Its a 92 with the 4.0L... It needed new plug wires so I replaced them along with plugs, cap, rotor, and a good used coil. The car starts right up and idles very smooth until you give it gas. It did have a very bad shake as well, but it was from a broken blade on the cooling fan. I pulled that off and the vibration went away. I also cleaned and tested the injectors. The car was in a bit of a fender bender and the core support got pushed back just enough to touch the air filter box, I wonder if this bump could have damaged the air flow sensor?

 

Anything is possible.

My thoughts, reading what you have stated, is that the Jag has been a tad neglected, I might be wrong, just a "gut feeling".

The TPS is a prime suspect at those revs, as it is the "common spot" for cruising, so the resistance coating wears more in that "spot", and gives a flaky signal to the ECU for fueling accuracy.

Being as how you are "over there" and have an EGR (exhaust gas recirculator) system that gives all sorts of problems, or so I have read, we did NOT get that stuff down here, so NO idea.

Usually a damaged air flow meter will see the engine NO GO, so I doubt that is the real issue.

The fact you got "starts right up" and "idles smoothly" sort of eliminates the intake trunking, coz that would give erratic idle due to air leaks.

Does it smooth out at higher revs????. If so then the TPS is a real #1 on the list.

 

It does seem to smooth out at higher rpms. It is odd because if you increase rpms very slowly it will run smoothly up to 2k rpm then sputters. I took the air flow meter off the car and cleaned it up a bit an checked it out and it seemed fine, I agree if that were the problem the car would not run.

 

Update. No real question here but if anyone has any advice

due to moving, new job, and life in general the Jag got put in storage for 3 years. Over the weekend I decided it was time to continue working on the Jag. Hooked up some jumper cables and it fired right up, idled nice, and stumbled and cut out when I gave it gas. I went to back it out of the storage unit and now it has no reverse so I pushed it out and put in in drive and it just wanted to stay in first... I drove it around the block a few times to try and get the fresh gas in the system, the trans was still acting weird not wanting to shift. I think the rotorary switch on the side of the trans is corroded or wonky, the rev lights don't even come on and the shifter is real stiff.

So its back in the garage for now, going to give the throttle body a once over and check the voltage on the TPS. The road to my house is pretty muddy...

 

First of all, did you put in a new battery? Jumping it with a dead battery (most likely after 3 years) and then taking off the jumper cables when it idles is killing your alternator.

Second: how is the transmission oil level? if it's too low, it can feel like a gear isnt working. Box will make rattling sound also.

Actually, check all fluids (fresh GAS! coolant, engine oil, power steering, brake, and tranmission) and then just let it run for quite a while. Let the engine get warm, carefully push the throttle a little bit. After 3 years, you want a slow start but then a full run to get the engine and box in operating conditions. Then see if you can make a good run.

If you parked the car with all working well, I wouldn't bother tearing stuff apart before just letting it run for a while.

 

New battery is not on the list, not unless I can get it running well. I'll just put one from my Jeep in when I am working on it. The stumbling issue was something I have been trying to figure out since I got the car, the big reason it went into storage instead of being driven for the last 3 years. And coming out of storage the problem persists exactly as before. I'm assuming TPS and/or fuel issues at this point.

However the no reverse is a new issue. I plan on putting up on a lift and giving the car a good once over. I did check all the fluids before I started and ran the car after its 3 year rest.

 

Hmmmmm.......I would hook up a fuel pressure guage to the rail, and see if the pressure starts to cut out at the higher rpm.

 

If the voltage readings are smooth and ok on the TPS, try cleaning out the intake plumbing and throttle body, decoke the egr port under the throttle body too.

 

So I tested my TPS tonight going by the picture below

4.85v input

.57v at idle

4.73v at wot

And as slowly as i could move it the voltmeter went up in smooth .01v incriments.

Next question would be what is the firing order for a 1992 4.0 I-6? I keep finding 1-5-3-6-2-4 which is pretty much the standard firing order for any I6 motor. #1 cyl is at the front of the car, 6 at the bulkhead? Which spot on the dist is the number 1? I can't seem to find a diagram. I would imagine if I had it 1 post off in either direction it wouldn't start.

Still fires right up, idles fantastic, give it any throttle and it starts to stumble. I guess fuel is next to test. I don't see a port on the fuel rail to hook up a gauge?

 

Unfortunately there is no port on the fuel rail to test pressure, but if the fuel pressure regulator (FPR) is original it is almost certainly not holding proper pressure in the rail (+/- 40 psi), which can lead to fuel starvation under certain operating conditions. One easy test you can do on the FPR is to pull the vacuum hose from its fitting, crank the engine, then check for the presence of gasoline at the vacuum fitting - if it's there, the FPR diaphragm has failed and is allowing un-metered fuel into the intake manifold.

Here's a link to photos that show the FPR on our '93, which I believe is identical to your '92:

Welcome to Jag-lovers - Members Photo Viewing Page


If you want to go as far as checking the fuel pressure at the rail, it is possible with a rig like the one in the photos at the link below, courtesy of Bryan N at the Jag-Lovers XJ40 forum:

http://www.jag-lovers.org/snaps/snap...?id=1357201999


Another related and common issue is failure of the fuel line check valve or non-return valve, which prevents fuel pressure from escaping back into the tank. I can't remember if a '92 has an external fuel pump or the pump in the tank. If it's external, the check valve is at the output of the pump and is replaceable. See part 2 in the diagram at the link below:

Fuel Pump and Mounting - Parts For XJ6 (2.9, 3.2, 3.6, 4.0) from (V)500001 to (V)667828 | Jaguar Classic Parts UK


If your pump is in the fuel tank, there are two check valves, both of which are part of the plastic fuel pump canister, so it's easier to add a new check valve in the fuel line somewhere (the easiest place is in the engine bay, the best place is right under the tank). Here's a link to photos of how I added a check valve to our '93:

Welcome to Jag-lovers - Members Photo Viewing Page


And here's a link to the parts diagram showing the in-tank "Fuel Pump Module" or canister (part 21):

Fuel Pump and Mounting - Parts For XJ6 (2.9, 3.2, 3.6, 4.0) from (V)500001 to (V)667828 | Jaguar Classic Parts UK


I can't remember if you have cleaned your Mass Air Flow Sensor (MAFS), but since the MAFS signal is a principal basis of the ECM's engine load assessment and timing and fueling adjustments, it is well worth flushing the internal heated wire with special zero-residue MAF Cleaner Spray or Electric Contact Cleaner Spray, and also flushing the electrical connectors on the MAFS and the harness.

I also can't remember if you've cleaned the Crankshaft Position Sensor (CPS), but a buildup of gunk on the sensor body, or oil contamination of the electrical connector, can lead to signal problems that can disturb the ECM's timing advance adjustments (and if your CPS is original it may be failing, which is a very common issue).

Another possible problem is the O2 sensor - you can measure its output with your voltmeter - check the manual, but I think that once it reaches full operating temperature (500C+), its voltage should swing between just above 0V and just below 5V. If it's stuck on one voltage or its voltage swings are lazy, or its heater circuit tests open or shorted to ground, it's time for a new one. Here are links to photos of that job:

Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page


I doubt a weak battery is the cause of your stumbling problem, but if you get the car running again and intend to drive it, it may be worth buying a new battery since Jags tend to be very sensitive to even slightly weak batteries. Before you install the new battery, it's a good idea to go through the car and clean all the battery power connections and grounds to optimize battery charging so the new battery doesn't die prematurely. Let me know if you get to that point and I'll send you links to photos of all the grounds and battery power connections.

Cheers,

Don

 

Wow, nice reply. Next on my list is to test the fuel pressure regulator and build that test gauge. I don't remember myself if I changed out the cps, I want to say I swapped in another used one with no change. But i'll go over it again this weekend and report back!

 

Fuel pressure regulator is dry with the vacuum line unplugged.

I wonder what kind of fittings are needed to put a fuel pressure gauge inline?

Also the fuel filter is not going to come off without a fight, and breaking the lines probably Michigan rust.

 

See the photos at the link below, courtesy of Bryan N at the Jag-Lovers XJ40 forum:

Welcome to Jag-lovers - Members Photo Viewing Page


Cheers,

Don