Have you checked your cylinder pressures? It could be possible that you have valves are worn in two cylinders, hence the misfire.

I've had a similar problem with my Volvo. It was rough at idle, shuddering during acceleration, then fine at ~30-40kph. As it turned out, there was no pressure in 1 or 2 of the cylinders so my uncle lifted the head. It turned out that the 2 valves were worn and 1 was beginning to wear. The valves were replaced, the head was reconditioned, we got a new head gasket and the Volvo ran great after that..

Maybe thats worth a try?

 

Thanks for the reply. I was thinking that so I am going to get a compression tester today. I'm kind of hoping it's not, as that probably means more work than I wanted to get into.

When I got the car it had no gas in it, and the delivery guy told me they ran it without fuel. Do you guys think maybe the fuel pump is malfunctioning due to this?

I had a 94 xj40 and the fuel pump was on its way out, and the car lost power upon accelleration similar to this. The only difference I can tell in this car is the shudder around 0-20 mph.

Thanks!

 

Thanks for the info. I'm going to send the injectors out for a cleaining...crossing my fingers that helps the issue.

 

So I'm back again... I'm sure you guys are sick of this post by now lol.

Anywho, I haven't had the injectors sent out, and I know that's totally my fault. I run a business so my time is somewhat limited during my busy season.

The car started to run A LOT better after the MAF, but the sputter from start off still existed. Well I live in PA and it has been COLD here and today somewhat warmer. I noticed that the jag runs way better in the cold than it does once warmed up. Is this common?

So, today it was warm, and the car wouldn't stay running. I was like GREAT, and took the MAF off again and did some cleaning on my intake. Car stays running great now.

Do you think the MAF I got is defective already. I was cheap and got one that was a remanufactured one from Fuel Injector Corp. It was 235 vs 500 for an OEM one. Should I have spent the extra and got the OEM?

Also, upon my review of the fuel pump, it is a cheap aftermarket one. Do you think that this in combo with the reman MAF could be causing most of my performance issues?

If you guys don't think this has anything to do with it, I am taking the injectors off and sending out for cleaning this weekend. I am also going to explore the loss of compression issue more so.

I took some videos of the car and what it is doing. I plan to upload them to youtube over the weekend and post links.

Thanks again!
Cheers

 

I had this exact problem recently and although your car may have a different cause than my car, I will share my experience.

First off, I knew my drivers side fuel tank had rust particles in it when I bought the car. So I installed fuel filters (pre-pump) in the boot. That did not clear up the car running rough at idle speeds.

Then I took off the injectors and had them sent to :
http://www.jaguarfuelinjectorservice.com/

While the injectors were being serviced, I replaced all the rubber fuel lines in the bonnet and boot which was not too difficult nor too expensive. I also put different fuel tanks in the car. These tanks had be restored by a company called Renu. Happen to get them off a parts car I bought which is just luck of the draw.

After about ten days, the injectors and fuel rail came back. I reinstalled them and crossed my fingers... the car ran perfectly at idle and high speeds. So my problems were sediment and clog related.

 

Is there a place where you reccommend getting the pre pump filters?

I checked out the injector site, and I have decided to take them off and send them out.

Do you happen to have instructions about how to take the injectors off properly? I don't want to make any problems worse.

Thanks again for your help!

 

I bought my pre pump filters from Napa. They were part #3248 and cost about $10 each.

As for taking off the injectors, I used a reference guide that had pictures on it. Here is the link: http://www.backglass.org/duncan/jag/injectors/

They were not all that hard to take off other than getting the clips to open on the injector electrical connections themselves. Fortunately this is the first step and once that is done the rest is easy. I suggest you buy a set of little pick tools that resemble a dentist pick. They will come in handy for step one.

I sent in the fuel rail and 6 injectors and it cost me about $240 for cleaning, new parts, and shipping both ways. The only thing they may not have is the little o-rings that are on the tip of the injectors. These will usually be baked on the manifold openings. Make sure you get those out if they do not come out with the injectors. As a precaution I ordered 8 o-rings even though I only needed 6. Inevitably, you will drop one while re-installing and good luck finding it. Get a couple spares, they are cheap.

All in all, this was the first time I did anything like this on any car and it was not too difficult. Maybe took me 90 mins to take off and 60 to re-install. My car runs very smooth now and should be much more reliable from the the fuel delivery perspective.

 

Oh and I suggest you consider doing something with the fuel tanks if they are original. Once I took my old ones out it was apparent that I would never have gotten rid of the sediment issues without taking the tanks out of the car.

Yes, it is an investment of many hours but it can be done. You could either have your original tanks cleaned and coated by a company like Renu or buy new ones. Problem with new ones is that they rust eventually as well. When I peeked in my old tanks once they had dried and I could shine a flashlight in them, I saw a pile of sediment/rust that would fill both my hand cupped together. That would be a constant problem for the life of the car in my opinion.

The only PIA in taking out the tanks is getting to the bolt behind the mufflers. That one tried my patients but it came out. Luckily they should be clean and easy to move once you get a wrench on them. I was unable to put that one back in so I plan to do that when/if I ever change the mufflers. I will have the muffler guy pop them in. The tanks seem to be very stable with that one bolt missing.

 

Wow great info and the visual aid is good too. I work best when I have a reference guide.

Lastly, will any jag site have the orings? I can see myself losing those and obviously needing new ones.

Many thanks

 

http://www.motorcarsltd.com/contact-us.html

This is where I bought mine...

 

Hey, I remember the bolt behind the rear exhaust silencers !
It was when I was replacing the rear valence and much else besides in the early 90s. I took the silencers off. I think these bolts are there for a purpose, which is probably to stop the tanks shooting forward in an impact, but I may be wrong, only the designer can tell you, and he is dead.

Anyway, I put back ALL the tank bolts

 

Sad update on this car:

After tons of troubleshooting and money, turns out the transmission was starting to go bad. I had a pro check it out, and they said the converter. That was causing the shutter from start which I thought was a misfire.

The car was also leaking coolant and had a clogged radiator.

The car also had a terrible gas leak from the right rear tank. The leak just seemed to popped up out of no where. My tank was empty one night and all over the ground.

Also, someone put an aftermarket fuel pump in which ran all the time. If the key was in the "on" position the pump would continue to run instead of prime the line then shut off as most do. I believe that may be what caused the leak because of too much pressure.

I really loved the car but have to part with it. The people that sold it completely misrepresented the car.

I understand the car was 28 years old but to be described as a daily driver with no problems was very misleading.

I'm going to keep my eyes open for one that is a few k more and in better shape.

Thanks to all for the help!

 

That's too bad all these problems cropped up. Wise decision to cut your losses and move on to a car you can drive everyday like you want.