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96 blazer 4.3 hesitate on acceleration

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Old 11-15-2005, 07:41 PM   #1
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96 blazer 4.3 hesitate on acceleration

ok i have a 96 blazer with a 4.3 TBI. not that it matters, but its a 4x4 and LT package.

i bought it 2-3 weeks ago, so i know next to nothing of the trucks history.

the problem that i am having is........

when i start my truck it idles fine. but when i try to drive i get a big hesitation and it spits and sputters. not all the time, just when trying to drive around town with slow speeds, as i accelerate off a stop sign it will sputter and fall on its face, if i give it more gas it go just fine. after it warms it gets better. (does not go away). i noticed that it shutters some wile having cruse set around 65MPH but as i said if push the gas pedal down more it will go fine.

normal driving its hesitates
flooring it, it does better
idle seems fine.


when i bought the truck it had no problems. i did some maintnence considering i know nothing of the truck

--plugs
--plug wires
--dist cap
--button
--alt
--battery
--brakes, rotors, drums, wheel cylinders...etc....
--air filter
--fuel filter

the truck drove perfect for 100 miles. then it started to studder around. i took it to autozone to get scanned, the scanner said random misfire. i then went back to the shop and looked at it. i found that i didnt have the air intake snapped down tight on the throttle body, i bolted it down securly and it no longer leaked, ran great the rest of the day (5 miles....maybe????) the next morning i started it and it was running crappy again ( still idles fine, just hesitates while trying to take off. but once it was warmed up it seemed to do ok, i ran a tank of plus through it and some injector cleaner drove it for a week, ( i live 4 blocks from my shop).
this whole time i got no check engine light, so i took it in to auto zone to have it scanned again. this time i pulled a week MAF signal. so i bought a new MAF ($99). put it on, seemed to do fine, parked the truck the rest of the day, went to drive home 4 hours later, same thing, spittin sputtering, hesitatin..etc.....


any ideas?????? i dont wanna keep buying $100 parts every other day if there not gonna fix the problem.

thanks
joe
Old 11-15-2005, 07:57 PM   #2
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Re: 96 blazer 4.3 hesitate on acceleration

It sounds a lot like a maf related problem to me. It could be a vac leak, or tb leak. Try unpluging the maf all together, and see if that does anything for you, i know mine with a bad maf runs a lot better with it unpluged. Did you happen to use a k&n when you replaced the air filter? If oil wicks off those, and gets on the maf it will cause drivability problems, usualy cleaning the sensor will fix the problem.

The only other thing i could think of would be checking the fuel pressure, it should be around 52-60psi.
Old 11-15-2005, 08:42 PM   #3
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Re: 96 blazer 4.3 hesitate on acceleration

Quote: Originally Posted by rat
It sounds a lot like a maf related problem to me. It could be a vac leak, or tb leak. Try unpluging the maf all together, and see if that does anything for you, i know mine with a bad maf runs a lot better with it unpluged. Did you happen to use a k&n when you replaced the air filter? If oil wicks off those, and gets on the maf it will cause drivability problems, usualy cleaning the sensor will fix the problem.

The only other thing i could think of would be checking the fuel pressure, it should be around 52-60psi.
very interesting - i didn't know you could drive around with the MAP disconnected. maybe that will help with my problem....
Old 11-15-2005, 08:44 PM   #4
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Re: 96 blazer 4.3 hesitate on acceleration

Quote: Originally Posted by ( o )( o )
very interesting - i didn't know you could drive around with the MAP disconnected. maybe that will help with my problem....
maf, mass air flow sensor, not map. The map is what is used when it is unpluged, called speed density. Don't unplug the map(manifold absolute pressure).
Old 11-15-2005, 08:57 PM   #5
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Re: 96 blazer 4.3 hesitate on acceleration

shot in the dark here, ok ,you said you have a 4x4, so you sure it is disengaged fully? cuz i know with mine, if its in 4x4 on dry pavement(which is supposibly bad), my truck aint happy. unless i give it lots of extra gas.
Old 11-15-2005, 09:50 PM   #6
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Re: 96 blazer 4.3 hesitate on acceleration

Quote: Originally Posted by rat
maf, mass air flow sensor, not map. The map is what is used when it is unpluged, called speed density. Don't unplug the map(manifold absolute pressure).
even more interesting. thanks for enlightening me. good luck to the original poster of this thread on fixing your truck.
Old 11-15-2005, 11:29 PM   #7
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Re: 96 blazer 4.3 hesitate on acceleration

like i said it has a brand new MAF in it, i out it in today. im gonna check my vaccume lines tomorrow. as far as teh 4 wheel drive, im pretty sure that it disengages, in fact i know it does, cause today it was rainin bad, and my bald tires kept spinnin when i would take off from a stop sign. my 91 had a similar problem. it had a bad IAC i changed it and it fixed some problems. does my truck have an IAC? also would it make sense that maybe its my 02's i changed my plugs and everything but not my o2's. if i remember right this thing has 4 o2 sensors and there not cheap right? but wouldnt it throw a code?


joe
Old 11-16-2005, 07:11 AM   #8
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Re: 96 blazer 4.3 hesitate on acceleration

I would only change the 2 o2 sensors up near the manifolds, they are the ones that affect fueling. They don't always throw a code.

Your truck does have an iac, it is part of the throttle body, i don't know why it would cause hesitation while you are in the throttle though.
Old 11-16-2005, 09:11 PM   #9
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Re: 96 blazer 4.3 hesitate on acceleration

changed the TPS and it runs great, took all the problems away, thanks for all the advice

joe
Old 11-16-2005, 10:24 PM   #10
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Re: 96 blazer 4.3 hesitate on acceleration

what exaclty does the MAF do if it doesnt need to be there to run? if its working fine, should i try to pull it and see whether it runs better? or it ownt help at all?
Old 11-16-2005, 10:34 PM   #11
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Re: 96 blazer 4.3 hesitate on acceleration

Quote: Originally Posted by greencactus3
what exaclty does the MAF do if it doesnt need to be there to run? if its working fine, should i try to pull it and see whether it runs better? or it ownt help at all?
Your maf is used to measure air into the engine. There are backups if the sensor fails though. If your truck seems to be running ok, then don't unplug it, you will not necissarily gain anything. It won't hurt anything, but you will get an ses.
Old 11-18-2005, 10:12 AM   #12
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Re: 96 blazer 4.3 hesitate on acceleration

ok, runs great still.......AS LONG AS ITS WARM. getting in first thing in the morning, it still does the same shit, only worse. after a good 5 minutes of drivin, it all smooths out. even if i remote start it for 20 minutes, it still drives shitty, until im DRIVING for 5 min. it was 20 degrees this morning with a wind chill of 12 degrees, so its COLD. any ideas???

joe
Old 11-19-2005, 01:22 AM   #13
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Re: 96 blazer 4.3 hesitate on acceleration

well today i realized that its still doing it, not near as bad, but its still there. what else could possibly be the problem? IAC?
Old 11-19-2005, 10:50 PM   #14
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Re: 96 blazer 4.3 hesitate on acceleration

I had this problem a couple of weeks ago. My cold air sensor in the intake was unmounted and dangeling inside the engine compartment. It should be on the right under the tubeing from the airfilter box to the the engine itself.
Old 11-20-2005, 08:47 AM   #15
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Re: 96 blazer 4.3 hesitate on acceleration

mine is plugged in, i was gonna put a 4.7k ohm resistor in line to see if maybe the sensor is reading funny. i also bought a new IAC im gonna try that today too, any other ideas?


joe
Old 11-20-2005, 09:21 AM   #16
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Re: 96 blazer 4.3 hesitate on acceleration

I had a similar problem on my 96 earlier this year. Spit and sputter on normal acceleration when it was cold. Would go away when the engine warmed up. Check the coil for arching. It was pretty obvious on mine. It was arching to the bracket, and was dicolored.

Last edited by Lt_Dusty; 11-20-2005 at 09:23 AM.
Old 11-20-2005, 08:13 PM   #17
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Re: 96 blazer 4.3 hesitate on acceleration

ill check that tomorrow thanks
joe
Old 11-21-2005, 09:08 AM   #18
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Re: 96 blazer 4.3 hesitate on acceleration

any other ideas?


joe
Old 11-22-2005, 09:05 AM   #19
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Re: 96 blazer 4.3 hesitate on acceleration

nothing.........nobodyelse has any ideas?

joe
Old 11-22-2005, 09:41 AM   #20
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Re: 96 blazer 4.3 hesitate on acceleration

hey man check the tps sensor.
Old 11-22-2005, 04:09 PM   #21
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Re: 96 blazer 4.3 hesitate on acceleration

i changed the TPS sensor last week.

joe
Old 11-24-2005, 03:20 PM   #22
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Re: 96 blazer 4.3 hesitate on acceleration

figure out whats wrong?
Old 11-25-2005, 01:28 PM   #23
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Re: 96 blazer 4.3 hesitate on acceleration

no, i changed the IAC and alos put in a new EGR, still when its cold it chugs down the street, when it warms up some it gets better, i think im gonna change my 4 o2's and my MAP sensor. after that im clueless.


joe
Old 11-26-2005, 06:13 PM   #24
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Re: 96 blazer 4.3 hesitate on acceleration

Quote: Originally Posted by wheel_to_sky
no, i changed the IAC and alos put in a new EGR, still when its cold it chugs down the street, when it warms up some it gets better, i think im gonna change my 4 o2's and my MAP sensor. after that im clueless.


joe
TEST FUEL PRESSURE
Old 11-27-2005, 07:44 PM   #25
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Re: 96 blazer 4.3 hesitate on acceleration

fuel pressure reads 58psi with truck not running, and key turned on. didnt get a chance to check while running cause my fuel pressure guage sprung a leak.

so far ive changed......

egr
tps
iac
maf
plugs
wires
fuel filter
airfilter
dist cap
button

and i sea foamed it before all this

still havin the same problem........nobody else on here has any ideas?

joe
Old 11-27-2005, 08:03 PM   #26
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Re: 96 blazer 4.3 hesitate on acceleration

Quote: Originally Posted by wheel_to_sky
fuel pressure reads 58psi with truck not running, and key turned on. didnt get a chance to check while running cause my fuel pressure guage sprung a leak.

so far ive changed......

egr
tps
iac
maf
plugs
wires
fuel filter
airfilter
dist cap
button

and i sea foamed it before all this

still havin the same problem........nobody else on here has any ideas?

joe

check fuel pressure while truck is running
try check fuel pressure when the problem happening but first you need to fix fuel gauge to get a good reading
Old 11-28-2005, 10:23 AM   #27
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Re: 96 blazer 4.3 hesitate on acceleration

to fix the fuel guage ill be fixing my whole sending unit, i guess that would that would also fix the pump if it was the culprit, however it was 55-60 degreed this morning and it ran fine, i could feel a very little hesitation, but only because i was looking for it.


joe
Old 11-28-2005, 04:24 PM   #28
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Re: 96 blazer 4.3 hesitate on acceleration

i think you problem is you fuel pump but you need to verfity fuel pressure
Old 11-30-2005, 07:21 AM   #29
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Re: 96 blazer 4.3 hesitate on acceleration

If your fuel pressure checks out, I would still suspect the coil. I went through basically the same as you, and although the coil arching was fairly obvious on mine, you might want to check it at night, or even use a fine mist of water from a spray bottle.

I don't know your mileage, and 02's can get lazy or fail, but an 02 sensor even if bad would not cause these symptoms. The computer has a failsafe incase the 02's go bad, and you would surely get a CEL.

Last edited by Lt_Dusty; 11-30-2005 at 07:27 AM.
Old 11-30-2005, 12:16 PM   #30
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Re: 96 blazer 4.3 hesitate on acceleration

What is the TPS and where is it located?

I have similar simptoms with my blazer...
Old 11-30-2005, 12:30 PM   #31
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Re: 96 blazer 4.3 hesitate on acceleration

Quote: Originally Posted by lovetheblazer
What is the TPS and where is it located?

I have similar simptoms with my blazer...
Throttle position sensor. It is on the drivers side of teh throttle body. There are two connections, the tps is the one toward the front of the truck.
Old 11-30-2005, 12:50 PM   #32
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Re: 96 blazer 4.3 hesitate on acceleration

Quote: Originally Posted by rat
Throttle position sensor. It is on the drivers side of teh throttle body. There are two connections, the tps is the one toward the front of the truck.
When this part is not in OK condition what are the symptoms in the truck?
Old 12-25-2005, 02:14 AM   #33
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Re: 96 blazer 4.3 hesitate on acceleration

Did you ever check the ECT? It might think that it's always hot...
Old 12-25-2005, 02:32 AM   #34
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Re: 96 blazer 4.3 hesitate on acceleration

could be a clogged injector, you can take the manifold cover off and take the injector out and clean it. If it only reads a single cylinder misfire and you know the fuel and air is good then it could be the dist cap. I had one go bad in less than 10k miles. go under the truck and bang on the cat converter, if it sounds like something is rattling around then your cat could be bad, but it would smell like eggs. But if it's ok after it warms up then I think I would change the Idle Air Control sensor before anything else. That and the egr and you already changed the egr.
Old 01-11-2006, 07:32 AM   #35
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Re: 96 blazer 4.3 hesitate on acceleration

Did you ever find out what the couse of your hesitation problem was? I am having the exact same hesitation problem with my 1999 blazer. I replaced the coil ox2 sensors wires and plugs last night. This A.M. hesitation was still there with no Mil light. TPS and EGR are next on my list to replace. Can you please let me know what you did to solve your problem before I go replacing everything?
Thanks





to fix the fuel guage ill be fixing my whole sending unit, i guess that would that would also fix the pump if it was the culprit, however it was 55-60 degreed this morning and it ran fine, i could feel a very little hesitation, but only because i was looking for it.


joe[/QUOTE]
Old 01-11-2006, 09:46 AM   #36
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Re: 96 blazer 4.3 hesitate on acceleration

Mine ended up being the fuel pump. Causes all kinds of weird problems. Anyway, you should be able to test the TPS with a voltmeter. Just test the resistance across the middle and one of the outside terminals and you should have a smooth sweep from either high to low or low to high depending on which side you hooked up to. As far as the EGR, just take it off and see if it's dirty and take some carb cleaner to it. There's the possibility the diaphragm could have ruptured I suppose, but that's easy enough to test too. Just take some vacuum hose and hook up to it then suck and see if it will open.
Old 01-11-2006, 10:05 AM   #37
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Re: 96 blazer 4.3 hesitate on acceleration

exact same problem on my 88 tbi, changed the coil, plugs, fuel , fuel filter, everything, turned out to be the fuel pump, apparantly when the start to go, the points in it or smg are wearing out so sometimes it will work, sometimes it wont, im 98% sure thats ur problem, i know whats its like, mine was at 2 shops till someone figured it out! and the only reason they did was cause one of the mechanics drove it home and on his way back to work it almost quit on him
Old 01-12-2006, 06:45 PM   #38
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Re: 96 blazer 4.3 hesitate on acceleration

Seems to be a big replacement on the newer blazers my bros 96 had to have the fuel pump replaced big 600 dollar replacement with the shop doing it. ouch! hope mine doesn't go on my truck but at least mine isn't as expensive.
Old 03-12-2006, 02:07 PM   #39
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Re: 96 blazer 4.3 hesitate on acceleration

This is worth investigating.
The following virtually eliminated acceleration/hesitation problems similar to those described at start of thread. I replaced the splice connector that is inline of the EST wire below the dash on the passenger's side, i.e., the wire that is decoupled when the timing is checked (or set). A "wiggle test" of the wires, with ohm meter attached, revealed that the continuity of this connection was intermittent; apparently the fleeting transient nature of the disconnect did not generate an error code.

The problem was originally diagnosed by driving with this EST wire disconnected--no difference in driveability was noted; acceleration with hesitation was still obvious and the acceleration seemingly topped out with pedal to the floor. There was no apparent gain in speed. Connection of this wire at the module was first suspected (distributor and module are new), but there is not much to the connection--wire "wiggle test" was negative. The connector was next in line as I worked systematically towards the computer. Obviously, if the connector HAD checked out okay, then my next step would have been to find out which wire was the ground wire for the EST circuit so that I could test the voltage drop before and during acceleration, when timing was advanced.
Old 06-04-2013, 06:16 PM   #40
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Re: 96 blazer 4.3 hesitate on acceleration

Quote: Originally Posted by wheel_to_sky
ok, runs great still.......AS LONG AS ITS WARM. getting in first thing in the morning, it still does the same shit, only worse. after a good 5 minutes of drivin, it all smooths out. even if i remote start it for 20 minutes, it still drives shitty, until im DRIVING for 5 min. it was 20 degrees this morning with a wind chill of 12 degrees, so its COLD. any ideas???

joe

did you ever get aresponse on this? I have a 96 and a 99 astro 4.3 both do the same thing your describing
Thanks
electricguy
Old 06-19-2013, 03:23 AM   #41
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Re: 96 blazer 4.3 hesitate on acceleration

Thanks all for the info. I have an '88 S10 that I just swapped a '91 motor into. Obviously I had to use most the parts off my '88 as I didn't want to fight changing the computer over. Its my daily driver didn't have time to waste over the weekend. As I am doing repairs on a budget buying parts is out of the question so, Thanks again and I'm going to try out these different tips.
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