Ok so I got a 92 f150 M5OD 300 I6 2wd SCSB it has 236K miles the only mod done is a the muffler removed and it exits before the tire.


So far the only thing I have done is change the Air control temperature sensor out.


replacing it and cleaning the plugs up helped make it run smooth for a couple days till today on the way home it started spitting and sputtering until I got above 45 MPH it kept doing it. After that it ran perfectly smooth.


I then stopped and turned the truck off for maybe 2 minutes and tried to start it back up and it just cranked and cranked. I then floored the pedal and cranked it and it fired up but barley stayed running I kept revving the engine up till it smoothed out the entire time it was pouring black smoke like a cummins.


I drove it home with no issues 4 miles after that. Right when I got home I put a code reader on it and here are the codes I got:
KOEO:
116 Engine coolant tempature higher or lower then it was suppose to be (temp gauge on the truck doesn't work but the truck isn't overheating or being overcooled)
114 Air control tempature sensor higher or lower (Brand new sensor on it)
522 I believe this is because the neutral safety switch is bad.


Continuous:
113 ACT above
118 ECT above
332 something for egr flow (I just found a vacuum line to the egr purge solenoid off)


KOER-1st time
173 rich 02
332 again
225


KOER-2nd time
311
332 again
225




The second time I did the KOER it had sat about 10 minutes since doing the first one.
Both times I did the tests it was running almost perfect.


It is firing on all 6 cylinders, the vacuum at the FPR is good, no fuel came out of the FPR when I removed the line, Fuel pressure has been tested 3 times now before and after replacing the ACT and all have been within spec and I even checked to wait for a leak down.


I don't know enough about the 300 trucks really to be able to diagnose it.
The PO said he put a new front fuel pump in but it still doesn't work but the rear tank works without a flaw not sure if it matters.


Please tell me where to start this is suppose to be my daily driver while my 88 is down for a High performance transmission rebuild.


Thanks guys
Trav

 

Getting different codes after doing the test, point to erratic PCM behavior.

If it were me, I'd pull the PCM and check the board. I know I mention this a lot, but if new sensors arent fixing the problem, or diagnosing them and replacing if needed doesn't work, PCM is showing signs of capacitor problems.

23+ years are taking a toll on capacitors, especially with voltage spikes and surges. Not to mention the environment, hot, cold, cold, hot....

 

Forgot to mention a couple of vacuum lines were incorrectly routed to the wrong spots Could this be the issue?
The EGR purge valve is one of them the top line goes to the EGR valve but not is wide open on the bottom.
The vapor canister had the line from the coffee can to it and barely. The purge valve for the vapor canister was routed to nothing. Could this be an issue?


I am either way going to put all new vacuum lines on so that I have little chance of any other issues.


Also I never pulled the battery cable off after replacing the sensor should I maybe do that?
If it is the computer will one from a 91 F150 4x4 300 I6 SCSB M5OD work?
If it is the computer those cost the same as my rebuild kit for my C6 in my 88 especially since their isn't many EFI 300s around.
Trav

 

Doing the same KOER test and getting a different code even with the same 2 already tells me something isn't right..

I'd pull it and rule it out. The worst thing Is the electrolyte fluid eats through the traces and ruins it. Best thing, if you pull it and can salvage it if it's not in bad shape.

Your only gonna lose 1/2, 3/4 hour getting it out and inspecting it. So even if its not the problem, you ruled it out.

I only wish I had done it to my '92, 300, 4wd, before it was unsafe to drive, then one day the fuel pump wouldn't shut off. Opened the PCM, and the electrolyte fluid ate through the PCB, destroying the copper traces. That was a $275 mistake... It would have only taken 1/2 hour..

 

Haven't pulled the computer yet only because I didn't know it was such a PITA in the OBS trucks unlike my Bricknose.
I did however wipe the codes then warmed it up and pulled codes again and got:
KOEO:
522 truck not in neutral or park (I am guessing it is a bad neutral safety switch because I can start the truck in any gear).


Continuous:
111


KOER:
116 ECT voltage higher or lower (obviously something in it isn't working if I got no gauge)
173 Rich HEGO/O2 sensor (maybe the EGR causing this?)
332 EGR flow (vacuum line is still off on the EGR parts)
225 Knock sensor not detected (I thought only 302s have knock sensors?? Again don't know 300s enough to tell.


The test was done twice with the same codes.


I am trying to rule everything out before the computer because that thing looks to be extremely hard to pull to possibly find out it is good. I am sorry if it sounds like I am not taking advice when asking for it.
Trav

 

Got rid of the ECT code with a new ECT (stupid masterpro part in it before never buy masterpro electrical parts never had one good one).


Still have 173, 332, and 225. Again can't figure out the 225.


I did new vacuum lines and got them routed correctly plus did a test to see if I was getting vacuum.


I am down to fixing the EGR issue hoping that will fix the run rich code.


I have an extra known working EGR Vacuum solenoid on my 88 I am going to try since I deleted the emissions on my 88.


What is weird is after the new ECT it didn't smell rich and it ran great with no issues at all I left it idling for a good half hour and before I could never leave it idling before it would stumble.


Also I know the Coolant temp sender (not sensor) is bad could this communicate incorrectly with the computer causing a run rich condition?
Trav

 

Ok more updates for y'all


New egr gasket as the old one didn't get replaced when the Previous owner replaced the egr valve.


I also found an open vacuum line that I missed. Fixed that and it ran ok minus still running rich first two times I started then started missing like my moms 5.3L.


So I put a fuel pressure tester on it again just to double check my work and sure enough as soon as I put it to key on engine off it went to 30-35 psi and immediately dropped off to just above 0. Did it 3 times and same thing.

Decided to try it at key on engine running and it went to 40 which is 10 under the limit. Even reving it up it only got to 42.

I am almost sure it is bad injectors (stuck open) or a bad fuel pump.


Figuring injector since it is running rich.
Got one more day off to diagnose weather it is a bad injector mechanically or electriacally (have noid lights).


tryin to fix the truck ASAP since the car I am driving now is fallin apart and I am needing something more reliable.
Trav

 

The fuel pump can supply plenty of fuel even if an injector is stuck partially open IMHO. Pull the plugs and inspect for a fouled plug. If they all look good, it's not an injector bleeding off pressure.

 

3 5 and 6 are all showing carbon build up and slightly fuel soaked. 1,2,4 all look like they are burning perfectly clean like it should.
Trav

 

Cylinders 1,3,5 are batched fired together. 2,4,6 are fired the next round. So perhaps you have more than one injector fouled/stuck.

 

Found the issue out when going to do a noid light test.


3 and 5 are completely fuel soaked so I check out those ones first and sure enough the PO when they rebuilt the engine put 19lb orange injectors in those cylinders and left the 14lbs white injectors in the rest.


I am going to replace all 6 injectors with the correct 14lb injectors.


I did put the noid light on every single one of the plugs and they all worked like they should.


Luckily I was able to move the truck out of my driveway over and get it to where I can work on it once I buy the injectors.
Trav

 

Great find!

 

Well replaced the injectors today with upgraded 4 hole injectors (still 14 lbs) and still have a run rich code.


It runs smoother and fires up like it should but to me still not perfect.


When I first fired her up and let her idle she didn't puff nothing then reved her up to around 3K-4K rpm to see if everything seemed right and it blew a wet black soot all over mom's Chevy Spark. Was a little funny.


After that time it never threw anything out.


Wondering if the 02 sensor is covered in fuel and soot causing a code. I only ran the truck for a couple minutes.


I may replace it anyways since I need to work on the exhaust (cuttin the cats out and sticking in a glass pack since the cats are clogged up I believe.)


It did look like it had leaky injectors especially the 19lbs and the 6th injector.


My time has been limited on working on her between my 88, the weather, and my new promotion at work.
Trav

 

Good progress. I would bet the O2 sensor is gas fouled and/or carboned up. Worth a shot to check it out.

Congrats on the promotion!

 

After running like that, your cylinders and exhaust likely have copious amoumts of carbon/soot buildup that needs to be blown out.

A long high rpm trip down the highway might help. You could also (right aftet the long trip) while its good and hot, remove the air filter tube going to the throttle body, and with the engine running, put a light light spray of water into the intake to steam clean the engine.

A two litre filler with water and a pin ***** near the base spraying water in the TB is a decent way to do it.

Aftet that, another trip down the highway to dry out any water that didnt turn to steam yet.

Good luck! You might not even need the steam treatment if it ckears out on the highway to begin with.