02 Tahoe Z71 5.3L Flex fuel (VIN Code Z)

[TahoeJunky]

Update: once again I've never had this issue with any vehicle that I've ever had in my life. But the whole issue with the vehicle was the catalytic converters were completely clogged and I change those out and my driveway along with the O2 sensors and I'm getting engine knock sensors and also getting misfire multiple cylinders which were driver side only, so I went around tested the ignition module and everything in between and then I had the right idea of pulling out a spark plug, extremely carbonized on the driver side only while the passenger side was perfect and so I went up and grabbed some new spark plugs and seafoam came home seafoamed it changed the spark plugs out after and cleared all the DTCs, I had one more group of DTC's pop up which I cleared out via autel scanner that I have and it is now running absolutely perfect even put on my aftermarket cold air induction and I'm loving it now finished it as of an hour ago, just wanted to say thank you to everybody who responded and tried to help figure this out with me I really do appreciate it everybody!!


Everything was fine, then i got to my other development property with the wife, truck ran exceptionally well that night, pulled in and it stalled. Just did a full ignition tune up as it's never had one since factory, restarted it, fired right up, tapped the gas & it sounded like a deep hollow cavity from the pass side engine area and will not stay running, when it does catch it bounces on its mounts all of a sudden, as soon as any fuel is added it dies. I already put dye in the coolant expecting a head gasket leak, i have dye on my dipstick, still need to stop the pan. Everything turns over fine without obstruction. Did a compression test yesterday, each cylinder had 6 revolutions, or as close as possible, wife was cranking i was recording. Cylinder 1-170psi, C3-175psi, C5-180psi, C7- 176 Cylinder 2-170psi, C4-185psi, C6-175psi, C8-170psi. Pressure test is next but does anyone think I'm on the right track or am I missing something here. Lack of engine experience kills my diagnostics & really need some help here to get back rolling as I'm a new contractor and being broke is my specialty at the moment. Any help is much appreciated

 

[Scottydoggs]

check the fuel pressure, pump might be taking a slow death. you plug into a shrader valve on the fuel rail on the engine with the gauge. or you can go down and dirty..... turn key to run and push the needle in the valve, gas should fly out like 2-3 foot like spray good. if it just dribbles out the pump is bad. 02 have a in line fuel filter? that might be clogged solid too. if you have one its gonna be under the drivers seat under the truck mounted to the inside of the frame. cant miss it if you have one.

 

[TahoeJunky]

check the fuel pressure, pump might be taking a slow death. you plug into a shrader valve on the fuel rail on the engine with the gauge. or you can go down and dirty..... turn key to run and push the needle in the valve, gas should fly out like 2-3 foot like spray good. if it just dribbles out the pump is bad. 02 have a in line fuel filter? that might be clogged solid too. if you have one its gonna be under the drivers seat under the truck mounted to the inside of the frame. cant miss it if you have one.

Thanks for replying, attempted to change the filter the day after i bought it, right and i got lazy but i checked the Schrader valve already and spray is still amazing. But that deep hollow sound on the passenger side engine is scary to say the least engine turns over no problem and plenty of compression. Which is why I'm sitting head gaskets or the heads themselves.

 

[Scottydoggs]

check engine lights not on? or flashing? if you got a code scanner plug it in and scan it while its running like crap for codes, or after it stalls out, just dont turn the key off id think you'd have a pending code. maybe a bad coil, or coil harness and one side is not firing. you can use a spark tester to see if each coil firing.

if the head gasket was blown id think you'd find lower compression on your test on one or two next to each other.
or the oil being over filled and the coolant low.

 

[TahoeJunky]

All coils plugs wires battery all new say after purchase, all the way to differential fluid, i gotta drain the coolant anyway, i didn't have any pending codes when i tried it, didn't have enough miles to register memory either before it took a crap. I do have translucent dye on dipstick, so I'll have to check oil

 

[TahoeJunky]

But other then doing a pressure test idk

 

[rockola1971]

Thanks for replying, attempted to change the filter the day after i bought it, right and i got lazy but i checked the Schrader valve already and spray is still amazing. But that deep hollow sound on the passenger side engine is scary to say the least engine turns over no problem and plenty of compression. Which is why I'm sitting head gaskets or the heads themselves.

If head gasket between cylinder and water jacket or cylinder and atmosphere then your compression readings wouldnt be near that high. While engine is running is the CEL flashing? Constantly on? The engine didnt mysteriously just start running like crap right after a plug and wire change. You likely have a misfire(s). Incorrectly seated plug wire at plug or coil. Broken plug wire. Wrong spark plugs.

 

[TahoeJunky]

It did indeed just happen after i drive it 40 miles to my other property I'm selling. It literally just died, no knock, no bang, turns over fine, but when it catches it idles for a bit fine as soon as i tap the pedal it sounds like crap, as described above, engine knocks around a bit, which is why i suspect internal bearings, maybe cam? Stuck valve/lifter? I'm banging my head against the wall with this. Never had a issue like this before, nobody to ask. Ill attempt to get a video and post if possible

 

[TahoeJunky]

I also replaced everything with oem replacements, broken wire im going to check into. Thanks again!!

 

[rockola1971]

I also replaced everything with oem replacements, broken wire im going to check into. Thanks again!!

CEL flashing while idling or off idle? Did you cross a spark plug wire or 2?

 

[TahoeJunky]

Sorry, no lights flashing, body control module and passenger restraint system as it has no airbags upon my purchase. Before that was knock sensor 2, (rear valley), they never sealed it so antifreeze leaked into the valley, changed both twice with new harness and get proper volts from main harness, stayed until that night, catalyst code as well as fuel pressure unit, (sending unit as mine is a one piece unit i believe). No knocks, no bangs, even before this, it ran rough until the tune up and fluid change and smoothed out after. Negative on the cross as well, i had removed one at a time and replaced one at a time. Before this happened all was good

 

[rockola1971]

Check Mass air flow sensor wiring harness for damagae or unplugged. Check for codes. Is CEL on steadily at idle?

 

[TahoeJunky]

Steady at idle affirm, i have a revamp chip attached to the MAF harness I'll disconnect and try it out

 

[TahoeJunky]

Also old plugs came out looking like crap, smelled like gas, probably due to the catalyst code and faulty o2 sensors, covered in soot after 2 months

 

[rockola1971]

Also old plugs came out looking like crap, smelled like gas, probably due to the catalyst code and faulty o2 sensors, covered in soot after 2 months

The downstream 02 sensors didnt cause your wet and dirty plugs. More than likely the cause of your wet and dirty plugs caused the downstream sensor to pop a code for bad catalytic converter because it got flooded with gas.

 

[TahoeJunky]

The downstream 02 sensors didnt cause your wet and dirty plugs. More than likely the cause of your wet and dirty plugs caused the downstream sensor to pop a code for bad catalytic converter because it got flooded with gas.

I spoke to a friend of mine and he thinks i might have a clogged cat so im going to take the y pipe off since i already have a new one with cats on it and see if thats my issue with the thumping, jumping and shutdown

 

[rockola1971]

I spoke to a friend of mine and he thinks i might have a clogged cat so im going to take the y pipe off since i already have a new one with cats on it and see if thats my issue with the thumping, jumping and shutdown

You may very well have a clogged B1 cat and your downstream o2 sensor for that side might not be lying to you. Question is...what caused the clogging up of your cat.

 

[TahoeJunky]

Probably lack of maintenance honestly, as long as it runs i really don't care, looking at a rebuilt engine for under $2500 and do a 383 convert to the original. If it works and happens again ill straight pipe it and put o2 back in it to pass emissions at this point. I burned up my grinder and my brand new sawzall so it'll take a minute for an update after i cut them open