4.3 only half firing

[astrosafari]

its not an astro, its my 91 blazer. 4.3l. been sitting all winter in the garage. i try to start it and it seems as if maybe only 4 of 6 spark plugs are firing. it tries to start and run but it just cant do it. i noticed i have a torn up spark plug wire, its still in one piece but theres a chunk of it missing. could this be causing all my problems? i checked all the sparkplugs and cleaned them, and took the dist cap off and cleaned up the inside of that with some sand paper. still same issues. its backfiring through the tbi. any idea what i could do?

http://www.stylintrucks.com/parts/super ... tst2-.aspx

i just bought this today. have to wait for it to be shipped here. if that doesnt fix my problem, oh well. its still some new parts... help plz?

[astrosafari]

i didnt get the dist cap i bought. they were out of stock and sent my money back. i can pull off a spark plug wire, turn it over and it seems to almost want to start better then with all the wires on. seems like maybe i have a stuck valve or something? what can i do to check for this? im on the search for a 350 or a new 4.3..

[Smiliesafari]

Fuel injectors can get gummed up after sitting for a while. Also, I had a new fuel pump get gummed up to the point that it had to be replaced. Try putting a small amount of gas it the TB and see if it will run. I doubt that one bad spark plug wire would stop it from starting.

[1Gary]

Corey-does it fire using starting fluid??.Could it be that you have a load of bad gas from setting??.Smell it at the filler tube and if smells like varnish the gas turned bad.I don't know about Blazers,but does it have a in-line fuel filter like Astro's?.Might want to give that a thought about replacing it.Just like what Skip said x2.

[astrosafari]

fresh gas, its getting fuel. i tried dumping gas in the tbi but it makes no difference.

[doyoulikeithere]

have you put good spark plug wires on it yet? they are notorious for poor firing even if they seem to look OK.
Same with a cap & rotor. cleaning it with sandpaper or whatever is done, but a new quality unit is the answer there.
What is your timing set at? manually confirm your timing if you arent sure where it was.
Is the coil ok, Are you getting a decent spark? If you are getting a fat blue spark at the plugs, then move on.
Are all of the computer sensors hooked up & working or mouse chewed? do you get any codes?
I agree that a stuck injector can happen after sitting, take off all the air-cleaner so you can see them and maybe even shine a timing light at them while you try to start it.
Should be fuel spraying out of both in a cone pattern. if not flowing at all, or dripping in a solid flow not spray, or you need the injectors cleaned, although the solid flow should still start.
keep an extinguisher handy if youve been having backfires.
Keep us posted with your findings...

[astrosafari]

there is a good flow of fuel in the cone shape at the tbi. i dont have a timing light. any idea what they cost, or what my timing should be set at? ill check for spark at the plugs today.

[CaptSquid]

Timing lights are relatively inexpensive. Your timing should be set at 0º. The electronics takes care of any adjustments.

[doyoulikeithere]

there is a good flow of fuel in the cone shape at the tbi. i dont have a timing light. any idea what they cost, or what my timing should be set at? ill check for spark at the plugs today.

in the mean time. you can rotate the crank untill you line up the timing mark on the pulley at the zero mark, and then just verify that the distributor rotor is pointed at the #1 lead, and the star on the reluctor wheel is at the contact point. That should get you going and a light will fine tune it from there. Some crank pulleys have 2 marks, use the correct one! If it ran fine before it was parked, and no one messed with the distributer, it shouldnt be too far out if any.

check for spark at the plugs and get brand new wires cap and rotor is my guess.

[astrosafari]

so i disconnected the fuel injectors, pulled each wire individually and checked them one at time. they all have good spark. so i figure why not try to start it agian. and i did, and it fores right up. runs like sht tho. its been sitting for six years. i have only driven it about 3 times since i got it, and alot around the shop i had it at. so a few days later i fire it up again. then the next day i try it again, and its doing the same thing all over again. feels like trying to start with only 3 spark plugs... ill go get a rotar and plugs today and see if that helps

[astrosafari]

changed wires rotor and cap and no difference. this sucks. when it does run, it runs strong but you can tell it hasn't had a good run in a long time. i checked for broken vacuum lines and for disconnected wires and every thing. i cant find nothing. my other cap rotor and wires arent that old..

[astrosafari]

so check this... yesterday my dad got it running. he held the gas at almost all the way while turning it over, and it started running but severely missing on 2 or 3 plugs. but he held it almost wide open and they all started firing and it was running alright. but then i showed him how it runs differently with the ac off and on max a/c. with the a/c off it idles lower then on max a/c. but then the a/c started squeaking and making tons of noise. the a/c still worked tho. blows strong and cold... my dad thinks theres a bad vacuum some where. any opinions or thoughts?

[1Gary]

Hi Corey.

A/C vac lines have been know to leak on these vans.Not saying with certainty that is your problem,but might be worth taking a look.When you say turning on the A/C it makes all kind of noise,the compressor does effect idle and maybe it is on the way out.But the thing is your have the issue all ,well almost all,the time.A/C on or not.Might want to go beyond just the A/C vac lines and check out all of the vac lines.

Keep us undated as to what you find.


The other times we have see misfires it has involved sensors.Sorry bud,I am running out the door and can only suggest you do a search on the terms of misfires.I'll check back later tonight.

[astrosafari]

it seems as if it sits it goes back to almost trying to start.

its got 360,000 km
leaks oil
been sitting for almost 6 years
burns oil
runs like sh!t.

should i just find a donor vehicle and start swappin? im thinkin 5.7l. already got the posi rearend put in...

[astroturf]

Sounds like a good plan.

Jim