False Engine Codes?

2004 Ford Ranger 3.0L v6

Okay, so I just recently dropped in a new factory short block. Forked out the dough and just did the whole motor myself. Previous motor was misfiring like a mofo, compression was low, and she had 120k on her.

Dropped in the new motor, new ported heads (one old one was cracked), ported the stock exhaust manifolds, replaced pretty much every part on the engine.

After about a month, I am now getting P0305 and occasionally P0303. The plugs were new (all are within gap spec, all burning as should), plug wires are fairly new (replaced right before motor swap), and the coil pack has been replaced. Now, the trick. I'm getting the check engine light for those codes, and its flashing. But its only when im doing 50mph+. I don't get it on street speeds or idle. Feels like its running fine?

I've been chasing these misfire codes since before the motor swap, but before my swap, it was at idle. Now its at 50mph+. Any suggestions? First hand experience? Since I had a thread going, whats the best way to check for a vacuum leak? My AC is only blowing out of my defrosters. Whats the best way to pinpoint the leak?

Thanks,
Joey

Smoke is the best way to pinpoint a vac leak. Can be hard to do without the machine though.

As for your codes, did you have the heads decked? How sure are you that your port/polish job was evenly done on all cylinders?

After a certain year, and I don't remember the exact year, Ford says don't port, don't polish, don't machine a warped head, because the misfire monitor is too sensitive and even a variation of a few thousandths on the deck height from one side to the other will cause misfire codes even if it isn't actually missing. I doubt that is the problem since your concern affects both sides of the engine.


I have also seen clogged cats cause your issue, flashing CEL, misfire codes, when loaded up, like highway or uphill, but I didn't feel the miss.

Flashing CEL means severe misfire, "get it checked soon"

You don't hear any pinging I assume or you would mention it, pinging and knocking can be picked up as a misfire, and really are misfires.

Computer picks up misfires in two ways, for the P030X it is the Crank(CKP) sensor.
Computer reads the "teeth" on the crank sensor gear by the crank sensor sending a pulse when each tooth passes by it, one tooth is wider(or missing), that is TDC for #1 so the computer knows #1 TDC and from the Cam position sensor(CPS) it knows which cylinder should be on its power stroke.
The computer calculates and expects, say the #3 cylinder to fire and then it should see the next tooth within say 10 milliseconds, based on throttle position and RPM at that time, if crank doesn't speed up or stay the same the computer knows the #3 cylinder didn't add power to the crankshaft spin, so must have misfired, and it will set a code, but not flash.
If there are several misfires the CEL will flash because the unburnt fuel will damage the Cat converter.

Since your problem is #5 and #3, and you don't "feel" a misfire it could be the porting as adsm08 said.

Second misfire detection comes from coil feed back but that would cause different codes

Still using stock fuel injectors, and the stock PCM tuning? Does the problem occur while accelerating up to speeds over 50, or while maintaining speeds over 50 like a long highway cruise?

I'm going to agree with the other guys here and say that the porting may be the likely culprit, depending on how extreme the port work is. You've increased the airflow into the combustion chamber with your porting, but you haven't increased your fueling to compensate according to your post. Maybe it's going lean at higher speeds because your fuel injectors, or the factory PCM tune can't keep up with your new fueling needs?


It's unusual for some simple porting to cause this big of an issue though. I've seen guys run much higher valve lift by using higher ratio rocker arms and they haven't been running out of fuel with the factory injectors and PCM calibration. Have you checked the entire fuel system? Fuel filter? Fuel pump?

adsm08 said:

Smoke is the best way to pinpoint a vac leak. Can be hard to do without the machine though.

As for your codes, did you have the heads decked? How sure are you that your port/polish job was evenly done on all cylinders?

After a certain year, and I don't remember the exact year, Ford says don't port, don't polish, don't machine a warped head, because the misfire monitor is too sensitive and even a variation of a few thousandths on the deck height from one side to the other will cause misfire codes even if it isn't actually missing. I doubt that is the problem since your concern affects both sides of the engine.


I have also seen clogged cats cause your issue, flashing CEL, misfire codes, when loaded up, like highway or uphill, but I didn't feel the miss.

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All that was done for the portin was the sharp edges rounded, etc. nothing was opened up besides the exhaust manifolds. The believe the heads got decked .001. Just weird that I'm just now seeing these codes about 2 months after the engine was dropped in. The cats sound like a probable cause. Things look beat.

stmitch said:

Still using stock fuel injectors, and the stock PCM tuning? Does the problem occur while accelerating up to speeds over 50, or while maintaining speeds over 50 like a long highway cruise?

I'm going to agree with the other guys here and say that the porting may be the likely culprit, depending on how extreme the port work is. You've increased the airflow into the combustion chamber with your porting, but you haven't increased your fueling to compensate according to your post. Maybe it's going lean at higher speeds because your fuel injectors, or the factory PCM tune can't keep up with your new fueling needs?


It's unusual for some simple porting to cause this big of an issue though. I've seen guys run much higher valve lift by using higher ratio rocker arms and they haven't been running out of fuel with the factory injectors and PCM calibration. Have you checked the entire fuel system? Fuel filter? Fuel pump?

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I am running the stock fuel injectors. I do have a super chips programmer but it does it no matter which tune is used, also stock. Fuel filter is 2 months old and never seemed to have a problem with the fuel pump. I only run 91 in my truck also.

Do you have access to a dyno shop? If you can run simulation of running conditions that create codes that would help with diagnosis. Using scope and CO monitor can tell a lot about how an engine is operating.

Rearanger said:

Do you have access to a dyno shop? If you can run simulation of running conditions that create codes that would help with diagnosis. Using scope and CO monitor can tell a lot about how an engine is operating.

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I might have one local. Haven't really thought of that. Any idea what that would run? Almost ready to sell this and get a tundra.

Olsin6 said:

Any idea what that would run?

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Not a clue, but it might be cheaper and less hassle than replacing parts just to see.

Almost ready to sell this and get a tundra.

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I've regretted getting a Ranger a number of times over Toyo. At the time the Ranger had the build I wanted and was at least $3000 less money. Toyo wanted me to buy all sorts of factory options, the Ranger I built from the factory. I've found the quality about what I suspected in a Ford.

Every dyno shop charges differently. Some charge by the hour, others charge by the pull. Usually, a dyno tuning session with a few pulls is 150-200 dollars.

Is the CEL being triggered when you're accelerating, or when you're just maintaining speed? Does the truck do anything else while the CEL is flashing, or does it run normally?

Olsin6 said:

I only run 91 in my truck also.

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Wait, you run 91 octane in a 3.0? WTF is wrong with you??!?!!!?

Time for a lesson on octane ratings. Octane is not a rating of awesome, it's a rating of RESISTANCE TO IGNITION. You are running the stuff that is hard to burn. Higher octane is needed in high compression engine to keep them from pinging or knocking like will happen just from compression with lower octane ratings.

In a plain jane 9:1-ish 3.0 you are not going to achieve complete combustion, ever, running 91. The result is dumping a portion of unburnt fuel down the exhaust, which will damage the cats.

Unless you have done something to bump your compression like a stroker kit or a blower all you are doing with 91 octane is blowing money down the tail pipe. It's probably how you managed to fry a 3.0 at only 120K (you probably washed the cylinders), and I'll bet you cooked the cats as well.



The reason the 91 costs more than the 87 isn't because it's a much higher quality than the 87, it's because the stuff they put in it to keep it from lighting off before the spark plug does is expensive.

stmitch said:

Every dyno shop charges differently. Some charge by the hour, others charge by the pull. Usually, a dyno tuning session with a few pulls is 150-200 dollars.

Is the CEL being triggered when you're accelerating, or when you're just maintaining speed? Does the truck do anything else while the CEL is flashing, or does it run normally?

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The CEL isn't triggered until my speedo hits 50. But it stays on during cruising. Runs normally fine. Maybe slightly sluggish when trying to accelerate at the higher speeds but that's it.

I didn't start running 91 until I put in this new motor. I decked the heads and put in a domed piston to bump compression up a little bit. I bought the truck with 89k on it.

Friend had a VW engine in a small RV. Unit was factory. The VW kept giving flashing CEL light at certain accel conditions. VW dealership checked it out but could not trace problem. It seems it was an overly sensitive knock sensor design that was triggering false code.

Maybe just a false code.

Olsin6 said:

I didn't start running 91 until I put in this new motor. I decked the heads and put in a domed piston to bump compression up a little bit. I bought the truck with 89k on it.

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Yeah, that's not what you originally said.