So my 86 blazer is having some serious hesitation problems. It hesitates when I am trying to accelerate. If I baby the crap ot of it it won't buck or hesitate or anything. But if I give it just a little too much gas it bucks so hard I feels like the engine died but as soon as I get off the throttle it fine. It does it especially bad when going up hill and the rpms start dropping. At idle the engine purrs , the idle is too high and I can't get it to come down (like 1200 rpm and the idle screw it all the way out), but it's running like crap when ever I try to accelerate quickly or go up an incline ... Any Idea would be great. BTW I already searched and couldn't find anything. Thanx again
CK5
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hesitation problem please help
- Thread starter pornorob
- Start date
Muddytazz
1 ton status
From what your describing, sounds like what happened to me last yr. Come to find out it was my fuel pump going out.
shane74
1/2 ton status
pornorob said:
How did you determine that? Have you pulled the codes? What have you done? What have you done to the engine? Is it a stock 5.7 TBI? Or is it a 305? Is it carbed, TBI, or full on injection. The more information you supply, the better responses you'll get. I just went through a 3 week long ordeal with my '87 burb and it had similar issues. What EXACTLY are we dealing with here?
I know its not the fuel pump because I went out and bought on today and put it on. It is a stock ( asfar as I know ) 350 carbed , non computer controlled engine with an hei ignition. if there any other info that would be relevent let me know.
shane74
1/2 ton status
Ok, well that helps simplify things a lot. Have you checked the fuel filter? What kind of carb is it? quadrajet? Made by who? Does it smell like fuel when you get on it? It sounds to me like it is under fueling the engine. Is this truck new to you? I'm not trying to be a pain, but the more specific you can be, the better your chances are of figuring it out. I had similar issues once with my '79. It was the float inside the carb. If your getting good fuel flow to the eng. but it still runs like crap when you get on it, it sounds like carb issues to me. Do you know anyone that has a carb you can swap on for a test run? If you swap it and all the prob's disappear..bingo!
Yeah the truck is new to me. It has a q jet on it and i'll include a picture(it has been cleaned since the picture was taken). There is a definate smell when it stutters and dies. I really can't describe it but is defianately not fuel. when I really get on it like WOT and hold it there is just kinda surges then dies and goes pop pop pop pop until I take my foot off of it and then it runs like normal. I have not changed the fuel filter yet bu it didn't look dirty at all when I pulled it out. I wish I had a carb to put on it and try that would make this alot easier.
dave_90_blazer
1/2 ton status
the choke wire in the pic is not hooked up
shane74
1/2 ton status
dave_90_blazer said:
niether is the vaccum advance.
Pornorob - is that all hooked up now?
muscle
1/2 ton status
sounds like the engine is starving for air.
PaloAlto_K5
Registered Member
I may be an idiot, but mine used to do that when my timing was too retarded. Also, are you running a points system or electronicly controled ignition?
PaloAlto_K5
Registered Member
I am running the Accel set-up, and if I retard my timing below 700rpm at idle, I get nothing but bog when I step on the gas hard, even though the fuel is being dumped into the carb....just something else to look at, and re-timing is a hell of a lot easier than replacing parts.
~art
~art
Sounds like a combination of timing and fuel problems.
Check to make sure your plugs are in good shape, and that the gap is correct for an HEI (0.045) Make sure that the timing advances are both working (vac and mechanical) and that the base timing is correct. Also, if it is bogging worse on hills, check to make sure that your float isn't saturated with fuel, causing the carb to flood itself.
The high idle sounds a bit like a bad carb to me as well.
Check to make sure your plugs are in good shape, and that the gap is correct for an HEI (0.045) Make sure that the timing advances are both working (vac and mechanical) and that the base timing is correct. Also, if it is bogging worse on hills, check to make sure that your float isn't saturated with fuel, causing the carb to flood itself.
The high idle sounds a bit like a bad carb to me as well.
The problem sounds more like your mixture is going lean when you try to accelerate.
Possible problems:
1. Carb is not getting enough gas - measure the volume of gas getting to the carb. I forget what the flowrate is but it should give you a good squirt every other crankshaft rotation. It could be a clogged filter, crimped or collapsed hose, plugged line, etc.
2. The accelerator pump on the carb is not working - See if it squirts gas into the throat of the carb when someone presses on the accelerator. A bad diaphram will cause that.
3. Q-Jet out of adjustment or plugged main jet - Its not a simple job to adjust a Q-jet, so I'd pull the main jets first. Then check the float valve to make sure it's not sticking closed or partially plugged
Try these and good luck,
J.
Possible problems:
1. Carb is not getting enough gas - measure the volume of gas getting to the carb. I forget what the flowrate is but it should give you a good squirt every other crankshaft rotation. It could be a clogged filter, crimped or collapsed hose, plugged line, etc.
2. The accelerator pump on the carb is not working - See if it squirts gas into the throat of the carb when someone presses on the accelerator. A bad diaphram will cause that.
3. Q-Jet out of adjustment or plugged main jet - Its not a simple job to adjust a Q-jet, so I'd pull the main jets first. Then check the float valve to make sure it's not sticking closed or partially plugged
Try these and good luck,
J.
backcountry
1/2 ton status
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Sounds to me like the accelerator pump/plunger in your carb is worn out.
To check it: Vehicle and ignition off, remove air cleaner, get flashlight, look into the primaries, now grab the linkage and open it up full throttle. Do this a few times. You should see a steady stream of fuel enter the carb. If not, I believe this is the problem and it is time to rebuild the carb.
To check it: Vehicle and ignition off, remove air cleaner, get flashlight, look into the primaries, now grab the linkage and open it up full throttle. Do this a few times. You should see a steady stream of fuel enter the carb. If not, I believe this is the problem and it is time to rebuild the carb.
