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

nickb2

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#16
So, if the PCM is seeing zero at idle, something is wrong. Usually, no engine will run at 0hg. That means no compression, no four stroke action going on. But back in 1996, when the transitional stages were there between carburated and injection, one of the first things engineers needed to combat, was how to process vacuum to a feasible number for algorythm. O is not in anyway connected to a 14.7 to 1 ratio.

WOT or whatever it is for a 1996ish truck should still be 20is hg vac. So ask yourself why @ 2370rpm you are reading 0 hg on the EVR?

One question I ask often of my apprentices, is a old sherlock holmes quote. which is as follows.


When you have eliminated the impossible, whatever...
"You will not apply my precept," he said, shaking his head. "How often have I said to you that when you have eliminated the impossible, whatever remains, however improbable, must be the truth?
 

nickb2

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#17
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
 

nickb2

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#18
Why is EVR% 0 @ 1012rpm?

And still @ 0
ANST 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
@ 2600rpm?

Shouldn't this have cycled by now?
 

grcauto

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#19
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.helps determine

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.
Not a trick and not needing info. I was asking the OP what he gets with the vacuum gauge to analyze internals. If that engine has 14" at idle it has jumped time. 20" would be real good and 18" normal. I don't think I've seen any engine that pulled 23 at idle but I digress. 18 and steady is OK. Low is possible mechanical timing or VE from worn rings etc. Bouncy is bad valve seating. If it's around 18 and steady we run it up to 3000 rpm and notice if vacuum slowly drops indicating restricted exhaust. WOT snap helps determine VE problem as opposed to mechanical timing.
Now if the OP will do the tests and report we can help HIM or HER.
I'm not on here to test your skills.
 

nickb2

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#20
For informational purposes, egr works on back pressure. What IS BACKPRESURE. It is a positive response to negative normal 4 stroke cycle.engine.

Are egr and evr the same thing? one might ask, yes and no. Both work on same principle.
 

nickb2

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#21
Not a trick and not needing info. I was asking the OP what he gets with the vacuum gauge to analyze internals. If that engine has 14" at idle it has jumped time. 20" would be real good and 18" normal. I don't think I've seen any engine that pulled 23 at idle but I digress. 18 and steady is OK. Low is possible mechanical timing or VE from worn rings etc. Bouncy is bad valve seating. If it's around 18 and steady we run it up to 3000 rpm and notice if vacuum slowly drops indicating restricted exhaust. WOT snap helps determine VE problem as opposed to mechanical timing.
Now if the OP will do the tests and report we can help HIM or HER.
I'm not on here to test your skills.
Wow, your a touchy one. But I respect you more than you know. In the mean time, I really appreciate what you bring to the table.
 

grcauto

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#22
Wow, your a touchy one. But I respect you more than you know. In the mean time, I really appreciate what you bring to the table.
My question about vacuum was directed at the OP and not you but you made a point to jump into the question. Now this question is for you. Why do you say "Wow, you are a touchy one." What's that about?
I'll say this while you think about your answer. You have posted at least a half dozen times about his or her scan readings without answering a single question but have asked several. You make assumptions and talk about how things work or at least as you think they should. Do you think this is helping him./her? Ask a relevant question that can point us in a direction to go so we can help him or her from that point going forward.
The scan data indicates this engine is not breathing correctly thus my question about vacuum.
 

nickb2

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#23
I'll say this while you think about your answer. You have posted at least a half dozen times about his or her scan readings without answering a single question but have asked several. You make assumptions and talk about how things work or at least as you think they should. Do you think this is helping him./her? Ask a relevant question that can point us in a direction to go so we can help him or her from that point going forward.
The scan data indicates this engine is not breathing correctly thus my question about vacuum.
In regards to this, you are absolutely right.
 

nickb2

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#25
Thank you for keeping me in line, I needed that. I often let my ego get in front of what this site is really about.

Excuses are for suckers, and I am not about to make one up when a reality is put up front. So for that, I invite you to listen to a cool french singer, he really rocks. Your response hits home cuz it true. So again, thx. So here is a nice "tranche de vie" home grown talent.

 
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#26
UPDATE:

In the process of checking off the items on my diagnostics check list I encountered an error made by the last mechanic to work on my engine. The EVAP system hoses were connected all wrong. I'm surprised the mechanic got it so screwed up since there is a diagram right there in front of the engine under his nose. In any case that helped out with my vacuum problem but did not solve the stumble issue. Next item on the list was compression testing. All cylinders report around 176 psi and the plugs look OK. I did notice that one of the spark plug boots crumbled when I was trying to remove it. Since I had it all apart I installed new plugs and wires. (A very difficult task on cylinders 1 & 2 on these vans). A test drive afterwards revealed my issue was gone. Apparently my wires were leaking/cross arcing.
So that's it, fixed, thanks to all for the input and suggestions.

PS> I wish someone could explain how this ignition system works. The injectors are controlled by only two wires from the PCM (each wire feeds 4 injectors) and all the grounds are tied together. Since the injectors are tied together in two banks of four how does each injector know when to inject fuel at the proper time. The cylinders fire sequentially, not in groups of four, so how the hell does that work?
 

billr

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#27
Why do you think it is sequential injection if the injectors are wired in banks? Oh, maybe I'm missing your real question. Fuel doesn't have to be injected at a specific time in the engine cycle for an engine to run pretty well. Sequential injection is mainly for squeaking out the best emissions and CAFE numbers.
 
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#28
I just assumed it would be a good idea not to have fuel being injected during the exhaust stroke, and that it would also be nice to have it at just the right moment to get the most efficient burn. My shop manuals cover all the 96 FORD engines and all of the other engines have an injector wire from the PCM for each cylinder. So from what you are telling me I'm thinking this engine sucks and it's why I only get 12 miles per gallon? Just my luck I got stuck with a half-assed system some engineer came up with for the 5.8.
Out of all the explanations I have been given regarding how this ignition works I think yours finally turned on the light. What's happening is fuel is being injected into four cylinders at the same time while those four cylinders are in various stages of the compression stroke and then fire sequentially. Correct?
 

billr

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#30
If your fuel economy is that poor, you have some other problem. The difference between batch and sequential injection is quite small, and batch-fire of injectors has been used quite successfully in many, many types of engines. Even with full-sequential injection, fuel is being sprayed in during almost all of the four engine strokes when the engine load and rpm are high. You keep saying "ignition" but ask questions about the fuel injection. Is there a specific question about ignition that we are not addressing?