My 1990 F-150 L6 is acting up in a fairly odd way. It starts and runs fine when cold. It also starts and runs fine when hot. When it's in the "middle" temp range (typically between 5-10 minutes of driving), it starts fine, but idles erratically, trying to stall, and when driving under little load (say, maintaining speed on level ground), it starts bucking, as if the fuel or ignition was being erratically interrupted. If I accelerate, it smooths right out. Curiously, if I switch the ignition off/on while underway, the bucking stops. Depending on the temperature, it might come back but often doesn't. "Temperature" seems to be more than just coolant temperature. The cabin temperature also affects the manifestation.

My working theory is that the ECU is acting up, and that a "re-boot" without the load of the starter puts it into a happy state. I'm also pretty sure it's fuel (and not ignition) since the computer only messes with the spark timing while it directly controls the injectors. The bucking is far worse than a timing shift. The problems changed slightly (temperature-wise) when I removed the driver's side kick panel, probably affecting the ECU operating temperature.

Convinced it was the ECU, I took it out and found that it had suffered some corrosion around some component leads and PC board etch. Being an electrical engineer, I found a broken trace on the board, and repaired it. Re-installing, the problem became far less obvious, but still happens over narrower temp ranges. I actually thought it was fixed for a few days.

Convinced it was ECU related, I ordered a F0PF-12A650-VA, but the distributor backed out, saying they don't have one, and won't get them. The repair services will probably barf at seeing my ECU has been DIY-repaired, besides bring out-of-service for weeks of cross country shipping.

Is there any data available comparing the differences between the many ECU part numbers that are more commonly available?
Or is there a junk yard that specializes in ECUs that doesn't show up in a Google search? Ford says they have no records for this era trucks. The engine was rebuilt just a few years ago, so I hate to scrap the thing.

 

Easiest thing to do would be go to a junk yard and get a ECU out of a similar truck or E series van. Put it in and see what happens. Ive went round and round with my ECU. Changed out the caps and had to fix a few traces. Then I found one on eBay for like $40. Which the same one as mine otherwise goes for $299 if you can even find it. Mines a F0TF-12A650-R2A. I never found any information that gives any reference to cross compatibility. If you happen to come across something I'm sure it would help if you could post if you do find it. Good luck

 

O'Rileys has plenty for your truck. Of course they are reconditioned and if you bought from Ford direct theirs would be a rebuilt unit also. The reason I went with O'Riley for mine is not having to ship it to an unknown with unknown delays, warranty etc. With O'Riley I got a year warranty and if mine fails I can get it replaced overnight with no worries. Both I bought were Cardone units and no issues with either one yet. Sandy

 

My advice is to change all the capacitors on the PCB, and go over everything with a magnifying glass checking for corrosion, broken traces, and corroded IC leads.

 

O'reilly's only has the MasterPro brand available, and it claims it "Requires Local Reprogramming" which I have no idea how to do. O'reilly's had a phone number for a transmission shop, but they don't return phone call, so they might be out-of-business. Can someone explain what's involved?

 

You spoke with someone incompetent. They do carry Cardone and those and the Master Pros do not require local programming. Call and speak with the manager or another store. You will need to have one that is for your year and engine. You also must get one that is compatible with your transmission either manual or automatic. Sandy

 

The manager is the one I was dealing with. He was basing it on the counter computer screen. Didn't seem like a very savvy guy, though. I drove 40 miles to get to the store, and the next one is another 50 miles. Argghhh!

 

I always call first for that very reason. Tell me your type of transmission and I will get you the model number of the unit you need. I think AutoZone carries them to if you have one located closer.

 

4sp manual with O/D. The MasterPro is ECC1702. The Cardone would be 78-4843 if it was available.

 

Those numbers appear to be correct . Try this. Call Cardone tech line and ask them which one you need. Call 888-280-TECH (8324) That way you will know for sure from the supplier. Again I like getting mine locally for returns if needed. If you have problems locating a store that is unsure etc. you can get one on Ebay or Amazon, but I like the local aspect, Sandy

 

The F0PF-12A650-VA number you listed is not right for a 1990 4.9L truck.
That should not be a P but should be a T for a truck.
I list no 1990 Truck 4.9L PCM numbers ending in VA, maybe KA?
Was this truck converted to mass air (MAF)?

I would need you calibration number off your door pillar to find out what you need.
Attachment 283763
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Sorry but the ECU number is very readable AND O'Reilly's and Autozone list it as F150 compatible. My calibration number is 0-61E-R02.

 

Ford does not show a calibration number of 0-61E-R02.
But if it was 0-51E-R02 then the PCM part number should be F0PZ-12A650-VA and r/b F0TZ-12A6050-CB and in the right column it shows F0TF-12A650-CB.
This is from parts list #21 that 0-51E-R02 corresponds to.

 

I don't know what to say...

The truck ran fine for the first 20 years we owned it until few years ago. My wife bought it from a dealer, so we don't have any prior history.

 

subford, if you have a minute please tell me why the Cal code is so necessary. What does it contain that is not available from these manufacturers of reconditioned PCM's. They APPEAR to have all the necessary components of your particular vehicle to identify the correct PCM without the code.. Not doubting you just a question. Thanks Sandy