I have a 2004 x type 3.0 with 146,000 on the clock. It runs like a champ, gets great mileage and has no issues but one; it has an intermittent "misfire".

I quote misfire as I'm not absolutely sure that's the case. Here's how it happens. Just as the engine warms sufficiently to allow the trans to go to overdrive (top gear), if at that time I'm under light acceleration with some load (like a small hill) the car will jerk a couple times as though it's misfiring. If I give it more throttle so as to force a downshift, it won't jerk. If I lift my foot slightly, it won't jerk. I have an ELM327 and have watched MAF flow, air/fuel, timing, manifold vacuum and fuel pressure during such an episode and I have not seen any changes in any of those readings. The engine temp will be above 170 but less than 185 degrees F. No codes are set or pending. I don't think the ELM and the Torque app will show injector pulses.

I've searched this site and the net in general and have not read anything about such a quirk in the trans.

I don't have a record of the last tune up (having bought the car with 144,000 miles last year) and the only plug reachable looked decent (it was an NGK) with gap being in spec. I am going to do plugs, IMT seals and plenum seals soon.

But in the meantime, I was just wondering if anyone else had experienced anything like this. Mind you it is only once during any drive cycle, right after the ecm allows the trans into overdrive (or top gear) and then only under light load.

Thanks in advance for your help.

 

Hi Silkcat,
Is this just on start-up or at regular intervals after driving, say 10 miles or morestopping etc?
It could be a few things and I'm not certain at this stage but maybe Thermo or one of the more experienced mechies will know.
I am thinking it may be your throttle body control/censor (TBC), which would affect the flow of fuel or fuel pump/fuel filter.
Hope you get sorted soon? Regards, Stu

 

Silkcat, I would say to dive into the engine to do a plug change and see what you find there. I am betting you will find that on the plug wells nearest the firewall that you are going to find the ones near the passenger side of the car will have some oil in them and that is what is causing the issue that you are seeing.

While you are into the engine, it would also be a good time to clean the throttle body just to eliminate anything there and also cleaning the MAF sensor would be a good idea since you will have easy access to it too.

 

Hi Silkcat I have a car with similar miles and age...........and a similar thing going on. It is very infrequent on my car, and only happens between 4th and 5th and last time was under gentle acceleration going up a hill. I don't recall the time before that it was so long ago - when it happens it is noticeable but then it's gone and I'm left thinking what was that?

the transmission seems to be hunting between the two gears in certain specific conditions that don't occur very often. It struggles to choose. I half expect "what gear do you want?" to appear in the message centre.

My guess is that for an engine problem to only occuur when shifting from 4th to 5th would be pretty freaky but I have no clue really.

I feel this is another lovable trait of the old dog to go with 30mph whistle, etc - reminds me I'm in something a bit different and a "never mind, not to worry" sort of thing!

 

Thank you all so much for the replies.

Stuart - it only happens from a cold morning start. This appears to be the only time the ECM holds the trans in 4th until the engine or trans (whichever it is monitoring) has reached a specified temperature. The coolant temp is around 175F when this happens and I get the "misfire". If I drive thru that point, it won't do it. I should also add that the rpm's will be less than 2500 when it acts up.

Thermo - I had a 94 Thunderbird that had a like misfire at low rpm under light load. Ended up being a bad plug wire. It never set a code either (of course that was OBD1). Just that the one on the X Type is temp dependent where the TBird would do it anytime rpm's were low and load was high. When I bought the Jag last August, I replaced the fuel filter, pcv and cleaned the MAF and throttle body. I noticed a big improvement in power after those items were done.

Danny - yes, it feels like the trans is trying to decide which gear. If I manually leave it in 4th, it never "misfires". And if it's in 5th and misfires and I accelerate hard enough, it effortlessly downshifts. Mine doesn't act up every time I drive it either. Tends to be worse in winter, seldom acting up in the summer.

I'll report back after the plugs and seals go in. Thanks again gang.

 

Good luck Guys,

I think Thermo is spot on with the plugs.

I tend to go easy after start-up, with my automatic, especially after cold/wet weather as I think the AJV6 is fragile as I do sense a lull in up-changing and especially uphill when cold and just starting out.
I think the engine is great after initial warm up and I feel my jag can do anything!!!

OR maybe I'm getting older and cautious!

Danny, go with the flow, you sound happy! and thanks for the input, Chris, I am taking notes here, thank you again!

Silkcat, you sound good too, good luck with the plugs! Stu

 

Cheers Stu - yep, fat dumb and happy as they say and going with the flow....... that is until the car grenades under me ..... at which point my wife will think xmas has come early because she'll get a new(er) car!

Maybe a 2006 X.................... ;-)

 

Plugs, plenum and imt seals installed today. Felt pretty good about it having accomplished it in 2.5 hours. No oil in any of the holes. No traces of flashover on any of the coils. It had green seals and it has one replacement coil. Given it had NGK's and 140+ on the clock, whoever did it the last time upgraded the seals. I replaced them anyway, having no idea how long they've been installed.

Fired right up and idled perfect. Tomorrow it gets a test drive as that will give me results from a cold start.

I'll report back if this solves the mystery "misfire".

 

Nice 1 Silkcat!

Wish you good luck and congrats on the job... Job Done

 

One cold start run so far and no misfire. I didn't have the opportunity to run with the ELM327 so I don't have comparison readings yet. But it felt more sure of the gear changes. Perhaps the electronics for the trans look at vacuum as a measurement of load and maybe one of seals was leaking when the engine was cold.

I'll report again when I run with the ELM.

 

Didn't see anything obvious on the ELM. But then I only had the misfire just as the engine reached operating temp, a very short window to analyze. Regardless, I'm very satisfied. I feel better knowing the state of the plugs and seals. Now to drive and enjoy.

 

Hey everyone. Sorry to resurrect this post and sorry for the LONG reply, but I have a similar situation however it seems to be the opposite scenario. I have the similar "misfire" issue uphill, but it seems to be occurring when the car is at operating temp. A little back story. In 2012 I had to replace the TPS and apparently in order to replace the TPS you have to replace the whole Throttle Body. Well, I did that and everything was fine until Feb of last year when I had to replace the Pedal Assembly. Both times I received the Gearbox Fault message and it was traced down to these two things. The car has run very well since although I always felt like there were little misfires or, as I would describe it little bubbles popping, when I'd go uphill. I could feel it in the peddle and it was ever so slight. I don't know how else to describe it and it never really affected overall power it was just an annoyance that I thought was because the car needed a tune up. Never had a misfire like what's described in this post though. With the assumption that this was a result of a needed tune up, I took it down to have it tuned up as well as had the plugs replaced. When I got it back the car ran much better, but I didn't notice a huge difference than before. After driving around for a bit I drove home, which is up a hill, and it misfired like described in this post. I took it back down to have it checked as I though it was tune up related. They tested it and experienced what I experienced. They took it apart and checked the plugs and coils, all looked fine. They hit the coils with some Dielectric grease and adjusted them a little and reported no further problems. I picked up the car, drove it around and it was smooth and glided along with ease. Gave me the warm fuzzy feeling since I hadn't realized how much better it could have ran than how it was running before the tune up. Had good power throughout with get up and go. Progressively over about 2-3 weeks it started to run really rough. A one point I was stopped at a light and it jolted slightly. I was prepared to anticipate a Gearbox Fault message and sure enough I got one a day or two later. I took it down to the shop who replaced my Pedal Assembly and Throttle Body and they diagnosed it as the codes reporting it was a Throttle related. They completely reset the points for the TB, which they stated they didn't do before and only reset the ECU, and said that hopefully the car will re-calibrate the TB based on my driving. This occurred a week ago and so far, as I write this post, I haven't had a Gearbox Fault message. Yesterday though, while at operating temp, heading home I was traveling uphill and it misfired. I had it in 4th and just gave it more gas and it stopped. Nevertheless it's still bothersome. I'd like for the car to run how it did right after the tune up when they put the dielectric grease on the coils. It literally felt brand new! Any ideas what I could be looking at as my next fix, or suggestions on what my issue might be? The car has 96K on it and it's always been well maintained. I'm not sure why I'm encountering these issues. I've never received any other message, like a constant check engine light, except the Gearbox Fault message.

 

my jurking issue when remaining on gas was fixed with o rings on the intake manifold valves. fixed all the issues i was having. the rich bank 1 and 2 went away and all sorts of stuff. $6 fix. all the pros kept telling me to replace tranny and other stuff. i read in one place after searching for ever that the orings had needed changed and it worked.

the 2 unites on the end of the manifold have 1 oring a piece. the old ones were warn flat and shaped weird. the ones i got were round and 3.5mm thickness. worked great. dont know the diamiter off hand on those unites.

 

o ring part number is 25271 (thermostat o ring) does the job. made for hot application and very cheap

 

If one of plugs is oily, it would show misfire code for that cylinder.
that is what people do pretty often: any problem, let us change spark plugs and fuel filter!
I had clogged converter with really strange symptom: engine begun shaking and fuel pressure dropped twice.
Finally I made exhaust back-pressure checking tool and found converter problem.

 

ANTBOSS, do you mean the IMT O Rings (there's two i believe on the left side facing the engine bay) or the Intake Manifold gaskets (I believe there are 6)? I can start there and see what happens. I thought about replacing the MAF too, but I don't want to start randomly replacing things without getting feedback. The place that reset the TB points said they thought the TB might need to be replaced again. But how could it already be bad? Any chance this is simply (maybe not so simple) O2 sensors or something? Nothing on these cars are cheap, but it would be great if it wasn't something like the catalytic converter that's apparently $1200 + labor.

 

Car5, the place I took it to for the Tune Up has got to be one of the most honest mechanic shops I've ever encountered. Their track record has garnered them their deserved credibility. So when they said everything was fine, even when they double checked everything, I trusted their feedback. I don't think i'd begin to doubt them either. I haven't had any engine shaking or fuel level drop, knock on wood, and i hope it's not a Cat issue. If it is hopefully it the less expensive one. Would i get a code or dash light if it were the Cats or the O2 sensors???