New to me '08 XJ8, my first since a bunch of X300's. Bought it with a CEL and a code for MAF sensor. New MAF, found a few vacuum leaks, but it's still acting weird. Smells like it's running rich. Lumpy idle at cold start, but evens out fairly quickly. Runs great, but I smell raw gas coming through the vents before the a/c switches to recirculate every time I start it. I keep getting intermittent running rich error codes in one bank or the other from time to time, and my drive cycle just will not complete so that I can pass inspection.

I don't know it my old reader is reporting properly, but it shows short term fuel trim at -24 stopped at idle. On neighborhood streets it will get up to -6, but drops quickly back to -20's as soon as I take my foot off the throttle. It will rise to around zero on the interstate at speed, but again drops quickly when I let off the gas.

I do not see anything wet or leaking anywhere on the engine, but I believe I smell fuel around the left side fuel rail while running.

That's all the data i have. What are the symptoms of a leaking injector? Is that a possibility? I've never had that problem on any other Jag before. How would one check? Any other ideas? ANY suggestions would be VERY appreciated!

 

Under the circumstances described, I would first safely rule out the possibility that leaking air cause the problems. As long as this cannot be ruled out, further searching does not make sense.

Advanced workshops have devices that generate fog smoke, which is directed into the intake area. If there is a leak somewhere, it becomes visible.

In addition, I would have the vehicle diagnosed with the original SDD, actually only with SDD reliable diagnoses are possible.

Fritz

 

Air leak causes +ve trims.

Look for other causes.

 

Thanks to you both. I've got a homemade low pressure smoke generator that I've used to track down a leak or two. For instance, the hard emission line that comes from a splitter just behind the throttle body and runs to the sensor at the front end of the fuel rail on the left side looked good, but snapped in my hand when I noticed tiny whisps of smoke coming out. I'm not finding any others, but it's a fairly low pressure rig.

I'm going to pull the injectors next and maybe see if I can put together a test rig on my bench. But if anyone has any other suggestions, I'm all ears.

 

The sensor on the LHS at the front end of the fuel rail sounds like the FRP sensor

There are two types and one type measures pressure v engine vacuum and if

that vacuum line is cracked or broken and leaking it can cause problems.