The Check Engine Light lit up on my '92 4.0 a week or so ago. I didn't notice it had even come on. It was in the middle of a 35 minute drive. Zero driveability issues.

So fast forward to a couple days ago. I printed out the flowchart for Code 39.

-Ran engine to operating temperature, manually opened EGR valve with fingers, and engine stumbled and ran rough. No blockages to the intake, good.
-Checked vacuum at EGR hose with engine idling. No vacuum, good. -Checked vacuum at EGR hose with car in drive, parking brake set, and service brakes on, idling at 1500 RPM. Vacuum present, excellent. That rules out the vacuum solenoid and hoses.
-Tried to pull vacuum on EGR valve itself, couldn't achieve any vacuum. Vacuum kept dropping as fast as I pumped.
-EGR Valve Defective, Diaphragm torn

Autozone wanted $160 plus tax, Advanced Auto similar price, RockAuto was $85 plus shipping. These are all aftermarket.

Searched eBay for EBC2737 (OEM EGR Valve) New in Box. $73 plus shipping. Sold!

Will be arriving tomorrow, I'll stop by the dealer today and pick up the three EGR gaskets which need to be replaced when servicing the EGR valve. I'll let you guys know how it works out!

I'm excited to finally get that Check Engine Light off!

Nick

 

Came back on a road trip yesterday, Rhode Island to Lake George, NY. Round trip was 471 miles, averaged 21.1 MPG for the trip.

Got the new OE EGR valve in this morning, will change it out tonight and post my results.

-Nick

 

Changed the EGR valve out, the new one holds vacuum very well like it should. I didn't grab the gasket from the dealer, so I used the original which appeared to be in okay shape.

I disconnected the battery to reset the light and allowed the car to warm up from cold to operating temperature at idle to relearn the idle air position. I'm getting a slight misfire at idle, especially noticeable at stop lights in park with my foot on the brake and lights on, heater on. It's a little stumble. Nothing when the engine is running over idle.

Could my old gasket be faulty and allow a small amount of exhaust gas to enter into the intake? Wouldn't that throw the light on, if the computer saw high temperatures in the EGR adapter at the intake while the EGR valve is commanded OFF? Or would slight leakage not cause a high enough temperature in the intake (525 degrees F) but cause stumbling at idle?

Any ideas?

Nick

 

I have the same code. Put new egr valve on and ran worse. I don't have vac gauge. Smelled something weird after putting on new valve. Ran rougher with new valve even when driving. Put old valve back on, no smell. Only runs rough when cold, fine when driving. Good mileage. Cleared code, came back next morning. Do I need to take off hard line to intake and check for clog? I guess I can go barrow vac gauge. I hope someone chimes in. Thanks.

 

Code 39 comes on when there is an issue with the temperature sensing circuit for the EGR. This can be caused by three things:

-The computer enables the EGR solenoid and the EGR temperature is above 525 degrees Fahrenheit. This is when the EGR system detects an overheating condition and disables the EGR system.

-The computer enables the EGR solenoid and the EGR temperature is less than 212 degrees Fahrenheit. This means that EGR gasses are not flowing, or the temperature sensor is bad. If the EGR passages are clogged, the vacuum solenoid or hoses to the EGR valve are bad, or the actual EGR valve is defective and not opening up like it should, you should not notice any driveability concerns, as no EGR gasses are flowing. You will have higher emissions and the engine will run a bit hotter than with the EGR operational.

-The computer does not have the EGR solenoid enabled, and the EGR temperature is greater than 122 degrees Fahrenheit. This means you're getting EGR gas flow when you shouldn't be. Perhaps at idle, or when the engine is cold, when EGR gas flow would cause the engine to run rough. A defective vacuum solenoid or a wiring issue to the solenoid could cause it to allow vacuum to the EGR valve, opening it when it shouldn't be open. Also, a defective EGR valve that's leaking EGR gasses could cause this.

To quickly check for clogged passageways, start the car and let it idle. With gloved hands, press up on the vacuum diaphragm through the bottom of the EGR valve. The engine should run noticeably rougher when you do this. If the car runs rougher, and misses, you know there is plenty of EGR flow through the hard lines and into the intake.

To quickly check for a faulty EGR that might not be opening due to a torn vacuum diaphragm, keep the car off, remove the vacuum hose from the EGR valve, and with one hand, press up on the diaphram to open the EGR valve fully. Place a finger over the vacuum fitting on the valve, and release pressure on the diaphragm. If it's not defective, it should hold a vacuum and stay open until you remove your finger from the fitting.

If you suspect the EGR solenoid vacuum valve is faulty (the part that converts the engine's EGR On/Off signal into a vacuum signal that the EGR valve can use to open and close), swap it with the AIR Injection Solenoid Valve. They are identical parts and can be swapped out.

When replacing the EGR valve, make sure you replace the gasket as well. You might have a bad solenoid valve that's commanding the valve open all the time, even when the engine is cold and idling. Try disconnecting the EGR vacuum hose at idle and check if you have vacuum. If you do, somethings wrong. You should only have vacuum when the car is in gear, with a warm engine, at above about 1000 RPM.

Nick

 

Warm engine. Idle below 1000 rpm. Pushed up on diaphragm, runs rough. No blockage. Took off vac hose from valve, no noticeable vac. Turned off car, took off hose at valve. Pushed up diaphragm, valve did not stay open. Did same thing with new valve off car, valve stayed open. Old valve bad! Like I said, already put new valve on and made car run worse all the time. Can swap air injection solenoid and see what happens? Vac hoses look okay. No noticeable vac hissing. Are the temp sensors known to fail? And exactly where is it? How do I use a digital multimeter to check the battery voltage to the solenoid? Thanks for helping Nick.

 

Have you downloaded the AJ6 Engine Management System Diagnostics Manual yet? It's invaluable when diagnosing problems like this. Check this thread out and download the manual:

https://www.jaguarforums.com/forum/x...o-xj40s-53536/

Pages 106 and 107 will have tons of info on this code.

The next test in the flowchart is to see if the EGR valve is getting vacuum when it should be. You'll need a helper for this one, or a vacuum gauge placed in sight while you're inside the car. Warm the car up. Apply the parking brake. Apply the foot brake. Place the transmission in Drive. Hold the engine speed at 1200RPM. Do you have vacuum at the hose to the EGR? You should. If not, then the vacuum solenoid valve (or wiring) is suspect or vacuum hoses are disconnected somewhere.

After these steps, you're starting to look at faulty EGR valve, faulty temperature sensor, bad wiring or bad ECM.

 

Changed EGR solenoid and put on new EGR valve. Code 39 and 37 gone. All is well so far. Sorry it took so long to get back. Got solenoid from british parts uk. They are good prices for oem parts.