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Discussion Starter · #1 ·
Sorry for the Long first post but I wanted to give you all the info.

We have a 94 E350 15Pass Club wagon with the 460 that has developed a problem this spring.


First off the van only has 28K miles on it so it does do a lot of sitting. When we started driving it this spring it would start bucking and what seems to be missing when cruising along. Under a hard acceleration it would run perfectly and have all the power you could ever need.

When idling in park, neutral, and drive it also has a distinct miss.


Here is what I have done so far:

1) A fuel drier was added thinking there is water in the fuel
2) Fuel injector cleaner was added
3) Fuel filter changed (on the frame rail under the driver’s seat)
4) Plugs and wires. I also cleaned the rotor and the contacts on the cap.

In messing around with things I have also looked at the MAP sensor:

1) Disconnected the vac. line to it with the engine running and it stalls

2) Disconnected the Electrical connection and the truck idles smooth (but rich) also it does not buck when driving but shifts very harsh.

After looking online I have seen talk of the MLP sensor but would that cause a miss at idle in PARK? or could I have 2 things going on?

I know the MLP sensor has never been changed and is not the updated one.
 

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Discussion Starter · #4 ·
Sorry for the really long delay in response. Somehow I was not subscribed to my own thread so I was never notified that there was a response and I got busy with other stuff so the van had taken a back burner.

The MLPS would not cause a miss in park.

Why not pull diagnostic codes and see what you get?

How to pull OBD1 codes in your driveway
Ok that rules out the MLPS. I have an Actron code reader and I just go the end to read EEC(?) and the van is throwing no codes at all.

I am starting to suspect the O2 sensor so for the heck of it I disconnected it to see what happened. No codes were thrown and I was getting a voltage reading. Is this normal? Or is the ECM (?), I’m used to GM terms, going?

If it helps any the sort term fuel trim at idle and cruising was really high (rich) i want to say around 11.
 

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Where your throttle body bolts on to intake or plenum there is a gasket that mounts it on.
Sometimes it will come apart in the center and suck air.
 

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I say check your Plugs & Wires they will not throw codes except for a misfire, but age takes a toll even when Mileage is absent. The plugs may have bridge gapped, if deposits from the cyls & heads got to them and /or wires may have gotten moisture laden internally in carbonized linen leads.
Also make sure all your SPOUTS & Plug In connectors are clean & tight. WD40 will get rid of the ambient moisture as it is an anti-dessicant, but be sure to use a dielectric when you put connectors back together to be sure.
When sitting for long "in-op periods", internal deposits can moisten & degenerate which allows them to break loose when engine is refired. Particulates can bridge plug gap causing a miss. The conditions
can be even worse if you are using single platnum or non platnum plugs and/ or very old plug wires.
CIAO
FBp
 

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Either read the instructions that I linked to above for pulling codes, or read the instructions that came with your reader. I like my instructions better.

Before pulling codes you are supposed to check your coolent level, and give a good look for vacuum leaks.
Squirrels, mice and other rodents may have gotten in there and chewed up some vacuum hoses, or dry rot may have settled in.
 
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