HELP!! Trouble diagnosing acceleration stumble, 96, FORD, E350 van, 5.8, EFI EEC-IV, E4OD

DJ40

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#1
Make
FORD
Model
E350 base
Year
1996
Miles
265,000
Engine
5.8
Hello trouble shooters. I have an issue with my van that is driving me nuts. 96 was the transition year from OBDI to OBDII and my van was early on the line so it did not get the OBDII system. I am getting what I describe as a stumble when trying to accelerate in the higher gears. The transmission shop say it's not the tranny, it is not slipping, and telling me it's an engine problem. The only code I am getting is a 172 HO2S lean. When this stumble happens I can also hear a knock in the engine like the timing is off. I have checked the base timing and it good. Because it's OBDI the scan data is limited. One thing I am noticing is the Loop is going Open intermittently as I drive.
I would appreciate it if someone with the talent to interpret the data below could to tell me if there is anything so far out of whack that it might provide a clue about what might be causing my acceleration stumble.
Thanks

Also, I should mention that this van has no MAF, only a frequency based MAP / BARO.

Here is a frame where the van is in Closed Loop:
CANST PURGE On
ECT(V) 0.7
ECT(°F) 185
ENGINE SPD 1012
EVP(V) 0.2
EVR(%) 0
FUELPW1(mS) 2.0
IAC(%) 4
IAT(V) 1.3
IAT(°F) 142
LOOP STATUS Clsd
O2SEN 1(V) 0.75
SPARK(°) 12
ST FTRM1(%) 10
TOT(V) 1.3
TOT(°F) 145
TP MODE C/T
TPS(V) 1.2
VPWR(V) 14.1
VREF(V) 5.0
VSS(MPH) 41

Here is a snapshot where it jumps to Open Loop:

CANST PURGE On
ECT(V) 0.7
ECT(°F) 185
ENGINE SPD 1016
EVP(V) 0.2
EVR(%) 0
FUELPW1(mS) 2.1
IAC(%) 4
IAT(V) 1.3
IAT(°F) 143
LOOP STATUS Open
O2SEN 1(V) 0.75
SPARK(°) 11
ST FTRM1(%) 10
TOT(V) 1.3
TOT(°F) 145
TP MODE C/T
TPS(V) 1.2
VPWR(V) 14.1
VREF(V) 5.0
VSS(MPH) 41

Here is another snapshot at a higher RPM, but I am not sure what was happening because it looks like I am accelerating pretty hard but VSS speed is zero. I do not recall racing my engine while standing still:

CANST PURGE On
ECT(V) 0.7
ECT(°F) 180
ENGINE SPD 2636
EVP(V) 0.2
EVR(%) 0
FUELPW1(mS) 2.5
IAC(%) 62
IAT(V) 0.9
IAT(°F) 167
LOOP STATUS Open
O2SEN 1(V) 0.00
SPARK(°) 35
ST FTRM1(%) 10
TOT(V) 1.1
TOT(°F) 157
TP MODE P/T
TPS(V) 1.5
VPWR(V) 13.9
VREF(V) 5.0
VSS(MPH) 0

Steps I have take that should be mentioned:
Round of Injector Cleaner
New fuel filter
Throttle body cleaner
Checked motion of EGR valve, it responds to vacuum testing
Check MAP / BARO (As this is a frequency output device and could not do spec test because I do not have a scope, but vac holds and supply voltage is good. Borrowed a new one from NAPA and it did not change issue so I assume MAP is OK)
Found distributor loose, pulled SPOUT and set base timing 10 degrees BTDC
Checked cleaned PCV valve
 
Last edited:

kev2

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#2
p0172 is only code? going lean and knock in eng - that could be a lean knock- fuel trims are double digit, right at the issue no issue limit, the o2voltage is .75 or 0 injector issue
SWAG thinking fuel issue...

there is a fuel pressure schraider valve on fuel rail, attach pressure gauge, observe fuel pressure
remove vacuum line at regulator, NO fuel in vac line, did pressure increase?
then with KOEO observe presure drop, record in 5 minutes pressure dropped Xpsi,


change frame mounted fuel filter,
add a can of 'seafoam' or techron inj cleaner.
 

DJ40

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#3
Thanks for your prompt reply. Yes 072 is the only code.
Here is the report:
DTCs (Codes)
111 ECM
Sys Pass Code No Faults Detected During
KOEO Test

KOEO

------------------------------
111 ECM
Sys Pass Code No Faults Detected During
KOEO Test
MEMORY

==============================

DTCs (Codes)
172 ECM
HO2S System Lean Bank 1
KOER

First thing I did when this started was to do a round of the inj cleaner. Then I also did throttle body cleaning with Top Engine and changed the fuel filter.
I have been wanting to measure the fuel pressure but the plate that holds all the emissions solenoids runs over the top the the valve so I can't get my hose on there without taking everything apart. I guess I'll have to bite the bullet and do that.
What do you think about the fact that the EVR% never seems to rise above zero? I am not real familiar with how that system is supposed to operate but it seems like it should change at some point, correct?
 
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#4
Check EGR flow, does engine stumble or stall when vac is applied manually?

Snapshot three, temp is at 180, IAT is 167, VSS is 0. Are these reasons to drop out of closed loop?
 

DJ40

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#5
Interesting that you should mention the EGR. I tested the EGR valve itself and it seemed to be working fine, in fact I repleced it about a year ago, but today I was testing all the vacuum lines and discovered the EGR solenoid valve is stuck in the open position. So I'll need to change that out tomorrow. Plus I am beginning to think I may have more than one issue. I don't think the EGR solenoid would have any effect on my having 2636 RPM's showing on the engine speed while I'm not moving (MPG 0), and I know the VSS is working properly or my speedometer and cruise control would be freaking out, so I may have a problem with a PCM glitch. At first I thought I might have a bad engine speed sensor, but I discovered this van doesn't have one of those, so I don't know where the PCM is getting the engine RPM's? Maybe just calculating X2 off one of the cylinders firing?
 

nickb2

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#6
At first I thought I might have a bad engine speed sensor, but I discovered this van doesn't have one of those, so I don't know where the PCM is getting the engine RPM's?
This a wrong assumption, the engine is getting rpms from the hall effect in the dizzy.
 

nickb2

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#7
here is a snapshot to prove what I am saying. Engine speed is determined by the cam sensor/hall effect.

See key word "purpose" in following snapshot.

I will help you further if you want . Screenshot (259).png
 

DJ40

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#8
Cool, then I was not far off... it's not using one cylinder, it's calculating RPM's off the spark signal to all 8 cylinders, where each cylinder spark represents two relovutions of the engine.
 

nickb2

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#12
Here is a hint on your PID data, I find it hard to beileve your EVR% is @ 0 when engine is @ 2grand rpm. 0.2v, no vac at 2grand.

Something is not right here. Timing is maybe off cuz obd 1 system is seeing 0 vac, when in fact, it should see more.
 

nickb2

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#13
BTW, I don't think anyone answered your previous question in regards to what EVR means. It means electronically regulated vacuum. Or as ford liked to call it back then, electronic vac regulator.

I was apprenticing back in 96, just fitting tires and changing oil, but I remember the old guy's bringing down saints from heaven to hell because this regulator would throw all readings out of whack, or not at all, missed diagnostics due to lack of info from ford. Mind you, back then, internet was in the infant stages.

Sometimes, my sorry a$$ English gets in the way cuz I am french from canada. But I do put alot of effort in my translation. More than most. But stick with me, we will get this gem of a ford caught in between two generations back to working order. This was a very bad era for transitional thinking.
 

grcauto

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#14
Hello trouble shooters. I have an issue with my van that is driving me nuts. 96 was the transition year from OBDI to OBDII and my van was early on the line so it did not get the OBDII system. I am getting what I describe as a stumble when trying to accelerate in the higher gears. The transmission shop say it's not the tranny, it is not slipping, and telling me it's an engine problem. The only code I am getting is a 172 HO2S lean. When this stumble happens I can also hear a knock in the engine like the timing is off. I have checked the base timing and it good. Because it's OBDI the scan data is limited. One thing I am noticing is the Loop is going Open intermittently as I drive.
I would appreciate it if someone with the talent to interpret the data below could to tell me if there is anything so far out of whack that it might provide a clue about what might be causing my acceleration stumble.
Thanks

Also, I should mention that this van has no MAF, only a frequency based MAP / BARO.

Here is a frame where the van is in Closed Loop:
CANST PURGE On
ECT(V) 0.7
ECT(°F) 185
ENGINE SPD 1012
EVP(V) 0.2
EVR(%) 0
FUELPW1(mS) 2.0
IAC(%) 4
IAT(V) 1.3
IAT(°F) 142
LOOP STATUS Clsd
O2SEN 1(V) 0.75
SPARK(°) 12
ST FTRM1(%) 10
TOT(V) 1.3
TOT(°F) 145
TP MODE C/T
TPS(V) 1.2
VPWR(V) 14.1
VREF(V) 5.0
VSS(MPH) 41

Here is a snapshot where it jumps to Open Loop:

CANST PURGE On
ECT(V) 0.7
ECT(°F) 185
ENGINE SPD 1016
EVP(V) 0.2
EVR(%) 0
FUELPW1(mS) 2.1
IAC(%) 4
IAT(V) 1.3
IAT(°F) 143
LOOP STATUS Open
O2SEN 1(V) 0.75
SPARK(°) 11
ST FTRM1(%) 10
TOT(V) 1.3
TOT(°F) 145
TP MODE C/T
TPS(V) 1.2
VPWR(V) 14.1
VREF(V) 5.0
VSS(MPH) 41

Here is another snapshot at a higher RPM, but I am not sure what was happening because it looks like I am accelerating pretty hard but VSS speed is zero. I do not recall racing my engine while standing still:

CANST PURGE On
ECT(V) 0.7
ECT(°F) 180
ENGINE SPD 2636
EVP(V) 0.2
EVR(%) 0
FUELPW1(mS) 2.5
IAC(%) 62
IAT(V) 0.9
IAT(°F) 167
LOOP STATUS Open
O2SEN 1(V) 0.00
SPARK(°) 35
ST FTRM1(%) 10
TOT(V) 1.1
TOT(°F) 157
TP MODE P/T
TPS(V) 1.5
VPWR(V) 13.9
VREF(V) 5.0
VSS(MPH) 0

Steps I have take that should be mentioned:
Round of Injector Cleaner
New fuel filter
Throttle body cleaner
Checked motion of EGR valve, it responds to vacuum testing
Check MAP / BARO (As this is a frequency output device and could not do spec test because I do not have a scope, but vac holds and supply voltage is good. Borrowed a new one from NAPA and it did not change issue so I assume MAP is OK)
Found distributor loose, pulled SPOUT and set base timing 10 degrees BTDC
Checked cleaned PCV valve
Is that thing breathing right? What does a vacuum gauge read/do at idle?
 

nickb2

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#15
Ok, this will be either a trick question asking me if I know my stuff, or you need good info. Either way, I just want to help you.

So, 14 to 20 is good vac at idle.

Now what we need to know, is how to decipher a proper working engine with one of the most tried and tested way to test proper engine breathing, as you so aptly wrote.

Ideal is 23, but that rarely happens in a loose engine. Snapping/WOT should produce 5 vac drop and rebound to 22 or close to it. Anything else is indicative of a problem.