I can't seem to pin point the problem that just started in the last few days. The car runs OK at idle. I just replaced the Air assisted injector control valve or bypass valve because of a fault code. No warning lights are present at the moment.

I still get this stutter and vibration over 40 mph. It feels as though the engine is being choked out. Anyone got an idea of what my problem could be?

Thanks for any help.

 

Do you have a fuel pressure gauge?

 

I have a similar problem with my car. What year is your car? I was told by the Jaguar dealership that the problem lies with the transmission.

 

Hey guys thanks for the replies. My Jag doesn't have a fuel pressure gauge. I wish it did!
My Jag is a 2000 4.0. This wouldn't be totally bad news if it is the transmission causing these anamolies. I have a life time warranty on it and the repairs would be free.
For some reason it doesn't feel like the transmission is the issue. Though I could be wrong. The last time I had tranny work done. I could feel the tranny slipping before vibration..this time I can't detect any slipping . Just the car feeling like it's running on less than 8 cylinders. it is very noticable when pulling hills and such when more demand is placed on the engine and tranny.

 

Have you checked/replaced your ignition coils?

 

Sorry you sounded very mechanically inclined, but I should have been more specific.. What you need is an in-line fuel pressure tester made by snap-on or a similar company.. Its a big gauge with a hose that comes out and lets you test the pressure right at the fuel rail.. This can often times let you know if your issue is fuel or something else.. You may also be having injector problems, but usually if they are serious enough to cause a miss while driving the car will throw a code.. When was the last time you replaced your fuel filter? and how long ago and did anything happen before this start occurring e.g. you filled up with gas or the car sat for a long time? Eric

 

I was considering coils too snooktarpon, but he says he has no CEL or warning lights..

 

Mine is a 2000 3.0 and does the samething around 40-45mph. other forums I've been on have many people with the same issue. They seemed to have worked out this problem in the 02 ST

 

Sounds like misfire. The '00-'02 wont set a misfire check engine light until the engine has nearly died. If you have a scanner that will read pending codes you should see misfire codes there. If its a V8 pull the coils out and check for oil contamination due to leaky valve covers. When is the last time the plugs and coils were changed?

 

I replaced the fuel filter about 15,000 miles ago. I also replaced all the coils and spark plugs within the last 5000 miles. I was thinking the fuel pressure is a possible cause. Or as mentioned the injectors. The problem just started a week ago and seems to be getting worse. I stopped driving the car over the weekend.

I checked one side of my engine and cleaned two of my plugs and changed two coils. I haven't checked the other side though. Apparently the coils were fine, because it didn't make a difference.

 

You guys think a Mass air flow sensor could be my problem?

 

The mass airflow sensor wont cause a misfire but more of a general, runs like crap, sort of problem. When you say you cleaned 2 and replaced 2 are you talking about cleaning the sparkplugs and replacing 2 coils? Why did you replace the coils? Did they have oil on them or did the boots look wet? Did any of the plugs look rusty or the coil boots look rusty like they have been under water? What color are the tops of your coils? There are yellow, green and black coils, I'm talking about the color of the paper label on the top.

 

Yes two of the coils had a little oil on them. No rust though..I've seen that in the past with the very back right rear coil. Made a mistake and went through a automated car wash...had to replace all the coils and plugs before it was said and done. lol

I thought that would have been the problem this time, just from moisture creeping in. But it was dry as a bone. I made sure to use dielectric grease on them the last go around to combat some of that moisture and seal the covers well. The coils only have 1107E printed on the side..they are all black.

The only thing I've done recent, was change the oil. Probably a week before the problem showed itself.

 

Oil on the coils indicates a valve cover gasket leak and this can easily cause your misfire problem.

 

So, in my instance, VCG, done, fresh Iridiums, done, fresh coils, done.... Still got the miss and code on psngr bank, plug 3... Even when you disconnect each coil one at a time while she's running, P3 is the only one that doesnt do anything when disconnected, so I pull coil and plug out and ground the plug against the strut tower and I get a spark

 

Fuel - injector...

 

Are the injectors Piezo style, two wires like the coil?

 

Where are they on the 4.0?

 

Dig a little harder with your right foot when racing that Recaro office chair - jaysus ya gotta be freezin' in Calgary mate........eh?

 

Performance chair for performance surfing Was outside in shorts, sandals, and a hoodie for the time we were out muckin with the 'Guar, +6C