97 Explorer EGR Excessive Flow Question

[mcicardo]

I have just bought a 97 Ford Explorer XLT 5.0 AWD that has 195000 miles. The check engine light is on and it had two fault codes. An O2 sensor fault (which I cleared by replacing the Downstream, Pasenger side sensor) and it also has a EGR Excessive flow fault. I took the EGR Vacuum Solenoid off and checked that it is getting 12 Volts from the battery and when checking the resistance of the actual solenoid; it reads 30.1 ohms. The vacuum line running from the solenoid to the EGR was crumbling in my hands, so I replaced it. I pulled the EGR off and cleaned it up (it didn't really ned much cleaning). I don't have a pump, but by sucking on the EGR by mouth, I verified that the Diaphram in the EGR is still working. I didn't check out the EGR Position Indicator sensor on top of the EGR, and that is going to be my next step. I did notice that the gasket for the EGR was no there any more. I got a gasket kit and carved a new gasket for the EGR valve (none of my local auto stores carried the right one) and put everything back together. Went and cleared the codes and drove for about 10 miles with no issues. The next morning, I started driving and got maybe a mile before the Check Engine light came back on with the EGR Excessive Flow fault.

Any help with what my next step needs to be, or a better way to check these componets would be greatly appreciated.

Mike

 

[mcicardo]

Here's some more information:

The build date on my Explorer is July 1996. This means that it's one of the early model 5.0L engines for that year and they didn't come with a dpfe sensor. I crawled all over the engine looking for that rectangular box and never found it. On one of these forums, someone pointed this out to another guy trying to find the same part.

Mike

 

[2000StreetRod]

P0402?

The following is from the Ford 1996 MY OBD System Operation Summary:

"The Sonic EGR system is a closed loop EGR control system that consists of a vacuum-operated EGR valve with an EGR Valve Position (EVP) Sensor for feedback. The EGR valve is regulated by a duty-cycled EGR Vacuum Regulator solenoid. The PCM uses the EGR Valve Position Sensor for feedback control by measuring the position of the EGR valve pintle. On a sonic EGR valve, the valve is designed such that the position of the EGR valve pintle is proportional to the amount of EGR flow, independent of the downstream manifold pressure. The PCM calculates the desired EGR rate and adjusts the duty cycle to the EVR to obtain the desired EGR rate by monitoring the EGR Valve Position signal. As the EGR valve opens, the EGR Valve Position signal voltage increases. Normal EVP sensor voltage at idle (closed EGR valve) is between 0.24 and 0.67 volts.) The EGR Valve position signal only detects EGR valve pintle position. EGR flow is inferred from the pintle position. Actual blockage of EGR flow cannot be detected using the EVP signal. . . .

If the EGR valve position indicates that the EGR valve is stuck open at idle, a P0402 is set."

The PCM thinks the EGR valve is not closing when the engine is at idle. Either the voltage being sent to represent the pintle position is inaccurate or the EGR valve is not closing. After no telling how many years of not moving due to the broken vacuum hose the valve may be stuck open. Without a vacuum pump it will be difficult to determine if the diaphragm/valve is stuck. I'm not familiar with your EGR type system. Is there an electrical connector on the EGR valve that you can probe to see if the voltage changes? If you had a vacuum pump you could connect it to the EGR valve vacuum line to see if vacuum affects the idle speed when manually provided by the pump.

 

[mcicardo]

Early Model 97 Ford Explorer XLT 5.0L Diagram

Here's a diagram that I've drawn of my EGR system. These are located on the backside of the engine between the engine and the firewall and are a pain to get to, but not impossible. Tomorrow, I'll be pulling all of these parts and can attach actual photos of the equipment and their condition. Here's the diagram and a photo of the parts new:

Mike

 

[2000StreetRod]

EGR tests

The resistance reading (30.1 ohms) for the EGR vacuum regulator (EVR) seems reasonable. Electrical failure modes for a solenoid are usually an open or a short and would be detected by the PCM which grounds the path on a duty cycle basis. The following is from my EGR System O&T thread that can be found by following the link in My Helpful Threads. The wire colors may not be correct for 1997.

"The EVR is a fast acting electromagnetic solenoid that operates from 12 volts provided by fuse 13 (15 amps) in the battery junction box. Reconnect the electrical connector to the EVR and backprobe the 12 volt source pin (light blue/orange wire). Turn the ignition on and measure the voltage between the probe and ground. It should be battery voltage. Turn the ignition off, remove the backprobe, and backprobe the return line pin (brown/pink wire). This wire goes to the PCM that activates the EVR by grounding the line. Start the engine and let the idle stabilize. During normal operation there is no EGR at idle. Briefly ground the probe to energize the EVR solenoid. The idle speed should immediately become unsteady. Unground the probe and the idle should become steady."

The above tests the functionality of the EVR, EGR valve and in your case the EGR valve position sensor. However, if the test fails it doesn't isolate to the failed component. That's why I suggest testing the EGR valve first with a vacuum pump.

 

[jremington59]

I had the same codes, with the same engine when I got my Explorer.

There's a sensor that mounts to the top of the egr valve with three little bolts. There's a rubber gasket that goes between the sensor and the egr valve. First, make sure the gasket is still there. Mine wasn't. It seems a few years back there was a rumor floating that if you removed that gasket you would have better performance. Second, if it is there, make sure that it's not leaking.

If it isn't, my first step If I were you, and you're sure the EGR is ok, would be to replace that sensor. It's a thirty dollar part.

Did you put vacuum to the EGR while the engine was idling to see if it stumbled?

 

[mcicardo]

Found part of the problem

Went and bought a hand vacuum pump to do the checks that both of you guys were suggesting. The EGR Valve is fine. It holds a vacuum and when opening the EGR while the engine is running, caused it to almost stall. Next, I checked out the EGR Position Sensor and it passed as well. resistance checks showed that it is about 1500 ohms when the EGR is closed and it drops smoothly to about 400 ohms with the EGR opened. On to the Vacuum Solenoid. Used jumper wires to get 12 volt and ground to it and tested it with the Vacuum Pump. It failed. $28 later, I replaced the Vacuum Solenoid with a new one. Finally, I was driving the Explorer around to see if the Check Engine light would go out. It didn't. I drove to Auto Zone and used their machine to clear the code, but it was no longer a EGR Excessive Flow fault. Now I'm getting a P1409 MANUFACTURER CONTROL AUXILIARY EMISSION CONTROLS fault. I haven't looked into this one at all. Either this is a new fault, the failed Solenoid was masking this fault, or I've caused this on during the repair. Any new suggestions?

Mike

 

[2000StreetRod]

P1409

Glad to hear you fixed the bad EVR and thanks for posting the results.

P1409 is set when the EVR voltage to the PCM is outside of the range 4.81 volts and 0.048 volts. The DTC may have been set when you shorted the EVR and the PCM read the voltage as less than 0.048 volts. I suggest that you clear the DTC, drive the vehicle and see if the DTC occurs again.

 

[jremington59]

All you have to do to clear the cel is to remove your neg battery terminal for a couple minutes. If it comes back on have the code read again.

 

[mcicardo]

I disconnected the negative battery terminal and let the explorer sit there. Then I connected everything back up and I've just put about 30 miles on it with no Check Engine light. Now, I know that the OBD system had to re-turn on after being off like that; but I'm assuming that 30 miles is enough time for it to get back up to speed. So it looks like everything's good to go. Thanks a whole lot 2000StreetRod and jremington59 for helping me through this. You guys were right on top ef everything. Now I can take the explorer to the garage and get the Connecticut required Emmission Test done before the state suspends my registration. Once again, thanks guys.

 

[mcicardo]

Ugh....I jumped the gun. I had the Explorer idling this morning in the driveway and the Check Engine came back on. I haven't got the code read yet. Looks like my Explorer is making a move sequel to the "Never Ending Story" and it's featuring my Check Engine Light.

Mike

 

[jremington59]

Go get it read again and tell us what code you have.

That's the wonderful thing with the EGR system. It can take a while to kick a code.

 

[thumper477]

You need to find a way to read the EVP voltage.I have had problems where the voltage was too high with the EGR valve closed with all new parts.I have found that a little grinding of the EVP sensor pintle will lower the voltage to an acceptable range.Don't grind too much off at one time.A little goes a long way.You can backprobe the wires at the sensor to test the voltage with a mulitmeter or hook up a real scanner to read it.

 

[jremington59]

You said you checked to make sure the egr was opening. But did you check and make sure there wasn't carbon build up preventing it from closing completely?

You're code was for excessive. Was your initial code P0402?

 

[96eb96]

That system looks very similar to the mid 80s 5.0L egr valves on the crown vics. Except they had 2 or 3 solenoids instead of 1!

Like another poster said I remember this EGR valve having issues closing fully, and keeping the position sensor a bit higher and giving codes and other issues. If you can blow air into it you can tell if its completely closing. That may involve making out with it though

P1409 indicates a problem with the EVR, maybe you got a bad one? Or the wiring has an issue? You would need a good scan tool to read ford extended codes to see whats going on.

Maybe this will help?
http://www.justanswer.com/questions...ing-report-ed-troubleshootting-p1409-probable

 

[mcicardo]

Yes the original code was P0402 and the new code that is on right now is a P0402 EGR Excessive Flow. When I had the EGR valve in my hand, the valve looked like it was closing completely. When the Explorer is just Idling in the driveway, there is no sputering or stalling like there's an Excessive Flow issue.

My next question is how does the PCM detect the Excessive Flow problem? What sensor(?) is setting it off? Could the MAF sensor or a leak in the exhaust header cause this?

I guess my first step will be to pull the EGR Valve again and draw a vacuum on the exhaust outlet side on it to see if the EGR is completly closing.

Mike

 

[jremington59]

Blow LIGHTLY INTO the egr. Don't blow to hard because you can blow the diaphram up. I almost did. While you have it out take some wd or blaster and clan the egge where the valve seals. Also make sure slides easily with no binding feeling as it could seal one time, but stick open another.... Did you say you replaced the solonoid. If not, take it off and make sure the lever pushes in and out freely.

Your engine doesn't have a DPFE so there's only a few things that this can be....

 

[mcicardo]

Problem should be solved (for real this time)

Alright, I pulled the EGR valvbe off and tried blowing into it. Air was coming out. Not alot of air, but enough that you could hear it. I tried to clean it up as best as I could, but it still was letting air through. Had to drive about 50 miles to get to the Auto Zone that actually had the EGR Valve in stock. Actually, the first Auto Zone had one, but one of the 3 post on top of it (where the Position Sensor sits) was bent. The guy behind the counter bent it back into shape and tried to sell it to me, but I wasn't going to go for that. That's why it took 50 miles. I had to find one that was in good condition.

Installed the new EGR Valve (plus new gasket) and started it up. Took a few trips in the Explorer around town and the Check Engine light went out. I've driven it about 90 miles on Sunday and still no Check Engine light. Looks like everything is good to go now. Tomorrow, I'll be taking the Explorer and having the Emissions Test done and we'll see if it passes.

To Everyone, thanks for the help. It's awesome that something like this forums exist with people willing to take the time and help someone without a whole lot of mechanical experence out. You guys made this repair happen; along with the new O2 Sensor, new EGR Vacuum Solenoid, new Vacuum line running from the Solenoid to the EGR, and a new EGR Valve plus gasket.

My next project will be the Driver Side Front Wheel Bearings. They're grinding when I turn the wheel; but that will be another Thread.

Thanks again,

Mike

 

[jremington59]

If you've driven that many miles and it hasn't come back on you should be good to go.

You're probably going to have to drive a little more to load all the banks because you undid the battery. When you did that it cleared the computer. Mix in a little city and highway driving and they should all be ready......

 

[mcicardo]

Issue Solved

I took the Explorer in today and had the Emissions Test done. Everything passed with flying colors.

Again Thanks.

Mike