My daily driver has started doing something bizarre. It stalls either rarely during the day /week or I wonder if I'm going to make it home.
Here is what is consistent:

It happens when moving and my foot is off the gas or ever so slightly on it, as in coming to a stop, braking or turning a corner.

It only happens when the car is up to temp.

It's a dead stall, no sputtering

The car will easily restart and usually will idle fast ~1500 RPM It stalls when shifted into Drive. If I get lucky the idle will be normal at restart <1000 and it wont stall when shifted into gear.

I think it happens more often with the AC on.

It hasn't stalled while idling in park.

Over a week ago I sprayed about 1/3 can of carb cleaner into the AFM while it was running and the stalling went away for about a week.

Many parts have been replaced in the past year. The temp sensor is a year old, Thermo-time sw. and cold start system work fine, Starter relay is 6mos old, Fuel pump and smog pump therm. sw. are new.

Aux. air valve? over-run valve? AFM?
Help..

 

Start with something simple....and you've already touched upon it with your carb cleaner.

Clean the throttle body thoroughly with a rag, brush, and carb cleaner and make sure the throttle blade is set to the proper .002" clearance.

While your at it, remove the air distribution block for a good cleaning as well. order a new gasket first.

Cheers
DD

 

hmm... I had a car acting very similar to this before, and it was actually caused by a faulty ignition switch that kept shorting out. This may be something to look into, but with my experience with s3 jaguars a week ignition coil can have some strange effects, I believe it could even disrupt the ignition switch. I'd check that all my connections were clean and tight from the distributor to the electronic ignition amplifier to the coil all the way to the ignition switch, can't hurt, maybe look into getting a new coil, cheap and easy to replace and a strong coil is always a plus, these cars are thirsty for electrical juice! anyways, there is a bit of my limited knowledge, hope it helps, if not there are some really experienced jag-wise guys on this forum that are sure to chip in.

 

Had a bunch of keys on the key ring and the ignition switch was going bad.

Would die mostly going around RH turns.....changed the switch and it has been
great from that time forward...

 

Thanks for the replies.
I'll fiddle with the ign sw but I don't think that's it.
The ignition stuff is all less than a year old, relay, coil, injectors,amp, plugs, wires, cap, rotor, starter, alternator, water pump, a/c compressor and fan clutch to name a few..

I think the clue to the problem is that when the car is restarted after a stall the idle RPM's range 1000-1600 and it stalls when the car is put into drive.

Normally idle is 700-800

I'll do some cleaning and check the gap and see what I find..

 

Cleaned gunky build-up from the breather pipe and deposits in the throttle and over-run valve. The butterfly was tight and reset to spec.
Runs great, feels a little more powerful too.. Let's see if the stall returns..

 

Fingers crossed. If the stalling continues other possibilities are out there. This t/b cleaning should be done every few years just on gen'l principles anyway

Cheers
DD

 

Stall came back while I was braking for a red light. Ignition switch is tight so I rule that out.
The aux. air valve reads 22 Ohms, Manual states 33 Ohms... Is that deviation significant?

Thanks for the tips!

 

i could be wrong but ide expect at least one splutter if it were the air valve. even when you block the airflow through the air filter off completely it splutters and carries on before it dies.

to me it seems more electrical if it just dies suddenly, and if it restarts strait away the ignition switch makes sense because obviously you have to move the switch to restart it, thus disguising the problem. if i were you ide stick a wire on the positive side of the coil and connect up a test light inside the car. you could just run it and leave the bonnet open but latched then run the wire through the window.

failing that take the ignition amplifier off and clean the mountings as these are the earth for it, then clean the connections on top of the water rail and the earth strap under the exhaust manifold so you can rule that out. could even be that strap is lose and at idle looses contact.

otherwise never trust a relay, just because its new out of the box doesn't mean its any good. also its possible its a dirty connection somewhere that drops the power in the circuit enough to unlatch a relay if the battery voltage drops back at idle

first ide check you have power at the coil when it dies,
then make sure the ecu has power, this can be done by carefully routing a test wire and test lamp.

also, check the injector trigger wire that goes from the coil negative terminal (i think) to the injection loom. mine was making a bad connection as the insulation had fallen away and caused problems.


can you simulate the problem in your drive way as that would make it much easier for troubleshooting.

regards,
jay

 

This past week it stalled twice, once while braking for traffic light; it restarted right away in Neutral, no problem.

Then again while driving about 40 MPH but I was coasting, foot off the gas. This time it restarted by itself because I was going fast enough, I guess the rear pump in the tranny is still good..

Tonight it went into demon mode: Stalled while braking, didn't want to restart, stalled when it did. Had to give it gas and keep revs >1500 to keep it running, drop it in gear and go, stalled several times on the way home, stalled when I let off of the gas.

Consistent items:

Only happens when hot
Wants to idle fast when re-started
Headlights ( if on) go out when I re-start the car, must use switch to turn them back on, normal?

I've checked connections and ignition sw. coil, ign. amp and relays less than 1 yr. old.

I'm going to swap aux. air valve this weekend but wonder about the AFM. My "city" mileage has dropped to about 10 MPG as well..

 

Well I changed the aux. air valve and put the old coil back on the car: cleaned electrical contacts.
The car has been normal lately however the stalling fits come back when the air conditioning is turned on. so it has to do with the a/c circuit somehow.

When it stalls it will restart but I must keep my foot on the gas just a bit or it will stall. If the car rests for a few min. it will restart and behave normally.

So is there some communication to the injection system when the a/c is on? Is it the AFM going bad and not regulating idle?

Again it seems to ONLY stall when the a/c is on AND the car is hot AND my foot is off of the gas.

Without the a/c on the car runs great, does not stall, only complaint is that it get about 11MPG city driving when last year it was closer it 16MPG.

Thanks!

 

No electrical tie-in between fuel njection and A/C.

What's your idle spped in "D"?

Yours is not the first Ser III to suffer this. The A/C is very parasitic and the 4.2 F.I. engine just barely sustains llife at idle to begin with. Jaguar even made a retrofit kit to increase idle speed with the climate control on. It was installed as standard issue in some markets.

Try increasing idle speed 100 rpm using the adjustment screw and see what happens.

Cheers
DD

 

In gear D, R, 1,2 it will idle at 750-800 In Park & Neutral it idles at 800-1000 cold and 1000-1200 hot

 

That should be high enough unless it's also running too lean....and borderline "too lean" is how these were built, thus difficulty sustaining idle on some cars.

Have you tried richening the mixture a bit with the adjustment on the air flow meter? It's under a plug that you'll have to pull.pop out

Cheers
DD

 

Running through the checklists in the Jag. Factory Manual, I think I am down to the AFM or CPU as a culprit. The AFM seems to have smooth action and the tracks aren't very worn so I don't think that it is the problem..

Did find that the vac hose to the distributor was split, replaced that, changed plugs, reset timing..
The TPS appears to be dead, checked it with an ohm meter, this only has function in full load situations, yes?

Car is now running with slightly more power but still randomly stalls when the motor is hot and the a/c is on. When it restarts idle is really fast, ranging to 1300. What I've learned is that if I try to restart it right away it will stall again if I don't give it some gas, BUT if I wait 20 seconds or more the car will restart just fine...

 

OK I was mistaken, did a 70 mile highway trip today. The car does the stalling nonsense when it is well up to temp. 82*F ambient and ran 75-80mph dash gauge read 90-100*c and the a/c was off stalled on the exit ramp. drove fine otherwise..
When restarted after stall it will idle 1300-1600rpm although it idles normal when "cold" When hot the car stalls immediately when put in gear. I must give gas and brake at the same time to deal with traffic / stop lights..

Can't find any air leaks, hoses etc. Changing the TPS next..

 

Just wondered where you are with this, as my car is doing the same thing. You are a little farther along than I: I checked the throttle plate clearance and it seemed spot-on; I will remove the TB and reclean, also the CC vent, etc. I have replaced the coil and the module inside the Lucas ign amp. Thanks for the help.

Update: read this: http://www.jagweb.com/aj6eng/42efi/index.php more specifically, look at the air flow meter. Seems like it may be a prime suspect.

 

Two ideas:

1. Intermittant ignition feed issue. Jump battery + to coil +. This will eliminate any switch, connector and wire issues. If it no longer stalls, follow that clue and fix any anomaly.

2. Fast idle on restart suggests two things;
a. Vacum leak. Takes a bit of sleuthing to find.
b. leaky distributor diaphragm and/or sticking advance weights.

Don't rule out a lean condition because of a fuel feed issue.

Carl

 

I put a jumper wire from +12volt at the battery to + at the coil, and mine stopped dying. I will now troubleshoot the ballast resistor and ignition switch, and the wiring.
I suggest you might make some progress with the jumper wire.
Good Luck, and thanks to Doug.

 

The car has been out of service as the alternator died, well something cause a jam or a short and caused the brush box to melt and one of the brushes went at an angle..
I've replaced the alternator and will drive it today to see what happens..

I just tried a jumper + bat to + coil and I can hear a relay energize and the seatbelt buzzer goes off / dash lights come on as if the key has been turned to 1st. position.., The key was not in the ignition.. Is that correct or is there something suspect in that circuit?