Here's an over view of this truck and quick history. I bout this truck last summer was an automatic that had split the case and destroyed the transfer case. It is a 95 f150 5.0. I had a 94 long bed with a 302 and 5 speed that had a nasty crack in the frame and could do little to repair it. I swapped out the the auto for the Mazda. The swap was all good for the exception that the 94 ecm would not run the truck. With the 95 ecm it runs fine at idle no engine lights no stored codes.

Now for the pertaining issue, while driving under load (up hill, accelerating quickly, towing) it will hiccup around 2000-2500 rpms. This does not happen all the time like clock work but enough to make your Sunday drive a pain in the ***.

Here's what I have done to attempt to solve the "ghost miss". Fuel pressure is good. Running and at idle so difference when the gauge is connected and is bucking and choking. MAF is tested good. Spark is good wires are good and laid out per Ford decal. No crossfire visible. Properly gapped plugs. Zero exhaust leaks. The intake was pulling 3in vacc. I thought for sure that would be it. The intake manifold had a leak from someone putting longer than stock bolts toward the fire wall so it wasn't sealing the back side of intake. Now pulls 17in from the intake.. problem is still there. No vacuum leaks. Fuel filter is good.

Still scratching my head on this one any suggestions would be greatly appreciated.

 

How did you get your ECM to not show codes when you deleted the automatic?

I see you have a MAF. That explains why the 94 ECM is not running the 95 MAF engine. Is there possibly a lot more pins on the 95 ECM connector? There was an OBDII version as well. They are similar in appearance, but the connector will not fit.

I suspect all this may be relevant because Ford does limit the engine when transmission codes are present in some applications. If Mark Kovalsky answers, I know he can explain much better than I can.

 

Yeah, I'm curious how swapping in the 5 speed hasn't caused a plethora of codes related to the electronic transmission not being there.

Not to mention that without the correct transmission in place, the PCM will default to "Limp" mode in an effort to protect the missing electronic transmission. Hence that would produce driveability problems.

 

Right, so I forgot to include that the EGR and lines are functional as well.

As for the cel it was illuminated for a while with nothing but transmission codes as you can imagine. Also had one for the oxygen sensor. Fixed the o2 sensor harness and ever since the cel never came back on.

So what your saying is find an ECM from a 95 manual 302 with a MAF and plug it in to see if it takes care of the irratic missing?

Same number of pins on both ECMs

 

What condition are the smog(air injection) components in? Is is all still connected and functioning or has it been partially or completely deleted or disabled?

 

They are partially disabled. The smog pump is there. Hooked up to the thermactor. The line coming from the cat is not there to the thermactor. Also I'm not sure where it's supposed to lead to but the larger line looks like a 1" hose coming from the smog pump is cut off 4" from the nipple. Would this cause it to run lean?

 

I saw you said good spark but it sure sounds like a misfire. How old are those plugs and how old are your rotor and cap? Ever look under the hood in the dark?

 

Yup whole distributor is good. No corrosion. Newer plugs that still look good. I did the oil pump a few months ago and did the timing chain while I had it apart. I did check for crossfire but had no idication that it was jumping.

I'm now trying to figure out a part number for the ecm for a 95 MT 302 equipped with the MAF in hopes that it solves the issue. ... Finding the part number itself is proving to be a pain. None of the local salvage yards have anything. The only ones they have are the S/D

 

Normally I wouldn't think it was the computer but these trucks are so old now anything could be wrong.

Have you seen the threads where people resolder the joints in the computer?

How old is the coil? Did you ever look for stray sparks in the dark?

 

The coil is a year old. I put it in with the tune up I did last summer. I also checked it over in complete darkness for any crossfire and saw nothing.

 

What part are you calling the thermactor? There is a crossover tube at the back of the motor connecting ports at the back of the heads into this smog system. The ports in the heads lead directly to the exhaust ports so if any part of the smog system is open to atmosphere fresh air can get in and mess up the O2 sensor readings. You would think this would make the system run rich but it has the opposite effect and makes it run lean and that will make it miss under load.

If you are referring to the air pump intake then no.

 

They are there and intact with no visible or audible leaks

 

They are there with no visual or audible leaks

 

I am not sure what the difference is but the PMC's in the Manual Transmission have a different PCM than the Automatic. I am referring to the 4.9 motor like in my truck so yours may be different but I doubt it. Sandy

 

[QUOTE=Conanski;17385382]What part are you calling the thermactor? There is a crossover tube at the back of the motor connecting ports at the back of the heads into this smog system. The ports in the heads lead directly to the exhaust ports so if any part of the smog system is open to atmosphere fresh air can get in and mess up the O2 sensor readings. You would think this would make the system run rich but it has the opposite effect and makes it run lean and that will make it miss under load.


I certainly don't doubt you but I am curious as to WHY it would run lean. As you said, a novice like me would think just the opposite.