Pretty new here. Got P0300 Code and running like garbage. Had flashing CEL. Got a love/hate relationship with this rig. (More love than hate)
Here’s a rundown on the rig;
-2003 H2
-115k miles

Brief mechanical history over past 10 months;
-Was throwing codes like crazy 10 months ago
-P0300, P0137, P0157, P0442 and a couple others I can’t recall.
-Rough idle

Performed the following;
-Replaced plugs, wires, coils with premium AC delco parts. Properly gapped etc
No help
-Replaced intake manifold gasket and knock sensors.
No help
-Replaced external fuel filter
-Replaced fuel injectors
-Replaced fuel regulator
-Replaced 02 sensors (all four, that was a bitch)
No help

The problem was;
-Bank 2 plugs were quickly fouled
CATS WERE CLOGGED
-Cut opening in both cats, emptied the guts out (came out in a pile of dust) welded openings back, sealed up nicely (SC has no vehicle inspections)
-Replaced all spark plugs again
-CEL lit up with only codes P0137 and P0157 (to be expected after gutting cats. Even with anti foul extensions installed on downstream 02 sensors. No impact at all on how the truck ran)
Truck ran like brand new for 6 months.

Next problem (4 months ago);
-Truck died while driving home from work
​​​​​​-No start condition
Fix;
-Replaced fuel pump
-Replaced crank shaft position sensor
(Should have done in reverse order as it was actually the sensor but at least fuel pump was now new. Story of my life)
Ran great for next 4 months. Several 9-10 hour round trips to include a couple pulling 23’ boat.

Todays condition;
-Flashing CEL. Very rough idle but no “lope mode”. Only 5 miles from home. Drove home and parked.
-Codes-P0300 (misfires) P0137 and P0157 (02 sensors as expected due to no cats??) P0442 (small evap leak)

What I’ve done so far;
-Removed plugs one by one, checked each coil with inline spark tester between plug wire and plug (all coils firing very consistently) replaced each plug with properly gapped AC delco plugs. Wires only 10 months old and were not damaged when removed (popped off and back on nicely)
-Checked all ignition and injector connections
​​​​​-Confirmed intake manifold bolts all tight
-No visible loose or detached vacuum lines
No change!

What I did discover with old plugs;
-Bank 1 plugs fouled
-Ban 2 plugs have fuel on them

I do have a coolant temperature sensor issue that gets stuck every now and then. If it acts up I turn off truck after warmup and restart and it works fine. Not sure if this is a factor??

Still running like crap……same codes 300,137,157 and 442.

I’m a pretty mechanically inclined weekend warrior and perform majority of work on all my cars, motorcycles and boats. My ODB reader is pretty basic however so I’m limited in that regard.

Any suggestions?
MANY THANKS

 

Bulletin No.: PIP4925B
Bulletin No.: PIT4943D

 

Thank you. I just got done spraying everything I could think of with carb cleaner while running but nothing detected. I know a smoke test is much more effective. Any thoughts on condition of the plugs? Pretty fouled on bank 1 side and wet with fuel on bank 2 side. Would evap leak cause this and lead to misfire?

 

replace the coolant sensor or check its harness. the coolant sensor is very important to the ecu programing for injector timing.
the foulers should work. you need to find the pinholes you missed when welding on the exhaust pipes or you might need to retighten the exhaust manifolds also check for missing exhaust manifold bolts and repair, or flanges are not properly sealing. the exhaust need to be airtight till after the secondary o2's.

 

Thanks for the reply. Changed coolant temp sensor today. Easy job and temp gauge functioning properly. (No change) I’ve got manifold leak brackets that I installed 10 months ago.They work well and stopped the small exhaust leaks at manifolds from broken bolts. Not sure about the welds being an issue because it ran very well for 10 months after gutting cats until now. I will check it however. Maybe some deterioration at the welds.
Appreciate the response.

 

i just had to do the same thats why i mention it.
the leak brackets had backed off 2 turns and the fouler had rusted a bit so i used dish soap and water in a spray bottle to find a few pinholes on the foulers i used some 2 part epoxy putty, warmed up the pipes a bit and smeared it into the pinholes.
i did your procedure about 8 months ago.
i wonder if in your case having your cats disintegrate all that material had to go somewhere and might have plugged up the muffler baffles inside the muffler restricting the exhaust flow causing back pressure and miss fires.
it would be the same symptoms as plugged cats.

 

Good point. I’m pretty sure I got all of it out. Busted out what was left in there with a hammer and chisel and shop vacced the rest out but a chunk or two could have been still stuck in there. Think maybe it would rear its ugly head after 10 months? Now I’ve got a good mind to open the cat back up and see if I’ve got some blockage in the pipe at the 90 degree turn after the cat. It’s doing the same exact thing the other side did 10 months ago. Blocked cat that fouled all plugs on bank 2 which caused misfires. Now doing it on bank 1 side. Did you use a high temp epoxy to seal your welds?
Man I think you’re onto something. Stay tuned and thank you.

 

Bronxteck, quick question on the antifoulers on the downstream 02 sensors. I installed them no problem but I never was able to lose the codes. Read somewhere to stuff a little steel wool in them. Mine are still in good shape and not rusted. Thoughts?

 

like i said revist the exhaust bolts and your clamps. snug them down especially the four corner bolts front left right and fierwall left right. i used the harbour freight epoxy putty log tube stuff that you cut and smash together . i did not turn it back on til the next day to let it cure.
one question. did you do the crank relearn after replacing the crank sensor? it is usually required after replacement. it properly sets the firing order for the ecu.
also you have to make sure that the crank sensor is perfectly flush in the block and has no play if the retaining tab gets bent or damaged it can cause issues.
the matinf surface has to be clean and flat with no rustscale between

 

Thanks. I was prepared to get a relearn done but it ran perfectly right after I replaced the sensor. Ran great for 4 months after I replaced it until this new issue.
I’m digging into the your cat suggestion now.