This past winter my son swapped $200 and a non-working go kart for a 2001 F150 XL 4.2L regular bed/cab 4X4. Really, just the tool box and the tires/rims are worth that. It started and ran when we checked it out, and that was good enough for us. It ran rough and was looses power on hill climbs, but we figured we could work on it. When we got it home, we found #1 wire just dangling. Closer look and we discovered the ceramics was gone from the spark plug with the remaining metal in there.

We tapped out that plug, and proceeded with the tune up. We put on new plugs, wires, ignition coil, air filter, fuel tank with new pump (old tank leaking past 1/2, and we found a cheap new pump, so we figured we'd put it on at the same time). Got new rear/downstream O2 sensors, PCV valve, and of course oil and filter change plus other drive train fluids. MAF sensor looked pretty clean but we cleaned it just in case.

Because it was still throwing the P0171/0174 codes, we took off and cleaned the intake plenum, cleaned the top of the intake removing all the carbonization, replaced the isolator bolts and all the gaskets. We put on a new EGR valve, and replaced the IMRC plastic bushings and replaced a missing actuator arm while we had the plenum off (for some reason it did not thow any codes for the disconnected IMRC). We also replaced the camshaft sensor while we had access to it.

We replaced the missing & loose bolts on the exhaust manifold flanged but there is a small rust hole in the exhuast manifold. I don't think it's too much of a contributing factor. We put a muffler on it but kept the old cats. There is a unburned fuel smell at times, but not a sulphur smell you could find when the cats are bad. According to the codes, the 2-5 are all misfiring.

It kept throwing the codes. My son was taking it back and forth to college about 1 hr away, but we are going to leave it at the house until we can fix the problem. I've been reading all the links I can, and I feel confident there are no vacuum leaks. The intake is spotless. Fuel pump is new. Ignition is good, no harness leaning on exhaust, no visible cracked wires or hoses.

If it was the injectors, I would have that I would get a code for their sensors? The Catalytic converters could have become clogged with unburned fuel I suppose so I could vacuum test those. Also do the compression test at the spark plug holes.

I was hoping others could help me trouble shoot some other easily fixable areas, or maybe something I looked over. I think I missed some of the stuff we tried, but you get the general idea.

I am going to try to include some pics of the live data stream from my sensor as I was rrev'ing it in the driveway while the codes were active. You might be able to help me translate what all the information means. The photos posted in order, so I had it at around 2500rpm and let it slowly drop to about 800.

Shoot me a line or post it here if you have any good ideas!

Thanks a bunch!

Cliff


4.2L from our 2001 F150





Frame 0




Frame 1




Frame 2




Frame 3




Frame 4

 

Just in case you came across this link, and wanted to to know what the data stream abbreviations mean, I will include this snapshot!



Translation of the Live Data scanner abbreviations.

 

Your Long term fuel trims are setting the 171/174 codes.
There is an intake air leak some where.
With 4 cylinders out of 6 in misfire, it's a wonder the motor will even move the truck.
Are you sure the plug wires are on the coils and cylinder in proper order?
Good luck.

 

I sprayed all around the engine with carb cleaner to see if it would suck in and rev, but couldn't find any air getting in. No cracks in the upper or lower plenum.

I did think I messed up the wire order at first, so I had my sons check it out separately. Even swapped out the newer generic wires and ignition coil with Motocraft products just in case it was because of inferior products.

I used my Haynes for the wire order, guessing it's right. I think the misfires are a cumulative error, not that they are misfiring all the time. Could it happen with a broken timing gear tooth?



Spark plug wire diagram 2001 F150 4.2L

 

Edit, nevermind I see you have a chart already.
It never hurts to go back and check that this is how they are actually connected.
Also make sure all the plug wires are "clicked" on the plug and coil really tight.

 

The carb cleaner spray deal doesn't really work with modern fuel injected engines, the computer compensates faster than you can tell a difference.

 

Thanks S.I.A, Is there another way to check for air leaks? Smoke?

 

If your carb cleaner is non combustible it won't work..
Second, believe the Long Term Fuel Trims. They are way out.
They are shifted because there is excess unaccounted for air getting into the intake tract.
The Ox sensors detect this and richen up the fuel trying to correct. That's why the LTFT are shifted.
Next, are the misfire codes old history or is the engine still missing.
I would clear all codes, see what comes back and start over so you know what is still an issue.
If misfires, clear them first then work on any air leak problem.
Only way to use combustible spray is to watch the short term fuel trims for reaction, not idle speed.
Your working on very fast acting computer system, not a carbureted engine.
Go0od luck.

 

The easiest thing would be a cracked or open hose somewhere. We will go over the hoses one by one and check it out. Check the wires again.

If the exhaust header has a small hole/leak, will it allow air to be pulled in? I would think the positive pressure would keep from entering, but if it did, and since its ahead of the upstream O2 sensor, could the computer think there is too much air?

Hoses are a lot easier to change than a header......

 

You have to dispense with the easiest thing thoughts and repair for the issues no matter what it takes.
You have Scanner capability.
If it will respond in real time, the air leak should be able to be detected with a flammable spray in that area.
Are misfire present now or not?
It makes a difference because you would have two interacting troubles at the same time.
The OX sensors see both conditions.
Misfires are detected from crank rotation time measurements.
Ox sensors are at the end of the line and see everything that affects combustion content.
When the air leak is fixed, both LTFTs should go down low, STFTs will fluxuate +\- around 5 or so according the throttle openings.
LTFT is a slow acting table , STFT is fast acting table.
If you were to reboot the computer, all tables return to base setting and begin to get modified again according to the conditions that prevail, over time.
This is one way to see if all issues have been cleared.
Good luck.

 

The misfires and lean codes seem to happen simultaneously. I crawled up in there to see what the hole looked like, since it was my boys that told me about it. Turns out it was a rotted EGR tube just off the manifold. I did a quick fix with strips of an aluminum can, Tiger Patch and aluminum foil. Drove it fir 20 minutes to let the patch cure, then I cleared the codes and disconnected the battery to dump any hidden codes.

It runs about the same, the codes haven't matured yet and I didn't move, but the fuel trim is still 32.8 on both 2&3. So back in there to check all the hoses. I am hoping its there on top somewhere, but I've looked most of them over and everything looks good so far.

We'll keep going at it......

Cliff


Hole in the EGR line just off the exhaust header.




Live data stream after patching the rotted EGR tube

 

With the engine running and warm, we sprayed some carb cleaner into a vacuum port on the plenum, and my O2S B1S1 etc hit around 0.8-0.9 from around 0.00-0.015 before spraying, which means my my upstream O2 sensors are good, and it is most likely a vacuum air leak, just don't know where.i pulled a bunch of hoses off and inspected them and the look okay.
Does that sound right?

We'll keep looking........

 

We sprayed around the air intake with carb cleans and discovered an air leak at #5 cylinder. At first I thought maybe we didn't seat the plenum correctly, but as soon as we took off the top of the cover, we found a bigger problem.

I am guessing that all that extra carb cleaner, etc in the intake cause a fire at #5. Can't be sure when it happened, but it is pretty frustrating because I spent hours scrubbing the plenum clean.

Ever see anything like this before?

Cliff



Apparently we melted our plenum right above cylinder #5. Sucks, but at least it wasn't a full-blown engine fire....