Bad ECM ?

rusty ol ranger · Jul 29, 2018

87 Ranger 2.9.

What are the symptoms of a bad ecm?

I changed everything out in the EGR system trying to get rid of a code 33. Originally i cleaned everything and thought it went away, but it came back.

I swapped over everything from rusty #1s EGR system. Half ass maybe but it ran good....

So i swapped the valve, the black control sensor, and the vaccuum solenoid. It did make an improvement somewhat, but ive had a code 32, a 33, and a 34, that seem to float around. Im also getting a code 41 for a lean O2, that also comes and goes, and sometimes a code 21? Whatever says the coolant sensor is low on voltage, once again, it comes and goes, and every once in a while i get a code 11.

So after all this i swapped out the ignition module, just for shits and giggles, again off rusty #1.

Now, during the KOER test my code reader is showing CM codes, and will not pick up on the number of cylinders of the engine.

Im also getting a high rpm/under load missfire. The low end bogging seems to be somewhat better but its still not like it should be.

Im just wondering if its possible the ECM is junk? I dont understand what the hell else can be doing this.

I miss carburators...

Either way, i need some damn help.

RonD · Jul 29, 2018

Computers are way better that carbs, you would be on your 10th rebuilt carb by now and still chasing problems

Anyway pull out computer and open the top

Should look like this: http://www.auto-diagnostics.info/ford_eec_iv

The 3 Blue capacitors can leak after 20+ years(you are on 30+) so can cause odd issues.
They can be replaced for under $5 if leaks are seen, black area under cap

And generally look around the circuit board for anything unusual.

rusty ol ranger · Jul 29, 2018

Ill do that. The reason im concerned is untill recently i had a water leak that would soak the pass side floor, but im wonderinh if some was dripping in from the computer area. Hopefully the water didnt get into and fry it.

All i gotta do is pull the plastic kick panel and its right there right?

RonD · Jul 29, 2018

Yes, should be behind passenger side kick panel in 1987
Unhook battery first

rusty ol ranger · Jul 29, 2018

RonD said:
Yes, should be behind passenger side kick panel in 1987
Unhook battery first

Copy.

Maybe ill tear into it tomorrow. Theres no difference in computers right? As long as its a 86/87 2.9/5sp im good right?

adsm08 · Jul 29, 2018

86/87 5-speed are all the same. An 88-92 will work, as long as it's not a California computer going into a non-Cali truck, or vice versa, and is an arguable upgrade.

dirtymike · Jul 29, 2018

87 is obd1, 89 is obd2. map to mas

fastpakr · Jul 29, 2018

dirtymike said:
87 is obd1, 89 is obd2. map to mas

OBD2 doesn't occur until 1995, and MAF was only on California ECM's.

adsm08 · Jul 29, 2018

dirtymike said:
87 is obd1, 89 is obd2. map to mas

No. Not even close. So far off that I question if you actually know what all those words mean.

OBDI, or in Ford's proprietary parlance EEC-IV, was used in Ford vehicles until 1994. The earliest appearence of OBDII in full force was 1995. I have seen, in person, a 1992 4.6L T-bird with a functional OBDII port in the glove box, but it also still had the OBDI port under the hood.

MAP (Manifold Absolute Pressure) more commonly called Speed/Density vs MAS (Mass Air Flow Sensor) is not the same as OBD1 vs 2. Both systems of air metering can be found in both control setups. The ONLY 2.9 that ran a MAF sensor was the 1990/91 California emissions. All Ford EFI engines used an S/D system until 1990ish. The 4.0 always used a MAF system from day one. Many other Ford engines were switched around that time. With the rise of EcoBoost it is coming back because it is a simpler way of measuring air in and boost pressure at the same time.

rusty ol ranger · Jul 30, 2018

I was wondering about an 88-92 CPU. Since they dont run an EGR thats why i was wondering if itd work on an EGR truck.

But, that would kill 2 birds with one stone cause i could just delete the EGR.

Either way, itll pry be the ECM from rusty #1 going into it for testing purposes, just to see if anything gets better.

I really dont know where else to go with it.s

adsm08 · Jul 30, 2018

If you have a spare to swap in for testing do it. If it works I'd probably leave it there.

An 88+ would delete the EGR and the knock sensor. You have seen the EGR issues, the knock sensor was a problem because it could be fooled by the 2.9's noisy lifters into thinking the engine was pinging and that would cause the timing to begin to retard for no real reason.

rusty ol ranger · Jul 30, 2018

So i did some further diagnosis today....

Got a fuel pressure tester as well as vaccuum.

According to my fuel pressure gauge i had a steady 40psi with the key off, 45 psi with it running, and stayed pretty steady as i nailed the throttle.

Vaccuum also held steady around 45-50 lbs with normal drops/increases as i goosed and laid off. It wotld drop/rise then come right back.

I took it for a longer drive today (65-70 mi round trip), my fuel mileage seems to be better and no more rich type symptoms. However, im still getting code 18 and 33....and no KOER codes. Not even an 11 and still no readout of number of cylinders.

Its not bogging out as bad coming up hills, and seems to have some mojo back down low, but, im still getting an odd missfire higher in the RPM range. Also if you whind it out, or downshift hard you get a popping thru the exhaust, and when you push the clutch in the engine barely stays running, untill you hit the gas a couple times and it comes back to life.

Now that the rich symptoms seem to be gone im going to go thru and do the plugs/wires/cap/rotor and both fuel filters.

If that doesnt take care of it, is there really anything left besides the ECM?

I havent ran a compression test, but i see no reason for it. Im almost 3000 miles into this change and i was about 3/4qt low on oil (it leaks), and the oil is still pretty damn clean given the age of the motor....

Im open to any and all input at this point.

RonD · Jul 30, 2018

Vacuum in inches?

18"-21" is good at sea level to 2,000ft

Steady is good

Blip throttle, quick drop to 0 then quick return to 18-21 is good

rusty ol ranger · Jul 31, 2018

RonD said:
Vacuum in inches?

18"-21" is good at sea level to 2,000ft

Steady is good

Blip throttle, quick drop to 0 then quick return to 18-21 is good

Guess inches woulda been more helpful eh?

Either way it was in the green "normal motor" band on my tester.

After relooking at the tester i was around 17-19 @idle.

Alao, if it makes any difference we are 915 ft above sea level.

dirtymike · Aug 2, 2018

Yes i understand the acronyms, just the years of production where not clear. Please excuse my error. Dirty

Bad ECM ?

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