Well, it seems it time for a smoke test indeed. Do any of you happen to know what cigar brands are Jaguar Certified?

Noted, noted and noted. Thank you for your wisdom once again NBCat.

 

Any $2 cigar will work. Just put it in a Jaguar package and charge yourself $18. I believe that's how Jaguar operates with their spare parts, anyway...

One more thing to consider with the vacuum leaks you've discovered so far. Medium and large leaks can make smaller leaks undetectable until you get the big stuff fixed. This can be very frustrating as you may have to disassemble all sorts of stuff a second time for access, not to mention having to procure any additional parts.

A troubleshooting workaround is to temporarily block off the obvious leaks with heavy clay (edit: non-hardening) or similar. This makes the smaller leaks easier to detect, and hopefully will save you some aggravation.

 

for the orings just buy a couple of oring assortment kits that are compatible with oil and just match them up so the are tight. I use a little silicon grease on them to help seal them.

 

Portuguese,

I found my 05’ S-type 4.2 on my birthday, for a song. She was on her way to the junk yard, scrapped by 2nd owners who tried to service it at a BMW shop. Cosmetically perfect, mechanically questionable. Got her for half the cost of a new set of tires.

Mine behaved similarly when I bought it, needed a jump to start it, and I didn’t think it would make it the 5 miles in stop and go traffic to my indie Jag Shop without a tow.

If they aren’t maintained consistently, a vehicle if this age is likely to have vacuum leaks and I’ve dealt with two, plus an air flow sensor.

My initial underlying issue with the rough performance was a bad ignition coil (only $75 usd to replace)...but it’s well worth it to do all coils and plugs at the same time because if one fails, the rest will.

She purrs and glides smoothly after addressing those issues and gas mileage improved to just under 30 mpg.



I’ve spent $2000 usd total on this beauty.

These are such great cars when maintained well. I’ve now passed the 200k mile mark and still going strong.

 

I can't express enough my gratitude to all of you. Really.

Thank you so much as well for your encouraging words Susie Q, a beautiful specimen with a background to match. I hope you drive yours for 200k more miles.

At the moment, I am getting my hands into a smoke contraption that can get enough smoke with enough pressure so I can make sure all the leaks are found. I will update all of you as soon as I give it a try. It should only take a few days.

 

hello, my S Type Sport had the same problem, the long and short is; you’ll need to order those coil packs and check your fuel pressure at the rail. My Jaguar was very very happy after replacing all the coils and changing the spark plugs to triple platinum. A new fuel filter is a plus as well.

 

Yes...those a re the plugs that work for mine as well.

 

Were either of you getting any misfire codes (P0300-P0308) or anything else related? What's very unusual with this thread is he is experiencing the rough running but with no fault codes.

 

Quite often the coil units can be failing and not set a DTC. It's best to replace the coil units as a set when the spark plugs are replaced.

 

I have a 2000 xjr with similar shaky at idle weird exhaust sounds etc but I have low compression could that just be the heads need to be rebuilt ? I don’t know what’s going on but I’d love some input I’ve changed plugs and sealed various vacuum leaks as it is and also rebuild the sc I checked the timing chain which is tight and not broken

 

Check engine light came on and there were several codes, including those listed.

Here's the sequence of events for me:
It ran fine at higher speeds for a while. I was out of town so stopped by an auto parts store to have them get the codes. I notified my mechanic, to make sure it was OK to drive it back, and I did with no problem other than that check engine light. Then the misfires began and instrument panel message "restricted engine performance, " which threw more codes when checked again, and I was told to bring it in.

Portugese, if you're having misfires with no codes, are you getting any messages or lights on the instrument panel? If not, is it possible something electrical/ or fuse-wise might be interfering with that?

 

I did get codes like the one you showed and I have a few that don’t clear also I have the check engine and restricted performance lights on just a side note I took it to a jaguar “professional “ and he told me all of this was bc I had a lower but consistent compression in the engine all cylinders at 120 psi he told me I’d have to either spend $7k to “fix the problem” or junk the engine and put a brand new one in for $5k

 

I second NB Cat's post, and I'd never consider the expensive replacement suggestions without a second opinion from a reliable independent shop that's been working on Jags for a long time.

There are a lot of other issues that could cause a pressure change.

 

Any updates on checking the fuel pressure? As previously mentioned, the fuel pump can be prone to recalcitrant behavior after extended periods of disuse.

Another thought is China (Coil) Syndrome. When you replaced the spark plugs, did any of the coils look new? Any visible brand name on them? OEM coils (and equivalent) are quite robust and can last a long time. But perhaps the previous owner decided to replace the coils for reasons unknown. Maybe there was a problem. Maybe they got changed just because. However it happened, the $34 set of coils on eBay is no bargain. Many forum members have learned this the hard way. So if the coils look relatively shiny and new, that could be part of the problem..

 

Just had an epiphany. How much have you driven the car since acquiring it? If running poorly, I'm thinking not much at all. Are you still on the existing tank of fuel? If so, that's a Yuge problem. Drain the old stuff and fill it up with fresh premium fuel.

Fuel is only good for a few months at best. As it ages, the more volatile elements evaporate. High octane fuel is the worst for this. You end up with low octane crap that does not burn well.

 

@kr98664

I did not check the fuel pressure on the injector rail, I did on the OBD scanner tho. It read 270kPa while the normal value would be 300kPa. That difference doesn't seem to be significative.

Regarding the coils, yes, I did notice something when changing the spark plugs. Two of the coils (and only two) were different from the other 6. These two did not bear any marking and are clearly aftermarket. But again, that is only two of them that were like that, the other 6 had markings on them (I believe they are the OEM ones).

And regarding the fuel, I did already went through a gas tank of brand new premium fuel. If that was a problem, it is gone now.

I am pretty certain the vacuum leaks are the issue, it fits all the symptoms.

 

Watch out for that one. The value from the pressure sensor not only feeds the scanner, but more importantly, it also controls the pump output. If this sensor was inaccurate, the computer will happily adjust the fuel flow until it sees proper feedback. The computer would be totally unaware of the actual pressure. If the sensor was reading high, the resultant pressure will be low, and visa versa. Checking fuel pressure with a mechanical gauge is part of basic troubleshooting, so please don't skip this one.



Do the two oddballs look new? Just wondering if they were installed recently in an attempt to fix the same problem you are experiencing, but were no help. "These parts can't be bad because they're new..." goes the thinking and so the nightmare begins. Could be whoever installed them had correctly diagnosed the problem (2 bad coils) but got waylaid because the new Fling Dung brand coils were also bad.

If those two coils look somewhat older, it's more likely they had been working fine. Shiny and new is more indicative of a potential problem that was never fully corrected.



Phew! The fuel itself won't be a problem. Have you changed the fuel filter yet? You may have had some nasties growing in the tank, after sitting all that time. Once again, a new filter is part of basic troubleshooting. Cut open the old one to look for evidence of excessive crud.


​​​​Once again, be careful. You've found a problem, but there may still be other issues at play. For all we know, in addition to the vacuum leaks, you could have a bad fuel pump, clogged filter, and two bad coils.

 

Olá Portuga,
I had a similar problem with my 3.0 V6 which eventually showed a misfire dtc. I swapped the respective coil to another cylinder and the misfire followed it. Replaced the coil and it has been perfect to date.
Boa sorte!