Throttle sticking

1996 XJ6. been sitting last couple years a lot, not run on highway last 2 till now. i replaced the ECM and the throttle positioning stepper valve. cleaned throttle body well. the sticking seems to be the shaft itself, looks like a steel shaft is in a bore thru to the top cruise control attachment. hard to explain but if you know the car you will understand. i found in the archives about trimming off some of the spring to give it more tension. i see 3 torx screws , if i remove those does the assembly lift off with out finagling, and it will return ok too??? idle is good till you give it just a little throttle, then it hangs there around 1400, pop the pedal and it returns to 800. I was thinking the steel center shaft needed polishing where it go thru the pot metal/ alloy whatever. i have given generous amounts of PB blaster to the shaft and tried to work it in well with engine off. its better but still not safe to drive by the wife. her car so… got to get it going so i can go back to my E project. its sure a nice car though, still smells new 98,000 miles.

Here is what we did at the dealer in the late 1990s and early 2000s.
Jaguar issued remedies for this affliction.

05-1-15 Intermittent High Idle.pdf (127.2 KB)
05-1-23AM2 Throttle Deposits_Sticking Closed.pdf (29.5 KB)
05-1-26am5 1995 MYRecall R493.pdf (256.2 KB)

Sometimes you just need to completely disassemble the throttle, clean, polish and reassemble.

bob

interesting reading bob, thank you. the ECM i installed had the rework tags on it, last one in 2001. my friend that has the electronic checking machine is still having serious heart issues so for now i will only be able to check the spring. in the archives it was mentioned that they modified the spring at some dealerships. ill have to go back read that again as i do not have a new one. will post results

Don’t modify the spring!
Spray throttle body cleaner on a rag!
Wipe BEHIND THE BUTTERFLY AND SHAFT.
Don’t spray direct as it will blow out the sensor.
Just do what I’m telling you and report back.
That will do it. Hopefully.
You will see a CRUST line that will keep the butterfly from completelty closing.
Use the rag again and really really clean it all out on the engine.
The x300 saved Jaguar, the xj16 is a bullet proof engine, because it was still old school it created ALOT OF BLOWBY inherent in all straight 6 at the time.
When new they recommended “bg oil additive” every oil change, 20/50 in the summer and 10/40 in the winter.
I had 5 of them 2 since new, 150 to 200,000 miles is a no brainer.
Just clean the throttle body real good.
Good luck
gtjoey1314

Just saw your post now. i pulled the throttle cap off of the lower spring. lubricated it. there is nothing binding on cable or throttle cap. the butterfly just does not like to return completely. so like a Model T ford i added a light spring up top, did the trick, doesn’t interfere with anything. Ill have to get into the throttle body i guess. we did clean that out when we installed the new stepper valve but my friend did that and i did not see all that was involved getting things off. i know we drained a lot of coolant out for some reason, lots of things were disconnected. I dont like to go in blind, ill have to research whats involved getting to the throttle body to clean it. maybe it will sort out after a couple tanks of gas with the spring on? probably not. Its headed up to the farm in Illinois april 22, i want to drive it as much as i can before hitting the road. need some new tires. cant decide what to buy, good year michelin or vredestein. want a quiet ride is all. why does it close when i blip the throttle or hook on more spring if its crud under the butterfly? at start up its always at 800, trouble doesn’t start until you give light throttle pressure and then let off without a blip. will hang up 100% of the time. with spring go right to 800…

I’m assuming you took the throttle body completely off of the intake manifold. That’s the only way to make sure it’s clean.

While you’re in there, remove the TPS so you don’t have to concern yourself with the costly sensor. There’s a chance that the gum could be in the TPS as well?

Then have at least one bottle of carb cleaner on hand and get to work! There’s a small bypass hole that gets clogged as well as some other nooks and crannies. Bring the shine back to the brass butterfly and silver opening. That thing will be snapping back all on it’s own.

…unless of course you’ve already done this? It’s just bolted on by 4 bolts…

My mechanic friend ( the one with new heart condition) told me today that the cleaned the throttle body completely. he had his own shop for 30 years doing lots of special cars , Mercedes, Jaguar and domestic. a very good mechanic. he says there is something amiss, i shouldn’t need the spring . however i’ve read Jaguar routinely replaced this spring for free on recalls. So everything seems free , well lubricated. it works perfect with my spring. i’m leaving it as is. i thank all for suggestions given. if it acts up again ill go in otherwise, don’t mess with something that is working. my motto. what does the bypass hole do? my idle is consistent at 800 after start up . a little higher initially but never over 11.

Dude, do it yourself, it’s really not difficult, when the weather gets nice, it will take you maybe two hours.

I’m not saying that your mechanic didn’t do anything, but I wouldn’t be surprised if he cleaned it in place.

Have a golf tee on hand and there is a small hose running coolant just under the throttle body, where the tps is. You’ll need to disconnect that hose (shove the golf tee in the hose so the coolant doesn’t leak out and tighten the hose clamp), unplug the tps, disconnect the cruise control bellows and then four bolts and it’s off. No gasket to worry about!