Hello. I'm in the process of sorting out a Fuel Fail 37 and after checking wiring and swapping EGR valves and solenoids, my EGR valve is still being commanded at too low an RPM and during deceleration.

I'm thinking it may be a fault with the ECM's EGR output so I'm going to find another ECM.

I've read that 1993 and up have adaptive idle fueling, and don't rely on the MAF potentiometer for idle mixture adjustment like my 1992 does.

Would it be possible to install a 1993/1994MY ECU in place of my 1992 ECU as long as I take the MAF potentiometer out of the circuit?

Also 1993+ have plate-type fuel injectors instead of the pintle-type of my 1992. I'm not sure if this would've necessitated a change in fueling calibration of the ECM.

Theyre the only differences I remember coming across, but I'd like to see if anyone knows of any other MY changes that might make this impossible.

Thanks,
Nick

 

Hi Nick,

It's late so I'll give a quick reply and if you need more info I'll try to respond tomorrow.

Off the top of my head, the EGR vacuum solenoid has constant 12V power and the ECM connects the other wire to ground to activate the solenoid and apply vacuum to the EGR valve. If your solenoid wiring is shorted to ground somewhere that could activate the EGR valve all the time. By the way, the EGR solenoid is the same Denso part as the secondary air injection solenoid, if your car has one, so you could try swapping those too. The solenoid coil resistance can also be measured per the diagnostic manual linked further below:

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See the diagnostic info on page 104 and the diagnostic flow chart on page 105 of the pdf manual here:

http://www.jagrepair.com/images/Elec...tems%20S91.pdf


I suspect the wiring harnesses for the ECMs may be different for the '93/'94 cars. You could compare the electrical schematics for the '91 and '93 cars here:

1991 Electrical Guide:
http://www.jagrepair.com/images/Elec...Electrical.pdf

1993 Electrical Guide:
http://www.jagrepair.com/images/Auto...ec%20Guide.pdf

The fuel flow rate for the '92 injectors is 240 cc/min while the fuel flow rate for the '93 injectors is just 210 cc/min due to the greater efficiency of the dual-orifice design. Here is some info on injectors that I compiled when I was trying to buy a new set for our '93 (it was an unbelievable ordeal):

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Cheers,

Don

 

Thanks Don,

There also seems to be some differences in the signals passed to the Instrument Pack, as well. My '92 gets the tach signal from the coil, 93+ gets it from the ECM.

I think there might be too many differences to make it a simple swap.

Also, I have replaced the Injectors with New units a while back, but didn't notice any real difference. Maybe I should check to be sure I received the right ones!

I've tried swapping the solenoids, and both check out out at 41-45 ohms. I even ran the EGR hose to a vacuum gauge and tested the system with the car in gear and the parking brake/service brake on. At exactly 1000 RPM, the vacuum gauge quickly responds, and when the RPMs drop below 1000, vacuum instantly dissipates, it's a nice clean cut. This doesn't rule out a sticking EGR valve, though, but I've replaced it twice...

I should mention I'm also getting a FF44 code for the Oxygen Sensor. After the car warms up to operating temperature, it stumbles and almost stalls, then after a few seconds, the CEL lights and code 44 is set, and the car runs in Limp Home Mode (quite well, I should add - just thirsty).

I also had a random code (14, I believe) for the Coolant Temperature Sensor Circuit. The code was current and would not clear, instantly triggering again. I turned the ignition off, then back on, reset the code, and it hasn't come back since.

I did follow the flow charts for FF44, and found the heater circuit to be fine (battery voltage at the connector pins with the engine running). My PDU was showing HO2S RAW Voltage at .02V - .04V, and it stopped swinging during my test. With the key on, voltage between the harness-side of the Oxygen Sensor signal wire connector and Ground was .4V as per the flowchart. So I bought a new Oxygen Sensor.

I did clear the code, and after 2 days of driving, the car didn't throw the FF44 code yet. Not sure why...

Maybe the slow O2 sensor is lagging enough to cause the stumble when the EGR valve cuts out? I've had that smoke puff on startup since I bought the car, so I'm sure the O2 sensor isn't in prime shape.

We'll see...

 

If I understand the above, your EGR circuit seems to be working properly, but you're getting a recurring FF37 and possibly FF14.

It might be worth cleaning your engine bay ground points, especially the ones used by the ECM - the two on the intake manifold and the one on the firewall behind the cylinder head.

The puff of smoke is common and usually due to oil leaking down the valve stems, particularly on the exhaust side since it sits lower than the intake side. I hadn't thought about the possible impact on the HO2S but you're right, it can't help. O2 sensors don't last forever, though, so maybe it was just time for yours to die.

Please keep us informed, Nick. You have the advantage of owning a PDU, so what you ultimately figure out could be of great help to those of us who don't.

Cheers,

Don

 

Hey Nick, Jim 's "Redd" Car (which he is currently parting out) was a fine runner and the only reason he scrapped it was the bodywork.

It's a 92 and I think he still has the ECU - drop him a PM - he might take a day or two to get back to you as he is very busy at work ATM, (but he will definitely get back to you)

his user id is manwich66

Jaguar Forums - Jaguar Enthusiasts Forum - View Profile: manwich66

the vin of the car is in his sig

cheers

Larry

 

Thanks Guys!

I've frantically been cleaning every ground I can find under the hood, including the intake manifold studs and firewall stud.

After days of driving, the O2 sensor code still hasn't set. None of them have. The car gets up to temp fine with no FF44 code and just has the usual stumbling from the EGR.

I don't get it! I still have the O2 sensor ordered so I'll replace it, but this is driving me mad... Is this a typical failure mode for O2 sensors, Intermittent complete failure?

 

Possible? ...the O2 sensor and heater connections to the harness were loose/bad and now unplugged/cleaned/replugged and therefore ok again?

That's what caused my (temporary) FF44

Larry

 

Nick,

One possibility that comes to mind is that the EGR port on the underside of the intake manifold behind the throttle body could be clogged, so the ECM is not seeing the results it expects from the O2S when it opens the EGR valve. If you haven't cleaned the port, it would be worth doing:

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Also, while you're cleaning the engine bay grounds, don't forget the engine ground strap, which is the ultimate path to ground for many of the engine-mounted components, including the two intake manifold grounds used by the ECM:

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One other thought: does the O2S you ordered have the correct connector factory installed? The sensors on the XJ40 draw reference ambient air down between the conductors in the wiring harness for comparison with the exhaust gasses. The internet is full of stories of owners who had trouble with the "universal" type O2S that required them to install the correct connector. My theory is that they crimped or soldered the connector on in such a way that this flow of air between the conductors was blocked, preventing the sensor from operating properly.

Cheers,

Don

 

Now that engine ground strap is one ground I didn't check yet.

As far as the O2 sensor connections, the first thing I tried was cleaning them, and FF44 kept coming back. They looked excellent too, even before I cleaned them.

I did make sure to buy the Bosch OE O2S with the original connectors already attached.

Could the EGR valve port be clogged and cause issues if I'm getting flow (enough to stall the engine) when I lift the valve by hand?

I'm replacing the O2 sensor today so I'll be sure to check the ground strap and alternator connections while I'm in there.

Thanks guys!

 

You can check EGR port "clogging" at the manifold without disassembling the intake if you remove the IACV assembly.

The EGR manifold port is directly below and you can get good access through the IACV area.

When I first examined mine, it was so encrusted with carbon that initially I couldn't even see a port!
I used a 1/4" dia. rod with a bit of a "blade" (a 45° hacksaw diagonal cut) to dig most of the crap out and open up the port. You'll need a vacuum cleaner to get rid of the carbon if it's as plugged as mine was - the car must have had a lifetime a lot of short trips without a real warm up before it came my way.

BTW - When you replace the IACV assy, take care with the gasket - a small vacuum leak here will play the bear with a smooth idle!

Another thing ....
- my car had the occasional stumble at one time but a new set of OEM Champion plain jane copper plugs gapped at 35 thou put an end to that!!!

Larry

 

Yes, if you still have some flow but not full flow. When you lift the EGR by hand, the engine may not be running under the correct conditions for the EGR valve to open, causing a lean air-fuel ratio (AFR) just like an intake air leak.

Another issue the clogged port causes is obstruction of the hose from the carbon canister, which feeds fuel tank vapors into the intake under certain operating conditions as determined by the ECM. If the AFR does not change as the ECM expects, that can contribute to poor running also. It's possible that you have more than one issue contributing to your symptoms.

Cheers,

Don

 

Thanks Guys.

I removed and replaced the O2 Sensor, the FF44 code hasn't come back in a week of driving, and my gas mileage is noticeably better! Always a plus. The car feels the same, though, and If I connect the EGR hose, it still stumbles.

I'll have to check the EGR passage at the intake for clogging. I was unable to get the EGR port adapter off the intake due to the Oil Filter being installed, and I didn't have enough room to put a wrench on the EGR transfer pipe to disconnect it.

If I still have stumbling issues after checking the EGR port, I'm thinking about temporarily wiring up some passive components inline with some OE connectors to connect the EGR solenoid connector harness with the EGR temperature sensor harness.

I'd like the temperature sensor wiring to see the proper voltage whenever 12V+ is supplied from the EGR vacuum solenoid harness. That would "trick" the computer into thinking the EGR is functioning as it should while it's disconnected, so I can at least drive the car without the code setting every 3 days, until I can sort things out.

-Nick