New ECU still runs rough

[410Fortune]

Your 93 has no EGR and no CAM sensor correct?
CA trucks in 93 did have a cam sensor and EGR

Any loss of coolant?

A leaky EGR system can cause you fits like this, the miss will only occur when the EGR opens

a 93 OHV likely needs new lower intake and upper intake gaskets.

 

[92exp4x4]

I'm starting to suspect 02 sensors or the injectors, I believe it's running rich the exaust

Very true ik the modulator has to be good it was replaced again when the transmission was rebuilt, I need more equipment to run tests my self I feel as shops I've taken it to do a terrible job when I took it to have some vacuum lines replaced today they somehow managed to break various clips holding wires down in the engine, and most shops want nothing to do with it for some reason I've called around for ends and odds of things to be replaced on it and they try to say no parts are still in being made for this vehicle which is BS and when I offer to supply the parts they tell me they can only supply parts,

Yeah, most shops are flat rate, and most mechanics are not diagnosticians. OBD1 vehicles are nearly as alien a form of vehicle as something with points ignition in todays repair environment. If the scanner can't tell you what to replace, they don't want anything to do with it.

I'm not taking anything away from the people running the shops or wrenching in today's shops, but the vehicle systems today are about smart enough to diagnose themselves. Its almost to the point where a mechanic is more of a parts replacer than a troubleshooter most of the time. With older systems, the computer is pretty dumb. The tech has to fill in the blanks and actually troubleshoot a problem. A code could have multiple root causes and because the feedback circuitry is minimal or non existent compared to today's systems, one would have to narrow down those multiple causes. Because of this it takes more time; more time = more money, that can't always be justified to the customer. Just diagnosing a repair could be more than the value of the vehicle. If it's not quick and easy, they don't want anything to do with it. Most people won't put $3000 in a $2500 vehicle. They don't see the value.

I can't imagine how many vehicles are junked because of a non obvious simple problem, that is expensive to troubleshoot. The company I work for has a labor rate of nearly $150/hr. The troubleshooting costs can add up quickly.

 

[92exp4x4]

Also, the O2 sensor is the most quickly replaced but incorrectly diagnosed component. Its a perfect example of mis interpreted code meanings. If the truck is running rich, it may throw that code. Unless one stops to think about what its telling you, the root cause can be easily overlooked and now a mis diagnosis is the result.

If the intake is leaking air beyond the MAF, the system will interpret this as a lean condition and will richen the mixture to compensate. It cannot monitor air taken in past the MAF because the system assumes a perfect seal beyond that point. When the leak gets worse = more air, then it will compensate again. The O2 sensor is giving feedback of current conditions and eventually the system will reach its compensation limit and set an O2 code for system being too rich, or too much compensation to be within allowable limits.

It can only electrically monitor the sensor, it cannot detect or monitor vacuum leaks. Its just not complex enough to do that. Therefore it tells us it has a feedback error. The result is an O2 being replaced for doing its job and the code coming back later.

I agree with 410's comment. I think you have unmonitored air getting in or too much fuel being delivered. Vacuum leaks or dribbling fuel injectors. If you have a fuel pressure gauge, install it and turn the key on. See how long it takes for fuel pressure to bleed off after turning off the key. It really shouldn't loose any pressure within about 30 minutes. If it drops off quickly, you've got something leaking off. Lower intake manifold gaskets are a common fail point on these engines for vacuum leaks.

 

[Nadams01]

Yeah, most shops are flat rate, and most mechanics are not diagnosticians. OBD1 vehicles are nearly as alien a form of vehicle as something with points ignition in todays repair environment. If the scanner can't tell you what to replace, they don't want anything to do with it.

I'm not taking anything away from the people running the shops or wrenching in today's shops, but the vehicle systems today are about smart enough to diagnose themselves. Its almost to the point where a mechanic is more of a parts replacer than a troubleshooter most of the time. With older systems, the computer is pretty dumb. The tech has to fill in the blanks and actually troubleshoot a problem. A code could have multiple root causes and because the feedback circuitry is minimal or non existent compared to today's systems, one would have to narrow down those multiple causes. Because of this it takes more time; more time = more money, that can't always be justified to the customer. Just diagnosing a repair could be more than the value of the vehicle. If it's not quick and easy, they don't want anything to do with it. Most people won't put $3000 in a $2500 vehicle. They don't see the value.

I can't imagine how many vehicles are junked because of a non obvious simple problem, that is expensive to troubleshoot. The company I work for has a labor rate of nearly $150/hr. The troubleshooting costs can add up quickly.

The OBD1 system for ford is actually a lot more complicated then OBD 2. as previously stated the ECU follows a pre set planned directory essentially with if then choices. Let's say you start the truck Cold and let it idle. The ECU sees you are not driving and wants the motor to heat up as fast as possible. If you drive it cold it sees this and goes to a then plan and then more and more and more options pre programmed in the ECU itself. This differs from OBD2 because OBD2 can communicate across modules and essentially run based off of a base plan and sensors giving it information instead of having a if then decision route like fords. This means certain sensors like for example BARO are not giving the pcm information untill it is needed for a chosen if then tree so you might not being told what is making the pcm mad because it's only being read occasionally. To access all codes you have to pass a koeo with code 11. Then pass a cylinder balance test wiggle test then you can do a koer check. If at any times these tests fail it means it is popping a fault during that test. That's why shops charge so much for OBD1 diags, at least for ford. A good scan tool for this is a Innova with ovd1 support. I use it at my shop to do OBD1 diag and it's about 300 bucks. I would say it's worth running through all these checks before throwing any more parts at it. Also check primary ohms and secondary ohms on your ignition coil.

 

[410Fortune]

See how long it takes for fuel pressure to bleed off after turning off the key. It really shouldn't loose any pressure within about 30 minutes

excellent responses dudes

Is the little orange "sock" on the end of our fuel return line (in the tank) the only thing that is keeping the fuel pressure for that 30 minutes?
Or is it the vacuum regulator? or both?

 

[92exp4x4]

excellent responses dudes

Is the little orange "sock" on the end of our fuel return line (in the tank) the only thing that is keeping the fuel pressure for that 30 minutes?
Or is it the vacuum regulator? or both?

System pressure is held by the pressure regulator, injectors, and check valves in the system, more than likely in the pump. The sock I think you're referencing, probably just keeps the fuel from back feeding through the return if that line is opened for service. The sock on the intake side in the tank is just a pre filter screen to keep big particles put of the pump itself.

 

[410Fortune]

check valves? I can see the injectors and pressure regulator I do not see check valves?

the "orange" plastic thing I reference is in the tank but it is not part of the pump, it is clamped to the end of the return line with a green clamp, and I think like you said it is there to keep the return fuel in the line.
Mine was torn years ago and then removed, has had no effect on my 5.0 engine in 15 years now.

I am aware of the pumps strainer LOL LOL you're silly

 

[92exp4x4]

check valves? I can see the injectors and pressure regulator I do not see check valves?

the "orange" plastic thing I reference is in the tank but it is not part of the pump, it is clamped to the end of the return line with a green clamp, and I think like you said it is there to keep the return fuel in the line.
Mine was torn years ago and then removed, has had no effect on my 5.0 engine in 15 years now.

View attachment 422598

I am aware of the pumps strainer LOL LOL you're silly

The check valve is probably a ball and seat made into the pump itself. I've not ever taken one apart to see. It could also be a reed style valve. That picture doesn't show the actual pump itself, just the sending unit. The pressure regulator is on the fuel rail at the engine. The in tank assembly does not include a regulator on it, at least in this application.

The little orange silicone deal on the return tube is just an anti siphon valve. Theoretically if the line was open and left below the tank level, it would siphon the fluid out of the tank. That would be no fun left overnight in a closed shop.

I had a tech do this in our shop once. He left a hydraulic return line open from a removed component from the forklift he was working on. He didn't tie it up or plug it. It slipped from its hanging point and dropped below the tank level. That particular line tied into the main return. Overnight it emptied the 40 gallon hydraulic oil tank onto the floor. It made one hell of a mess.

 

[92exp4x4]

check valves? I can see the injectors and pressure regulator I do not see check valves?

the "orange" plastic thing I reference is in the tank but it is not part of the pump, it is clamped to the end of the return line with a green clamp, and I think like you said it is there to keep the return fuel in the line.
Mine was torn years ago and then removed, has had no effect on my 5.0 engine in 15 years now.

View attachment 422598

I am aware of the pumps strainer LOL LOL you're silly

The check valve is probably a ball and seat made into the pump itself. I've not ever taken one apart to see. It could also be a reed style valve. That picture doesn't show the actual pump itself, just the sending unit. The pressure regulator is on the fuel rail at the engine. The in tank assembly does not include a regulator on it, at least in this application.

The little orange silicone deal on the return tube is just an anti siphon valve. Theoretically if the line was open and left below the tank level, it would siphon the fluid out of the tank. That would be no fun left overnight in a closed shop.

I had a tech do this in our shop once. He left a hydraulic return line open from a removed component from the forklift he was working on. He didn't tie it up or plug it. It slipped from its hanging point and dropped below the tank level. That particular line tied into the main return. Overnight it emptied the 40 gallon hydraulic oil tank onto the floor. It made one hell of a mess.

 

[410Fortune]

40 gallon!!!!!!! Oh man I know when I spilled 6 quarts of mercon V on the shop floor it took every rag we had for 3 miles to contain that spill....that floor is still slippery when wet!!! HAHAHAHA Thanks for the lesson on the anti siphon valve, I have heard that before now that you mentioned it!

 

[92exp4x4]

40 gallon!!!!!!! Oh man I know when I spilled 6 quarts of mercon V on the shop floor it took every rag we had for 3 miles to contain that spill....that floor is still slippery when wet!!! HAHAHAHA Thanks for the lesson on the anti siphon valve, I have heard that before now that you mentioned it!

Oh man it was bad! We cleaned the floor for two days straight. For months afterwards oil would seep up from the cracks. It just had to be one of the largest machine too. A CAT GC70K. Its a 15.5K capacity machine. Much larger than your standard warehouse lift truck.

 

[RADIOACTIVE_TOOL_SHED___]

Your 93 has no EGR and no CAM sensor correct?
CA trucks in 93 did have a cam sensor and EGR

Any loss of coolant?

A leaky EGR system can cause you fits like this, the miss will only occur when the EGR opens

a 93 OHV likely needs new lower intake and upper intake gaskets.

No cam sensor and no EGR, Im fairly certain that the intake gaskets are factory they're the green ones

 

[410Fortune]

any loss of coolant?
Its a good idea to pull the spark plugs and have a look at them, may give you an idea of which cylinder(s) are having the issue and can tell what the issue is

 

[92exp4x4]

No cam sensor and no EGR, Im fairly certain that the intake gaskets are factory they're the green ones

It would be worth a reseal. Check the entire air intake system for any possibility of leakage. Any point past the MAF. Even the plastic intake tube. They can crack on the bottom where it attaches to the throttle body. I've got at least one tube wrapped in electrical tape right now for this reason. Does the truck "ping" or spark knock under load or heavy acceleration?

 

[RADIOACTIVE_TOOL_SHED___]

It would be worth a reseal. Check the entire air intake system for any possibility of leakage. Any point past the MAF. Even the plastic intake tube. They can crack on the bottom where it attaches to the throttle body. I've got at least one tube wrapped in electrical tape right now for this reason. Does the truck "ping" or spark knock under load or heavy acceleration?

No pinging or spark knock I actually had the firing order wrong, fixed that no change in idle, I'm going to be doing upper and lower intake gaskets and all 6 fuel injectors

 

[RADIOACTIVE_TOOL_SHED___]

any loss of coolant?
Its a good idea to pull the spark plugs and have a look at them, may give you an idea of which cylinder(s) are having the issue and can tell what the issue is

No loss of coolant, I've already pulled the plugs none of them are fouled or steam cleaned,

 

[410Fortune]

with new plenum gaskets, new injectors with new O rings, I bet she smooths out
When you get to the lower intake gasket take a look at what you see. Usually its pretty obvious where the gasket failed
Installing the new lower intake gasket, there are a couple of little tricks to know to get it done properly, there are 4 spots that need a little RTV to make sure its all sealed up

 

[Nadams01]

No pinging or spark knock I actually had the firing order wrong, fixed that no change in idle, I'm going to be doing upper and lower intake gaskets and all 6 fuel injectors

You had the firing order wrong and it didn't change the idle? The coil from left to write back to front is 123 465 I believe. If you had it wrong it would run like absolute garbage.

 

[410Fortune]

Not always, remember these are waste spark ignitions. The coils send spark in pairs, one plug is firing on exhaust stroke while the other is firing on compression stroke. Hence the term "waste spark DIS ignition"

So sometimes the firing order will cause huge issues and sometimes it will be a small misfire if you do not get it right.......
If your engine is already misfiring, well then messing up the firing order slightly can just add fuel to the fire......meaning no change in how it runs visually, but you are compounding issues

 

[Abramwithda1991fourdoor]

No loss of coolant, I've already pulled the plugs none of them are fouled or steam cleaned,

Hey dont know if the truck will even run with maf sensor unplugged but if you might suspect it I would try unplugging it and starting it. Also you can do the same thing with the iac. I had an inline six in an f150 and I think that is a way do rule out the iac