MAF codes, 02 codes, Misfires, now barely runs HELP!!!

Going back a few weeks, I put a new K&N cone filter on my spectre CAI tube. Shortly after, I started getting a "MAF circuit" code. Cleaned the MAF and put the factory intake tube and air filter back on. MAF code came on once maybe after than then was fine for a couple weeks. Then when I was driving the check engine light was flashing, indicating a Misfire, and also had the MAF code again (wish I wrote down the code numbers). When the CEL is flashing, the truck physically is running really rough, and if I floor it, the rough running clears up and the exhaust belches gray smoke like a diesel. CEL usually flashed at cruising speed with little load on the highway. Only twice did it do it at idle. I ran some Lucas Fuel injector cleaner through it a couple tanks, and it made misfires lessen for a week or so, then was worse.

The MAF code did not come back, I kept getting the ?Multiple random misfires? code and ?02 Circuit voltage out of range Bank 2 Sensor 1?. SO the misfires were so bad last Wednesday, when I got home I shut off all my lights, stuck my head under the hood and could see the coils arcing out to the mounting brackets. I started testing the coils by pulling one plug wire at a time ? 6 out of the 8 coils, when I pulled the plug wire would not affect idle whatsoever. Also, 6 of the coils would arc out the side of the coil to the bracket when the wire was removed, while the other two arced to the screw directly below the terminal that the wire plugs into. I started and shut off and started the truck at least half a dozen times while checking parts out Wednesday night. So I ordered 8 new coils and a new O2 Sensor.

Friday morning, I went out to start the avalanche and first try it wouldn?t start. Then it started and was idling at like 350 rpm, and was ?chugging? and belching smoke like I poured a whole bottle of Seafoam in the intake. If I feather the gas pedal like 20 times, it will backfire out the intake as Rpms slowly increase, I can get it to rev up to about 4500 rpm or above, but once it returns to idle, same thing. Runs like it?s on 2 cylinders and chuffing gray smoke. That is when I get the P0461 ?Sensor A 5 volt reference voltage? error and P0101 ?Maf or Vaf? code

I wonder if I backfed power and shorted a sensor out when I was testing my coils. I just don?t understand why I restarted the truck 5 or 6 times while testing the coils and it ran, but the next day it wouldn?t run.

I changed all 8 coils and the bad 02 Saturday, no change.

I swapped the MAF with a known good one, and it ran crappy as well. Swapped the MAP sensor with a known good one, same thing. Only thing so far that has made any difference is if I unplug the temp sensor on the drivers side of the block, it makes it idle up and down like it has a huge cam, and it does rev up easier, still feathering the pedal 2 or 3 times.

I was reading that the ECM has a couple 5 volt references, and if a sensor shorts or a wire gets chafed, the voltage can get pulled down. I can start unplugging sensors and re-plugging them one at a time to see if it makes a difference. All my gauges work fine, so I know those sensors are ok.

HELP HELP HELP! I am on my last straw with this truck!! It's for sale, and I can't sell it till I fix it!

Check the engine ground strap.  I bet it's broken or disconnected.

Codes are very telling of an Intake leak...

Arcing is likely bad spark plug wires.

Check that your ground strap and other grounds are all solid and not corroded, if that doesn't do it and you are seeing arcing then change plugs and wires...

If still doing it after plug/wire change then look into changing intake gasket with felpro. Factory manual says to also replace the bolts and washers because they are one use but some have had good luck with the original ones. Did this with my truck last year and did not use new bolts/washers and the code did not return.

I don't see where you mention the year but the early 5.3 are especially prone to intake gasket leaks and common codes for the intake leak are MAF codes, O2 codes and random misfires...

Some suggest you can use something like a carb cleaner or wd40 and spray it around the intake to see if the engine runs differently but I have seen others say that doesn't work well with the 5.3.

Good luck!

I did the plugs and wires with delco ones about 5k miles ago.

The truck is a 2004.

If it was an intake leak, why would it happen all of the sudden? Like I shut it off one night when it was running fine, and the next day it wouldn't run right. I've never had an issue like a leak happen instantaneously. I think it's an electrical issue. I'm gonna start unplugging and re-plugging one sensor at a time to see if I can isolate a shorted sensor. I will check the grounds, but again, I know nothing broke while I was looking at it, but I will check...

It's sitting till I get my '91 K1500 back together. Had to do some rust repair on that.

Late to the game here.  Has the weather in your area taken turn to the colder?  That could exacerbate an intake manifold leak and bring it on suddenly if the temperatures dropped.  Keep us posted as to what your find and good luck.

So this saga is weirder than imagined...

After all the work I did previously, changing the coils, cleaning MAF, changing O2, nothing seemed to help. Then all of the sudden, it ran ok for a few months- Then my Oil pressure sensor (which I had just changed before the MAF issue) stopped working. Then I got the O2 code again... The misfires cleared up after the coils were changed.

So I figured I had better start ooking at my grounds, my wires going to my oil pressure sensor (because I figured since that sensor burned out twice in a year, maybe it's wires were chafed and causing the voltage to drop as it arced out), but the problem was much weirder.

I started unwrapping all my wiring harnesses to the computer, sensors, fuse box, etc, and I could not find anything wrong. The grounds for the sensors were fine, the blovk to body ground was fine... So I pulled the fuse box out, and lo and behold... Mice had been in there...

This was one of the sensor grounds on the back of the block


And this is what I found under my fuse box:












So I am pretty confident this is what was causing all my issues-
it always seemed to run worse on damp days.

The mice had chewed throug the coating on several wires, including one that was a 10 or 12 gauge, so pretty big circuit...
Also, there was a scotchlock on a wire going to my stereo for backup camera... I pulled the backup wire off, pulled the worse wires out of the fuse plugs, heat shrinked them, put the harness back together, taped up all other exposed wires, taped the groups of wires together, then put all the other wires back in place, cleaned the snot our of my MAF with Isopropyl alcohol till it was spotless, and for over a week now, no MAF code (which was previously persistent), and saturday I replaced the O2 sensor again, and the oil pressure sensor, and about 60 miles with no codes active or pending.

This one was one of the worst problems I have ever chased. The truck still isn't perfect, I have to do some rocker rot repair, and a little work on one back quarter, but I think it should be ok as far as driveability is concerned.... My gas mileage went up from 13.4 to over 16 too!

     

Glad you found this.

Squirrels like to chew on wires too.

I have a family of squirrels that like to nest under the hood of my seldom-used Ford Explorer.

When I first got my EXT, I found a squirrel nest, complete with a good-sized stash of acorns in the air box.

Thank goodness they didn't try to get past the K&N filter.

And I once had a Doberman that ate all of the exposed wires on my bass boat trailer.

But that's a different story for another time.

Glad you sorted it out and kind rekindle the love for the Avy.

Good job for staying with it.

I suggest you check the Passenger Seats, Front & Back for cookie crumbs and worse. Or else you'll start attracting rats and other vermin.

Just read all the problems you were having with your AVY.Great find I was impressed with your persistance!

I had the same weird stuff with my old dodge ram and it was squirrels chewing things.  I used to be nice to squirrels but now it's a vendetta since they destroyed some of my house too.  I bought an air rifle just for them, but I've only bagged 3 in a year and they breed like...  squirrels!!!!