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2005 X type, 3.0 awd. I'm having an intermittent problem where, so far only when braking, the engine will stall. It happens when around 10 mph or less, the engine cuts out without any warning, no lights turn on, and no codes are set. Sometimes it's not noticeable until you go to accelerate again and everything is dead, that's how seemless and quiet this issue is. I cannot reproduce it reliably.
I currently have an abs light on for two bad front wheel speed sensors (ordered, waiting for parts to arrive).
I've cleaned the battery terminals, and the alternator is working with 15v at idle.
Are there grounds I should check? I'll read the fuel pressure tomorrow, what value psi should I see at idle and driving?
Besides this, the engine starts and runs fine. Any suggestions on where to look?
Jaggyjag: How many miles on the fuel pump? If your X-Type has many miles on the factory original fuel pump, say more than 80K miles, the pump may be nearing end-of life. Unfortunately it's not easy to diagnose and also not easy to replace.
When these fuel pumps near end-of-life, they work fine most of the time and generate ~50+ psi pressure in the fuel rail. But when they falter, the engine dies suddenly without error codes.
An aging fuel pump is more likely to hickup at low engine RPM. Why? It's powered by a square wave called a PWM - Pulse Width Modulated wave from the fuel pump control module (under the rear seat, on the right hand side). At high engine RPM, the pulses are long with short gaps between and the fuel pump spins quickly (see 80% modulation in attached picture). At low engine RPM, the pulses are short with long gaps between and the fuel pump spins relatively slow (see 20% modulation). An aging fuel pump is more likely to falter at low engine RPM when the pulse width is short and the fuel pump spins slower.
An old, faulty fuel pump is not easy to diagnose because it can fail infrequently at first, and gradually fail more frequently. After the engine stalls, when you restart the engine, the fuel pump likely powers back up as if nothing is wrong because it receives a long pulse signal from the fuel pump control module to re-pressurize the fuel rail before the engine restarts. As the fuel pump continues to age, it will fail more frequently and more predictably, and take longer to restart after the engine stalls.
Under the rear seat, lower cushion you'll find a large rubber plug with wires thru the center. Dislodge the rubber plug to see the top of the black polyethene fuel tank. Sit in the driver's seat with the engine off and place one hand behind you, touching the top of the fuel tank. With your other hand, turn the ignition key from the off position to the run position (not the start position) and your hand on the fuel tank should feel the soft vibration of the fuel pump energizing for ~5 seconds (to pressurize the fuel rail), then shut off (because you didn't yet start the engine). Each time you turn the key off and back to the run position, this cycle repeats. When the engine stalls unexpectedly, it may be an aging fuel pump that falters and stops at low engine RPM. But as you know, intermittent problems are tough to diagnose.
If the fuel filter is old, replacing it (relatively easy and cheap) may extend the life of an aging fuel pump, but the only solution is to replace the pump, if this is why you X-Type stalls at low engine RPM.
Bad brake booster. Disconnect and plug vacuum hose to brake booster. Start engine and push brake pedal, it will not affect engine anymore. don't drive w/o brake booster.
Where, specifically? I've looked at the intake to brake booster line and it appears solid with no cracks. It is loose on the intake side, but does not come off.
Originally Posted by dwclapp
When these fuel pumps near end-of-life, they work fine most of the time and generate ~50+ psi pressure in the fuel rail. But when they falter, the engine dies suddenly without error codes.
There is ~114k miles. The fuel pressure holds ~55 PSI, although I haven't see what happens just before it dies. I will try to find a way to narrow down the pump as the culprit. Any ideas there?
Originally Posted by car5car
Bad brake booster. Disconnect and plug vacuum hose to brake booster. Start engine and push brake pedal, it will not affect engine anymore. don't drive w/o brake booster.
The problem does not happen reliably, in fact it's happened only a hand full of times. Some times when slowing down, another time when the foot was on the brake and just starting to move. How can the brake booster be tested to know for sure prior to going through all the work of replacing that?
Essentially, what I am wanting is a way to 100% identify the cause, so I am not throwing parts needlessly at the vehicle in hopes that it fixes something.
So far there have been fuel pump suggestions, and vacuum leaks, but no suggestions on testing and verification to ensure the correct fix is applied.
You could follow the advice so far as an alternative.
I think you misinterpreted what I meant. Of course there are ways to 100% diagnose problems, otherwise mechanics would always throw random parts at vehicles until they're fixed. Some diagnostics are more obscure than others and require a bit of knowledge about the vehicle. That obscure info is what I'm asking for, in case I'm missing something specific to the vehicle. Responses like "check for vacuum leaks" don't actually tell you how, or expected normal functionality.
Additionally, what resistance should I be seeing in the wheel speed sensors if they are good? I suspect I received two bad replacements, measuring 458k ohms, and registering zero voltage when spinning the wheel. The originals read at 8.9M ohms, and also no voltage. For comparison, my truck shows 1.5k ohms and reads 0.4V AC spinning the tire. Again, I'm not sure if this is something specific to jaguars and expected.
Or the alternate to the suggestion "check vacuum leak(s)" would be to actually do a search on here as it has been posted where and how to do that innumerable times. This is the alternate to wanting everything handed to you on a plate.
How do the abs sensors work? From what I understand they are hall effect sensors riding close to the encoder magnet on the bearing, and since they are 2 wire sensors they are passive and should generate voltage as a magnetic field passes by. And yes, they will have a resistance.
I have been searching this and other forums, and Google for a few days looking for answers. I'm finding the biggest hang up is not knowing the terms for a car I'm unfamiliar with so I can properly search for an answer.
Thank you, the first one was informative. It helps, although my car isn't stuttering or having any abnormal signs of running besides just randomly dying. I'll check the valves and try to rule out vacuum leaks on the booster hose and pcv. I never did come across that post in my searches, but I also wasn't looking for stuttering issues.
The second one confirms what I was asking, that passing a magnet by the sensor should create a voltage. My new sensors do not create any voltage. Only difference is they are on the front versus that post was talking about the back, but I'd expect them to behave similarly.
The front versus rear do not act the same. The front sensors read the teeth on an iron ring as it passes the sensor no magnet. It doesn't generate a voltage. You can connect a mutli-meter for resistance and pass an iron object in front of it and see the resistance change as it passes by, the change signals the ABS unit. I don't have access to my JTIS at the moment so I can't tell you what the OHM value should be. Jaguar changed them from years to years. My XK8 and X308 both have a max of 5 ohms for a good sensor while the X300 has a range of 850 to 1.065 ohms. From the sounds of the ohm value on the new ones they are probably correct for the X400.
You might also examine the condition of the reluctor rings, if they heavily corroded or cracked they will need to be replaced.
So as to not make one post to long and to separate you problems. It is possible that the interment dead engine could be the result of nothing more than a dirty fuel filter. If you haven't changed it or don't know when it was last changed I would start there. Because the fuel pump is modulated when you are braking the pump drops off and with a clogged filter it may be starving the engine.
Avern may be on track with filter. My pump failed gradually, fuel pressure was usually always good. When it finally gave up the ghost, p.s.I. Dropped very low. But next day was fine again. Thermo explains some of what might be going on in my thread about "wear" causing lower "suction" from old pump. The entire saga including replacement (if needed) is in this thread =
The National 510099 brand bearing manufactures the magnetic ring incorrectly (I went through 2 bearings, this is not a one off issue with National, do not use this brand). Replaced with an SKF OEM brand bearing and all problems went away.
As to why it was stalling, one possible explanation from a user on another forum;
Different animal but I had it on a focus and it was a speed sensor, usually when this is the fault the clocks will misbehave as in, although you are still cruising the speedo will drop to zero the trip distance may disappear but the rev counter will still show revs. As soon as it fires up again it is back to normal so very easy to miss the signs if unaware. Next time it cuts out have a quick shufty at the clocks to see if they act up.
Also, to correct myself, the wheel speed sensors on this car are not passive. They are active 2 wire sensors, meaning resistance checks done on passive ones will not work on this one. Additionally, they will not generate their own voltage because they modify a provided voltage signal, instead of how passives work by generating their own signal. This means to DIY test them you need to probe into the wires while the vehicle is on and sensors fully connected, tire off the ground, and spin the tire while watching for a changing voltage.
10-01-2018, 03:49 PM
Engine dies when braking
