This is a really weird situation. Four times in the last year my engine has just shut down with no warning lights, no codes and I can start it right back up by shifting into neutral and restarting. I've checked the usual culprits...ground straps, relays, ignition..( I thought maybe I was bumping it with my knee). Each time this has happened it has been on the same stretch of road...and I mean within 1/4 mile of the same spot in the road. It seems to happen just when the car has reached normal operating temperature. These events are weeks apart so troubleshooting has been tough. It never happens after a restart and it might not happen again for months. I'm open to any and all suggestions as to what could be causing this quirk. I've already checked for alien spacecraft above me when it happens and if it's a gremlin then he's staying low key. Any help will be appreciated. 98 xk8 vert Thanks

 

Can't tell you much about your car, but I can tell you that when I purchased my 97 Coupe about a month ago, the old maintenance records had a few entries on the engine shutting off at speed (usually around 70 mph). That would get one's attention on a busy highway.

Anyway, in my car's case, the records show that they replaced the original throttle body and the problem wasn't reported again.

Good luck.

 

at highway speed, throttle body connector is my only suggestion. Disconnect, clean pins (check for irregular pin materials), reconnect snugly, waterproof it.

 

first, let me state that i know nothing about cars. my 97xk8 was factory recalled, even though im the third owner. i ignored the recall cuz "it wont happen to me." when the car just quit, i took it to the dealer. looking at the paper work right now. says.... reprogram existing e. c. m. using w. d. s. ecm needs a software upgrade attempt to reprogram ecm. it says it took four attempts to reboot. but you probably knew that, right?

 

Here are the 2 service actions from years ago

bob gauff

 

You might try cleaning your throttle body bore as an attempt to correct your stalling. I think it is possible it might be coked up some and sticking at times.

A little background: The 4.0L V8 has a function in the ECM that causes the throttle plate to fully close itself about every fifth closed throttle coast. My understanding is that this function was added in a software change somewhere in mid 1997. They said it was to help keep coke from building up and causing butterfly sticking, and to continuously re-zero the throttle adaption for more stable idling. They also added a molybdenum coating to the bore surface, also to reduce sticking.

Coke can still build up though, especially if the part-load breather gets plugged up. If that happens, every once in a while when it closes the butterfly, [it just snaps it closed and then releases it] it can stick and bingo, it stalls. It will almost always immediately start right up leaving you wondering "what the he** happened"??

You just have to be sure to use a cleaner that will not harm the molybdenum coating. Valvoline SynPower is one, and Pennzoil's Gumout is another. There were a couple of others, but I can't remember them.

Hey, it's easy to do, might be worth a try!

Cheers,

 

It does sound like the TB and chances are it is but you can try a few things as suggested. Check the TB plugs "TBoddyPlugs" Also cleaning the TB is a good idea, This is how I do mine now "XK8 Throttle Body Cleaning" It is a shame that you did not take advantage of the TB recall when it was available. However, you can get a rebuilt unit from several venders. If you need vendor information let me know. Try this http://www.jaytanindustriesinc.com/index.aspx

 

Thanks for all the responses. I guess we are looking at the throttle body. The vin on my car indicates that the fix is TB replacement and not reprogramming. Too bad I didn't own the car when the recall took place. So far it has just been a minor irritation and my wife refuses to drive it because of this. (probably not a bad thing) I'm going the cleaning route first...see how it goes. If that doesn't fix it then I'll replace it with a rebuilt. The service action exactly describes what is happening with the car. It happened once a year ago but now it has happened 3 times in the last month. Again thanks for the responses and I'll keep you all posted.

 

The TB plug has been a problem on many cars so be sure to clean them and refit.

 

these cars sure have a lot of / not ifs, but when it will go bad. we got timing chains, water pumps, throttles, rear view window mirrors, convertible top pumps and hoses. i havent had the convertible top problems yet, but then i only have 62000 miles. after reading the stories on the forum, im afraid to put the top down. but, i guess i can wait until i get the car out of the shop to worry about that. (timing chain). the book at the secretary of state says this car cost 70000 grand new. so i pay about 260 for the plates. this is my first time in a forum, so im going to assume ford and chevies all have these problems too. i just never hear of them, right? other wise how could jaguar sell any cars?

 

Just a comment... I had a 1996 XJ6 that did just exactly the same thing. Once every 6 months or so, I'd drive along, it would die, shift to neutral and re-start. My super-master Jaguar mechanic cleaned every electrical plug, cleaned the throttle body and just about everything else he could think of. Usually happened after 3-4 miles of travel. I put over 100k miles on that car and we never could figure it out.

So I'd be curious of you get it cured to hear the solution.

 

With response to Mike Mitchells post.
Im also on the Merc forums as my Dad owns Mercedes (Tried to tell him his error but he wouldn,t listen) Mostly he takes them in to the local Merc swindler to have his wallet fleeced and from this experience I can say that Jags are no more unreliable.
The nature of these forums is for "Problems" No one ever posts to say "Drove 30k miles this year and fk all went wrong" ..... How boring would that be!

 

When the Service Action was going on I talked to Jaguar 'tech line' and one of the guys told me that the replacement Throttle Bodies had the throttle 'CLOSED' stop adjusted so it would not close COMPLETELY. You could find the stop screw and turn it until the plate stops with a few thousandths of an inch gap (like setting the earlier mechanical throttles on the 6 and 12 cylinder). I never tried it but it sounds like it is worth a try. I have a box of old throttles (AJ26 and AJ27) so I might look at one and play with it a little.

just a thought

bob gauff

 

I cleaned the TB and MAF sensor today. There was a ring of "coke" in the TB that could have caused the butterfly to stick. The engine runs smoother at idle and seems to accelerate better. Thanks for the help and we'll see what happens.

 

its definetly the throttle body. those things are computers themselves. when seal crack in those it let oil and water get into the electronic parts of them.