So, of course, I did my research and searched various different related topics to my symptoms and such. But, I couldn't find anything specific, so here goes.

My Truck:

year: 2001
Model: Silverado 2WD
Motor: 5.3
Mods: Pacesetter long tubes, ORY, Powerbond 25% balancer, MSD 8.8 wires, TR55 plugs, K&N filter/ stock air box, custom tune through my Predator by RPMOnline


Symptoms: I started getting hesitation from the truck, like a brief stumble or jerk at lower throttle levels/ mild speed increase. I had just recently replaced the Bank 2 o2 sensor, after repairing an exhaust leak around where the ORY fed into the rear exhaust pipe. that particular repair got my gas mileage back up where it was suppose to be, and the power was there. But, the jerking and hesitation started shortly afterwards. Most recently, I got the dreaded check engine light flashing in my face, with horrible misfiring symptoms.

What i've done so far: I've checked all the plugs wires, and they were fine. The plugs were recently replaced. (not that they might not be fouled now) I bought a fuel pressure tester, and it was right around 49-50 PSI. close enough for government work. I have no cats, so obviously it's not that.I ran a log, but haven't reviewed it yet. What is going to be my best bet next? Injectors? (I hope not) I have ran a full can of seafoam through my truck, and no change. I didn't notice anythign around the headers that would make me believe there was a leak. I did, however, get a code (for some reason, didn't have a check engine light on) saying I had low voltage on the bank 2 o2 sensor (the one I just replaced). I thought that was wierd. HELP!!!!!!

 

Don't really see how it could be an injector, I think that would be more noticeable at idle. If you have checked all the plugs and wires. The next thing I would do if you had access to a tech2 is watch misfire data and you might have a coil going bad. Just my .02

 

I forgot to mention, the code that flashed was a P0300. My question is, woudl a bad coil cause misfire on multiple cylinders? I do not have access to a tech2, but my predator does a pretty decent job of laying out the information. Specifically, what shoudl I be looking for?

 

Have you cleaned the MAF? This may be something to try, because they can cause a whole mess of different codes to appear when dirty.

 

I have not cleaned the MAF. I can try that next. i did notice that, I was getting a stumble at idle speed this morning. Moving my way around a parking lot, it was stumbling. WOT, I don't seem to have issues.

 

No other input? I'm surprised with all you great minds, you don't have more input than that.

 

Did you have any luck after cleaning the MAF? Its easier to rule out these simple fixes before diving head first into the tough ones...

 

If you have a code for low voltage on a sensor you just replaced then you need to dig further into and see whats going on. In accurate readings can cause this type of issue. You need to monitor the engine data to see whats going on.

A random miss fire could be caused by several items.

Have you ever changed the Fuel Filter under the cab??? Did you test the fuel pressure under load??? Just be cause its good at idle doesn't mean it's preforming well under load when the actual issue occurs.

 

I had p0300 with my truck too, you could check your intake manifold for vacuum leaks and check your maf.

 

OK, so yesterday afternoon, I cleaned the MAF with automotive electrical cleaner. The MAF didn't seem dirty though, FYI. I also serviced the vehicle. (fresh oil, air and oil filter) I checked the header bolts and looked/listened for leaks, and notta.

I got another Bank2/ upstream O2 sensor low voltage again. (the O2 sensor I just replaced) I've not had any issues on Bank 1. (strangely enough)

I did not check the fuel pressure under load, mostly because i'm not certain the best way to do that. But, it seems like the problem is on bank two?? Correct me if i'm wrong here.

The truck started stumbling pretty noticably yesterday afternoon after all this stuff above was done. Right around 45 to 50 mph, and light throttle. At WOT, it still seems to be OK. Only one exception though. At a dead stop, when I stomp the gas, it stumbles around for a second and then finally takes off, and doesn't seem to pull very hard until the RPM's get up there.

So what's next?

Oh, and a couple questions:

1. Can a single faulty injector or bad coil pack cause random misfires accross all cyclinders?
2. What type of issue would seem to be rooted on one bank, but causing misfires accross the board?
3. What are the chances that I just got a bad O2 sensor when I replaced the last one?
4. With the mods I have, what would happen if I put the tune back to stock? Would the truck run right? (I know i'll get a check engine light from the rear O2's)