil leaking into the cylinders. Then again, a dirty maf sensor has also caused my fuel trims to go to the extreme. Then again, maybe you have a faulty coil pack. Usual basket of possibilities I guess.

 

The car is now running perfect and starts fine. After resetting the ecu it seemed to get better over time. It is still using more petrol than it should and can smell a slight petrol smell from the exhaust. I am thinking it's the maf sensor as they left the hose slight disconnected where the maf sensor is. After I reconnected it properly the problem started.

 

You need to have your OBD II read for codes and LTFTs. You are running rich. Did you get your coolant leak fixed?