Hi All,
After 11 months trying to get my 2000 XK8 Titled and Registered, she is finally on the road. But now she is idling roughly. I put a few gallons of Premium Gas in the day before. With no codes being shown and not running in Restricted Mode, I'm not sure where to look. Vacuum leak? Fuel filter? Battery voltage?
All of the above?

Much thanks!

Eric "erjent" Jordan
Punta Gorda, Fl.

 

If it's been sitting a while the fuel pump may have gone south. You can check the fuel pressure with an OBDII reader (I think, not sure about MY 2000). Fuel filter might help. Techron wouldn't hurt either.

 

Many thanks!

 

When you say no codes, are you talking about the dash display or did you put a good code reader on it and pull codes?

AFAIK there's no fuel pressure sensor to monitor, so you'll need a pressure gauge that attaches to the Schrader valve at the fuel rail. Memory is fuzzy, but I think it needs to be in the 60 PSI neighborhood. Weak pressure could be a bad regulator (an easy fix), bad filter (messy to change, don't forget new o-rings), or bad pump (world class PITA to replace).

Voltage is the first thing to check. Engine off, battery should be around 12.5 volts. Running it should be just over 14. Then check for vacuum leaks. Smoke test from the MAF, or spray some brake cleaner around the base of the intake manifold while it's idling.

 

Wow! Lots of good stuff to look for! No OBD codes. This morning I was getting Misfire rate exceeds emissions. I'm wondering if wrong Spark Gap could be the cause.

 

It won't hurt to pull a plug and check its condition. Usually misfires are a fuel problem - not enough. So, the usual suspects are vacuum leaks and low fuel pressure. If it's none of those three you have to dig deeper. Usually the code reader will tell you which cylinder(s) are misfiring. A tried and true diagnostic method is to swap the coil on a misfiring cylinder with one from a good cylinder and see if the misfire follows the plug.

What code reader are you using? These things are super finicky about readers. I have access to five different ones, and none of them work well for all modules and situations.

 

Thank you!

 

You always have either P1111 or P1000 so which have you got? Change OBD tool if neither!

That's a sign of serious problem(s) so code(s).

Dodgy OBD tool?

 

Just a P1316 Misfire rate excess emissions. I just ordered a new fuel filter as a start.

 

Odd.
The 2000 DTC list states:

"
Misfire excess emission
NOTE: This DTC will flag only when
accompanied by an individual
cylinder misfire DTC: P0300 –
P0308.
"

 

Thanks! That's what I was driving at. Misfire codes are always accompanied by a cylinder number. It's really tough to chase down misfires if you don't know which cylinder is misbehaving.

 

This may not help, but then again it may. When my previous 2005 S-Type threw the P1316 OBDII code while still under the factory warranty way back in 2009, the issue turned out to be a faulty throttle body. A new throttle body immediately fixed the issue. While I was glad to get a brand-new one under warranty, I always wondered if it was just my original throttle body gaskets that needed to be replaced....

 

It doesn't send any other code.