The reason I ask about the different versions is that I do not think or I read that the old version you notated does not report throttle body issues and if nothing esle has shown a code, perhaps it is one that does not get reported, although back to the dealer issue and whether you can trust what they say. I have had enough outright lies and damage coverups by them- I just now assume a lie.

Tom in Dallas

 

It can report TB issues and some extras (TACM), too.

 

The coils in my car actually are the original and have a Denso part number on them. You can go to Rock Auto and get a good price. However consider this a tuneup as compared to solving the problem.

I agree with Jagv8, I would find a hill, start at zero and push all the way to the floor and get up to about 100mph on a hot day. It it carries the load, then I would have a hard time thinking it was the coils..

If you consider al that makes for proper combustion and only at a low speed, then something is having problems with a spark (such as a wire that could be stretched and strands broken and shows not enough juice at lower rpm) or one of the fuel injectors is partially restricted, but not enough to show an injector fault and these injectors I understand are fairly bullet proof, but age can cause buildup. Or you have a throttle position sensor that might be throwing a problem at lower rpm. Just random thoughts. If the dealer could not find anything and you can believe them (their software should show if any one cylinder had too many misfire as it runs a count of all misfires- did you get a print out from them?)- then you are having some weird combustion problem- even at the age- could be a simple as fuel filter- but doubtful

Other than misfires at idle- do you have a rough idle? (discounting anything caused by the ac compressor) If you turn the ac off, do you still get misfires?



Tom In Dallas/Plano

 

Don't use WOT to do it, as then proper sensor monitoring is vastly reduced (PCM too busy).

About 50mph is fine, no need for a heavy foot at all.

 

I am suggesting this as it was the only time other than idle that I developed a misfire initially. My symptoms started just like his for all intents and purposes. If he cannot get codes at idle and if he does a WOT at a higher speed and pushing the load of the engine and yes the pcm and does not get them, then he knows to look elsewhere. He needs to put as heavy a load as possible. Im ,y case it was a crimped and parted wire and I got the problem when I came off a heavy speed or had the load on the car near top or at idle- however it did force the showing of codes and pre-ignitation sounds. I just trying to suggest what several Jag techs (now gone from the ***********) have suggested to try and force an error. This can actually get scary when driving along in heavy freeway traffic at an even speed of 70mph and have it slip in to RP for no good reason.


Have you done an extensive wiggle wire test in an organized fashion around the engine?

Tom in Dallas

 

Wiggle test - good idea!

 

Mine was a wire, hidden away, that normally would not be seen and since it came plastic wrapped from the factory the crimp that was found had to come from the factory and it took this many years to fray and come apart on the inside of the wire- not seen from the outside.

Tom in Dallas

 

I haven't tried the acceleration test uphill but it will rev to 6,500 rpm's and not miss.I am sure it would rev to the redline but I haven't tried that.
Yes,I have wriggled,pushed and pulled every wire and connection I can see under the hood.I have driven it twice since the trip to the dealer and it is the same or possibly a little improved.Misses only at idle and occasionaly low speeds.The misfire is intermittent and not constant as it will misfire,idle normal and then again a misfire.
I will continue to drive it until it gets worse and locate some coils and plugs and have them installed soon.I know how to do it but my old back and poor eyes make it difficult.
Thanks again for the responses.

 

My 2001 stype 4.0 still has a misfire and no codes.I have driven it about 3,000 miles since misfire started several European mechanics and Jag dealer can't diagnose the problem because it shows no codes.The misfire continues to get a little worse but still very drivable.
I guess my next action will be to replace the coils and plugs.The car has 60,000 miles .
Any suggestions will be appreciated.

 

Maybe a bad cat.

Watch fuel trims at idle, rev to 2500, and when driving at high load.

 

If you had a bad cat or cats you would likely pull codes P0420 or p0430.

Do the misfires ever seem to sound like internal denotations especially under load or heavier acceleration? That could be the sound of a cat backing up. Are you getting a particular noxious smell coming from the car like un-burned gas or higher than normal combustion smells?

Did you ever see a flashing check engine light?

The Jag dealer can get into the back door of the computer system and look at the misfires on each cylinder.


I think you may have a coil or plug problem or water and oil leaking into the area, but why it will not show the codes is beyond me. Have you tried the simple 3 minute job of cleaning the Mass Air Flow Sensor and see if any change?

I had severe misfire problem that came from the trigger wire of the #3 and 5 cylinder. Because of the way it was crimped and covered with plastic, I happen to think it came from the factory that way and finally heat and time caused the on and off separation and misfires. But I had codes and a flashing CEL on all of this

Good Luck

Tom in Plano 05 S-type 3.0 92k

 

We've had quite a few blocked/damaged cats that didn't throw any P0420/P0430 or the like codes. Some (maybe all) had odd fuel trims, since the air/exhaust flow is affected especially under load.

Another possibility if you have not had the chain tensioners replaced would be timing being off. That sooner or later leads to engine destruction so be sure...

 

Thanks for the responses.I am not sure what trim levels are or how to check them.I will share this information with the next shop I take it to.I will do this next week and share the results.

 

The jag dealer should have already done this if they even ran a quick diagnostic. However, knowing Jag dealers as I do- they are worthless except to sell you overpriced parts and service.



Tom in Dallas

 

Avoid dealers (well, there are a few who are great - but the others are soooo expensive and not that good). You can DIY to get the fuel trims. OBD tool with live data, plugs into the socket in the car, you can do it wearing a suit (suit is optional).

Jag indy if you prefer but costs more money.

 

Look at the attachment. It is a great Fuel Trim Primer that Gus (JagRepair.com - Jaguar Repair Information Resource) has uploaded elsewhere. His site has lots of valuable info on it.

Hope this gives you a better understanding.

Tom in Dallas

 

It's good. Oddly though it's a FAQ on this site it seems not too easy to find https://www.jaguarforums.com/forum/g...ed-quiz-49317/

There's at least one more useful item in the FAQ.

 

Thanks for the response.I have an OBD scanner.I will try and read the fuel trims today.

 

You need to get the car to running temp.

Run at idle and look at short term and long terms, then go to 2500 rpm and do the same.

You should see if it is happening to both sides or just one and if lean or rich. If you post the trims, there are plenty of us that can help to interpret. Make sure the fuel system show closed and not open or that might indicate an 02 sensor problem.

Tom in Dallas/Plano