Hello....my 3.0 XJ runs very well except when idling warm/hot. There is a slight vibration in park...it's not bad but not 100%. It goes away with the slightest throttle input and not noticeable in drive. I don't see any codes. Any ideas? I only have 1mo of warranty left and am debating whether I should bring it in...if there is no code I doubt they will do anything besides prescribe cleaners for inflated prices.

Thanks for your help
TJ

 

tjankovs, you could try removing the intake tube from the throttlebody and then using a little bit of carb cleaner on a rag or some throttlebody cleaner on a rag, wipe the inside of the throttlebody. You will most likely see a nice brown coating on the inside of the throttlebody. Wipe until it is shiny silver again. Do not forget to wipe the edge of the butterfly valve (the silver disc that is blocking the air flow). See how the car idles after that cleaning. If it is still running rough, take it into the dealership.

 

interesting, i have a similar vibration, through the cabin when im standing at a stop light.....its noticable when the car is at certain angles. at first i kept thinking maybe its a motor mount or tranny mount, but a bunch of people have told me those are fine.

 

My opinion is motor and transmission mounts. I've had this exact issue and the mounts solved it.

 

A cheap suggestion?
Run a can of BK 44 thru it first.
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Thanks Thermo......I'll give the throttle body cleaning a try. This often worked on my 1996 Vette.

 

Thanks clubsirth1.....I already ran the BK44 with no improvement. Good idea though.

 

is there an instruction video for throttle body cleaning?

 

My opinion is also motor mounts. Mine were bad when in reverse, but under throttle no real issues.

 

I wouldn’t trust someone saying the mounts look fine. If they are old, they will need replacement.

Technically you can tell if the engine mounts are worn visually (they will crack and leak), but can’t really tell whether a transmission mount needs replacement by eye (though possible, ours rarely leak). You can see how much shifting of the engine occurs when you press on the throttle out of gear, but to my knowledge you can’t really do that for the transmission mount.

As an example, my mechanic told me that I needed one engine mount after looking at it. Afterwards it turned out both were really bad. But he said my transmission mount was fine. I later decided to replace the transmission mount anyway because of sounds coming on and off of throttle. Sounds went away even though the old mount looked fine.

So overall, I wouldn’t trust a visual inspection of the mounts. Mine we’re ready to replace after 8 years, 80k miles. Made a big difference.

 

Sounds like motor mounts should be replaced while I still have CPO! Any tips to get these replaced?

Thanks
TJ

 

I’m sure they are considered wear and tear items and are thus unlikely to be covered by any warranty. But it doesn’t hurt to ask.

If they are not covered by warranty, then I would have someone check your engine mounts for cracking/ excessive movement of engine. Then if one needs replacement, replace them all (both engine mounts and transmission mount). They age at a similar rate IMHO.

 

You can do a simple test for the motor mounts.

Open the hood and start the car. Put it in gear with your foot on the brake. GENTLY raise the RPM's while holding the brake and watch how much the engine moves in the engine compartment. Do it in drive and reverse. If the mounts are bad you should see some movement. Another clue is to check the flexible plastic intake tubing as it will take most of the abuse caused by worn engine mounts and excessive engine movement.

BUT be aware you may not see anything and still need to replace them. The XJ has fluid filled mounts for smoothness so also get the car in the air and look for stains or leaking fluid if they are really bad.

As was posted above the transmission mount is almost impossible to test and outside of just replacing it you can't really tell if it's bad.
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i guess i will bite the bullet and get them all replaced, even though 3 mechanics told me they looked fine. car is 5 years old now, just hit 33k miles....will do a tranny fluid change as well.

it also clonks and vibrates on shutdown...i think the supercharger snout (or that other piece inside, cant remember the name) needs changing

 

Have the super rough idle/full dash lights problem. I haven't been able to pull codes since I bought the car 2 months ago. Tried all the standard fixes suggested in here. Would buying Jag SSD or a more expensive meter (which mentions Jag compatibility) solve the problem? Indie had no problem pulling codes. That's the only reason my car is at his shop.

Odd that disconnecting ABS (C1095, module defective) got the car to idle perfectly smoothly. Installed a rebuilt (Module Masters in ID) and idle problem is back again. All coils replaced by seller. When the car runs, it's great. Too bad this doesn't happen more often. Codes are PO300 (random misfire), PO305 (#5), PO308 (#8). Indie thinks secondary circuits (coils) aren't triggering correctly and wants to replace the ECU. Comments appreciated.

 

Sorry this should have gone to the XK8 thread. Still learning!