Hello fellow Jag owners, I just acquired a 2003 S-Type 3.0 V6 with 94k miles on it. It starts right up and while the engine is cold it revs up willingly to red-line and pulls nicely with no codes. As soon as the engine warms up, the engine struggles to rev up and eventually throws CEL and Restricted Performance. It still idles smooth but from about 2500 rpm up it runs rough. Let it cool down and it runs perfect again for the first 3 minutes. I read all the posts related to misfiring codes but please bear with me as this seems a little different.

OBD2 codes are P0300, P0301, P0303, P0305 and P1313 indicating a misfiring problem in the odd cylinders (1/3/5 are on the passenger side of the engine, correct?). All the codes appear at the same time.

So far I tried swapping one coilpack from the other side of the V and it made no difference. I'm thinking it's not the coilpacks. Plugs definitely need to be replaced but I fear that's not going to fix the problem in itself.

Why would the engine run perfectly smooth when cold and then start misfiring when warm? Bad gaskets or o-rings would be bad regardless of engine temp, no? Crankshaft pos sensor, maybe? Or something more serious like valve cover gasket?

Thanks in advance!

 

Runs OL (open loop) when cold.

You can't rule out gaskets by guesswork, not least because things change as they heat up.

Likely the usual 3.0 issues covered well in the FAQs. IMTs, maybe coils, maybe air leak. Plugs are the last suspects unless they've not been changed in which case do them while you have it apart as they were due at 70K

You've not done enough to rule out the coils but they're not quite top suspects.

Don't panic, it's a good engine and these sound like typical and pretty ordinary issues with a good chance of fairly easy fixes.

 

https://www.jaguarforums.com/forum/s...ck-pics-49214/

 

UPDATE: I took off the intake, replaced all 6 spark plugs, both upper and lower intake gaskets (the lowers were in bad shape). The IMTs were bone dry with no sign of leakage so I left them alone. Overall the engine looked very clean with no apparent oil leaks, spark plug wells were all clean and dry. Put everything back together and sadly it didn't make any difference.

Still getting P0300, P0301, P0303, P0305 and P1313 when engine is warm. Pretty weird...as long as coolant temp is low the engine seems to run great, revs to 6k RPM easily but as the coolant gets warmer the engine starts misfiring and bogging down above 2500rpm until it goes into RP. Idle is smooth with engine warm or cold. When it is misfiring there seems to be a lot of noise that sounds like valves.

At idle I tried pulling the coilpack wire plug from cylinders 1,2,4,6 one by one and each time the idle became markedly rougher. So at idle all 6 cylinders seem to be firing well.

Any ideas what to try next? I would especially love to hear from people who had this same problem in the past. Thanks!

 

Since you "checked" the IMT O-rings, what color are they, yellow or green?

 

Green IMT o-rings, appeared to be in good shape. Looks like previous owner replaced them not too long ago. He probably replaced the upper intake gaskets, too, but the lower gaskets looked like they were never replaced, they were completely pushed in and leaking. Like I said I put in a brand new set of both upper and lower intake gaskets.

 

Ok, make sure that the green vacuum line in the following picture is secured corretly in the valve cover and in the air intake tube. When i did this job , a slight mistake resulted in cracking this tube. Look very carefully at your work, I had to replace this tube.



Did you clean your MAF sensor?

 

Yes I cleaned the MAF sensor. I can't see the image in your post above for some reason. You mean the tube that goes between the intake hose and the middle of the valve cover on bank1? Mine is black, not green but it is in good shape and connected properly.

 

Yes thats the one. I color coded all vacuum lines (in pictures only) on MY 2003 and up, all the vacuum lines are black in color. I just happened to use a green line for the black vacuum line you said above.

As a side note, to have full access to this forum, you need to follow forum protocol and go to the new member section and give an introduction.

I am thinking about the bind your in and will report my thoughts in a few minutes.

 

Ultra, all I can say after reviewing all my notes, is you need to double check that all vacuum lines, wire connections etc... Its got to be something overlooked.

 

UPDATE: There might be a vacuum leak after all. When I step on the gas with the hood up and the driver's door open I can hear a distinct "sucking noise" coming from somewhere in the engine bay. I assume this is not normal, right? At idle there's no audible sound but crack the gas open just a bit and whooosh... Tomorrow I'll get a helper to step on the gas while I look for a leak.

Keeping my fingers crossed. Oh I also forgot to mention in my original post that the brakes sometimes feel very soft, this is perhaps another sign of a vacuum leak?

Rick, thank you for keeping me on the right track. Without your posts I probably would've started taking off valve covers already looking for a timing issue.

 

Ultra, make 3 more posts and you will become a full member and be able to view pictures. The following link has pictures of all vacuum lines (color coded):

https://www.jaguarforums.com/forum/s...ics-faq-52720/


Yes the brake pedal will be funky with a vacuum leak.

 

OK I've double and triple checked all the vacuum hoses, made sure everything is tight. Used a can of carb cleaner to check for leaks and found none.

At this point I think I pretty much ruled out vacuum leaks and ignition issues. Next on the list is fuel system delivery or possible blocked exhaust. I suppose I can test the blocked exhaust by removing the pre-cat O2 sensor to allow exhaust gases out and see if misfire codes go away.

I have zero experience in testing fuels system delivery. Is it a likely cause here? How is the fuel rail designed? Is it possible that low fuel pressure would cause only Bank 1 to misfire?

 

Near enough impossible but not actually so.

I'd get a $12 elm327 and look at fuel trims on both banks. Compare 2500rpm with idle and see what happens. Lots of typical faults can be diagnosed that way.

 

And the answer is, tadatada: PLUGGED CAT on the passenger side.

Given the misfires were all on the same bank I kinda suspected this could be it. Took out the O2 sensor and she runs like a dream other than of course the expected P1646 code for the missing O2 sensor but no more misfire codes or RP. Bright silver colored shavings (platinum?) came out of the O2 sensor BTW. Man I hate doing exhaust work but at least I finally found the root cause of the problem. All the work I did with the intake, replacing gaskets, plugs, IMT rings turned out to be unnecessary. I'm glad I didn't buy a single coilpack or injector.

Now I have to figure out the best strategy to fix this. Go with ebay, risk one from the junkyard or just gut it and use an O2 spacer? Has anyone done this?

EDIT: I wish one of the many people who had the same problem in the past had followed up once they found what it was, could've saved many of us a lot of time and money.

 

If you found any problems with intake / coils / plugs then that'll likely be the cause of the destroyed cat. Misfires are probably #1.

 

Honestly I think the failed cat (like many problems on Jaguars) is due to poor design more than anything else. The catalytic converter is too close to the exhaust ports on that side of the engine. The cat overheats and melts over time. Then it's the melted cat that causes misfires, not the other way around.

I've read literally hundreds of posts in numerous car forums and it's always the rear (firewall) bank on FWD/AWD cars and the passenger bank catalytic converter on RWD cars where the cat fails and causes misfires. Many Mercedes-Benz, BMW, Jaguar, Ford models are plagued by the same one-sided cat melting because of the same flawed design. There is an excellent thread in one of the MB forums which concludes that misfires in all cylinders on the same bank are almost always due to clogged cats. Certainly turned out to be the case on my S-type.

 

I've read thousands of messages here in this specific forum and what you say does NOT appear to apply to these cars. Hardly any failed cats and looks suspiciously like badly running engines (usually misfires) are the cause almost always.

Failure to fix engine problems leads to another failed cat, regardless of jag, MB, BMW or whatever make. Just takes time.

 

You have it completely backwards. The cat cannot melt. It is a ceramic matrix. What happens is that matrix gets plugged or starts to mechanically break down. Either way the end result is the same. The converter gets plugged.

As was said above no the cats are NOT poorly designed and very few people have problems. Most of those problems are because the problem was not fixed and you kept driving the car.

Remember that if you have a flashing check engine light. That means the computer is telling you cat damage is occurring.

DO NOT KEEP DRIVING WITH A FLASHING CHECK ENGINE LIGHT!!!!

Finally do some more research. It has been posted that the V-6 Jaguar and V-6 Lincoln LS use the same converters. The Lincoln LS part is much easier to get and cheaper.
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The cat matrix is only partially ceramic as it contains a large portion of cordierite ( magnesium iron aluminium cyclosilicate). Cordierite WILL MELT when overheated. It is possible that some kind of ignition issue may have originally started the process but the point is the damage is much more likely to occur on the passenger side. You won't find any posts in the forum about P0300,2,4,6 but there is a fair share of P0300,1,3,5's.