I have been trying to troubleshoot this problem with my 92' 5.8L auto trans (e40d i think). The truck starts fine but as soon as i tap the throttle it dies. After pulling the codes i found i have code 334 and 311 (air system trouble?). If I pull the connector off the EVP the truck runs fine, with the irritating MIL on. Yesturday I decided to mess with it more. I ran a KOEO and got 327, I imagine because the EVP is unpluged. I let it run all the way through and did what Haynes calls the output state diagnostic mode. I depressed the throttle and the MIL, OD indicator came on. I depressed it again and they both turned off, as you would expect. I checked the voltage at the unpluged EVR and it was approximately 12 V. I depressed the throttle and its state didnt change (still 12 volts). In other words the EVR is always active. Do I have a bad PCM?
I tested the nearly new EVP as directed by the Haynes manual. The manual says resistance should be approximately 5K ohms with no vacuum. I measured about 3665 ohms. Is this acceptable? The book also indicates that the sensor should smoothly work its way down to 100 ohms. I was only able to get it down to around 300, even with the sensor removed from the EGR valve. Did Napa sell me a bad part? Ive read other threads on this subject and others have indicated that there are two different sensors, one black and one gray, and there is apparently a difference. The current sensor is gray, but i dont remember what color the original was. Stupid me threw it away I talked to the parts man at Ford and they show only one EVP for this truck, so now I am thoroughly confused.
Any help on this old POS will be greatly appreciated. Can anyone tell me why the PCM isnt toggling the state of the EVR, and are the resistance values I mentioned on the EVP acceptable?

Thank you so much
Brian

 

My chiltons says your 311 is "Thermactor air system inoperative" and 334 is "EGR closed voltage higher than expected". I can't be of any help but I can join you in your misery. I have a '89 that has somewwhat the same kind of issues. If no one responds, I think I'm taking mine to my Ford mechanic. I, like you, have replaced parts that didn't need to be replaced.

Good luck

Zig

 

Brian,
You need to get a Chilton manual. I looked up your '92. On drivers side valve cover, toward the back you have two square solenoids. One is Air Diverter, the other is Air Bypass. Therein should be the code 311 problem. Check for loose first. I don't know how to tell if they are bad. I am about to get into mine as soon as I sign off. I'm hoping that they effect the same curcuit as the EVP/EGR.

Good Luck

Zig

 

thank you for the reply. I'm aware of the tab and tad soleniods and the evr right next to them. Did you ever get your truck fixed? I am soooo tired of buying and replacing unecessary parts. If you ever get it figured out please let me know. One more strange thing about that silly truck... after runing a KOEO i get the following codes 111 (system checks ok) 334 (EVR) and 311 (air system trouble). If the system checks ok, why is the stupid PCM complaining about the air system and egr system?

 

I know how you feel. It seems that every time I replace some part, it runs better,, but,,,,,, the problem is still there. I am begining to think that I'm in way over my head. For all the unneccasary parts I've replaced, I could have paid someone who knows what to look for and been money ahead. Such is life. When these rigs run right they are unbeatable. So hang in there. Take a deep breath and maybe walk away from it for a day or two for a new prespective. It might be a Zen thing. I just replaced the canister purge valve, it looked like it's part of the same system interconnected by vacum line. WRONG!! I think I'll clean it up and tackle it again in a few days. Good luck, I'll let you know what turns the trick, when I find it.

 

Oh yeah, If you are getting the 111 before the 334 and 311, then the problem has solved itself.(it comes and then corrects) If you get the 111 after the 334 and 311 then it's a current problem.

 

Your KOEO test is 111: System Pass. This means all the sensors checked out OK at THAT time.

Your Continous Memory(intermittent) codes: 334, 331.

CM codes means that at any time while driving, the EVP (334) voltage was higher than the 0.67 Volts. It set the MIL off and stored the code in the memory.

Other problems that can cause this are vacuum leaks, or a stuck EGR valve. Try the following...

-Remove the EVP off the EGR valve, but leave it connected to the harness. Push the pintle all the way down and tape it down. Run a test again. This time, you should get 334 in the KOEO. If you don't the EVP or wiring is bad.

-While the EVP is in the EGR valve, backprobe the EVP with a voltmeter. It should read between, 0.24 and .067 Volts. If it doesn't, the EGR valve could be stuck open.

-Also while the EVP is in the EGR valve, backprobe it. This time, start the engine. The voltage reading should stay the same at idle. If the voltage rises, look for any vacuum leaks.

 

-While the EVP is in the EGR valve, backprobe the EVP with a voltmeter. It should read between, 0.24 and .067 Volts. If it doesn't, the EGR valve could be stuck open.


How do you backprobe the EVP with a voltmeter? What does it mean if the voltage is too low?

 

To backprobe, just poke through the wires with the voltmeter leads or a sharp metal. The EVP has 3 wires. Find the 2 of them(VREF and EVP) that will give you the reading. I can't remember exactly what color they are.

If the voltage is lower than .24, I would assume the EVP or wiring is bad. Just to let you know, these voltage readings are for the GRAY colored EVP.

There's a BLACK colored EVP around, and I'm not exactly sure what the voltage readings are. I beleive, the black one reads ~.5V higher.