Okay so this may be a mess, it is a 1999 jaguar xk8 convertible(not sure if thats important) the car won't start or stay on without stalling. Here goes, it has had restricted performance since we got it, (my husband assured me it was fine just an error code they couldn't trace down...) but I was driving on the interstate in stop and go traffic and it stalled... I got it to the side of the road gave it a few minutes and it started (close to home, praying to look at it when I got home) well it stalled again at 50MPH and would not stay on when started. I called a road ranger and they tried to troubleshoot it and we figured out that if I held the brake and the gas at the same time it would stay on and would not go above 25 with rpms maxing out at 3000 to get it somewhere safe, we have changed the fuel filter, it had gas in it so the pump is pushing gas to it, and we changed 4 of the spark plugs. I don't want to pour money into it if it won't fix it but we really need this car to work. I do not have a code reader and autozone had told me they cannot read the codes. I had also randomly been getting transmission failure warnings previously... Any help would be greatly appreciated.

 

Code reader starts at $5. Worth getting.

Could be an air leak, blocked cats, or various other things, but you've no way to find out without an OBD tool.

Most unlikely to be plugs!!

 

Hi Boymomjka,

Welcome to the Jaguar Forums! It's great to have you with us.

A basic scan setup can be as simple as a WiFi or Bluetooth ELM327 OBD interface (search eBay) paired with your iPhone or Android phone and an app such as Torque Pro or DashCommand.

But in your case, I would recommend that you find a qualified local independent shop that works on Jaguars and have them scan and diagnose the problems (there are probably more than one). There are many possible causes of Restricted Performance and Limp Mode, and there is no efficient way to get to the roots of the problems without the help of the Diagnostic Trouble Codes (DTCs) that will be stored in the various computer modules in the vehicle (Engine Control Module, Transmission Control Module, ABS Control Module, etc.). Some of the DTCs will likely be Chassis (C-prefix) or Network (U-prefix) codes, which cannot be read by most generic OBDII scan tools, which can only read Powertrain (P-prefix) codes.

While there are some simple potential causes of Restricted Performance and Limp Mode, RP and LM are measures the control systems employ to help protect your engine and/or transmission from potentially catastrophic damage, so they should never be ignored.

Have you had any other warnings, such as ABS or BRAKE warnings? Has the engine exhibited any rough running, either at idle or under load?

It can help us if you let us know at least the continent where you reside so we can give you responses relevant to your region.

Cheers,

Don

 

Is the Check Engine Light on in the instrument cluster? Any other warnings or idiot lights staying on? You say you changed 4 plugs but you do know it is an 8 cylinder engine, right?

Jaguar electronics absolutely need full voltage, so a good quality battery is the first thing to check for. Things like intermittent transmission warnings and other gremlins can be a sign of poor voltage. Check the battery voltage with the engine off if possible, and post it here for comments. Don't go by the voltmeter on the dash as it will not give you a correct reading, Put a charger on it overnight and look for a tag that gives the month & year of the battery, see if it very dirty and has ugly corrosion growing around the terminals. Next day, start it up with the charger still on, remove the charger and then test drive it.

On your test drive, take it to other parts stores until some competent counterman gives you the codes. Ask his interpretation of the codes, but in all fairness, one code number can mean different things to different cars and he cannot be expected to solve problems on the spot. Don't let him sell you a bunch of expensive sensors or other parts without getting second opinions and checking here first. Have him clear the codes and restart it to see if the Check Engine Light comes back on and codes return. Have him recheck the codes, even with the Check Engine Light off and look for pending codes because the computer won't report some faults until it reappears on a second trip. Bring the codes back here to the forum. Try to get an honest opinion from him on the battery. Like a doctor's visit, if you're not completely satisfied with his opinions, go get a second opinion, or third, even. What do you have to lose? If the battery is much smaller than the battery tray or more than a few years old, reward the successful parts guy by buying a new battery from him and do not buy a chincy little one. You may drive home a whole lot happier than when when you first left.

 

Thank you everyone for the replies, I am in Central Florida, I was able to get a code reader but haven't been able to use it because the battery is currently dead. It is a new battery (less than 6 months old). We cannot afford a shop currently to get it fixed otherwise we would gladly go there. I am going to read the codes sometime today and go from there. I know there is most likely multiple issues but I was hoping there was 1 or 2 that I can fix now and work on the others a little at a time, we need it to get to and from work...

 

After you read the codes and check it out, start & test drive, let it charge overnight to fully recharge the battery.

 

The scan tools used by most auto parts stores can only read Powertrain codes. They will usually scan your car for free, so that would be worth doing. But if they don't find any conclusive codes, it would be worth calling local independent shops to see if their scan tools can read Chassis and Network codes on a Jaguar and what they would charge to scan your vehicle.

Cheers,

Don

 

Yes, I had a similar problem, including a "transmission failure" warning. Turns out the alternator needed to be replaced. The battery was fine and only needed a good overnight charge.
It is true that the car absolutely requires a stout battery at full charge. Also, if one diode is out in the alternator, it will charge a little, but not enough. I got mine from rockauto.com in three days and I'm pleased with them.

 

We were able to get the codes checked, the battery was replaced within the past 6 months so I will get it fully charged before trying to troubleshoot further (for now we just jumped it to get the codes) these are the codes it has given currently,
P0116, P0125, P0201, P0202, P0203, P0205, P0206, P0300, P0307, P1000, P1314, P1316, P1646my first thoughts are O2 sensor then injectors, hubby thinks it may be the cat converter though. I appreciate everyone's advice and recommendations.

 

Glad to see you retrieved the codes. From the looks at all the faults, the first thought is voltage was too low. Now that they've been recorded, clear them a few times so the pending and historic faults are removed also. Some would suggest doing a hard reset to eliminate potentially corrupt data and the Engine Control Module has to start relearning how to run the engine properly. While hooking up the charger, examine the battery terminals are clean and tight, even consider removing both clamps (especially if electing to do a hard reset) and wire brush their inner surfaces and the battery terminals (yeah, 6 month old terminals ought to be clean enough), then snug them down. If you have your own OBDII scanner, you can look at parameters before and after starting the engine, like what is the voltage, fuel pressure, air & coolant temp (should be room temp before start), throttle position, rpms, engine load, intake vacuum, Mass Air Flow, fuel trims (see if O2 sensors are working and match)... Any questions about them, ask here.

It is too soon to think about ordering O2 sensors, injectors, temps sensors, catalytic converters..... especially on a tight budget.

 

Hi Boymomjka,

You can download the Diagnostic Trouble Codes Summaries manual at the link below, which will give you the definitions and published possible causes of each code:

Jaguar X100 DTC Summaries 1999

Before worrying about any of the codes you scanned, I agree with jrnsr that a prudent course would be to clear the codes, then only worry about any that recur once you're certain the battery is healthy and its static charge without the engine running is about 12.6 volts. Remember that even a 6-month-old battery can be ruined if repeatedly depleted. If you find your battery will not hold a charge, it is probably still covered under warranty.

Cheers,

Don