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

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#31
That's impossible. This thing has a distributor with a rotating rotor that is sending a spark to each plug sequentially.
 

grcauto

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#32
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?
They are hogs, but you should get a little better mpg than that. I don't think you would gain much if it were sequential. Think about it. If the intake valves are closed it's but for a very short period of time and the fuel doesn't burn but it does start to vaporize. When the valve starts to open and pulls in the air/fuel mix the vapors are ready for combustion.
 
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#33
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?
The only reason this came up is because I wanted to do that injector test where you disconnect each injector in turn to see what effect it has, you know, to locate a cylinder that's missing. Well, because it's nearly impossible to get to the injectors on this van I came up with this brilliant idea to install momentary push button switches in the PCM breakout box, one switch for each injector. That way I could do the injector elimination test without having to pull the connectors. Well I was shocked when I traced out the wiring and discovered I had only two injector wires to work with and no way to isolate them individually from the breakout box.
 

billr

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#34
Disable cylinders by disconnecting/shorting the spark plug wires, it was done that way for all the years before EFI.

Do you understand now that I'm not saying the cylinders fire in "banks", only that the fuel is delivered to the manifold in banks? The actual intake of fuel/air to the cylinder is sequential due to the intake valve operation.
 

DJ40

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#35
My last mileage test came up with 14 MPG, and while that may not be good by today's standards remember this is a 1 ton loaded with tools and materials to do several trades. Also, I looked up the original EPA ratings for these 96 vans and even the EPA rated them between 9 and 15 MPG when they were new in 1996, so I would say I'm right up to spec. and could probably get the 15 MPG if I emptied the van.
 

©hester

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#36
A lean condition can also be caused by unmonitored air, a vacuum leak. Check the rod holding the throttle body plates for slop between the rod and the throttle body housing..
 
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#37
I know I do have a small vacuum leak in the A/C Heat control system. I plugged it off at the intake manifold and it did not seem to cause any difference in the engine operation, but it is something I need to address. I'll be sure to check the throttle body plates. The intake is not monitored on this van as it has no Mass Air Flow sensor.
Thanks.
 

grcauto

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#38
I know I do have a small vacuum leak in the A/C Heat control system. I plugged it off at the intake manifold and it did not seem to cause any difference in the engine operation, but it is something I need to address. I'll be sure to check the throttle body plates. The intake is not monitored on this van as it has no Mass Air Flow sensor.
Thanks.
If it's speed density (MAP sensor) a vacuum leak will cause high idle. the lower vacuum due to the leak is looked at as higher load by PCM and it adds fuel.