Ok so new to this. Just bought my first foreign car and not really sure what i got myself in to. Its a 1999 XJ8 base model. I bought it knowing that it was throwing a P0300 code. I looked it up and figured it shouldn't be that bad of a fix. So to start I replace all plugs with NGK Iridium's. Out of the 8 Plugs i pulled only 1 looks like it wasn't firing so i had just ordered a new coil pack ( hoping that it will kinda help). Also had a vacuum line from the brake booster to the throttle body broke ( Just found one online and ordered it last night with new fittings also). But the main question to all this is need help and ideas of what could be going on. It wants to fire but it just cranks. Checked all the fuses and they are all good. Injectors are working, Fuel pumps kicks how it suppose to, Fuel in the fuel rails, Air filter is clean, New MAF sensor. Starting to get bummed that i cant figure this out. so any suggestions would be much appreciated. and any questions dont hesitate if. If i forgot anything im sorry. like i said i am new to this Forum stuff. Thank you.

 

Welcome to the forum and congrats on buying a long term headache. Your problem is almost certainly cylinder or bore wash at this point. Many threads discuss this if you use the search function.

Basically, cranking a cold engine without starting or shutting off before operating temp allows the rich starting fuel mixture to wash the oil off the cylinder walls, resulting in low compression. If you hold the pedal to the floor and try short bursts of the starter, then slowly lift the pedal part way you may get it to fire. Flooring the pedal shuts off the injectors.

If that fails, remove the plugs from at least one side and add about a teaspoon of oil to each cylinder. Then cover the bank with an old towel and crank with pedal floored for a few seconds to distribute oil, replace plugs and try to start. If it does start be prepared for clouds of oil smoke.

If it still doesn't start come back for more help. When you have time, please visit the new member area and introduce yourself:

New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum

 

Hey Nick, not usually here but in the XJS area, welcome my son, as far as whats what, there is a lot of help here as everyone here loves their JAGS. I will continue to look up things with ya,

 

found this post, hope the link works for you

https://www.jaguarforums.com/forum/g...d-first-30792/

 

well sold the xj8 found out the tensioner broke which through the whole motor. so thanks for the advice

 

Sorry you had such an unfortunate experience. Thank you for sharing.
May your next vehicle be the best ever whatever brand it is.