'86 EFI 5.0 Missing Lack of Power

[fords4life]

So on to the next problem.....  Truck is running rough and has a lack of power, especially down low.  Once up to speed, it holds speed ok and is smoother, but not perfect.  KOEO I'm pulling codes 18 and 31.  KOER I'm pulling a 44.  I tested the EVP sensor and it tested within range(voltage and resistance), but having the 31 and it being 32 years old, I'm guessing I should just replace it.  As for the 44, I just replaced the air pump so that's not it, but could be the diverter valve and if 31 is an issue, from what I've seen, it could be causing the 44 as well.  Either of the two could also be vacuum leaks and/or vacuum solenoid issues from what I've seen.

Anyone have experience with these two and thoughts on where to start?

[vjsimone]

Ref Code 44, the Self-Test is only testing the electrical operation of the TAD or TAB Solenoid. So, I would check for supply power, 12vdc to the connector. Unplug the connectors and measure the resistance on those 2 solenoid coils and compare the readings.

As far as I can remember with the KOER 44 Code, the ECA is checking to see that power is applied to the TAD/TAB Valve Solenoids when the ECA expects them to operate.
But, would like to verify.

[vjsimone]

As far as the Code 31, dead spots on the potentiometer can cause this fault.
If you replace it, sometimes the replacement shaft length is longer or shorter and may produce a different fault code.  You may have to remove or add length to the shaft.

Verify source voltage and ground path as well.

[vjsimone]

Are you getting a rich smell out of the tail pipe ?

[fords4life]

vjsimone wrote

Are you getting a rich smell out of the tail pipe ?

Yes.  It has always been slightly rich, but certainly seems richer after starting to "miss".  It does have a new O2 sensor pre-cat.  But is also running the factory original cat which I'm sure is worn out, although it did pass emissions.

Thank you for the other info.  I might have time before I leave for my hunting trip to check the solenoids.

vjsimone wrote

As far as the Code 31, dead spots on the potentiometer can cause this fault.
If you replace it, sometimes the replacement shaft length is longer or shorter and may produce a different fault code.  You may have to remove or add length to the shaft.

Verify source voltage and ground path as well.

I did verify source voltage at 5.04v with a digital meter, but did not confirm path to ground.

[fords4life]

I knew I should have logged on before I wrapped up for the night.  I forgot check resistance on the solenoids.

I did put a piece of aluminum between the EGR and the manifold and the truck no longer feels like it is missing, but it is still running really rich.  I did confirm voltage to the solenoids.

Pulling the vacuum line off of the EGR valve, I think I can feel vacuum on the line, but it isn't very strong.  I'm also wondering if a lack of vacuum is what is causing my soft brake pedal and brake light?  

[Gary Lewis]

I don't want to sidetrack things, but Vinny may be riding today so I'll ask: How much manifold vacuum do you have at idle?

[fords4life]

I asked myself that question last night.  Making a run to the junkyard this morning and then we'll get a vacuum gauge so I can check that.

[fords4life]

16" vacuum at idle.

[Gary Lewis]

That's not very much.  Oh wait, where are you located?  If up around 5000' it isn't too bad.

[fords4life]

Yup. I'm at 5600'.  

Regarding my note about the miss last night.  After letting it fully warm up, the miss is still there with the EGR blocked, just not as bad.

[fords4life]

After letting things warm up fully and a test drive.... Truck still feels like it is missing but not nearly as badly with the EGR blocked off.  I also confirmed timing is at 10* BTDC with the spot removed.

[vjsimone]

The MFI Bank Injector ECA programming ran the Engines Rich at Idle to smooth out the Idle. So, smelling Rich at Idle is normal. Now where is “really rich” on that scale? I’m not sure.

You have a new O2 sensor.

If you are running Rich, the O2 should sense that state and send a Rich signal to the ECA, about 0.55 to 0.99 vdc. You can measure this on pin 29 of the ECA to prove one way or the other. You can also check the signal path to see if there is any resistance along the way lowering the voltage.

[vjsimone]

“Pulling the vacuum line off of the EGR valve, I think I can feel vacuum on the line, but it isn't very strong.”

FYI;  The EGR Vacuum Valve is only operated during Cruising, not at Idle or WOT.

Don’t know at what rpm you checked the EGR-Valve vacuum. If you checked it at Idle, it would not have vacuum.  If you felt a little vacuum at Idle, the valve may be leaking. Also you did not say where you were taking the vacuum reading.

With the EGR-V blocked off, this won’t be an issue as far as the EGR-V leaking exhaust into the intake.

It is possible to have a vacuum leak within those Vacuum Valves that may not show up until the ECA turns them on at a higher rpm.  You could pull off the 3-way vacuum connection on the intake that supplies your Vacuum Valves and cap those 3 tubes temporarily to test.

All of those vacuum lines around the v-valves and reservoir are very fragile if they are original. A sneeze in the wrong direction can damage them.

[vjsimone]

Another thing to check is your fuel pressure. @ Idle, the Fuel Pressure Regulator is actuated from the increased vacuum, lowering the fuel pressure by returning fuel to the tank.

If the FPR is not working or the return line is blocked, additional fuel will pass through the Injectors and cause a Rich condition.

Sometimes the FPR leaks fuel via the attached vacuum line, causing a Rich condition.
 
Remove the vacuum line to check for raw fuel, and to see if removing the line increases the fuel pressure. Plug the vacuum line when removed to avoid a vacuum leak.

[vjsimone]

Gary Lewis wrote

I don't want to sidetrack things, but Vinny may be riding today so I'll ask: How much manifold vacuum do you have at idle?

Yes b'y, riding everyday for sure...  
The more minds on issues is always more better...

[vjsimone]

So why did you replace the O2 sensor?

[vjsimone]

Some of your original symptoms are typical of a failing MAP sensor.
You might want to test the output and run a temporary new vacuum line to eliminate the possibility of an original leaking brittle plastic line.

[vjsimone]

fords4life wrote

  But is also running the factory original cat which I'm sure is worn out, although it did pass emissions.

If your Cat gets clogged up, the back-pressure increases and fools the readings to think there is more load on the engine and the ECA adds more fuel.

[fords4life]

Still need to check the O2 sensor voltage and the map sensor, I did get the fuel pressure gauge installed on the fuel rail and it's a solid 30psi at idle.  I need to look up the spec on what it is supposed to be.  

Vacuum was being measured at the tree in the manifold.