Hi everyone,

Today I decided to see if I can figure out why the hell this truck is only getting 9 MPG, it's too much even for this pig. Here's the background on the vehicle in question.


1990 F250. I got it from the original owner. It was basically a light duty F250, it had a 5.0, M5 mazda trans, a worn-out-to-hell-and-back D44 front end, semi floater rear axle, a full size service body that had to weigh 2000 lbs by itself. I bought it cheap in not driveable condition because squirrels ate through the fuel lines. Obviously the service bed is gone. I've done a D60 swap and a ZF-5 swap. Last summer I took the wrecked up truck that's in my avatar and used it for the 5.8 engine and the full floater rear axle. When the 5.8 engine was out, I replaced the timing set w/ a good quality set, all of the seals were replaced, installed the correct flywheels for the 5.8, new clutch set, ect..

The exhaust is a dual outlet pipe (from a F350) that goes into an inverted "y" just behind the trans cross member to make it a single pipe, then an aftermarket cat, then to a Dynomax muffler, then to the tailpipe. The cat has the air tube hooked up. I used the AIR injection system from the 5.0 following the advice that I got from here. I used the engine wiring harness from the 5.0. The knock sensor connector is just zip tied up and out of the way, no sensor is installed.

I used a computer from a 1991 F250/ 5 speed. The gears are 3.55 and the tires are 265-75-16's.

These are the codes that I pulled today.
KERO:

32 & 85

KOER:

32


It would seem that there is an issue with the EGR system. I tried to isolate the issue, here's what I've done so far. I pulled the vac. hose off of the EGR w/ the engine running and hooked up a vac gauge, I had no measurable vacuum. I shut the engine off, kept the vac. gauge attached to the boot. I pulled the vac plug off of the TAD valve (see pic)



I applied vacuum to the green line, the vac gauge moved and held 25" of vac so I know that the line itself is good. I attached a vac source to the nipple on the EGR valve, I could see it physically move up and down and it would hold vacuum.

My first question is- should I have vacuum present at the EGR valve while the engine is idling? How can I test the vac solenoid in the pic? Should I be looking at something else for the EGR valve trouble code? Am I on the right path? I know that this truck will never get great fuel mileage but 9 MPG is just too low, I know it can do better than this.

Thanks for any help/advice.

 

Seems like the EVR itself may be bad. Did you check to make sure it was getting power?

 

There should be no vaccum at the EGR on idle....

 

Code 32: EVP circuit has intermittently failed below minimum voltage of 0.24 volts.(CM) or EVP circuit below minimum voltage of 0.24 volts.(KOEO and KOER)

This indicates the EGR position feedback signal, the EVP sensor, has been or is too low when the EGR should be closed. This can be caused by a faulty EVP, collapsed EGR diaphragm or weak spring, and last bu t not least an open circuit. In your case I would discount the open circuit because you did not get a code indicating the PCM did not see the EGR valve open. Perhaps the connector is loose or corroded.

Get a DVM and measure the EVP output signal. Verify the output is good or bad. If it is below 0.24 VDC then you have to figure out if it's a bad EVP or EGR valve. The EGR valve itself preloads the EVP sensor, it is hard to tell if it one or the other causing the problem. You can ohm out the EVP using this as a reference.

Code 85: Canister Purge Solenoid circuit failure.

This can be caused by a disconnected or faulty CANP solenoid. This solenoid is controlled by the PCM to open at certain times to allow fuel vapors into the intake stream.

I think you are barking up the wrong tree with the EVR, but here is some info about how it works: Fuel Injection Technical Library » EGR Vacuum Regulator (EVR)

 

Just curious....

Would it just be easier to simply plug the TAD/TAB solenoids, and any other open hoses, etc....?

 

TAB/TAD solenoids have nothing to do with EGR operation or any of the codes the OP got.

 

My bad.....UGH....LOOOONNNNNGGGGG day....

Ok...Scratch previous post...

 

Been there, done that

 

Is the EVR the same as the TAD valve?

 

No, two different things

For reference:


The TAB and TAD solenoids control the AIR injection system. The EVR regulates the amount of vacuum applied to the EGR valve. It's pulse width modulated by the PCM.

 

where is the EVP located? I'm trying to use "search" as much as possible so that I'm not being completely useless!

 

I took a picture of the damn thing, I called it by the wrong name...

I'll be back in a few, I'm doing some testing......

 

On top of the EGR valve.



EVP info: Fuel Injection Technical Library » EGR Valve Position sensor (EVP)

 

I called my wife by the wrong name once. The result was much worse than yours...

 

When you start going after the Code 85/CANP (Carbon Canister Purge Solenoid) issue here is a photo of what it looks like: