Hey guys, first post so let me quickly introduce myself. I'm a BMW guy (booooo, I know). E46, and have done extensive DIY repairs on it and very active on the e46fanatics forum. I have a 91 xj6 Sovereign with 82,000 miles on it. Bought it 6 years ago from a family friend when it had 43k miles. That family friend bought it in 2000 when it had 23k miles on it, so I've known this car since it was a baby. It has run without ONE single problem all these years until this year, first it was the brake accumulator this summer and now the car's been out of commission for about 3 months due to this current problem.

This is going to be a lengthy post because I like to map out my method of thinking so y'all know where my crazy thoughts are coming from.

So, the problem initially was that the car wouldn't start, then if you cranked it about 5 times it would start and run for like 5 seconds then die. Then after a couple more cranks if I would tap the gas repeatedly as it was trying to die I could get the car to "snap out of it" and idle. Once at idle, if I apply gas very VERY lightly I can get the car to redline, and sustain a high rpm. However, if I try to push on the gas quickly it starts bogging down and I hear the engine backfiring (loud metal popping sound) into the intake. So, I'm thinking the car is running lean.

BTW, the sx started randomly while stopped at a stop sign, car just died. LUCKILY it was 2 blocks from my house so I started it, took my foot off of the brakes and let the car naturally pull me home with occasional tapping of the gas to keep me moving.

Anyways, I thought it might be bad gasoline so I drained all the gas through the plug and even poured 2 gallons through to let it flush any dirt at the bottom of the tank. Changed the fuel filter as well. Put in a couple of gallons of V power and some Berryman fuel treatment. No real change. Car now starts on first start 90% of the time and will find idle without any assistance about 70% of the time. So, basically I've stabilized the idle at this point. I would love to check fuel pressure but I CANNOT find a T-adapter with a schrader valve that'll fit the threads on the fuel line.

I changed the MAF bc my dad bugged me to, I knew it wasn't the problem. Changed that, same problems, I was able to return it.

I then thought it might be ignition/timing related so I replaced the distributor cap, rotor, spark plugs, and wires to no avail.

Now I'm stumped. My next step is the TPS, CPS, fuel pressure regulator. I don't want to just start buying these expensive sensors though. Does anyone know what might be wrong my cat?? Sorry for the long post!

 

You had done most on what everybody would do. I would suggest that you clean the ignition amplifier and replace the ignition coil if that was not done. Kindly make sure that all connections and contacts are clean and dry. Hope that this help you along way.

 

Tiage46,

I think you're on the correct path in regards to fuel delivery, or lack of in your case. I have an '89, but have had no issues yet after 125K. That said, I recall seeing many entries on another forum in regarding your symptoms, following is such an example; (read entire string)

JagFORUM Logon

In regards to finding a guage, I found the following two examples on the same site, both are improvised devices:

An Image from the Jag-lovers Photo Album

An Image from the Jag-lovers Photo Album

You may have to sign up with the forum to view the pics, but the site is free and has lots of info if you search the archives under the XJ40 category.

It may be worth spending some time on this link as well, scroll down the page and on the right side there is a section for fuel delivery trouble shooting and specifics for settings:

http://www.jag-lovers.org/ebooks/boo...php?Vbook=xj40

Good luck

 

Just thought that I would update this thread... We have changed the fuel pump and the car ran nicely for about 5 minutes then went back to the way it was. So we then changed the fuel pressure regulator to no avail. The car is still the same as it was before. I really want to say that the problem is now 1 of 3 things. (having ruled out just about everything else lol).

1. vacuum leak
2. Throttle position sensor
3. Crankshaft position sensor

I would just take it to a Jaguar specialist but the closest one to me that I would trust is about 10-15 miles away. (should've done that from the start) If anyone in the DFW area wants to come take a shot at it its all yours . I will; however, make sure to update this thread when the solution is found.

 

Go for the TPS next, clean it, adjust and meter the voltage at idle then open the throttle (gradually) and measure the output from the TPS.

Do you have instructions on how to meter and adjust it? Look in the TSB and Quick Link threads in this XJ40 forum and look for the doc regarding the TPS. I you can't find it, throw up a flare and we'll find it for you. Then again, maybe Lawrence will come to the rescue and post it for you.

Another thing I didn't think about at the time you wrote your original post is the Oxygen sensor, it can cause the "bogging" effect at high rpm. It's a little piece of equipment with significant effect on the system.

Glad you did a follow-up. Keep posting

 

Found the document for the TPS settings, should be attached to this post