Help Please....my 1994 XJ6 began just losing acceleration driving down highway, as you coasted off the road, it would eventually die and wouldn't restart, engine turned over, it seemed almost like it had flooded, the inside of the car smelled like gasoline. The fuel pump and filter were replaced and a relay, still has the same issue, whats wrong?

Once it dies, it eventually restarts after 10 or so minutes, until then the engine tries and tries to start but doesn't. The car smells like gas fumes. I've been towed in 3 times this last week. I'm in a small town and the mechanics are stumped. I've owned the car since it was new, taken very good care of it, I believe it has 125,000 on the mileage. This started about a month ago, just once, so I ignored it, took it to get it washed after a snow fall, then starting it it seemed like it was flooded, it would eventually start, then didn't happen again for several weeks, after driving my mum to the hospital, a warm sunny day, it wouldn't start, engine just kept turning over, 15 minutes or so, it again ran like a top. Made an appointment with the shop for the next day, but on the way it died and it had to be towed in, They replaced the fuel pump and filter and front shocks, it ran great for about 4 days and then it died again after 5 minutes driving in the rain( it doesn't really die, it seems to lose power and there is no resistance on the accelerator, what power is left limps you to the side of the road and then the engine dies). They replaced a relay, he drove it about 5 miles and it did the same thing.

Thank You for your help

 

I've copied and merged two posts from you Intro for advice from members with the same model.

Graham

 

Hi jkm210,

Sorry to hear about your trouble. The first thing to check is for any stored Diagnostic Trouble Codes (DTCs). To do this, turn the key to position II (ON) but do not start the engine. Press the VCM (Vehicle Condition Monitor) button on the trip computer panel to the right of the steering wheel and watch the small display window below the speedometer for any displayed fault code, which will be in the form of "FUEL FAULT 47" or "FF89." If a code appears, write it down.

Sometimes multiple codes are stored, but the display will only show one code at a time. If you find one code you will need to delete it in order to see the next stored code. To delete a code, be sure you've written it down so you don't forget it, then open the fuse box under the arm rest in the center console. With the key in position II, pull the fuse for the instrument pack. On our '93, I think it is Fuse 9, which is the second fuse away from the driver's seat (our car is LHD). Once you pull the fuse, watch for the needles of the speedometer and tachometer to drop below zero. After you see the needles drop, count to 10 or so, then replace the fuse (with the key still in the ON position).

Now turn the key off, then back to position II, and press the VCM button and watch for another stored DTC. Repeat the process until no codes are displayed.

Please report any codes here and we'll do our best to help.

A few possible contributors to your symptoms come to mind, but I'd rather not get into all the possibilities until we know if there are any stored DTCs that will point us in the right direction.

Cheers,

Don

 

Thank You Don B, I've sent the info to the mechanic and he will let me know if any codes come up. Julia

 

Don, it only gave them old fault codes, they said nothing to do with the current issue. The mechanic said it is heat related, it drives for 12 miles then shuts down, after 7-8 minutes it will start up but only go 6 miles before it shuts down. He said it is not the fuel pump relay. Any further help would be very much appreciated! Julia

 

There is an additional relay on the 94 (on the firewall, passenger side, yellow base) that controls the fuel delivery. This is the Oxygen Sensor heater relay.

If this relay fails, or the connection between the relay and the base is corroded/no good the fuel will stop flowing.

Not a bad idea to clean the yellow socket and relay pins or swap the relay with one of the others nearby (air injection relay, [red base] might be a good one to choose) or just replace the relay with a new one.

That should eliminate the possibility of the O2 heater relay being the problem.

Also you mentioned that the fuel pump had been replaced - they removed the tank to do that, right?

ps
even if the VCM codes were old codes, what were they?


Larry

 

Thank you for your help! I passed along this info to the mechanic, and asked him if he wrote down any of the fault codes, I will let you know once I receive an answer.
Many many thanks,
Julia

 

Ditto, Julia. It may be very helpful for us to know the codes, since issues are often due to multiple, interacting malfunctions.

Also, does the mechanic not know how to clear the codes? We can help with that too.

Don

 

He said he cleared them. I still haven't heard back from him on the codes. I believe he said he was going to check for a spark, when the engine is cranking but not turning over! He said, they had it running in the shop( he said it won't die in the shop, they took it out and didn't die at all, he said we've taken it out driven it 10 miles, tow truck following so they can load it up and get it right back to the shop to hook to the scanner, he said, it starts right back up. I asked him about the codes again, he said there are no hard codes showing up and all others have been erased.
Can you clearly see I have no idea what I'm talking about? This has been so frustrating! Thank you very much for all the info you have been sending, it's very much appreciated. He said he will take the car back out again in about 60 minutes and try to see if there is fuel and a spark! I will keep you posted! Again, Julia

 

Hi Julia,

OK, without codes we may be guessing, but I'll throw out some ideas for your mechanic to check. This is assuming that all the basic tune-up items are in good condition: spark plugs, distributor cap & rotor, air & fuel filter.

Sometimes odd behavior is the result of multiple issues, so it could be more than one of these, or something else entirely:

1. The Fuel Pressure Regulator (FPR) has a diaphragm inside that is known to fail. When this happens, raw fuel is inhaled into the intake manifold and the Engine Control Module (ECM) cannot correct for it since the fuel is "unmetered" by the ECM's control of fuel injector pulse duration. To check for this problem, pull the vacuum hose off of the fitting on the FPR and look for signs of wet fuel. If none is visible, crank the engine and double check.

2. Another possible FPR issue, even if the diaphragm is still intact, is the loss of its ability to hold pressure in the fuel rail after the engine is shut off or dies. The sudden loss of pressure allows the fuel in the rail to boil and vaporize, leading to classic vapor lock and a no-start condition until the fuel has cooled enough to condense back to liquid. I have a photo album on replacing the FPR - see the link in my signature.

3. The FPR works in conjuction with the check valve, which is built into the fuel pump module inside the fuel tank. Often, both the FPR and check valve lose some or all of their ability to hold pressure. An inexpensive check valve can be added to the fuel line. I have a photo album on this topic also.

4. The Coolant Temperature Sensor (CTS) signal is one of the critical inputs the ECM uses to determine the Air-Fuel Ratio (AFR). One failure mode of the CTS is to tell the ECM the engine is cold even after it warms up. This causes the ECM to continue to apply cold-start fuel enrichment, which leads to rich running.

5. The Oxygen Sensor (O2S) could be contributing to your issues if it has become lazy and its voltage is not swinging properly between just above 0V and just below 5V. The O2S signal is another key input for the ECM's determination of AFR. The ECM ignores the O2S signal for an allotted time while the O2S heater is warming up to operating temperature (several hundred degrees F). During this warm-up delay, the ECM determines the AFR based on built-in fueling programs or "maps." This is called "open-loop" mode. Once the delay has elapsed, the ECM begins referring to the O2S signal, and it is said to have entered "closed-loop fuel metering," in which it actively adjusts the air-fuel mixture based on feedback from the O2S (and other sensors, including the CTS, the Mass Air Flow Sensor (MAF or MAFS), and the the Intake Air Temperature sensor (IAT or IATS).

6. It might be worth asking your mechanic to clean the electrical connector for the Throttle Position Sensor (TPS). The TPS is mounted on the underside of the Throttle Body (TB) and on your car the electrical connector is mounted on a bracket attached to an air intake elbow to the left of the TB. Oil contamination of this connector has been the most common cause of Limp Home Mode (LHM) on our '93, so it would be worth ensuring the connector is clean. In all likelihood, the TPS itself could stand to be cleaned (I have photos showing how), but if it were the cause of your current issues I think you would have had a DTC related to the TPS.

8. If the distributor cap and rotor have not been replaced, ask your mechanic to inspect them carefully for signs of arcing, cracks, etc.

9. One issue that can contribute to stalling, especially when slowing to make a turn or come to a stop, is low transmission fluid, so have that checked just to rule it out.

10. I'm no expert on symptoms of a failing catalytic converter, and I think failed cats have not been common on the XJ40, but it's possible that if your cat has deteriorated inside and is partially clogged, it could contribute to your problems.

Now you see why Diagnostic Trouble Codes can be so helpful!

Please keep us informed.

Cheers,

Don

 

Hi Don, well......They are waiting on a fuel pressure regulator to arrive that was shipped over night, but hasn't yet arrived. You mentioned XJ40, mine is a XJ6, is there a difference. I asked the mechanic if there was possibly something wrong with the computer because it did not produce codes, he said they are looking at that next. The catalytic converter has been ruled out and the gas tank was flushed and fresh gasoline put in. I reminded him, this issue started after going through a car wash and getting the under carriage washed, he said everything is enclosed, he didn't see an issue there. They have called the closest Jaguar dealership and asked the mechanics if they could offer any advice, they replied, sorry! The problem varies from 70 mph and losing power to fresh starts, after being parked outside for several hours, or just blocks from my home while driving 30 mph and it like the gas pedal feels soft under your foot when it loses power. I feel sick over this, I appreciate all your knowledge time and effort you have put into resolving this mysterious situation. Please let me know if you come across any other idea's. Many Many Thanks, Julia

 

Does your 1994 XJ6 have rectangular or triangular-ish shaped tail lights?

If rectangular it's a late XJ40 flavour of the Xj6, if triangular, it's an early X300 XJ6 ...

mmm ... not producing codes, eh? beginning to think the mechanics believe this is an obdb11 car - if it's an XJ40, it will only show codes via the VCM panel on the dash - no modern code reader will be able to interface with the car ...however if it's an X300, different story!

Are you positive the in-tank fuel pump was replaced??

 

Tail lights are rectangle, they are in fact using a modern code reader...interesting, I'm sure they are not aware of this, I will let them know asap first thing Monday a.m, yes very positive the fuel pump and filter were replaced, the boxes are in my trunk with the old parts enclosed. Your car is identical to mine, right down to the mileage, beautiful car, Thank you for your info, I hope this is the solution......I will keep you posted. Thank you, Julia

 

Julia,

There is no OBDII data port on your car for a modern code scanner to connect to. The XJ40 used the earlier OBDI protocol (On Board Diagnostics), which was proprietary to Jaguar. Is your mechanic using a scanning tool that can read the Jaguar information via the OBDI data port, such as the Jaguar Portable Data Unit (PDU)?

Don

 

Don, I have no idea, he said he had an expensive piece of equipment that scanned all the codes, I will have to ask him on Monday, would you like to know how very confused I am right now? Thank you for the information, I will let you know what he says. Julia

 

I doubt VERY VERY much that he has a Jaguar PDU and his scanner, no matter what brand or model will be unsuited to your car because as Don said, there isn't a way to plug anything but a big old obsolete and expensive Jaguar PDU in anywhere on our cars.

He may as well be using an "executive decision maker" for all the good his scanner would do.

However, there is a code scanner. It is part of the car and doesn't require plugging in anything.

From Don's first post, this is the built-in scanner that you have on your car and the instructions on how to use it:
Larry

 

Hi Julia,

I'm sorry this is all so confusing for you. Your car does have a data connector port, located in the trunk on the battery support bracket (you might ask the mechanic where the port is in your car just to see if he really knows). It is possible he has a system that can connect and communicate with your car.

However, your car actually has a built-in system for displaying stored fault codes (Diagnostic Trouble Codes or DTCs) on the instrument cluster in a small display below the speedometer. I'll be happy to tell you how this is done but your mechanic has probably cleared all the codes. Your mechanic told you the only codes he found were "old" and unrelated to the problem. I'm not sure how he could tell any codes were old, and forgive me for suspecting that he may lack the necessary understanding of your car to make determine that any stored codes are unrelated to your current problem.

One question that comes to mind is this: when the problem happens and you begin losing power or acceleration, have you noticed an orange warning lamp illuminated on the instrument panel that is shaped like a transmission with an X through it like this?




If so, that may help narrow down potential causes.

Thinking of your mechanic's idea that the problem is heat-related, he can test the operation of the Coolant Temperature Sensor (CTS). When the engine is cold, the resistance across the CTS terminals should be a few kilohms, and when the engine has reached operating temperature it will read near zero ohms.

Don

 

Thank You again! When the car loses power, my first instinct is to look at the dash for any warnings, there is nothing until the car is at 0 mph, then the battery light comes on. The mechanic said today, he was aware of only being able to check the codes manually via the dash. He said no vault codes have been present. They were starting from scratch today, pulling the fuel tank and retracing steps, he said, we are in the trunk working now! I appreciate all the help trying to rectify this dilemma, my 60th is this week-end with 5 of my brothers coming in to town, I was hoping I would have a car to drive.....

 

I hope you have a very happy birthday, Julia. Please keep us informed on your car. Learning from one another's experiences is what makes this forum so valuable.

Cheers,

Don

 

Thank you very much. I was at the gym this am, saw my car pull in to the filling station and saw the brake lights go on, I knew it had stalled, I ran over, the owner of the shop was, I'll go with angry, he said we have turned this car inside out, there has never ever been a car that I can't fix, it going to have to go somewhere else, he said, I drove it for 30 minutes yesterday and it purred like a kitten, I thought we had it fixed, today I didn't make it 5 minutes, he said it has to be something heat related, something from the ignition to.......I just don't know! I said I had sent him a new email from you with another suggestion, he said he hadn't read it yet........I attached a pic of my Jag, me and Blu, although about 5 years old. Again, many thanks! Julia