After a limp mode and spark plug/coil misfire message, took my 03 6cylinder in to the Jag shop in Portland and they replaced 3 coils and all spark plugs. Said only three needed to be replaced and they were on the side that required for the motor cover to be removed. Got it home, still does about the same thing. I did notice a bit more of a kick when I step on the accelerator, but holding the accelerator down, I carefully watch the rpms go from 750 up to 2000 and iratic in between while carefully holding the accelerator down. I'm bummed that the Jag shop couldn't figure this out after seeing the codes and their test drive before I picked it up and paid them $670! Called them and am taking it back in. What could it be? I'm thinking fuel filter/fuel pump? It's not missing, its just not holding rpms. I don't really notice it much while driving at higher freeway speeds, but once in a while the tranny will either **** too quick or too late,,,and I'm thinking the motor confuses it because of unsteady/erratic RPMs! Any ideas before I get it back to the Jag Shop for a diagnostic in a couple of days? Appreciate any ideas or suggestions.

 

Gary, the ignition coils and spark plugs were unlikely issues regarding your Jags presentation. However, you may be onto the "crux": Fuel delivery/management. A replace of fuel filter and pumps....

 

Interesting, the Jag Shop said the codes showed mis-firing and bad coils on 3 cylynders. This always irritates me when I'm the 'novis' and trust the shop to replace what they diagnose and then, it doesn't even fix the issue $670 later! Of course, new plugs doesn't hurt at 101K's as well as three new coils, I recon but it didn't fix the problem that I took it in for. I can't believe, if they put the car on their computer diagnostics that they didn't get some kind of a notice of irregular RPMs and poor fuel/or air management. What's a guy to do? The mechanic who test drove it after the repair said it run wonderfully! I noticed it about 2 miles from the shop, should have turned around instead of driving the 1/1/2 hours back to my home in Salem with the outside temp at 103! Oh well. I'm taking it back and they had better not charge me to diagnose it or it will be my last visit there. I'll keep you posted. Thanks for your suggestion.

 

Sounds like a possible vacuum leak from an intake manifold. Check the hose that runs under the intake to the rear of the V6.
good luck , VMV

 

VMV, excellent suggestion...check all vaccume lines. especially those to intake, etc. How come I did'nt think of this?

 

A common cause is a vacuum (air) leak. Often a perished PCV elbow (Search will find you details).

If you can post the actual codes it would help. One thing is that the way the cylinders are numbered CHANGED so it is possible the shop don't realise that and used the wrong way. The details are in this PDF https://www.jaguarforums.com/forum/a...4&d=1269505095

Another issue is that the PCM figures out the misfiring cylinder as best it can but it's a challenge for it to see the tiny differences and track them back to the right cylinders, especially if more than one is or appears to be misfiring.

Unless you have a lot more than 70K miles on the car, it's far more likely a coil not a plug problem (if it's not a vacuum leak). They can use a smoke machine to look for leaks.

 

my 03 'S' type has 101K on it, just for clarification purposes. I'll check hoses but will definitely mention this to the shop when I take her in this week. The new plugs gave her more pep at the start, when it doesn't hesitate. Outside of this, I think she would be running perfect. I'm hoping it is not the throddle mechanism going out! I'll keep you all posted as to what I find out when I take her into the shop.

 

Without the codes you risk swapping parts until you happen upon the problem. With the codes.... you still may do that if you're unlucky but otherwise will swap fewer.

 

I had chased a misfire situation for about a day or two. I replaced the coil pack, wires, plugs and plug wires and it ended up being a clogged fuel injector. You could have one or a few that might be giving you a fit. Use a quality fuel conditioner and see what that does. I use BG44k!

 

if you think is a air leak around the inlet manifold spray around the gasket area with wd40 ,for a few seconds the misfire will go away,but you'll know what the fault is.

 

I agree, what are or should I say were the codes?