Good afternoon all,
I'm working my way through a 2002 XJR. I just finished replacing both breather hoses, the octopus hose, throttle body hoses, and the vacuum lines that I could get at on that side of the engine. Flushed the coolant etc etc. I haven't driven it yet but i'm getting more or less the same issues I had before all these new parts went on. It idles pretty solid at 650 but there is a hickup every 8 or so seconds and it sounds like some kind of solenoid is actuating. The long term trim seems pretty high. I'm assuming this isn't normal? If you put it in drive it is a lot better.




Any idea's where I should start to look here? No CEL's before or after besides where I turned the key on with it apart to run aux in from the trunk.

 

Did you do a hard reset to reset the fuel trims after all your work...best to do it.

 

I took the negative cable off and put it on the positive. That does it right?

 

You just take the negative cable off and touch it to the positive for about 15 sec. Does that do it?

 

Yes that should have done it..
Your live data..is at about 650 rpm and the engine is up to temp, (with high LTFT's)
If you look at the data with the rpm at about 2500 do the LTFT's come down? (in park with engine up to temp)

If they do its an indication you still have a vacuum air leak.

 

They do come down but not a whole lot. Not sure where else to look for one. All the normal spots have been fixed with new parts and couplings. Going to have to delve into more difficult areas..

 

Have you replaced the part load breather tube that runs under the supercharger? It connects to the left front cam cover, runs under the supercharger, connects to the throttle body, and on to the firewall someplace. The plastic tube gets brittle from laying on top of the engine block under the supercharger, and will basically crumble in your hands. It's a common source of vacuum leaks.

I used a Stinger smoke machine with mineral oil, and gently blew it in through the brake vacuum line. Wait a while, and you'll see the smoke coming out someplace if you have a leak. That's how I located the vacuum leak on my 98 XJR, anyway. It takes the guess work out of locating the leak.

Edited to add: you could also try spraying starting fluid around the engine with the engine running. When you hear it rev up, you know you found a vacuum leak in that vicinity. I tried that, but ultimately the only way I found the leak(s) was by using the smoke machine.

 

Yes, part load breather is a common air leak problem and also, in my experience, the brake booster vacuum connection on the throttle body adapter. Replacing the o-ring will correct it.

also +1 on the mineral spirits smoke machine, mine has saved me a ton of time searching for vacuum leaks!

 

Yeah, I have already done those. Full and part load breather lines, all vacuum lines on the back side of the engine. Brake booster hose at the throttle body but not at the booster side.

I would love to get my hands on a smoke machine, have they come down in price at all?

I've since driven the car around and it seems to be running much better now. What it was doing was a lot like when you cut the A/C on. A sort of actuator/solenoid type noise and a dip like a big electric load. I will check trims again tomorrow and see where I'm at.