I'm having an issue with my 1999 XJ8. Every so often the message center shows performance degraded and the engine lopes while sitting still at idle. Any ideas as to what could be causing this issue. Any help would be greatly appreciated. Thank you.

 

You need to have the codes read, most auto parts stores will do that, and report the actual codes here. Chances are good it's a throttle body issue, so try cleaning the connectors with electronic cleaner.

 

After awhile it goes away and everything acts like nothing happened. The last time it did it I put my scan tool on and I don't recall if there were any codes. The next time it does it I'll check and see if any codes present. If there are I'll post them. I will try cleaning the throttle body connecters. Thank you.

 

Hi Chewy,

I second the throttle body check. Also, check the spark plug types, gap and condition. Stay away from AC Delco. Get Platinum NGK's. Made a huge difference in my 2000 VDP (2018,000 miles). The injector bodies have also been replaced.

 

Its happened again and it set the following codes;
P0305 Cylinder 5 misfire,
P1314 Misfire rate catalyst damage bank 2,
P1316 injector driver misfire emissions emissions damage/misfire rate excess emissions
P0355 ignition coil E primary/secondary circuit
P1266 Security input vehicle immobilized theft detected
I have changed the spark plugs with the correct temp rating plugs NGK Platinums, I have not cleaned the throttle body contacts yet. Gonna try and do that this weekend. If there is anything else it could be the information would be greatly appreciated. I usually do my own work on my cars, hopefully this won't be too big to handle.

 

Clean or replace the MAF sensor; clean the throttle bore and plate and connectors; check battery voltage; check for leaks along air tube from air filter; change the air filter. Run a good fuel system cleaner through the a tank (BG44K or SeaFoam).

If this is happening at the first cold start, it could be a bad temperature sensor failing to recognize the need to enrich at starting. Gotten cold here in Tidewater lately.

 

Might want to replace the ignition coil #5 or swap it and see if the fault follows the coil?
(sorry about the #3 comment, hit the wrong number key)

bob

 

Air filter is clean. It never stalls out and it sends the degraded performance after its been running for awhile. its not consistant as to when it does it. It does seem to throw the same codes. I will try everything else you suggested. and let you know. Thanks

 

How are the cylinders numbered? I know that on Fords they are numbered front passenger side, front to rear 1,2,3,4 etc, and on Chevys they are numbered 1,3,5,7 etc.
The reason I'm asking is that in my manual it says for code P0305 its number 2 cylinder. I tried swapping what I thought was the number 2 cylinder and the same code came back. Just want to make sure that I get the right one without playing musical coils. Any information would be greatly appreciated. Thanks again.

 

P0305 is cylinder No. 1 on the LHS bank. Here's the numbering and codes:

 

So looking at this they are numbered like a Chevy, Passenger side is 1,3,5,7 and driver side is 2,4,6,8.

 

Are you looking at the same illustration that I am?

FRONT
5---1
6---2
7---3
8---4

 

I'm sorry. I brain farted. It's numbered like a ford. Thank you.

 

It looks like I found and fixed the issue I was having. I had a coil pack going bad. I replaced it and haven't had the discrepancy come back yet. I would like to thank everyone for the suggestions and possible fixes.