That throttle body is held in place with four 10mm bolts. There's also a coolant hose that goes in and out of the throttle body underneath. Golf tees make a perfect plug for those hoses.

Pull it off and loosen those screws/bolts that hold the TPS in place, ju-u-u-ust enough to adjust it on the car with a little bit of effort. Put it back on the car and see if it made a difference. Once you find the sweet spot, lock in the TPS.

 

Thanks, Vee. I'll get back on it tomorrow.

 

While you have the butterfly off, I suppose it makes sense to check for the throttle plate clearance to be at .002"

You would need a feeler gauge for that. Most autoparts store would carry something like that. It is not common for the butterfly to fall out of tolerance, but you never know what has happened to it.

Also, while I am certain the throttle position is out of spec (we are targeting about 12.9%), you could have two overlapping issues. The oxygen sensor being the other fault.

The 10% throttle position reading is the one that would prevent the car from idling normal, and would cause it to choke off, so that does need to be addressed.

 

Vee, I managed to tweak the TPS mount to read out 0.61V with ignition on/engine off. That went up to 0.645-0.655V with the engine on and idling. My meter is telling me that the voltage is actually ranging between 0.645 and 0.655, but it's a digital meter and I can't tell if there's a pattern. Oddly, now the OBD is reading throttle position 0% at idle, but rises with a press on the pedal as expected. Is the ECU just getting used to the new TPS voltage and will eventually correct itself? Also, I still hear some burbling out of the tailpipes, but that's not really a problem as the engine seems to be idling smoothly and not hunting for idle speed. I did not check the butterfly since I have only wide, flat feeler gauges and it looks like I really need a flat needle or wire type. The car is idling in the driveway now and I'm waiting for it to spontaneously quit as it usually does. I have the OBD monitoring engine RPM, throttle position %, and Engine Coolant Temperature. I'll report back if something happens.

A few minutes later the engine quit with the monitor running. There was no change in TPS or ECT, the RPM just dropped to zero (as close as the OBD gets to zero, which is 32 RPM). Here's are the traces. I was driving for the first seven minutes or so, then the car was idling in the driveway for about 25 minutes before it spontaneously quit. It would restart, run a few seconds, then quit again. No MIL. I'm stumped.

 

The lack of a check engine light is the most maddening part of this all.

Did the change to the TPS do anything? I'm starting to wonder whether the program you're using just doesn't read the % accurately for the TPS? Does it look like this:
https://www.autoreservejaguar.com/me...m/img_1532.jpg

Coolant looks good. RPMs look steady at idle. 700RPM is where it should be, so this looks good.

How did the engine perform for you while driving? Smooth? Lumpy?

Are you trickle charging the battery? Have you had any issues with the battery?

I'm wondering if it might be time to revisit the EGR? I would recommend starting there. What happens if you simply unplug the EGR before you start the car? If you end up taking it back off, please check the spring. It should be snapping back after being actuated open. How does the gasket look? Maybe needs to be replaced?

I'm also wondering if we haven't discussed the Idle Air Control Valve enough. There are two test we can run for the IACV.
A. There is a temporary method to test the IACV on the AJ16. It works permanently on the AJ6, but once you turn the AJ16 engine off, the car will return to what it was doing before. If successful, this will confirm that the IACV is working. If unsuccessful, it doesn't mean anything.

1. Run engine until fully warm.
2. Switch off ignition.
3. After 5 seconds switch on ignition - wait 5 seconds - remove connector from stepper motor.
4. Switch off ignition.
5. Wait 15 seconds then replace connector on stepper motor.
6. Repeat operation sequence 3 - 5 twice - on the last occasion do not reconnect stepper motor, and start the car engine.

When you start the car engine, hopefully you'll notice a difference. Turning off the car will result in a reverting back to before, so let this run and see if the car stalls out eventually, like before.

While doing this, monitor the battery to see if it's not charging?

B. The other test is simply to unplug the stepper motor and see if the car stalls.

After performing both tests A&B, we should have an indication whether the IACV is helping or not?

 

Vee, thanks for taking the time (again) to help me work through this. I'll answer what I can immediately, then continue with the experiments.

I'm not aware that changing the TPS did anything. I didn't notice anything at all. Regarding the OBD reader, the TPS reading was non-zero before the adjustment, as we both observed, so I don't have any reason to think that the OBD reader is somehow missing it. Yes, the TPS looks like the one in the picture. I also have the extra one that the mechanic removed when he suspected it was faulty.

Driving is smooth and, honestly, an absolute pleasure. I LOVE driving this car. The battery is brand new and I haven't had any issues with it.

Regarding the EGR, I had it off and, as I mentioned earlier, one of the bolts was not seated so I replaced it with a shorter one. The gasket looked okay other than showing some leakage that should be fixed with the shorter bolt. I did not inspect the EGR spring - I can still do that.

I'll try that procedure for the IACV probably tomorrow. It's well into the 90s F here today and too hot to work in the driveway.

 

Vee, given that the car dies at idle and also at speed on the road, is there still reason to suspect the Idle Air Control Valve?

 

Steve,

The smooth idle followed by the sudden stall would seem to point to an electrical signal failure being received at the ecu. And the fact that it doesn't happen for over 30 mins would seem to indicate that it's not when the lambda sensors start to provide feedback. Bu do you have lambda voltage traces at the point of stall?

You've talked about changing various components, including the crank sensor etc, but have you checked the integrity of the wiring connections to those components and ten integrity of the wiring back to the ecu? Maybe there's a minute solder joint on the ecu that only opens when it gets hot? That could be a difficult one to check unless you had a spare one that you could swap in to try.

Although it does seem to be an electrical issue. have you checked the fuel pressure on the rail immediately after stall? Maybe the fuel filter is cavitating / getting blocked. When was it last replaced? Also, open the fuel cap and check for a sudden rush of air in that could be caused by a blocked vent pipe, where a vacuum builds up in the tank and prevents fuel flow.

Good luck

Paul

 

At speed....no. The IACV should be crossed off.

That leaves the EGR. Unplug that thing before you start the car next. Ignore the check engine lights and lets see what happens.

 

Paul, thanks for your thoughts. Pretty sure fuel issues have been ruled out as all the evidence points to electrical as you say. I have not done the lambda-sensor recording yet, so I’ll queue that up for the next run. Regarding flaky wiring or solder joints, yes, that’s definitely a place to look but very hard to isolate. The ECU does not seem to be heating up to the touch, but that doesn’t mean some component on the board is not doing a thermal runner. There’s not much evidence of degraded or damaged wiring anywhere on the car, but I’m getting to the point where I should be tracing every darned lead. I’ll report back when I have more info. Thanks, again.

 

Vee, I’ll disconnect the EGR and report back. Thanks.

 

We have to start crossing theories off the list.

The fact that your car will stall whether it's being actively driven, or idling is curious. The car will die as you have your foot on the gas pedal, not just at a red light or something, right?

The dying at idle crosses off things like the TPS and the MAF. I have to chalk up the OBD2 reader as not understanding how to read the TPS position, or the OBD2 computer on your 1995 as not knowing how to report it. I haven't heard about that issue in the past, but again, if the car is driving smoothly, and will stall out while idling, then it has to be working well enough.

If you have purchased the ECT, I would recommend installing it. It's a 5 minute job.

I'd like to cross off the oxygen sensors since you're not experiencing any rough idling. I don't think the oxygen sensors can stall out the car without at least giving the engine some bad fueling directions. Would like to know if anyone else disagrees with that.

Crankshaft position sensor has been replaced with a "known working part". I want to believe it, but this is a part that goes bad over time, not mileage. Amazon sells this part for $20 from A-Premium, or for $8, Walker (235-1439). I replaced mine with the Walker many years ago. I'm just saying.....It would take you about 10 minutes to replace.

I am not aware of any other sensor that would cause your problem.

Other things to look at:
1. When the car stalls out, put a multimeter on the battery. How many volts are you reading?
2. Fuel Pressure Regulator... if you pull the tiny rubber tube at the regulator, is it wet with fuel? Is there a fuel scent present? There could be failing diaphragm in that regulator. Fuel pressure should be at 43psi, and there's no place to check for pressure at the fuel rail.
3. Rochester Valve/Fuel Filter failure? - Upon stalling, immediately open the fuel tank filler cap and listen for any indication of a vacuum. You could also just disconnect the Rochester Valve, which is located in front of the drivers wheel well. (You'll probably have to take that wheel off) That is also the location of the fuel filter. If either of those get plugged, negative pressure can create difficulty for the fuel pump to send enough fuel to the engine?
4. Clogged cat converter or exhaust tailpipe somewhere.

I think that would be it at that point. I would be out of ideas then.

 

Vee, I am 100% on board with your comments. You've been very patient with me and my woes, and I appreciate it.

BTW, the CKPS was replaced with a new part, not used, so unless there's a new-part failure or gap-to-cogwheel problem, I think we should cross that off.

I drove the car for about 26 minutes today, right at the limit of reliability, and it just started cutting out about one minute before I pulled into my driveway. I was double-footing the brake and throttle to keep it going and just barely made it home. I was recording all the same parameters as the last run, plus voltages from all four O2 sensors. Below are the O2 Sensor traces, which I think show that an O2 sensor is not likely to be the problem.

Here's one observation that might be relevant: After it stalls, it has always restarted immediately and died again almost immediately. If I keep feathering the throttle, it will stay alive for a bit longer, as if whatever is trying to kill it can't sustain more than a second or two at a time until it wins the battle. It does not fail to start as you would expect if some electronic or electrical component or connection were failing - it just won't stay running. Does that seem weird? Kinda points back to fuel??

Responding to other ideas from you and Paul,

• A meter on the battery shows 12.2-12.6 V after the stall.
• No hiss indicating vacuum in the gas tank when I lift the filler lid immediately after stall
• Disconnected the EGR - no change in behavior, car starts and stalls immediately (after running 25 minutes or so)
• On pulling the little rubber tube on the fuel pressure regulator: Not wet, some faint shininess, faint smell of gas. What does that mean?

I'm starting to lean back toward a fuel problem. Earlier, I was completely convinced it was electrical because the first thing to blink was the tachometer. When the problem first appeared on the freeway and the engine cut out for the first time, the tach dropped to zero momentarily when the engine cut out even though the engine was still turning at 2,000 RPM (I even have a video of this happening). Now I'm wondering if that (electrical) problem got solved and another, completely unrelated, problem has taken its place. Evidence for this hypothesis: The tachometer does NOT dip to zero when the engine stalls now; it trails off with the engine RPM as you'd expect if something other than ignition were killing the engine. I'm sure weirder things have happened, but that would be up there in the top ten. What do you guys think?

Record of O2 sensor voltage up to engine cut-out

 

OK, so the 02 sensors look normal, until the end. Bank 1 appears to give up before Bank 2 does. I don't really know what to make of that.

Any gas in the tube means that the little diaphragm that makes that regulator work, is failing and letting gas get sucked by the little vacuum hose. That could help spot the fueling problem.

Your battery is fine, nothing to see there.

No hiss means tank is not gonna be under enough pressure to cause this problem. That's crossed off.

I guess the EGR can be taken off as well, since no change with it plugged in or not.

I agree that I think its a fuelling issue....with the only other answer is an exhaust issue. If a cat is blocked up, it could force the engine to shut off, but I think we would have seen something with the 02 sensors, so that's gotta be off the table too.

What could cause your fueling to die after 25 minutes? I don't think replacing an ECU will solve that.

Fuel Pump. That's not easy, so it's not cheap to replace. There are hoses within the fuel tank that serve the pump. Those hoses should now be melting after being in the fuel tank for 30 years. When I replaced my fuel pump just the other year, the shop (I paid a lot of money) said that he couldn't believe the hoses inside were holding up. Others have mentioned that too.

While it's not a full tank out job, you could conceivably do it in a whole day, more likely a weekend.

​​​​​​https://www.jaguarforums.com/forum/x...s-tank-236192/

 

I am trying to come up with a way that the fuel pump could be monitored. There is a sock filter attached to the pump to filter the fuel before it gets to the pump. If that is clogged, the pump could be fighting the clogged sock until it cant fight it no more, or until the sock clogs up entirely.

I wish they had a port for some kind of meter on the fuel rail.

 

Thanks for the thoughts. Is there a way to pull an injector to see if it's squirting fuel? (Or is that just too dumb and dangerous to consider?) Looking at the other threads on this topic, it seems there is often frustration around testing fuel pressure. I couldn't find a thread where anyone figured it out, at least not for this version of the AJ16.

 

You're definitely squirting fuel....at least for 25 minutes you are. You can pull them, and test them, with a 9v battery, but I don't believe the injectors can be the problem. It would more likely be the signal to them, or perhaps a ground cable that has gotten loose somewhere, but why after 25 minutes?

Something is either getting hot/overworked, or it's getting clogged....or both? One injector failing would cause rough driving/idling. All six shutting down at the same time is less likely.

There is a chance that the fuel filter is getting plugged up and needs to be replaced, but I'm starting to think that the fuel pump, or something around it may be to blame. It is difficult to troubleshoot that without some kind of pressure gauge on the fuel rail. Without going through the expense of brazing one on to a fuel rail, I don't know how else to do it.

https://www.jaguarforums.com/forum/x...essure-197887/

 

I agree it can't be the injectors themselves, I was just trying to think of a way to determine if fuel is reaching the cylinders after failure, testing the FI squirt after the failure. I think I'll call my Jaguar shop and see if they have any idea how to check fuel pressure.

 

Yeah, it's not necessarily JUST whether fuel is reaching the cylinders, its also at what pressure?

No matter what your Jag shop says, there is no valve anywhere along the fuel lines to hook a gauge to. I believe the AJ6 engine did, but this engine does not.

Only way I have thought to do it, without out the special JD208 tool, is to cut the soft hose return, just after the fuel rail and add a barbed tee in there. Then attach the fuel pressure gauge to the third leg of the tee.

I measured the threads leaving the fuel rail and it was m14x1.5. I was never successful in finding something that would work, but that was a long time ago. Perhaps there is a threaded tee that is available with those threads on it. You wouldn't have to cut anything then.

​​​​​​https://www.ebay.com/itm/225474540667?hash=item347f54747b:g:Gl4AAOSwSwpkDBu J&amdata=enc%3AAQAIAAAA4HmqfxrlAldja84gGNri8%2FxpO ll29mbvDlU4O%2FoZDmyXHrth2F9MApWqI1mkHh4r%2BF%2BZQ 0oNh%2BTGsjxOPBfRNyf7yK5jYwIxuiYUlL1Y3oPxuKmt%2ByZ 1KrLATSXU7vf7kYZw0O4E70ImoTZ4BTeSiSc15KwknHagQJwZo %2F49CEMJdFd%2FA6RtNOXYXp9JLKoI0KgYkI6qr0xAdibpu4J TiIiTPROhlAEjWtwNa3o%2FQFTcUXfusetIrXCMqD86nPAeQ70 ZzVlCd69SlNo%2FV%2FeuOvmdsv7uOd7LKjg53LtpHtvu%7Ctk p%3ABk9SR4yd26jKYg

Here's something that could work.

 

Thanks, Vee. I'm approaching my weekly limit of Jaguar troubleshooting (I was investigating the non-functional cruise control this morning, and replaced the ECT sensor that arrived yesterday). Again, I really appreciate your help and support. More soon.