More lost than ray charles....lq4 ss2

[Truffleshuffles10]

Well here goes nothin. I have an 04 2500hd that developed a misfire. No big deal. Ran through the norms. Plugs, wires, etc etc. Ended up finding a broken valve spring. Thought to myself "self, it'd be a shame to do all this work and NOT put a cam and springs in it"....so that's exactly what i did. Sloppy stage 2, decked the heads, springs, etc. etc. Fast forward. Now when i fire it up, the truck will run for a few seconds and then develops a misfire and starts popping and banging. I thought maybe knock sensors were shot, so i unplugged the harness and changed the dtc's just for testing purposes to no avail. Need some help with either finding the problem or finding a big enough hill to make it look like an accident.

[bk2life]

need to get it up to operating temp and closed loop.

did you do anything to the stock tune, or just hoped it works?

What have you done?

There is a list of things to do, but, you need to tell us what you have

engine, cam, exhaust, injectors, intake, fuel system, all the things we cant see.

[Truffleshuffles10]

2004, 2500hd, 6.0, 4l80, stock injectors, stock manifold, ss2 cam, long tubes, catless y-pipe, a few adjustments to the ecm by a "buddy with a beer". It wont get up to temp. It will run for about 25-30 seconds and then start to pop and bang like its on the chip, then dies. When this first started (before it came apart for the cam) i was driving. Light misfire that progressively got worse. Parked it at the house after about 3 miles of the light miss. Followed the diag procedure that we normally use here at the dealer. I don't think I'm a complete idiot, but I've been wrong before lol.

[abc]

Right now your O2's are not agreeing with each other. Check everything on bank two. Exhaust leaks, wiring is correct and plugged in, ignition system is functioning properly on that side, valve train is correct, and so on.

[Truffleshuffles10]

I've quadruple checked wiring and even put a new sensor in bank 2 because they were really far apart before as well.

What i also find kind of intriguing, is that its not logging tps. I'm going to try another ecm tomorrow. I'll forward my findings.

[blindsquirrel]

Did you verify that the connector for bank 1 O2 is going to the PCM pins for bank 1, and same for bank 2 to bank 2? Same for the injector harness?

What is the fuel pressure?

[abc]

There is a fairly quick way to test your work. Put the PCM in open loop so it will ignore what the NBO2's are telling it. You then can add a few percent of fuel at idle until it idles acceptable. At least that will tell you if you did the mechanical stuff correct, then track down why the O2s is not functioning correct.

[Alvin]

Did you verify that the connector for bank 1 O2 is going to the PCM pins for bank 1, and same for bank 2 to bank 2? Same for the injector harness?

What is the fuel pressure?

That's what I'm thinking. Some trucks it's easy to accidently cross the o2 sensors.

I don't see anything else glaring. It should run OK just have problems idling with the stock tune.

[abc]

That's what I'm thinking. Some trucks it's easy to accidently cross the o2 sensors.

This wouldn't explain the mostly full lean, most of the time, on one bank, would it?

[Alvin]

This wouldn't explain the mostly full lean, most of the time, on one bank, would it?

We see it once every few weeks.. TBSS's are sorta easy to make this mistake on too. Just how the harness lays out.


https://www.pcmofnc.com/2020/04/08/c...r-information/

https://www.pcmofnc.com/wp-content/u...4x673.jpg.webp

[edcmat-l1]

looks-good-to-me.jpg

Just here for the thread title LOL

[Truffleshuffles10]

edcmat-l1 lolol

The harness never came out of the truck. The block never came out of the truck. Just the heads, lifters, and cam were removed.

I've contemplated even the entire harness being replaced at this point.

[Truffleshuffles10]

I've even had wild thoughts of the reluctor wheel on the back of the crank being the culprit.

[SiriusC1024]

abc's idea of going OL will tell you a lot.

[blindsquirrel]

The harness never came out of the truck. The block never came out of the truck. Just the heads, lifters, and cam were removed.

Oh, so you didn't unplug any electrical connectors, didn't move the harness off to one side for access? Man, you must be good at this!

You're assuming that everything got put back where it should be and so that can't possibly be anything to do with it.

[Truffleshuffles10]

I guessed we zipped on by the part where i stated i quadruple checked all the wiring. So no, I'm not assuming. I know.

[abc]

So then, let's recap: it had a miss, you found a mechanical issue which you have since corrected.
Do you have logs prior to the repair that will show how it was running before the miss was present and while the miss was present?

Is it safe to assume the valve spring was the only issue at the time the miss was first discovered? If so, that would tend to lead us/you towards some part you disrupted or changed during the repair.
Sounds to me like you need to retrace your steps. After that, the fresh start up/idle tune should not be that difficult to get it to the point it will at least start and idle with some BRAF adj. and timing adj.

Right now your fuel trims are detrimental to success due to the NBO2s not reading correct. You can either take them out of the equation or fix it, I say fix it, but that's just my opinion.

[MarcWolfe]

Was it an exhaust valve spring? That would mean you were compressing and burning fuel in that cylinder without venting the pressure, which can be comparable to knock damage. You might be pulling that motor out again. Do a compression test.

[gametech]

Was it an exhaust valve spring? That would mean you were compressing and burning fuel in that cylinder without venting the pressure, which can be comparable to knock damage. You might be pulling that motor out again. Do a compression test.

Did you even think about what you just wrote, even a little bit? Even if a broken spring could magically keep a valve from opening, the rest of what you wrote is nonsense.

[blindsquirrel]

Did you even think about what you just wrote, even a little bit? Even if a broken spring could magically keep a valve from opening, the rest of what you wrote is nonsense.

Well what if everything worked backwards, not just the valvetrain parts but also even the process of combustion? Ever think about that?