Vacuum lines could explain both codes 34 and 41. If the EGR is connected to the "coffee can" reservoir, and the TAB/TAD solenoids are connected where the EGR should be, then two bad things could happen:

The EGR opens too much at high MAP (low vacuum), since it would incorrectly get vacuum from the coffee can, and the computer complains with code 34 (it knows what the MAP is from the MAP sensor).

The air pump diverter valves don't work right, and inject air into the exhaust in such a way as to confuse the oxygen sensor, causing code 41.

As for the EGR valve, the "blue tipped wrench" (torch) might be called for. Heat in the right place often helps a lot. If the fitting is stripped, try a big pipe wrench. But don't force it hard enough to break things unless you have a replacement or block-off plate arranged for.

 

Actually, my truck has been running better lately. Throttle response is great. Idling is smoother. Doesn't 'sputter' and 'stumble' as much.

How can I check for a leaky injector? I heard a method involving turning key to ON a couple of times. Then check too see if Injector leaks. Is that right?

 

You need a fuel pressure guage. Attach it to the Shrader valve on the fuel rail. Cycle the key as you mention. Turn the key off. If the pressure bleeds down more than 5 PSI in 30 seconds, there is the possibility of a leak. Leak sources can be the fuel pressure regulator, the check valve in the pump, or one of the injectors. If the fuel rail holds pressure OK, then none of the injectors are piddling fuel when they should be closed.

 

I think we may be having problems referring to different parts.

You say your EVP (position sensor?) has a vacuum line? Mine has no vacuum port, just a wiring connection.

Here's how my vacuum lines are hooked up.

Green - EGR valve <---> EVR solenoid
Black - coffee can <---> tee'd into all three solenoids: EVR/TAD/TAB
Red - coffee can <---> intake manifold
These last 2 (black and red) are part of one connector into the coffee can.
Orange - coffee can <---> either the TAB or TAD solenoid
Yellow - some non-existent Thermactor part <---> either the TAB or TAD solenoid (I plugged this line)

The previous owner removed a lot of the Thermactor system parts and plugged up the exhaust manifold ports for it.

 

Also, to be clear, I'm getting code 32, not 34.

 

No, EVP has no vacuum line. Sorry if I confused you in any way.

 

fefarm, you are awesome...man, I just followed the whole thread an your last answer blew me away. ...it was like a melodrama and then you walked in and shot all the bad guys...you and broken wire are very cool and amazingly on it ....I hope I never have all these sorts of problems but if I do I will be looking for help from the likes of you!

 

Yea, fefarms is awesome. Hope he can he help me on my 'Need Wiring Help.' thread .

 

I'v had similar problems with a 92' 5.8L. ... engine stalling and what not. every thing I've read tells me to energize the evr solenoid in order to test it. I did so and think i ruined it. The manuals say nothing about polarity. After putting a fluke to it i realized that its a dead short regardless of polarity. "bad solenoid right".... took the thing apart and noticed there's not only a coil in there, but also a diode. digging deeper the valve portion of the solenoid is only a washer shaped piece of steel without the hole, no rubber. Impossible to seal completely, right? I've temporarily given up on tracking this problem down, but i did remove the solenoid and plugged the vacuum line. The truck runs better without it. No more short and more importantly no more stalling. But i do need to get it fixed before next emitions test. Any help would be appreciated. Ive ripped out all the brittle vacuum line and replaced them with black rubber, so i dont have the luxury of color codes nor is there a routing schematic on the truck. I'd like to verify i have it hooked up correctly. After getting a new one of course. Like i said i think i ruined the current one by shorting the diode out. One more question i have is does the sponge side go up or down. It was installed down but every picture i look at shows it up. Please help! thank you soooo much.

 

I wasn't aware of the diode, but it is a common practice in electronics to put a shunt diode across a solenoid coil. When the current through an inductor is suddenly interrupted, there is a voltage spike. (Your ignition coil is a good example). The diode shunts the spike back around the coil to prevent an excessive voltage rise on the control line coming from the computer. The diode anode should be connected to the computer control line, the diode cathode would be connected to the +12 volts coming in to the solenoid. You should not run the shorted solenoid in the vehicle; the computer could be damaged from trying to drive too low a resistance.

For the benefit of bcdeines and austinbronco, I created an FTE album and transferred a couple of diagrams to it. They show the vacuum line routing for a 1991 F150 5.0 and the internals of the EVR. No warranty is implied or expressed as to the accuracy of this info. The vacuum diagram seems to differ slightly from my truck -- I will have to take a closer look at the truck.

The gallery is here:
https://www.ford-trucks.com/user_gal...&albumid=13815

I suggest that austinbronco try connecting the EVR directly to manifold vacuum, bypassing the coffee can. See if anything changes.

 

Do you think the red and black lines that go together into the the reservoir should be connected to the TAB/TAD solenoids?

And the other line into the the reservoir should be the check valve line that goes directly to the manifold? And is the check valve perhaps built into the reservoir? Because there certainly isn't one inline to the manifold.

Thanks for your help.

 

My guess is that the coffee can includes the check valve function, despite the diagram showing something separate. My guess is that one side is manifold vacuum, the other side is post check valve and has the contribution of the reservoir.

According to the diagram, the coffee can is for TAB and TAD, and NOT for the EVP. Not sure about how the truck actually works.

To sort out black and red, and match them to the diagram, I need to pop the hood of my truck and trace where the tubing goes. But I have some other stuff going on today, may not get to it till later. That's why I suggested routing the EGR straight to manifold vacuum. Add your own "tee" into one of the lines off the "Christmas tree" if you have to. Just see if it makes any difference in the EGR codes.

 

I looked at my truck this afternoon. From the "Christmas tree" atop the intake plenum runs two red vacuum hoses. One goes directly to the fuel pressure regulator, and nowhere else. The other red hose wraps around the back of the engine, and along the right side. There is a "tee" fitting. One branch of the tee runs over to the "coffee can". The other branch runs back around the back of the engine to the EVR.

The "coffee can" indeed incorporates a check valve internally. The red hose does not have vacuum on it when the truck engine is stopped. But the black hose does, if you pry the connector off you can hear it hiss. This black hose runs around the back of the engine and over to a "Tee". The Tee connects the TAB and TAD solenoids to the post-check-valve side of the coffee can.

A green hose runs from the EVR, underneath the intake plenum and up to the EGR valve. The EVR is installed "sponge side up". The words "Made in Canada" are visible and read from top to bottom.

The orange and yellow hoses run from the TAB and TAD solenoids to their respective valves, and nowhere else.

The three-way connection from TAD to TAB to EVR seems suspicious, but then we don't have the exact same model year truck. Does the three-way tee look factory?

According to the schematic that I posted, and according to the routing on my truck, the EVR should not be tied to the "black side" of the coffee can.

 

That sounds right. I'm not sure about that 'tee',but it's probably there.

Codes so far:
KOEO: 34
CM: 34
KOER: 34, 42.(At some tests, 21 comes on.)

Mileage is up somewhat so I'm kinda glad. If 34 is showing up even in KOER, wouldn't CEL be on when running truck; because its not.

 

I'll inspect that 3-way connection again tomorrow.

Since I don't have a Thermactor system running, can I just plug those TAB/TAD lines and forget that the "coffee can" exists? It looks to me like its only function is for the Thermactor system. All I need, it seems to me, is a line from EVR to EGR and from EVR to intake manifold.

Out of curiousity, what is the valve to the left of the PCV valve in the vacuum diagram you posted? The text is obscured.