1991 s10 blazer. STALLS AND BACKFIRES
 

91 s10 blazer 4.3 4x4,unknown miles(replaced cluster)


has not ran in 6 months. He said it ran rough and stalled at stop signs etc.

I just got it from someone off craigslist for 200 buckaroo's. After a while of tinkering with it i discovered the orings for the injectors was leaking and causing gas to leak everywhere. Fixed that. Well i THOUGHT maybe it ran rough because of the fouled plugs...well i changed 5 of em so far. It got dark and i couldnt finish the last one(driver rear plug,oh and F%$ the one behind the steering arm,i hated it)..

anyways it idles a TINY bit better. in order to get it to crank i have to full throttle it while cranking then once it tries to crank i tap on the throttle. it'll run at 3500 rpm still having the bad skip(that last plug is the problem hopefully,il change it in the morning) but as soon as i let off the gas,it will idle rough then die. while idling if i try to rev on it,it backfires through the tbi and dies.

few questions,
What would cause it to stall? Im going to clean the egr valve,iac etc tomorrow.
whats the timing on the 91 4.3? 0 btdc? I dont have a timing light right now. but i figured id play with it. maybe that'll fix the backfiring.
OH..and do it turn it clockwise to advance or retard the timing?


Short story. It starts rough,runs rough,backfires through tbi.

ALSO...im draining the gas out too.

got any pics??

Clockwise to advance.
Try grabbing that spark plug from the drivers wheel well to save some greif.
Borrow a timing light. The timing being off sure can cause the backfire cause its sparking while the intake valve is still open.
Have a peek inside your distributor cap for burned electrodes, or change the cap and rotor anyways. Then when its off wiggle the distributor shaft side to side, if should have ZERO play, cause if it wiggles, then the rotor will not touch the electrodes as it should and give you a random misfire.

If you are getting no engine lights when it stalls out, then its going to be fuel related for the stalling. I would be checking for telltale signs of a fuel leak: Black exhaust, smell of gas underhood, smell of gas on the oil dipstick. These engines are notorious for leaking internally. Do a leakdown test with your fuel pressure gauge and try fiddling with the injector harness too... it doesnt hurt to check it out. That would be the blue and red wires below and behind your alternator, give them a tug when its running and see if you change how it runs or if you make it stall. The injector harness has been my personal demon....

Do you have a W or Z engine we should ask. You mention the TBI, but I thought that was on the newer than 91 trucks...?

Got that plug out through the wheel well.ty sir. Although i still have a slight miss,or something that sounds like a miss.

I THINK i got the timing back right. or at least close enough for now until i get a timing light. its not backfiring anymore.

I checked for codes and after some confusement on how reading codes work i believe i have the code 24 and 33. Map sensor? il check again today

I tore apart the whole throttle body off the blazer all the way down to the regulator and cleaned it up. the whole pcv vacuum was clogged up. glad i did. I also cleaned the egr valve too. It was gunked up as well. didn't fix the problem but smoothed it out a tiny bit.

i will take off the cap/rotor and check them out today. I asked the guy when he did a tune up and he said about 5 years ago. I guess its time to replace those too.

Check the connections on all your spark plug wires. This past week I had a loose one and it was causing a mis-fire. So just double check, make sure there tight and clicked in.

I fixed the skip,loose wire.


Now i noticed im barely getting any fuel coming out of the driver side injector. and the other one is working as far as i can tell. If i spray ether in the throttle body it purrs like a kitten.
Should i replace the fuel pump? I was going to replace both injectors,regulator,filter,and pump to eliminate everything

yeah start with the injectors and work your way back to the pump, see if that helps.

The 2nd injector may only fire on WOT too, better wait for Swartkk to chime in here... Kinda like the quads on a 4bbl only open on WOT

Ether is a bad thing to be spraying into a gasoline engine... You should try using carb cleaner or something less explosive than ether. If it was to backfire with an intake full of ether you can bend the throttle butterflys or blow out a gasket...

I had a skip at idle from a loose plug wire this week too, just used my needlenose to reach up into the boot and squeeze the clip a little tighter so it snaps onto the plug.

Alright. ive gone this far with it.

replaced:
plugs,wires,cap,rotor.
tps
iac
cleaned egr
completely cleaned throttle body inside out.
replaced BOTH injectors,fuel regulator,fuel filter



still wont run. ARGHHHHHHH...

I cant check fuel pressure,i dont have a gauge and cant afford one right now.

I noticed this... if i try to start it without touching the throttle it wont start. if i barely tap the throttle and continue throughout the whole time it will start,and idle up to about 2000 rpm and nothing more. If i floor it, it will bog down and die. as soon as i stop touching the throttle it dies

1. Need to check the fuel pressure. 11 psi for TBI
2. You could have a faulty fuel pressure regulator. (Mounted on top of TBI and is controlled by a spring and a diaphram) If you get a TBI Rebuild Kit you will get a new spring and diaphram.
3. Dirty Fuel Filter.
4. Throttle Position Sensor could be out of adjustment
5. Idle Air Control Valve could be faulty.

Checking fuel pressure on a TBI is hard. You need an adapter and gauge to plug into the fuel line to measure. Auto Zone may have it as part of the loan a tool program.


Try pouring small amount of gas directly in the tbi and see how it runs. If it runs well for a little bit you know it is a fuel issue.