Hello Everyone...I am brand new here and am in hopes the many experts out there may be able to shed some light on my problem. I bought an 2002 XK8 last year with 39,000 miles on it and had a blast driving it all summer. I really love this car. I live in Connecticut so I took it off the road for the winter.

About a month after putting it back on the road it starting running a little rough. The car has 48k miles on it now. I took it to the dealer where I bought it and they cannot find the problem. They've had the car for 10 days and claim to have tried lots of things including coils and catalytic converter. They are now doing compression checks on the cylinders. I truly believe they are as frustrated as I am worried. Any ideas as to what this might be? It seems very odd that with such low mileage and a very well maintained vehicle that the cylinders have lost compression. Thanks in advance!

 

You've come to the right place.

Most of the time these are simple problems, let's start with the basics and a little more information.

Most important, get the diagnostic codes if you don't have them already. A Jaguar dealer or any good repair place should be able to read them and provide them to you. This is standard procedure. Post them here when you get them. (If your particular dealer can't or won't do this you're at the wrong spot, retrieve your car). The codes will indicate which component or system is not operating properly. There is no need to guess or play plug-and-play with components.


While we're waiting for that, you said it was misfiring/running rough - can you elaborate on that a bit? Was it hard starting, poor acceleration, misfiring while underway or at idle, etc. Did it get worse or did you take it in right away.

Sounds like you have a nice low mileage car...we'll sort this out.

 

First of all, thanks so much for the quick response. It was perfect when I put it away. I had it in a storage place so it was cold but garaged. I started it a few times over the winter and there were no issues. When i took it out it ran fine but the check engine light came on and the car hesitated if I accelerated to highway speeds quickly. I filled the tank with some 94 octane and halfway through the first tank of gas the engine light went out and the car was perfect again. I figured there was some condensation or something that worked its way out.

A few days before I took it in for servicing, I noticed that the engine wanted to rumble a tiny bit when idling. Not all the time but it was always perfectly quiet before so I noticed it was always that quiet. I made an appointment to have a 50,000 mile servicing, even though I was only at 48,000. I was feeling a little vibration in the brakes so I figured I get the whole thing checked out. They checked the car and told me two cylinders were misfiring and that they wanted to replace two coils...about $500. I was surprised because the car drove beautifully and accelerated perfectly. Just the idling issue. They also told me that the brakes were fine but that the vibration was coming from bushings on the front end that needed to be replaced...about $950.

So they replaced the coils but that did not solve the problem. Then they took off the catalytic converter but that didn't help either. I am not sure what other checks they have done and I don't have the diagnotic codes but I will get them.

Thanks again!

 

Is this a Jaguar dealer?

What came of the compression test?

Coils: If it is runing rough because of bad coils there will be codes indicating which coils (of the 8 present) they were. With a pair of bad coils it will run really rough at speed which you do not experience. It will also idle differently than normal. They should be able to document the codes that led them to the coil issue. Regardless, it didn't solve the problem and in the absence of codes I'd say they own the $500 coils.

Converter: I doubt that they removed it - that's a federal no no for a shop to do. They may have tested it in some fashion. See if you can find out - again codes. (I believe there are codes for a malfunctioning converter, someone will correct me if I'm wroing)

Bushings: Before you do anything let some other forum guys chime in - there is a lot of experience in that area here.

Overall, your suspicions are correct. The problem - rough idling - doesn't line up with the expensive solutions thus far. Perhaps they are fishing? Codes tell all...let's wait before we pass judgement.

Keep us up to date.

 

They did not get back to me on the compression test. They were doing it this afternoon. I called them for the diagnostic codes but everyone was gone for the day...4 pm here. They did put the old coils back in and indicated they were not going to charge me.

Regarding the catalytic converter, the service dude indicated that they take it off just to see if it fixes the problem, then put the new one on...$1500. But apparently that was not the issue.

I'll get those codes first thing Monday.

Buck

 

Ok. Stick with us. Is this a Jaguar dealer?

 

Cars that exhibit rough running at idle usually have a vacuum leak in the intake system. Another thing that can cause it is a clogged part load breather in the valve cover. Get the car away from the guys tht have had it, they are not looking in the right place from your description. If they ran codes and it said the coils were bad, replacing them would make sense, but I doubt this is what the codes said. If the car had two bad coils, it would not run! A reasonably competant mechanic would put the car on a scanner and read out all the sensors in real time (engine running, car moving) to look at the fuel trims (this will lead them to the leaking intake plumbing) and so on to hone in on the problem.

 

Yes this is a dealer. I bought the car from them last June. First day I had it it would not run right at all. They took it back and put a new computer in it. They told me one of the things they did to try to resolve this problem was to swap out the computer and again that did not fix it so they put it back.

This is frustrating for me because I have never worked on cars. Well I had a '72 Mercedes 220 Diesel back in the early 80's that I worked on but that thing was so simple anybody with a wrench could change stuff out. From what you guys are saying, it seems to me that the codes should hone in pretty closely to the problem, and then there are only a couple of things it could be. A little process of elimination should narrow it down to the actual issue....right?

Is putting the car on a scanner and reading out all the sensors in real time the same as the diagnostic codes? I'm a fast learner so this education is very enlightening.

 

Yes. Look in the "sticky" section of this forum and you will find listings that have summary sheets for all the diagnostic codes.

Also called "OBD" (On Board Diagnostic) codes from the original OBD-I and, later OBD-II systems these have been Federally mandated since the early 1990's all cars have the capability to report them. The original purpose was to capture emissions data to keep vehicles within EPA standards; these are "P" Series codes. The systems are constantly monitored by the computer on the car and when something is miss it will trip the Check Engine Light (CEL). This stays on until it is erased and the underlying problem addressed.

Look on this forum for the listing of codes for the XK8 (they vary by model and year) and familiarize yourself with them. For fun, look in the P1300 series and you'll see the ones relating to coil malfuncion. See...no need to guess. The P series codes can be read by just about anyone. Autozone, etc. will do it for free or you can buy a $50 scan tool and read them yourself. (Some of us read them on our andriod or i-Phones)

Beyond this there are manufacturer specific codes for all the various computers on the car. These, of course vary by manufacturer, model and year. For example, some deal with the ABS system, others the Chassis systems and others the Body systems. You need a more comprehensive scan tool to read these type codes - that's what the Jaguar dealer has. (A non-Jaguar dealer won't likely have this at hand)

It's all very detailed, specific and somewhat arcane. But, it takes a lot of the mystery out of diagnosis by highlighting what system is at fault.

Your idling problem should throw a code (or set of codes) pointing to a specific problem. Based on experience, we suspect that this should be in the easily accessible "P series" of codes. That's what you've asked them for and they should give you a printout listing the codes that were present. (To make it more interesting, there are Current codes, Historical Codes and even Pending Codes...)

To me, swapping out the coils and catalytic converter to no effect is not consistent with effective diagnosis. But, to be fair, I'm not there...

Let's wait until you get the codes and go from there.

 

Haha...I will be all over this research today. Then I will go visit the dealer tomorrow. He will think I'm a different person. Are there other questions I should be asking about there diagnostic process? If you were in this situation are there any other basic questions you might ask? Thanks again for the advice. This has been a bit unnerving.

 

You are doing fine.

If all you have is a rough idle don't get over your head with repairs. Simple stuff first.

Think of your engine as a sealed system with lots of sensors measuring things going on as air enters, is combusted and exits as an exhaust gas.

Rough idle is often simple a leak in the intake system. This is very, very common as plastic parts age and dry out from heat. If you have an intake leak, it represents "unmetered" air (unseen and unknown to the computer) so it unbalances the air-to-fuel ratio, particularly at idle.

You can easily check this yourself. Look to see that all the fittings are tight and sealed from the airbox (where the air filter is, passenger side front) down the intake plenum (long black tube) to where it connnects to the throttle body (back of engine). Part way along the tube enters the accordian type Full Load Breather Tube (easy to see, right there on top) - make sure it's seated properly at both ends and not split somewhere. There are also some vacuum and air supply tubes at the throttle body that should be looked at. Air filter clean and lid sealed tight?

This kind of examination would have been the first thing done in a diagnosis. (Some shops do a "Smoke Test" or spray WD40 or starting fluid at the various junctions looking for leaks) Make sure some sort of exam was done.

There are lots of posts with pictures on this site to help out. Gus and The Reverand have some particularly nice write ups, pictures and even videos on their websites. They are easy to find on the forum. Others have great stuff, too, usually on particular topics.

 

I was all set to go speak to the dealer today, did my homework, and he called me late morning. It was a fuel injector in cylinder 1! So needless to say I am relieved but of course I had questions for him when I went to pick up the car. The notes on the bill read as follows:

Found misfiring codes P0306/P0307 random P0300 and engine running rough at idle. Ckd fuel trims found bank 2 rich. Swapped out coils. Ckd compression. ckd timing. Hooked up converter pressure gauge to rule out converter issue. Swapped injectors to bank A lifted fuel rail and manually checked spray pattern. Found #1 injector spraying too much fuel. Replaced injector and reset fuel trims. Found normal now, road test OK.

So I pressed him about the wrong P code issue. He had told me that they put another computer on the car just to check if the computer was the issue. I asked how the two different computers could deliver the wrong codes and he said it was because it was a problem with the car not the computer. Does that make sense to you? That doesn't make sense to me. Notice there is no mention of the computer swap in the notes and as I mentioned before, they told me they put a new computer in this car last year. When I pressed further he gave me the "I don't know what to tell you...never saw this happen before." Then he hit me up for 6 hours of labor for all the diagnostics...claimed they spent waaaayyyy more time than that. They had the car exactly two weeks. Big fat bill for 2 spark plugs and a fuel injector.

So whaddaya y'all think? Do you trust this guy?

 

What's worse is that they decided that the catalytic converters are fine, and *still* charged for *new* catalytic converters. The old catalytic converters should have been just put back in.

edit: from a later post it appears the cat was not charged in the end.

 

I'm taking this information from the JTIS, you should get a copy (ebay, $10) if you are getting to like this sort of stuff.

For your model and year, P0306/P0307 and P0300 clearly point to cylinder B2 (#6) and cylinder B3 (#7) as suspect. The two cylinders misfiring they uncovered right away as I understand from your first post. The recommended diagnostic from P0300 the "parent" code for misfiring is:

Cylinder Compression low
Worn Camshaft
Fuel delivery low
Fuel injector blocked/leaking
Fuel injector open
Fuel contamination
Fuel injector circuit fault(s) with injector DTC's also flagged
Spark plug failure
ECM communications problem
Ignition module fault
Ignition module/Coil Failure

There are some additional notes regarding the severity of the misfire - if it's bad enough the check engine light will come on and you'll get more codes (P1316: excess exhaust emission and/or P1313/P1314:catalyst damage, along with the individual cylinder indication. This is not your case, however)

Hindsight is 20/20 but it looks like they were on the right track.

Checking fuel trims is a correct procedure, and it corresponds with the codes for Bank 2 (cyl 6 and 7).

The the compression test is logical and indicated. Looks like they went to the coil issue next, again logical and indicated and then finally landed on the injector, also logical.

The catalyst business wasn't in the code set and it's not logically (in my mind) associated with misfiring as a cause anyway, perhaps they were using it as a diagnostic aid?

Where I'm hung up is on the cylinder #1 injector problem with codes indicating #6 and #7. The notes are confusing with regard to "swapping to Bank A" - are you sure there's not a communication error?

Perhaps one of the real Tech's can chime in...

 

Also, it is important to know the correct Cylinder # corresponding to position:

 

Paul,

Good catch, especially with his model year!

 

Thanks for the feed back guys but I'm not really gettin' it. I can't see why P0306 and P0307 would be indicated if it was cylinder 1 that was the problem. The diagram doesn't clarify that for me. In my naive little world, the computer would tell you the cylinder where the misfire was occurring and then you would look there and find the problem. What good are the codes if they indicate the wrong cylinders? Is that a typical dillema? Again, I hope I don't sound ungreatful, it just does not make sense to me.

 

That's exactly the way it does work! That's why I think there is some confusion about what took place. (All the component swapping was confusing and perhaps fouled up the tech's notes)

Just ask them if the leaking injector was originally on one of the center 2 cylinders on the drivers side - the ones that tripped the code.

The way you are understanding it isn't logical. Not that it couldn't have unfolded that way I guess, but it would require 2 phantom codes and some guesswork...

Codes are good guides and indications but there is frequently a bit of detective work needed to track down the root cause. That's what makes a good mechanic. However, codes, never say one thing and mean another in the sense that you are thinking.


More background on codes:

Some codes appear as Current Codes and then disappear! This is by design because some "problems" are fleeting. An event may cause a code to be set but, if the event doesn't reappear in 2 or 3 ingition or drive cycles it will be erased from the Current Code list and stored in memory as an Historical Code. (All this detail is spelled out in the JTIS manual)

Sometimes there are codes getting ready to be set. In these instances the computer needs to "see" a particular condition 2 or 3 times before it sets the code. While it's waiting, the codes are held as Pending Codes.

Current Codes are erased to extenguish the Check Engine light. Clearing them can temporarily make a car look "clean" when, in fact it has problems. (Some of which may not appear for a while but are present, nonetheless) People that resort to this strategy to sell a car or pass an emissions test usually don't know that there is a code for "Miles Elapsed Since Codes Cleared".

 

Yes I will get a copy of the JTIS. Thanks for the additional clarity on the codes as well. I will be ready next time. The service guy did tell me that he had never seen this problem so I believe there were some phantom codes...and he was exasperated as I was paranoid! I am glad that you are cool with the process they went through to try to manually find the problem. I'm especially glad they found the problem and it was not something major. Now if we could just get the sun to come back out in CT!

 

I'm glad it worked out for you. Get a code reader, a copy of the JTIS and hang around here and you'll pick up quite a lot.