Hello All,

I have read these forums for years but, have never posted anything. Except I have this CEL that has been persisting for a year now.

I love my Ranger and have no interest in ever getting rid of it. I will openly admit that although I have a decent mechanical mind and am a certified aircraft mechanic... trucks arent airplanes. What you learn at one school is not directly applicable in a lot of ways. Im learning as I go. I'm also super stubborn. As such, OMG THIS CEL MAKING ME LOSE MY MIND. One way or another I will find this problem. It has to be solvable. But, I'm hoping that maybe someone here might be able to throw out some ideas I have not thought of...

I have a 2004 3.0L Vulcan V6 Ford Ranger with a Manual Transmission w/ (At the beginning) 170,000 Miles on the ODO. About a year ago my brothers car mechanic friend offered to show me how to do a tune up on my truck. We replaced the Fuel Injectors, Spark Plugs + Wires, Ignition Coil, Evap hoses. Him and I pulled off all the connectors, cleaned them with Contact Cleaner, Cleaned the MAF, ext. The engine definitely had much more power.

A few days later I got a P0300, P0301, P0305 code. We look into it. Nothing we did solved it.

I eventually ended up with P0300, P0305, P0301, P0303, P0304 (in that order of regularity)

I noticed that I never got a P0302 or P0306 code ever.

I have never felt any serious stuttering or sputtering or any obviously noticeable difference in my truck. But, these codes come up and only these codes. It does seem to happen at some point after the Emissions Test has completed after a Computer Reset.

The only issue with driving performance I did notice was that there was some extremely light power surging on cold mornings. However, only for a block or 2 and then it went away.

After double checking and triple checking all the work my brothers friend and I had done, nothing seemed to make a difference.

We replaced the O2 sensors. Didn't change anything.

EGR Valve, Didn't Change anything.

We replaced the Camshaft & Crankshaft Position Sensors, didnt change anything.

Checked for vacuum leaks, found one. Fixed it. Didnt change anything.

I take it to the shop my family has taken all their vehicles to for years, very trust worthy. They do good work. They smoke test the vehicle. Nothing.

I try replacing the fuel cap and fuel filter. Doesnt fix anything.

The shop says, "could be the fuel pump". So I buy a fuel pressure gauge. At this point I have also bought the Ford Workshop Manual for my truck. Pressure is within range at all different RPMs. On top of that, I never let my fuel tank go past 1/4 tank and the pump had been replaced maybe 2 years previous.

Shop checks everything I checked, came to the same conclusions I came to.

At this point, they're saying that it could be the compression, valves or timing chain.

My brothers friend and I check the Cylinder Compression. 160 psi average, Cylinder 6 is lowest at 158psi.

I am vague on the exact details at this point but i had 2 shops test the engine to see what condition it was in. Both came back saying the engine was in ok shape but not great shape. Then the question came up as to, was it the timing chain? was it the valves? Maybe the pistons arent great but theyre showing a good static pressure.

So, instead of trying to guess and have my truck in the shop multiple times (at this point i was getting gun shy to this damn CEL) I just had the shop do an Engine swap. I like my truck and I figured, I wanted to do it anyway, now is as good a time as ever.

So they do a full engine swap. Get the truck back, TONS OF POWER. OMG, I am so happy I made that choice.

Then, P0300, P0305, P0301, P0303, P0304. CEL still seems to only occur after the Emissions Check is completed.

So, grumbling and even more gun shy I say F it. Did the research, got the Motorcraft Fuel Sending Unit for my trucks Wheelbase. Had it installed.

Then, P0300, P0305, P0301, P0303, P0304. Except now, it seems to occur far less often.

I replace the EGR Solenoid and Canister. That helped too.

But the CEL still comes on.

I so, I decide to get new Cats. That also reduced the CEL. But, still, Then, P0300, P0305, P0301.

I replace the Throttle Position Sensor. The old one was reading slightly less voltage Closed then the new one.

Now I seem to only bet getting a P0300 and on very rare occasions, a P0303.

So I say, well, if nothing else did it, then it has to be the PCM right? I mean 1-5 and 3-4 are companions on the coil and 2 coils in (OHMs checked) its likely not the coil.

So I replace the PCM. This is the most recent thing I have done.

I have been getting P0300 codes with a P0303 soft code.

Then yesterday I got, something new. I got a P0300 code, a P0920 code a B2ERR (assuming that means its its a B2XXX code that my scanner couldnt read) and a DAT code.

I have no idea what to make of a P0920 code. I know that what it means for a manual transmission is that the Clutch Safety Switch had an open circuit. But, it happened on the same drive & after the P0300 code + I have never ever had one of those before. So I have bought a scanner that can tell me what the B2ERR code is about so I can see if it ties the P0300 and P0920 codes together and make sense of that.

As far as repeatability, I began working for JPL and on my way home there is a steep hill on the freeway where I can throw my truck into neutral and coast down the hill doing 70. On multiple occasions, I have instantly thrown a CEL light as soon as I throw the truck back into Fifth. It also seems to happen when my A/C Unit (Cus of defrost) and its cold outside.

So at this point im wondering, maybe throttle body? LOL maybe a $4 spring? Im sure itll be something stupid simple. Why the P0920 code? I read in 1 place that possibly the connector for my instrument panel being wonky could cause issues but I cant verify the possibility of that until my wiring diagram book arrives.

Anyway, thats my insane, probably self induced sob story. Yes, I know I'm insane...

I have had 6 mechanics attempt to solve the problem over the course of this. Obviously nothing panned out.

If anyone has the slightest clue where I MIGHT possibly put my attention that would be extremely helpful.

 

Welcome to the forum

Was it a new rebuilt engine or a used engine?
If used what year was it from?

2004-2006 3.0l engine can have valve seat issues, there is a TSB for it, codes, 300 to 306 plus 316 will show up, TSB here: https://www.tsbsearch.com/Ford/05-26-3

DTC codes P0xxx are generic, used in all OBD2 compliant vehicles since 1996, not manufacturer specific, all vehicle makers are required to use these and their definitions
P1xxx codes are Ford, GM, Audi, ect............specific, vehicle makers assign their own definitions to these

P0920 is not a Ranger code as it doesn't have a separate Transmission Control Module(TCM), even with an automatic
So not sure what your OBD2 reader is seeing or why the computer would generate a code like that
And manual transmissions don't have any "monitor" sensors, just an OSS(speed) sensor
Clutch switch couldn't generate such a code, it can do P1135 Pedal Position Sensor A Circuit Intermittent

Bxxxx codes are Body codes, in a 2004 these would be generated by the SJB(body computer) or the Digital Dash(HEC), wouldn't effect engine operation, includes restraint(SRS) systems

Cxxx codes are Chassis codes usually ABS related
Uxxx codes are Network codes, communication between modules

P0316 is usually set if there are misfires only on startup
P0300 means random misfires after startup
Both of these, and the specific cylinder misfire codes, are generated by the Cam Sensor
Cam sensor spins at 1/2 the RPM of the engine, so has better resolution than the Crank sensor but both can be used in misfire detection
When a cylinder fires it adds power to the cranks "spin" and cam, when a cylinder doesn't fire then spin slows, its all just millisecond timing, cam sensor can detect if its repeated at the same "time" every 2 RPM so can ID which cylinder is misfiring
In the case of P0300 and P0316 there is no steady "repeat"

Cam sensors are not infallible, lol, and the 3.0l Cam synchro needs to be swapped out every 80k miles or so because the bushings wear out, failing bushings can cause P0300 and P0316
So do you FEEL the misfires when going up hills?
Are they real?


And just FYI, one of the benefits of fuel injection is that the injectors can be shut off while coasting, one reason fuel injection is more fuel efficient
So when coasting in gear, foot off the gas pedal, throttle sensor under 1volt, and engine RPMs above 1,400 the computer will shut off fuel injectors to save fuel, it will add fuel now and then to keep Cats hot but otherwise 0 fuel use
So don't coast in neutral, a waste of fuel especially on a longer down hill grade, also better for the brakes, use the engine as the brake to keep speed in range, lol
Under 1,4000rpm computer will restart injectors at idle levels

 

Thank you so much for the reply!

So, for the new engine, It is a remachined, rebuilt engine. I'm not sure what year it is. However if the TSB includes misfires on all cylinders then and misfires before 1000 Rotations then it its likely not the problem. I do NOT get misfires on cylinder 2 or cylinder 6 (P0302 & P0306).

The lack of misfires on Cylinder 2 or 6 was common between both the OLD and NEW engine. In fact, I have 25 pages of printed Freeze Frames that I went through BEFORE deciding to do an engine swap. None of the 25 pages show a single misfire on Cylinders 2 or 6. Before I replaced my engine I was told by one of the mechanics that their scanner was in fact showing misfires on cylinders 2 and 6. However, these misfires never threw any codes, soft or hard.

The codes that I would get, In order of regularity were,

P0300 Multiple Random Misfire
P0305 Cylinder 5 (Coil 1)
P0301 Cylinder 1 (Coil 1)
P0303 Cylinder 3 (Coil 2)
P0304 Cylinder 4 (Coil 2)

On the cold morning when I would get light Power Surging for about 2 blocks, maybe 1/3rd of the time I would also get a P0316 Misfires Within 1000 Rotations. This code began to show up a few months in to this CEL light coming on.

I have been asked by multiple people, "do you feel misfires? are they actually happening?" As far as I know, NO. I never feel misfires. My CEL never blinks. Not on the old engine, not on the new engine.
But, then I was also told that "you might not feel the misfires" so I don't know.

I originally assumed that this meant that the problem was some where in the Ignition System. I replaced the Coil Pack and compared the new coil pack resistance to the old coil pack resistance. They were the same.

I checked the spark plugs, they seemed fine. I checked the plug wires to make sure they were seated well.

I was thinking that maybe the problem was the PCM or the Coilpack Connector. I was assured by multiple people that the PCM is almost never the issue and they also felt the coil connector looked ok (Im still not so sure and am going to replace the connector). Eventually I replaced the Injectors again just to verify that the problem wasn't injectors even though it didn't make sense to me. No one seemed to give any notice to my observation that the misfires seemed to be on the same 2 coils and only ever on those coils.

My friends Dad built racing engines for 30 years before he switched careers and became a pilot. He showed me how to check the Camshaft Synchro to see if the bearings were going. He felt that my synchro was in great shape. No wobble on the shaft. He is also one of the people I consulted. Albeit one of the people I consult more rarely. He is over building engines and his opinion is, "If you put your body on a new chassis, you can just say that its the same vehicle"

The 1-5 3-4 misfires wouldn't go away. I bought new OEM seals for the intake manifold just to make sure it wasn't a Vacuum Leak. I did everything I was told to do by other people. Finally, the various people I talked to plus the 2 mechanic shops I went to agreed that at 170k Miles it was probably something in the Engine.

I printed out the 25 Freeze Frames I had to Show & Tell what I had noticed. No one seemed to think anything of it.

So I get the new Engine. The same misfires continued on the same cylinders. 1-5 3-4. So then I'm really convinced that its the PCM. But once again I'm convinced by others that its really not likely that it is the PCM. So I replace everything else I could think of related to the Powertrain.

When I had the Fuel Pump assembly replace I finally saw a difference in the frequency of the CEL lights.

When I replaced the EGR Solenoid and Canister the CEL became even more rare. But, still in the background I would have soft codes for cylinders 1-5 3-4 and would eventually turn in to hard codes.

So then I'm thinking that I'm nearly to the bottom of the normal list of possibilities. If it has been the Cats all along I could be damaging my brand new engine (even though they were checked and declared ok).

So I buy new Flow Master Cats, I install those my self. Torqued everything to spec. Engine had Noticeably more power.

After I replace the Cats, Now only Hard Codes for P0300 Multiple Random Misfires come up + rare soft codes for Cylinder 3 Misfire and on very rare occasions the P0303 turns hard.

So I replaced the PCM and Throttle Position Sensor. No change.

However, I don't think I fixed my original problem. There is always the possibility that I had multiple problems. But I feel like what I have really done is muffle the original problem because everything is new and running like new.

I have noticed after installing the new Throttle Position Sensor that my Throttle Position when my Engine is off is 17.65% but rose to 18.04% when I turned my engine on. I don't know if that is normal or a sign of a weak butterfly return spring.

If you or anyone else run dry on ideas it'll just be par for the course. But I deeply appreciate the attempt.



P.S. when I throw my truck into Neutral its just so I don't have the slight engine back pressure slowing me down. I can coast at exactly 70 in neutral but ill slow down to 60 if my clutch is engaged and then the crazy drivers get angry and tailgate me. I can usually just coast until I get to the bottom of the hill and my speed slows down to 55. Then I throw it back into fifth (smoothly) and keep on truckin. I WILL totally take your advice and just leave it in gear. However, throwing the truck into neutral is something i have always done with my truck and never got check engine lights. Essentially What I'm trying to say is advice taken but one way or another I shouldn't get a code by doing it.

 

You WILL feel misfires, especially when going up hill, yes flashing CEL is a hard misfire

System voltage engine off is 12.3 to 12.8volts, battery volts
Engine running is 13.5v to 14.8volts, alternator voltage
So there can/will be differences in readings with engine off or running because of voltage differences

TPS is a 5volt sensor, like most
expected closed throttle voltage is 0.69 to 0.99volt, under 1 volt, 1volt is 20% of 5volts, so throttle closed should be just under 20%
Wide open voltage is 4.5volts, 90% of 5volt

 

Good to know.

So yeah, I don't ever feel misfiring then. I just get codes for misfires.

Long shot, is it possible that I'm getting a vacuum leak through one of my A/C Vacuum Motors? The highest vacuum i get is -13.5 and I have seen it go positive when I accelerate. I have read that some people are getting -18 Hg. I think mine is -11.4 at Idle. Thing is I have checked for vacuum leaks all over and done it multiple times. I also replaced the PCV with the engine.

Or maybe a slight flutter in the Throttle Body? Something that the PCM would see but I would not?

I'm just shooting in the dark. But I'm running out of ideas.

 

Any chance your vacuum gauge is inaccurate?

In Burbank you're less than 2000' elevation, you should be 18- 20hg at idle.

I would think that big of vacuum leak would affect all cylinders.

Another possible big vacuum leak is your power brake booster.

 

Where does the vehicle take its vacuum reading from? Those numbers are based on data I get from the PCM.

I do know that when my original engine was Smoke Tested I was told that the leakiest part of my vehicle was the throttle body. But they didnt seem to think that it was leaking enough to cause a problem.

I pulled off the hose to the brake booster and plugged it with my thumb. There was no change in pressure. Ill see if maybe theres a leak in my A/C system vacuum or my throttle body.

I feel like there is a chance that maybe the PCM channels that control coil 1 and coil 2 have a minor wiring issue. Then if there was a vacuum leak they would be more easily effected.

I'm still guessing. Should I buy a vacuum gauge and check that way?

With my luck the pressure would come back @ -19 Hg

 

Yes, buy a vacuum gauge, $15, good tool to have

There is no vacuum sensor

 

Alright, Ill get that ordered and see what I find.

 

So, I'm still waiting on my Vacuum gauge so I can get in top of testing my system.

However, just an update, I did change out my Throttle Body Return Spring and now when my engine is ON the Throttle Body Position Sensor reads 17.65% open instead of 18.04%.

I have no delusions that this was my problem. I have no doubt that something else is causing my problems. But I did bring this up in previous threads and so I thought I'd mention my findings.

 

Anything above 15% and below 20% is fine with throttle close

 

Understood. I'll see what the vacuum test comes back with.

 

I'm getting 18 Hg at idle. And 15 - 16 when I rev the engine.

Im going going to replace the Coilpack connector and see what happens.

 

Replaced my Coilpack sensor, went for a 2 1/2 hour drive. Got hard does for 1,3,4 & 5 + multiple random misfires. Same as always.

No cylinder 2 no cylinder 6.

So weird.

 

So its most likely down to the 1/5 and 3/4 coil drivers in the computer(PCM), but very unusual failure

V6 PCM has 3 coil "transistors"(drivers), 1/5, 3/4 and 2/6
They ground and unground(fire) each of the 3 coils in the V6 coil pack

You can remove the PCM connector and test each of the 3 ground wires to coil pack, if they test OK then problem is inside the PCM

 

I'll do that. I'm just sort of iffy about about the result as this is my second PCM that is throwing these codes as well as my second new coilpack.

I replaced the connector hoping it would be 2 bad ground wires at the connector. Ill do a resistance check of the grounds wires.

I had Originally assumed that it was probably a transistor problem. When I replaced my PCM recently I did it assuming that would fix it. But now I feel like the problem might be in the main connector for my Powertrain Wiring Harness

I was really hoping it wasnt that 😞

Other then the hard codes the vehicle had no signs of a problem at all over the 2.5 hours. Nothing.

 

Then its the wires

 

If it is a high resistance in my Powertrain Harness Connector, any tips of the trade that I could maybe use so I don't have to replace the entire Socket?

Could i just shoot some solder in the back of the connection and cross my fingers or something crazy like that?

 

Unhook one battery cable
Pull off PCM connector
Hook battery back up
Turn on the key
Test battery voltage at the battery, key on
Test each of the 3 coil pack wires at the PCM connector, each should show Battery voltage exactly, 1/5 wire would be the comparison wire the other two should match

You can re-pin the 2 wires, you just need a small screw driver or paper clip to release a pin and it pulls out of the connector
Or run 2 new wires, re-pin at both ends

Google: Re-pin Ford connector
Several videos and how-tos for all the Ford connector types, its not hard once you see it being done



And just to confirm, you can FEEL the misfires, they are not false codes?

 

I never feel misfire. I drove for 2-1/2 hours and my truck was quick. I put it through paces.

didnt give me a code for 1-1/2 hours. Maybe more.

I was half way home when i got a code.

I know Rangers were never power houses. But right now, my truck is the most powerful it has ever been. Even before i got these codes. In fact based on how I shift up hill, its way more powerful.

It FEELS like its amazing. Then a check engine light turns on.

When I go to turn it on, I turn the key and its on. No stutter, no shutter. Its just key turned, engine is on. Thats the best i can explain it.

I love my truck, its not just a thing to me. Its MY truck. As far as im concerned the condition of my truck is a reflection of me as a mechanically inclined person.

Im kinda l.. crazy, granted. Sorry, thank you for allowing me that.

If its the wiring, ill redo it. I don't care. But, I have to know the problem. It keeps me awake at night.

based on your explanation, I drove for almost 3 solid hours on a vehicle that FEELS new. Up hill, down hill, from 60mph to 90(flow of traffic) the truck was amazing to drive. Then i throw a code and my heart sinks.

 

Then you don't have actual misfires

Cam sensor issue maybe, false data

 

Ok, so i replaced my Camshaft Synchronizer. It had a tad bit of wobble. But, went for another 2 hour drive and same codes.

checked the coil ground wires resistance from the coil connector to the PCM connector. Highest resistance was 6 ohms and that 6 ohms was to the coil responsible for firing 2 and 6.

Not sure where to go from here.


Also, im a bit confused. The Ford Wiring Manual says the camshaft position sensor is only responsible for telling the PCM which cylinder its on.

The PCM Manual says that basically the crankshaft position sensor is the heavy hitter when it comes to Misfire detection. Only real reference to the Camshaft Position Sensor is a misfire will be thrown when the CMP & CKP dont agree on timing.

i did notice a high long trim of +15 after resetting my PCM KAM. Is that just cus i reset learned memory?

I know on average the Long Trim adjust is usually +10 and +8 at idle. Seems a bit high. They are new Motorcraft Injectors. Less then a year old.

Im sort of reaching at this point but idk where to look. Questioning everything now. Ive been looking for an issue that would effect only cylinders 1345 but everything they have in common seems to be ok.