Howdy folks,

first off, we are dealing with a 2001 f250 with a 5.4L 2v.

a (very) quick back story. Got the truck last summer from my girlfriends dad. It had been sitting in the yard for a number of years and I figured it’d be a “fun” project to bring back to life. 256,xxx miles on the engine and about 60 on the transmission. it took a lot of work but we finally got in on the road and inspected and all that, which was a big victory!

However the more I drove it, the more I noticed it didn’t feel right. Definitely lacking power and had some weird engine stuff. Took me longer than it should have to check compression and there were several cylinders that were low (60-80 psi if I remember right). So through that test we sorta determined head gaskets (we also discovered oil in the coolant).

we got to pulling heads off and when we did we did not see any obvious wear spots on the gaskets (not to say they weren’t there, though). For a number of reasons i decided to just go ahead and put in a ”new“ engine. Ended up getting a used 5.4 and put that in (in theory less than 100k on it).

got the truck all back together, started up great except my performance issues were still present. Slow acceleration. At highway speeds I put my foot to the floor and it just crawls. I am getting some occasional misfires in cyl 2.

I took off cat converter today to see if it was a clog (it sorta felt that way) and it did not change my issues. Fuel trims are at times very high (long trims at 25%). I also swapped spark plugs, coils and fuel injector for cyl 2 from cyl 1 and still have issues with 2. I also know compression is good. Had between 175-195 psi across the board when we tested today.

note, the “new to me” engine went in but I am using the original wiring harness, original air manifold and throttle body but have all new gaskets everywhere.

so is cyl 2 misfires causing performance issues? If so where to i start to diagnose that? Compression is good, the basic test of swapping plugs, COPs, and injectors proved those are good too. So now I’m kind of down to wiring at cyl 2 or the ECU.

ANY advise? At this point most things mechanical have been touched or replaced.

 

Brakes aren't dragging? fuel pressure at cruise speed? loosen both exhaust headers and stick shop vac on tail pipe look for no suction. Clog anywhere.
Check fuel filter/ air filter? Is cyl 2 running at all?
Misfire codes are lame in these trucks back then.
Check for vacuum leak / smoke test etc.

 

As the above stated, check for vacuum leaks around the intake manifold. You need to find the issue causing the elevated long term fuel trims. It can also be a bad fuel injector, which would also cause your misfire. Swap injectors with another cylinder and see if the misfire code changes to the new location.

-- Dave

 

based on the obvious signs I don’t think brakes are dragging (don’t hear it or smell it), I have not checked fuel pressure recent but last I checked it was fine. I am taking the gauge out today to check. the shop vac on tail pipe is an interesting test, but the clog would have to be in the y pipe which while possible, I doubt it. Air filter and fuel filter are both “new” from last summer but probably have less than 1k miles on them.

I also Did swap injectors, coil packs and spark plugs from different cylinders and it still comes back to cyl 2.

 

I hate to say it but even after you get cylinder #2 sorted out if the lack of " kick you in the seat of the pants " power is not there then.....your truck is normal and you probably have the crappy gears..

 

I have considered this as well. I do indeed have the crappy gears. However, on the highway the other day and i had my foot to the floor and it was crawling. Uphill it didn’t accelerate at all. With a machine that can supposedly tow thousands of pounds I would expect it to at least accelerate! I’m not looking for it to be fast but I need it to move a little when I push the skinny pedal!

 

if one cyl isnt working these engines do poorly...pull no2 plug see if its burning ok or is wet.

 

You need to test, using a noid light, to see if injector #2 is working.

-- Dave

 

So an update from yesterday. We did a few tests. 1. Checked vacuum pressure which was doing exactly what it was supposed to. Idle between 19-20 hg and 2000rpm between 20 and 21. Tap gas to full open and it drops to zero hg. 4000 rpm and releasing the gas spikes it to 27 hg. Everything I read shows that all of that indicates a healthy engine.

additionally we did a smoke test. It was a home made smoker so I am not entirely sure Of it’s effectiveness, but we pulled the Pcv valve and saw some smoke so in theory we would have seen a leak.

also, we did a test with an oscilloscope back probed into the injector for cyl one and compared the graph to cyc two and they looked the same. So it seems the computer is doing its job and the wiring is ok. And as I said before I had switched injectors a few days ago and the problem stayed with cylinder 2 and did not move with the Injector.

last I did a fuel pressure test. That was also in a normal range when we looked. However I did notice when I glanced later it had only 25 psi. A little low but why would that cause a miss in only cyl 2? Hm.

we got demotivated and gave up for yesterday haha. Any other suggestions?

 

Either do a leakdown test (to see if the #2 cylinder holds pressure) or pull the valve cover and see if there's a broken valve spring or rocker arm on the intake valve.

Either the intake valve isn't opening.

-- Dave

 

is the leak down needed if compression is spot on? It is 185 psi.

 

How about the coil signal for no 2? At idle if you disconnect the coil does the engine change? How about the short term trims are they still plus 25.

 

funny you mention this. It’s exactly what we tried today. Unplugged coil pack for #2 and there was no engine change. Tried the same for #1 and you could definitely hear a difference.

we measured the injectors yesterday with the oscilloscope, but failed to do that test for the coil packs. Today We tried it on the coil pack for #2 and found a consistent somewhat noisy 12v. Compared to #1 where we got very defined spikes on the scope. So, it seems we found the problem.

we tested continuity from the +12v and ground on the connector for the coil pack to the computer side of the main plug that’s mounted on the front of the engine on the driver side and that showed continuity.

at this point we think it’s the PCM. Thoughts on that?

 

If the intake valve spring is broken, or the intake rocker, compression will not be affected since the valve would be closed. A non-opening intake valve would cause your misfire due to no fuel entering the cylinder.

-- Dave

 

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Two options: make sure the 12volts is stable with a test light or some kind of 1 amp load 12 ohm resistor? Next check signal wire back to computer for breaks. That wire on scope should be 12v then zero during pulse with coil plugged in. Check resistance of coil? compare? Connector for corrosion. They corrode bad..

Good luck.

Dick