Cylinder contribution test 95 PSD?

[cdk4219]

I have a 95 PSD in an F450 that has at least one bad injector in it. The Contribution test always passes, even after 10 consecutive runs, with a definite miss in the engine. When the first part of the test initiates, the test drops one cyl at a time (or so it seems to do that). some cylinders show a drastic change, while one or two show little change at all.

The problem injectors i am looking for, arent totally dead, but miss at idle and under 1800 RPM, especially when hot. I was wondering if anyone knew if the cylinder contribution test was run in any specific order? If it is then I can go after the next injector, or possibly Orings that are bad, by listening to the one that doesnt change as much as the others.

I would assume that in 95 the ECM was new enough that this test wasnt totally de bugged. The only other way that i can think of is puling the valve covers and pulling injector wires one at a time, which I think I did a few years back to find the bad units. This was a messy ordeal as I remember.

[pipelayerjdh]

I'm not sure what order they go in, but here's a bump.

[adfields]

I would think they would go in the firring order. Why would they bother to write new program to test in some other order. But what do I know, it could be 1-2-3, and the programmer never saw a motor. Good luck with this one.

[SCUFFY828]

the cylinder contributiuon test is run 1 2 3 4 5 6 7 8 , not by the firing order ,the easiest but messiest way if you dont have the correct equipment to run a cont. test is to remove one wire a a time to eliminate cyl. like you were saying

[cdk4219]

Thanks for the reply, I will do my best to find the faulty one(s).

[cdk4219]

I actually have 2 scan tools, a Snap on and a Mac (OTC style) which will both perform the cont test. The 95 PCM just wont pick it up, even though the miss is there.

On another note, does anyone know if there is a thread showing the Datastream parameters for the 95 PCM? I think that the truck has been down on power, and I have the ability to check this data, but dont know where the data numbers are supposed to be.

[adfields]

You could try Alldata if you have an account. I was looking for something and came upon a bulletin on bringing all 94/95 pcm's to post 96 values due to rough idle and hard start issues. Sounds like Ford has a CDrom for doing this.

[fordmt]

There was a PCM reflash for the 95 PCM that changed the startegy for the cont test, which gave better results at pinpointing an offending cylinder. If you are passing the cont test, but it only sounds like it is making a single pass, you don't have the update installed. BTW, it runs the test from 1 through 8, not by firing order.

The other possibility is that you have a faulty dual mass flywheel mimicking an engine miss--is your truck a manual trans model?

Mike Cleary
Ford Certified Senior Master Technician and Powerstroke Specialist
Technical Trainer, Automotive Technical Support Services
P.O. Box 27522
Fresno, CA 93729
e: mcleary@atsstraining.com

[cdk4219]

I think that I have seen a sticker by the PCM that has something to do with an upgrade. The dual mass has been taken out, it went quickly with the persistant miss, which took out the pressure plate(loosening the rivets). The single mass works, but accentuates the miss, and it feels like you have a warped flywheel. When the truck is dead cold, the engine is as smooth as could be, this clutch problem is't there.

How can I tell if the PCM has indeed been updated to the newer specs?

[fordmt]

Look up the module ID number with your scan tool. Then let me know what it is and I will follow up.

Mike Cleary
Ford Certified Senior Master Technician and Powerstroke Specialist
Technical Trainer, Automotive Technical Support Services
P.O. Box 27522
Fresno, CA 93729
e: mcleary@atsstraining.com