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-EGP (new) tests good with Multimeter, getting 5.04V from EEC
-EGR (new) tests good with vacuum applied (looses RPM, threatens to stall, returns when vacuum is removed)
-Solenoid (new) does not seem to pass vacuum with increased throttle, but this was all very unscientific
-TAB/TAD visibly damaged, removed from system
-New O2 sensor (Delphi, three wires)
-Did not repeat WOT to confirm Knock Sensor, but not experiencing pinging
Please inform me about the Air Diverter Solenoid. I cannot locate this part. Is this the Air Bypass Valve? I just need to know to start the shop manual diagnostics.
Do I have the right O2 sensor for my truck?
What in the hell is with the EGR? I've been fighting this since the truck was a new to me no start a year ago. Frustrating.
My sincere thanks to anyone who made it this far and might give me pointers outside of what I've found going back in the forums thus far.
Last edited by AHHeck; Jun 1, 2022 at 11:25 AM.
Reason: Unclear Title
Disregard the KOER codes. You don’t perform that test until you get a system pass code from the KOEO test. Is the code 31 an active code or is it stored in the memory? Does the truck still have the air injection system?
@AHHeck ,Without knowing your symptoms, (i don't have access right now to 2 digit codes, my truck does 3 digit codes), I am curious what you mean by:
"TAB/TAD visibly damaged, removed from system"
There are 4 vacuum lines on mine, and electrical connections. These will affect the egr valve, and other components. How did you remove them, and what did you do for the vacuum and electrical connections? From my understanding, the air diverter solenoid is part of the Tab/Tads solenoids. If the computer is not reading a signal from these, it will throw codes.
I completely removed the air injection system on my 94, 7.5. Kept the Tab/Tads solenoids hooked up. I had to remove, and cap off at the solenoids, the line that ran to my non existent thermactor valve. I would replace these solenoids, ensure they are plugged in, and insure vacuum lines going out from them are either in good shape, or replaced. Our trucks are different years, and motors, but, when I started researching my build, I realized I needed these to run smoothly, and the computer needs these signals.
good luck
Is the code 31 an active code or is it stored in the memory? Does the truck still have the air injection system?
31 is active, all the codes listed are. EGR is functional, the TAB/TAD are hooked up electronically for better or worse, but I have bypassed the vacuum canister and those two solenoids from the circuit for to eliminate as many fail points as possible. If that isn’t what you mean by air injection system, I apologize and would appreciate clarification. Thanks for your help.
I am curious what you mean by:
"TAB/TAD visibly damaged, removed from system"
Thanks for the feedback. I thought the two solenoids were damaged because they were missing their caps and had cracking on their housing. Now that you mentioned removing your caps, I might need to put them to the test. Otherwise They are electronically connected but as of recently they do not have vacuum applied. The code however is brand new. I will give them a second try after diagnostics and see where that puts me.
Code 31 indicates the EGR Valve Position (EVP) feedback signal is too low. Use a meter to verify the signal output is between 0.24 to 0.67 VDC with the key in the On position engine off.
Thanks for the feedback. I thought the two solenoids were damaged because they were missing their caps and had cracking on their housing. Now that you mentioned removing your caps, I might need to put them to the test. Otherwise They are electronically connected but as of recently they do not have vacuum applied. The code however is brand new. I will give them a second try after diagnostics and see where that puts me.
From my understanding, they need to have vacuum applied. One of the solenoids can be capped off at one of the connections if you are no longer using the air pump and thermactor system, for air injection into your manifolds and catalytic converter. At this point, i would stop what you are doing. Verify all needed vacuum lines are present, and in good shape.
This is a picture of my solenoids after I did the air pump and thermactor system delete. Yours may look similar. But, these solenoids need to electrically activated, and have vacuum applied. If not, you are chasing codes forever. I know this from experience, as you can see the upper vacuum line was not plugged into both ports on the solenoid. Once this was discovered, and fixed, motor ran great. Fix this, then run your tests again would be my recommendation.
good luck
From my understanding, they need to have vacuum applied.
I will put vacuum to them as per your advice. When I got the truck a year ago the vacuum system was an unholy mess. Every other component was plugged with screws in hoses or what line was there was brittle and leaking badly. The whole TAB/TAD circuit was offline, but didn’t throw this code. I had just assumed they were damaged and I’ve had a hard time finding replacement solenoids. Thanks for your very helpful feedback.
Completely disagree regarding keeping the vacuum supply attached to the TAB or TAD solenoids when eliminating the air injection/pump system. Totally agree you need them connected electrically (or use comparable resistor values) to keep the computer happy.
When you remove or cap off the actual bypass or diverter valves you will fail a few KOER tests since the computer will not be able to sense the extra air (read that as O2) in the exhaust when it turns on the respective solenoids/valves during the KOER tests. There is absolutely no way for the computer to sense vacuum applied to the TAB or TAD solenoids so keep it simple.
Completely disagree regarding keeping the vacuum supply attached to the TAB or TAD solenoids when eliminating the air injection/pump system. Totally agree you need them connected electrically (or use comparable resistor values) to keep the computer happy.
That is how mine is set up: plugged into the engine harness with the vacuum lines disconnected. No check engine light or codes.
That is how mine is set up: plugged into the engine harness with the vacuum lines disconnected. No check engine light or codes.
Well, huh. You learn something new every day. My research prior to the delete, said it needed to register vacuum. Gonna go look at mine and see how many vacuum lines I can remove to unclutter my engine bay. Do you just cap off the vacuum ports on the solenoids?