bogging down when under stress
 

hey guys, i gotta 03 blazer with the 4.3 and 4wd. when i'm ascending a long hill after a few seconds my check engine light starts flashing and i start losing power. no matter how much i press on the gas the engine speed does not seem to change and it sometimes even gets to the point where it seems like its gonna stall. then there's a funny smell that starts when this happens. as soon as i reach the top of the hill and there's no additional stress everything starts to return to normal and after a minute the engine light stops flashing and it runs like normal. the only codes that we've ever been able to get out of it is misfire at cyl 3 and random cyl misfire. my mechanic cant seem to pinpoint the problem and i was hoping some of you mechanical geniuses could help me out. any help is greatly appreciated.

p.s. we had the fuel pump changed because the pressure was about 10 or 15 psi short of normal but this didnt solve anything. thank you again

1st, a dirty fuel filter can cause the power loss under load. It will run fine at idle and normal driving, but can't flow a high rate for increased demand = thus bogs down.

As for the flashing light and misfore codes - I had this about 2 months ago. Mine was caused by cheap low grade gas! As soon as I added 1/4 tank of the good stuff, it quit. I never had spark knock issues, the light came on with a misfire code - happened on highway with no load.

You might also want to look at your cat being partially clogged.

I agree ^^^^ actually had that happen the comb in my cat was busted and started clogging my cat

x3. Most exhaust shops can do an exhaust back pressure test to determine if the catalytic converter is causing a restriction.

I would say check your plugs wires and disty...

I had an old car do that once, and it was a plug wire that came out of the hanger brackets and melted the outside on the exhaust manifold. Whenever there was a load put on the motor, the wire was arcing to the block and doing the exact things you describe. I would certainly check everything else as well, it could also be a combination of problems.

yea the only problem is that we had the cat replaced about 15k miles ago, the distributor is new. i will make sure to have the back pressure tested and midnight, thanks for the info, i'll make sure to check that too... any other suggestions you guys have are greatly appreciated, thanks!

oh yea davis, thanks for the tips, we also had the fuel filter replaced when the pump was put it 3 weeks ago, ill try the gas, but i've been running the same gas from the same station for 4 years now, but thank you!