I thought my gremlins had been laid to rest with a new battery. Apparently not.
The title says it all - when I turn and brake at the the same time the engine stalls. When driving at, say, 75 mph, putting the gearbox to neutral causes the engine to die.
Main problem with this is that the power steering also dies!
The first symptom, starting a few weeks ago, was occasional heavier steering after starting up, but things have gone downhill since.
No jag dealers within 100 miles of here (Mt. Pleasant, TX).
My current suspect is vacuum, I haven't looked under the hood yet.
Anyone ever experienced this kind of issue?
I am due to drive home tomorrow, 100+ miles.

 

I'm not a tech, but it seems to me that it's a fuel starvation problem because it happens only when you're not on the gas pedal. Maybe the fuel pump, filter and/or one or more injectors. Any warning lights?

 

Stuart, its not fuel starvation, those symptoms occur under acceleration.
He is having trouble maintaining idle.

 

When(If) was the fuel filter last replaced?

 

I would expect a vacuum leak to INCREASE idle speed, not cause the car to stall. Also a significant vacuum leak should trigger a fault code. You might read the ECU for faults even if the MIL is not on. It usually takes two faults before the MIL turns on. The workshop manual lists the following checks for stalling:

· Breather system disconnected/restricted
· ECM relay
· Electronic engine control
· Ignition system
· Air intake system restricted
· Air leakage
· Fuel lines
· Ensure the engine breather system is free from restriction and is correctly installed
· Read DTCs and refer to DTC Index for electronic engine control tests.

Does it idle OK when parked?

 

I do not know when/if the fuel filter was replaced, certainly not within the past year, but fuel is certainly getting through enough for rapid acceleration and 90+ mph cruising.
The stall during coast does not seem to ocuur at 30 mph, but does at 50.

 

It almost sounds like the IAC is not functioning correctly or it is clogged.

 

It idles at a solid 600 rpm, even when coasting at 30 mph.

 

Because it costs nothing I would disconnect the battery and short the leads for 30 second to give the car a hard reboot. I've seen stuff just get 'confused' from short term adaption and need another chance to sort it out.

Lean makes a rough idle so it probably isn't that. Possibly IAC but that 'should' rest at warm idle RPM. Without better symptoms it's hard to guess what the ECU is thinking. No code usually means it's happy with the parameters but too confused to keep the engine running.

 

I had discounted disconnecting the battery as a potential solution since a brand new battery was just fitted and the problem started before that but hey, I'll give it a try. Unfortunately I have no tools nor code reader with me.

 

You only need a 10mm wrench to pop the cable off. A little adjustable will do it as well. I assume the vert has a cover that comes off by hand like the coupe.

 

In his Post #8, Nigel said "It idles at a solid 600 rpm, even when coasting at 30 mph." So it appears that he's not having trouble maintaining idle.

In his Post #1, Nigel said: "when I turn and brake at the the same time the engine stalls. When driving at, say, 75 mph, putting the gearbox to neutral causes the engine to die." It appears that his problem occurs when he takes his foot off the gas pedal. That suggests lack of fuel to keep the engine running. Maybe fuel starvation isn't the right terminology, but that was my first thought.

Lots of possible causes. Unfortunately, you can't see the ones that are computer controlled without the diagnostic tools. Hopefully, the Ranchero50 reboot will cure all. That's an easy DIY fix.

 

The big question is what is the ECU doing during engine braking? Is it closing the throttle and also closing the IAC? That could shut the engine down if it's doing it too hard.

The turning shut off makes me winder if there's a load pressure switch on the steering system to tell the ECU to bump the idle under steering load? I don't think so but it's something to ponder as well. A faulty switch wouldn't effect the straight line slowing shut off problem though.

 

Not sure I understand. What do you mean short the leads for 30 seconds?

 

You are overthinking this one. (even op is to some degree)
Simple fact is that the IAC is failing to take over in multiple scenarios, under load and with zero load. It could be that its getting a false reading from TPS or MAF, or as jagtoes said, itself faulty.

 

He does not realize that's not idling. The drivetrain is keeping the car running. That's why it dies when he puts it in neutral.

P.s. with a name like Nigel, they are bound to have him over a barrel in TX.

 

When you pop the battery leads off there's some capacitance back feeding voltage into the circuits from various components. Shorting the leads together kills that voltage and ensures a quicker more definite no power reboot.

 

Perhaps. The thought process is the ECU does engine braking under certain scenarios. I would assume that it's looking at the trans being in gear before deciding to engine brake. The ECU doesn't engine brake at lower speeds unless you are in a panic stop situation which it will rev match and decel hard with the engine helping the brakes (found that out the other day).

The ECU should be looking at the RPM drop and not seeing the IAC react as needed and fault. That it doesn't suggests that the processor is happy but confused.

 

Hi Nigel

This may be rubbish but the XK and especially the ZF gearbox has towing restrictions on it.
Both speed and distance. If you are freewheeling with the car in neutral as far as the gearbox is concerned is the same thing as being towed. With the engine running as well it could well be that car's S/W is shutting the engine down for protection

I can well imagine that towing at 75mph and the engine running as well then it wouldn't like it. Look up towing and it may well give you an answer

 

Sorry Q&C, I'm a little puzzled by your comment. The car is 'coasting' at 30 mph because the gearbox is in Neutral, i.e. the engine is disconnected from the drivetrain. It is not dying in Neutral but idling. At 40 mph and upwards it is a different matter, then the engine stalls.