Hmmm, we are on to something....

Ohms across the terminals- 33.

No measurable vacuum at the EGR valve when the EVP is electrically disconnected. I checked at the vac boot (green pipe) on the EGR itself.

With everything reconnected, engine running, I grounded out pin 33, the engine stalled! I had to manually rev the engine so that I could ground pin 33 to keep the engine from stalling.

With the engine stalled, if I grounded pin 33, I could hear the EGR valve move up and down.

I'm completely lost- any ideas?

 

As long as you didn't holler out the wrong name during "Activies" it couldn't be that bad...

 

wait a second, I'm getting the EVR and the EVP mixed up. I tested the EVR, per the link provided. What should I be looking for on the EVP?

 

depends on whose name you yell....

 

Pin 33 is the "ground" for the EVR. If you ground it manually that opens up the EVR for 100% of the time. Remember I stated before the EVR "on" signal is pulse width modulated. With the ground you applied the EVR is now at 100& duty cycle. That means 100% of the manifold vacuum is applied to the EGR. It has now been slammed open which is now effectively a huge vacuum leak. This proves the vacuum path from the manifold to the EVR and onto the EGR is good.

Move onto the EVP, EGR Position sensor, to see what the output signal is with the engine off/key on. Measure it again with the Key On and engine On. If the signal is below 0.24VDC, as noted by the code you got then shut off the key/engine, disconnect the plug then measure the resistance of the EVP sensor. USe this values from Ryan here: Fuel Injection Technical Library » EGR Valve Position sensor (EVP)

 

 

OK, I re-tested. The EVP is doing what I described a bit earlier. When I ground out pin 33 with the engine running the engine will stall unless I manually work the throttle to keep the rpms up. Once the engine dies, I can ground out pin 33 and hear the EGR valve move while the EVP vents.

I tried to get a voltage reading on the EVR with the engine running but I either wasn't getting a good connection or there just isn't any voltage present. After doing more reading about the EGR system it seems like I might be on the right track to the horrible fuel mileage.

In regards to the code 85, it makes sense that the code shows up. There is no purge valve present since I used the original 5.0 engine harness and the 5.0 doesn't use that valve. This is another reason why I cringe every time I read a response to a 5.8 conversion thread where someone tells the person looking for help tha it's ok to use the 5.0 harness because they're the same- well, they're NOT the same, there are some differences and this little purge valve is a perfect example.

Anyway, back to my issues. I don't know what to do or where to turn next with the information that I've gathered, anyone have any ideas?

 

we must have been typing at the same time! What exactly is the correct way to get these values with the plug still connected? I tried to push the tip of the VOM probe in from the backside of the plug.

The ohm value of the EVP was 33 ohms, I already checked that. I'm gonna have to finish this in the morning, I've lost my daylight to work with.

 

Sometimes you need to push in some pins into the wiring then hang the meter leads off of those. For the EVP, that should not be too tough with standard meter probes, IME. But if all else fails you can do that. Afterwards I take a little RTV and rub it into the pierce site to seal it back up.

 

Yes, I have seen this crop up a time or two. It is not a deal breaker, nor does it affect driveability. It will not put the PCM into limp mode. As long as you are aware of the this minor difference, it's all good. I really think the EGR/EVP issue is a bigger contributor to your crappy mileage. Of course, I could be wrong but we need to eliminate what we know is an issue.

 

I agree 100% about the purge valve. Thank you for taking time to help out. Between reading replies from you and more web surfing, I came across a great tech page from Tomco industries which covers most of the EGR, EVP and EVR issues. I'll get some paper clips to back probe the plugs tomorrow and see what I can get w/ voltage readings to help chase down the issue(s). I hope that I can give back some help to users of this site, it has been a wealth of information for me with people helping out.

 

Great plan

 

I'm making a bit more progress. I have test leads in the back side of the EVP. When there is no vac. on the EGR valve I have about 4.7V, when the EGR valve is fully opened I have about .86V so it seems like the EVP is reading movement and resistance. I don't have a good vac pump so I've have a vac gauge with a "T" between the EGR and a large syringe that I use to pull vacuum. It isn't pretty but it works.


If I'm getting a voltage fluctuation from the EVP, should I be casting a suspicious eye at the EGR valve itself?

 

Ok, here's the results. There's diffidently an issue somewhere.

Step by step:

* VOM (volt ohm meter) ground lead to center of EVP plug ( SRTN,), hot lead to VREF, KOEO, 4.8V.
* VOM ground lead at SRTN, hot lead moved to EVP, KOEO, .24V
* VOM ground lead at SRTN, hot lead on EVP, KOER (first start up of the day, below operating temp), .23V
* engine up to operating temp, no vac present at EGR, engine idling, .23V
**no change in voltage as engine warmed up, it stayed at .23V**
* Revved engine to 2500 RPM, no change in voltage or vac.
* introduced vac to EGR via hand pump, idle drops off quickly, vac went to 5" then immediately returned to zero,at the same time the voltage rises to approx 2.7V then dropped back to .23V

* noticed that the voltage is now reading .21V

Concluded the test.


From all of the info that I was given here and from what I could find on the interwebz the voltage should have raised to around 5-6 volts as the engine temp went up. Is there another sensor that feeds coolant temp info to the PCM that could be faulty? ( the temp gauge in the cluster works fine) It seems like the PCM never knows that the engine is warmed up, making the overly rich A/F mixture that is killing the fuel mileage. Then there is also the issue of the voltage that drops to .21V, making me think that there is still an issue between the EGR and the EVP sensor.

I think that I'm finally on the right trail, I think with a bit more head scratching from those who more experience than myself, we can get this issue nailed.

 

Now you're making it sound like an Oxygen Sensor....

On the OBD-I engines, they're the only ACTUAL feedback sensor, IIRC...

That directly affects A/F ratio's etc...