1989 Ford F250 w/5.8L

The truck runs very sluggish at 40 to 50 mph. If I really get on the gas I get white smoke coming out of the exhaust. At idle it runs a little rough but it's OK. During normal acceleration it seems OK and smooth.

I ran KOEO tests. Codes returned were:

31 - EGR Valve Positon (EVP) sensor or pressure feedback EGR (PFE) sensor - signal voltage below minimum specs.

95 - Thermactor Air System - problem on right bank (passenger side) air flow always upstream.

I have already done the following:

- Replaced Cap and Rotor
- Replaced Fuel Filter
- Replaced Fuel Pressure Regulator
- Checked Fuel Pressure (was 42 engine off / 35 engine on)


I think maybe the EVR is bad as I was unable to get any vacum at the EGR even running @ 3500 rpm. I did a check of the EVR and was unable to get it to open / close so it appears that it needs to be replaced.

Would this cause the problems I'm seeing ? Even the Thermactor problem code ? How about the white smoke under full throttle ?


I was also thinking that I might have a clogged cat. Would this cause any of these issues ?

Any help would be very much appreciated.

- Mark

 

Your on the right track, replace the EVR valve.

The 95 code: I think you need to check the TAD/TAB soleniods. one of those is not working.

Good luck

 

Before replacing any valves, run through the vacuum lines that serve the TAD/TAB and EVR. Maybe there is a break or loose connection and it is causing your symptoms.

 

Thanks fishin / billman,

I checked the lines before troubleshooting the EGR and EVR. They are solid and hold a vacuum. The EVR seems to be a Dealer only part so I'm trying to track one down now.

One other question. When I did a pressure check on the Fuel pump, I got the correct pressures. It was almost a minute however before the pump created the 40 psi. Is this normal or should the lines come up to pressure quicker than that ?

- Mark

 

Had EGR system problems for a while now. Codes 31 (EVP) - the sensor on top of the EGR valve. and Code 33 (EGR valve not opening). Replaced the EVR - which sends vacuum to the EGR valve to open and close per the computer. Replaced the EVP -which feedsback EGR valve positon to the computer. And finally replaced the EGR valve itself. Symtoms were/are stumbling and missing on acceleration- only when warmed up. Still does it .
checked the vacuum line from the EVR to the EGR valve, it's good.
Next is to check the vacuum source to the EVR. Still getting code 33.

Anyone have any other suggestions? Know where to find a Vacuum diagram for this model? Or a detailed description of the EEC IV system, such as the sequence of events, what happens after warmup, etc?

1989 Bronco 5.0L Automatic 160,000 mi

Thanks

 

Chrisberry, did you check to make sure that you had power to the EVR soleniod? I HAD a code 31, mine was the EVR valve. it was stuck open and would not close all the way. Full throttle turned the CEL on, any other position the light was off. I had a code 33 at one point too, that was the EVP for me, change it no more light and code. You stated you have already done these things, so it must be either vacuum related or electrical. The parts are new, right?

Mgiven, the smoke you saw: was it thick, bellowing smoke or just a light smoke that dissipated real fast? If the latter, its just water vapor, nothing to worry about. If the first, you may have a head gasket ready to go south, White smoke = coolant, black smoke = fuel, blue smoke = oil.

 

For my problem, yes all new parts. I'll check the voltage to the EVR, thanks.

 

I had the same problem and changed all my parts with no luck. I checked the plug in between the EVR and the wire harness plug and it had a resistor that had come undone. I found that you do need this plug in there so I repaired the resistor and got rid of all my codes. It took me about 4 months to do 10 minutes worth of work. Hope this helps.

JPF
wrenchinfool at earthlink.net
1988 F350 4x4 5.8l 351w auto srw

 

Can you tell me where the wire runs from the EVR (behind the engine?)and how far along the wire (inches)does the resistor sit.

Where is this "wire harness plug"

Did you just re-plug the connection or replace the resistor

Thanks

 

Thanks, this is good info. I have gotten code 31, 32, 34 now with no noticeable effects on performance. I haven't had time to try to track it down yet.

When I turn off my truck I can hear the vacuum from the coffee can ( or somewhere ) leak down through my EVR Solenoid (EGR valve regulator). The EVR buzzes until the vacuum is vented. Is this normal?

I looked at the wiring diagram in a Mitchell manual and it does not show a resistor in the EVR circuit, so this is really lucky to hear about this. Thanks again.

 

On my 351w the plug with the resistor plugs straight into the EVR sensor and the plug from the vehicle wire harness into that. The plug with the resistor looks like a little black box, when taken apart the resistor had separated from the connection so I just soldered the connection and it worked. I didn't replace the resistor. I got about 10 ohms of resistance when checked. Neither of my books says anything about this resistor. I found out the hard way so I hope this will help.

JPF
wrenchinfool at earthlink.net

 

I'll check it today.

 

I got ya. You are talking about the black box that looks like part of the EVR. I wondered about that, when I looked at it I thought it looked like it would come off if I tried. If you buy a new EVR that black box comes with it, right?

 

The new EVR I bought from the dealer didn't come with that box so you will have to remove it to check it.

JPF

 

My 1990 Mitchell manual give the following resistances for the EVR solenoid:
4.9 and 5.8 under 8500 GVW - 20-45 ohms
7.5L 100-135 ohms
All others 30-70 ohms

It just says disconnect the EVR connector, doesn't mention the black box. I wonder if the solenoids are the same and the variation in resistance comes from different black boxes.