Rough running '92 5.0...Check engine light comes on when engine's hot. Exhaust really smells...Ran KOEO test and got 173 (HEGO sensor-voltage singnal indicates "rich" (Bank #1)); 327 (EGR Valve Position (EVP) Sensor - signal votage too low; and 337 (EGR Valve Position (EVP) Sensor - signal voltage too high. Will replacing EGR Valve and/or EVP sensor likely fix this or am I barking up the wrong tree? Could bad fuel pump cause this or would other codes show up if this were the case? Any advice would be great...I'm a very AMATEUR mechanic.

 

Hopefully someone that is more mechanically inclined than me will chime in as well but I do think you need to either clean or replace the EGR valve assembly. You will also want to clean the intake area behind the butterfly valve. Don't do this with harsh chemicals or solvents. I have heard that mineral spirits are about as harsh as you want to go on it. Also check your oxygen sensors.

 

Hmm well a bad fuel pump won't cause the engine to run rich, I would clean/replace EGR valve, sensor.... and reset codes then go from there... rough running is most likely the egr system...

 

I think it is just carbon on the EGR stem. Probably will clean by just opening it with it off the engine.

tom

 

The EVP voltage is easy to check. Use a digital volt ohm meter ( DVOM) and remove the sensor from the top of the valve. check the voltage while you slowly push up on the pintle of the sensor. most EGR problems are caused by the valve getting carboned up and not closing all the way, causing a lean condition. It is poss. that the passages are completely closed and the valve is not moving ( might throw EVP codes that way, but I would check the sensor first.

 

I Replaced the EGR Valve and Valve Position Sensor, then cleared the codes and test drove it. Still running rough and getting check engine light when truck warms up to operating temp. Checked codes again and EGR codes are now gone but still getting 173 (HEGO sensor voltage signal indicates "rich" bank 1). Sensor voltages metered OK and sensor looks in good shape. Could old plugs cause this. I pulled one out and it looks pretty bad, going to replace them. Thanks to everyone for the advice so far, could use some more. One more dumb question...which side is bank 1?

 

bank1 is the passenger side of the engine. do yourself a favor and replace the bank1 O2 sensor. should cure your problems. just because you're getting a correct reading doesn't mean the O2 sensor is performing correctly all the time. i had the same problem with my 97 4.6L, it would work fine, but turned out the ac was draining on the O2 sensor in bank1, causing the problem from time to time. the O2 sensor should only be around $50 at Napa or AutoZone. don't go to ford for it.

 

also, your truck will not use the readings from the O2 sensors when the engine is cold. the computer runs in an open loop(preprogrammed mode) until the engine reaches operating tempertures. then the O2 sensors readings are used. that's why you're experiencing your problem when the truck is warm.

 

Replaced the 02 sensor and cleared the codes. After test drive, no CEL and no codes. Running much smoother. It's ironic that all these sensors that are supposed to protec the important parts go bad before the parts do. Thanks to everyone for all the advice.