1998 XJ8 83k miles

Ride was running great, until Ijust had throttle body completely taken off and thoroughly cleaned, ton of gunk cleaned out.This was definitely the first time it was done. This was Saturday, I've only drove the car about 35 miles since then. The whole car seemed a lot more chipper in general, but nowthe car has a hard time down shifting. It'svery jerky and you can feel it in the whole car. Seems that it really has a hard time coming to a stop getting back to 1st gear, as you almost get to a complete stop before it jerks into 2nd then 1st, slighty jerking the whole car.

My throttle body was replacedin 2005 for the recall at the Collection in Miami, FL, only about 15k miles ago.

I would hate to think that my tranny is dieing out of the blue now after cleaning the throttle body, but I wouldn't be suprised with this ride.Taking back to mechanic tomorrow for check, wanted to ask on here if this is common.

I had heard the car needs to 'readjust' to the cleaned out throttle body and takes a lil driving, but that sounds kinda like BS to me? Any insights. thanks guys, looks like i'll be driving the 04 again!

EDIT * Wanted to say that the dash presents no codes, no errors or anything. I will have them check tomorrow though and pull them to check.

 

Dunno, but if you're in "Sport" mode, try clicking it out for a while and running in "comfort", or vice-versa, see if it makes a difference. It may be that there are elements of the engine managemenmt system that do need to reset themselves after the clear out. Take it for a good long run, shifting between sport & comfort a few times. Might help, might not, but worth a try.

Peter

 

Hey there, thanks Peter for the quick reply. Actually yes I usually leave my ride in Sport mode all the time, and haven't really changed it out but maybe once or twice a while back, so that's definitely worth a shot never thought about it.

I actually just spoke to the tech at Moore Jaguar/Aston Martin 25 mins away on the phone and they had never heard anything like it, and said the "throttle body would have no effect on shifting like that", and said it's either just the transmission or try unplugging the battery for 20 seconds for hard reset. I'm about to do the battery now, I'll take it out of sport mode as well.

 

A HARD RESET IS NOT JUST UNHOOKING BATTERY FOR 20 SEC, ITS UNHOOKING NEG CABLE FROM BATTERY AND TOUCHING IT TO STILL HOOKED UP POSITIVE TERMINAL TO DISHARGE CAPACITORS ( MINI BATTERIES IN CONTROL MODULES) FOR 20 SEC, THEN HOOKING BACK UP, THIS IS A HARD REBOOT JUST LIKE WHAT YOU DO TO YOUR PC. ALSO YOU DID CLEAN THE PART LOAD BREATHER TOO DIDNT YOU????

 

Alright, well after unplugging the battery and resetting, it seems to have taken the shiftingproblem away, as the car is now shifting on the money, smoothly. Only been 20 miles andim off today so i'll give it a whirl. Ihave not tried taking it out of sport mode yet, will test that also and report back. Thanks guys!

 

Hrmm well I guess the dealership service guy wasnt much help then, not mentioning how the hard reset is really done. Or he just misunderstood me, mistakes happen!

AnywaysI unplugged the red and left off for about 5 mins and reconnected so ive no clue it seems to have helped hah..I dunno if we touched them together though. I can give that a shot also if need be.

Im assuming youre referring to resetting thecmos (complementary metal-oxide semiconductor) on a pc,by clearingit shorting thejumpers as the same deal. Only other way is to take the battery out and insert.

BTW yes they cleaned the whole deal, scrubbed it clean, they had spoke to jaguar about it as well (the stalling postI had previously back months ago)Anyways It seems to be doing very well still after another 35 miles of city driving shifting up and down. I've no clue, perhaps it just dislikes me! EDIT* ALSO thanks BRUTAL I will remember that information.

 

Don't know how you're getting on with this....but since you always had the box in Sport mode before the fuel clean out, it could be that you were just used to the car being more "slovenly" than normal, due to the c-ap in the system.

It sounds to me a little like normal Sport changing now, I have to say. My 98 XJ84.0litre stays in Comfort mode all the time and is a smooth as anything. I like to use Sport occasionally (especially if I'm on a country road run and need occasional extra overtaking power), and when in Sport the shifting is much more pronounced, as you describe. Maybe if you just try driving for a while in Comfort mode youll get to like it, and the gear shifts will feel a lot better! I could be wrong of course, and it could be something more sinister....

Peter

 

@Peter.H

Thanks for the info, i've no doubts the car runs a lot better after getting the throttle body completely cleaned after 10yrs. After unplugging the battery (soft-reset as I found out from brutal) it seems to be doing just fine again. I still haven't taken it out of sport mode, but I will give it a shot today and leave it on for a week or so and let the compy adjust. Thanks men.

 

just to update this post. the same throttle body problem has occurred to my car. i took off the throttle body last weekend to do the heater hoses running under the intake. I cleaned the tba also and i reinstalled everything the car started up on a high rev and stayed there. i turned off the ignition and restarted the high rev stopped and dropped to idle. however, while driving the high rev came back like i had it on cruise control. the dealer said i need a new throttle body assembly at 2k and change.

i will unplug the battery on a soft reset first. i will keep you posted.

 

Alckc,
Same thing happened to me after cleaning the throttle body / hard reset. Once I drove around for a while (with my foot over the brake) it seemed to go away in normal shift mode. In sport mode it seems to come and go. It's super dangerous, especially if someone who doesn't know about it is driving! I would like to know what is wrong also but am not shelling out for the throttle body just yet.

I'm really surprised that Jaguar hasn't had some kind of massive lawsuit in regards to this.

 

I tried both a soft and hard reset. Still having the high idle problem. Also, I switched back and forth from sport to comfort and stilll the same. Damn, it looks like I may need to get a new throttle body assembly. Well, its another addition to my already long "to do list."

 

Supposedly there was a one per customer recall on some models throttle bodies but my dealer was not aware of any such recall.

 

not a recall, service bulletins, totally different. the issue with high idle after cleaing is this. the idle air control solenoid in the TB controls the idle speed and the ecu knows how much to drive it open/closed to maintain correct idle(adaptive) what happens as the TB gets dirty is that the IACS(idle air control solenoid) has to open more and more as the opening in the throttle blade closes from deposits/ THen you come allong and clean the deposits away but the adaptive learning in the ECU opens the IACS to the same amount it always has(high idle now) it will relearn eventually but we always do a hard reset to clear adaptation and make the ecu LOOK at everything with new eyes. It starts back over at factory default settings and relearns from there. I would try a hard reset again and did you clean the IACS passage in the throttle body bore? it gets dirty too and sticky. This would be the ONLY reason I could see to replace the TB, I would clean it and go from there

 

A service bulletin, ah! I must have mis-read that being a recall somewhere.

 

Hi Peter, I had my 88 XJS taken in for an "induction" cleaning, and when I got it back the RPM was running high, it is supposed to run at 750 and 1000 and it was running at 1300 and 950, I had it adjusted to 750 and 1000 and then a few days later it dropped down to 550-600 and 900, the mechanic said it doesn't hurt it. So I have left it. One thing that bugs me is the fact that the car starts better when it is cold than when it has been run a hour or so, it still starts but not as easy....any ideas? Donna
So maybe the engine management system will adjust as mine did after running it.

 

This was my thread to start with my old ID, so an update.

hah my 98XJ8 had its throttle body replaced in 2005 from the dealer (I didn't buy until Feb 08 so it'd already been there for 3yrs)

It's been about a year and this problem for me appears it finally diminished (it has still done it once every blue moon on first cold start when put It into reverse) Turning the car off and back on fixes the deal. It's gotta be a computer having troubles with the brand new readings from the new clean pathways like brutal says.

Yes when I had mine done it was a hit or miss when it wanted to jerk around like this. Its not safe as the car would stick into 2nd until almost a complete stop, then it pops into 1st and jerks forward. Very unsafe if someone didn't know and rather hard on brakes i'm sure, as car didn't want to stop.

I can say that my car has probably relearned this by now, i'd hope after a year hah..because it really doesn't do it at all anymore.

 

For my problem, I will try the hard reset again before I go searching for a replacement throttle body.

 

@alckc

I just had exactly the same problem occurring after I did throttle body, part load breather, MAS cleaning. I folloed BRUTALs hard reset procedure and the car is now perfect and back to normal. I held the negative cable on the positive post of the battery for 2 minutes, just to be sure !

@BRUTAL

Great advice as usual from you sir. A question though..... after I did the hard reset, the first time I started the car it started fine but idled very high, around 1500rpm. The RPMs then very methodically dropped down and down and down until the engine stalled. When I restarted all was perfect, and after a quick test run I confirmed that the hard shifting and the high idling has completely gone. I was wondering if this stalling was normal after a hard reset ? It kind of looked like the car was trying to calibrate itself on its stall point ? If this is normal behaviour, maybe that can help alckc at least to confirm that his hard reset has been accomplished, and then if he still has the problem, it's more evidence to be an issue with the throttle body itself