Check engine light on

step 1 is always check all fuses(cab and engine bay)
ahhhhhhh 6.0L diesel engine not GAS.(petrol)
bad fuel> , lost pump prime diesel , bad pumps>
scan the PCM is next see glow plug errors?
"Is DTC P0670, P0671, P0672, P0673, P0674, P0675, P0676, P0677, P0678, or P0683 present?" FSM quote.

backfired to Air cleaner, end or backfired to exhaust pipe end.???
what is the blower thing/ (HVAC, CAB HEATING AND COOLING BLOWER DEAD?)
IF DASH BLOWER IS DEAD MOST TIMES THAT IS BLOWN F12 FUSE
AND IS NOT RELATED TO , the engine problems, most times
F12 battery junction box blown fuse. or worse(means scan PCM)
auto climate is F12 manual climate is f224.
know = NOW:?
engine crank okay.
but will not start, but does start with spray stating fluid but not told does it stay running or just runs for 3 second and stalls.
3 seconds is the starting fluid consumed, and normal if injectors are dead.
using too much spray invites backfiring, so don't do that.
3 seconds max spray ,crank , repeat 3 time, if runs 3 second
fuel pressure is lost or worse , means scan the PCM.
spraying real diesel oil can surely fail, if GLOW plugs are dead;
again fuses are checked first, for sure Glow plugs and BLOWER HVAC fuse.

read the glow plugs test here ,6.0L

https://eautorepair.net/Marketing/Default.asp

I voltage check fuses or ohm them in hand
some fuses can fail with super hair line cracks, not just classic blown to H3LL element. (smoke seen and metal dust there)
I test them if they look ok'ish, (looks bad is bad)

there is vital information missing here
to start with it is a v 6 so there will be 2--HO2S sensors one for each bank before the cat converter and 2 --O2ensors --one for each bank after the cat converter
there is a vast difference between HO2s and O2 sensors as each reports different information to the ECM
next slow acceleration can be accelerator position sensor or throttle position motor
every time you read the codes it cancels them so you have to run the vehicle for a few miles for codes to reappear
from the codes there can be up to 7 reasons for that code to appear so you don't pick on the first one as it could be another or a combination of others

You need to check for diagnostic codes on your cars computer and clear them before the check engine light will go out. Any codes you get will most likely lead you to what is causing your car to backfire. You can buy a code reader for 60 bucks at any parts store. It plugs in right under the dash on the drivers side next to the the left hand side of the steering column.

If the engine is not reaching optimum operating temperature it will indeed give you a "check engine light",the code will lean you in that direction as well.The noise your hearing more than likely is coming from the "clutch fan",they are very common on the TrailBlazers to make noise and fail.The oil light... you certainly need to have the oil pressure checked with a mechanical gage.

You are saying the injectors are allowing too much fuel into the cylinders. Or not enough air from the air filter.
Is the check engine light on, and have you checked the fuel pressure regulator ?

You need to have the carbuerator cleaned as it sounds like you main jet is plugged. I doubt it is a vacuum leak as if it was, your engine would have a hard time idling.

Engine system needs inspection on case of backfire:-----

Check out related help links to troubleshoot the vehicle backfire issues:-----

Feels like backfire from engine when decelerating?

http://schematicsdiagram.blogspot.in/2012/02/feels-like-backfire-from-engine-when.html

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Jeep Backfires?

http://technoanswers.blogspot.in/2012/02/jeep-backfires.html

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Nissan Pathfinder stalls and bucks on Acceleration?

http://technoanswers.blogspot.in/2012/02/nissan-pathfinder-stalls-and-bucks-on.html

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Nissan Pathfinder Backfires?

http://technoanswers.blogspot.in/2012/02/nissan-pathfinder-backfires.html
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These will help.
Thanks.

locate the mass air flow sensor. it's located inline with the air intake. it should be right after the air filter. disconnect the plug and see if the car runs better. also, when tapping on it lightly on the sensor with a screwdiver handle and the engine skips, could also indicate a bad sensor. these sensors will not always set the check engine light. suspecting the fuel system is also a possibility

you most likely have the fuse to the obd blown which in most cases is the cig lighter fuse then you should be able to read it and the light not coming on is most likely a short in your cluster and should not affect reading the codes

I am going through the same type of problem. I will be pulling the intake manifold off today to check and see if I have any fuel leakage coming from the fuel pressure regulator or injectors. I get random backfiring when motor gets under a load...I put my foot on the brake before I put it in gear and it backfires(sounds like a poofing), always gets worse when in gear, at idle it will do it every 30 seconds...under load when rpms drop...2-3 seconds between...hopefully I find a leak under intake manifold...