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alright so i have a 87 ss 305 5.0 H.O 4bbl v8 143xxx miles on it and its got a hell of a miss. it happens all the time no matter what gear its going into or where its at in the rpm field. it jerks like hell while accelerating and even while just crusing i can feel it but its not as rough. its got a new rebuilt carb on it its a duralast carb new cap and rotor new plugs new wires oil changed at the intervals. takes a while to warm up if i dont let it warm up for around 20-30 minutes when i try to open the 4bbl it doesnt take off but at the same time when i do get the ability to punch it the miss goes away and its smooth until i let off the gas then it goes back to having the miss. i can push it but it wont take off as it should has a new egr valve aswell as new catalystic converter and tailpipes and mufflers since the old cat ate them. any ideas let me know oh yea its got low power and gets horrid gas milage
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Has it been like this since the new carb?
Does it have a manual or automatic choke?
Make sure the choke is working properly.
Pull a plug out and see what it looks like to see if its running rich or lean…What does the exhaust look like when you punch it?
Good luck and please keep us posted.Did you get a direct factory replacement carb? That would have been a quadrajet. Those carbs are amazing when tuned right, but amazingly hard to tune right. I would be suspect of a Q-jet out of a box from autozone is what I’m saying. Also, that year would have a computer controlled carburetor, which sounds wierd, but it’s true. It has a metering solenoid built into it. Did the new carb come with it? If you aren’t confident in your ability to rebuild a carb, it might be worth your time to take it to a shop and have it professionally gone through. Also, are you sure that you don’t have a compression loss? I would run a couple other checks that are free, as well as verifying that your repairs fixed problem.
Start with a power balance. You will just unplug the wires at the plugs or the dizzy, but be careful that you don’t get zapped, which is honestly hard to do:
http://www.youtube.com/watch?v=bAOmUjAjNjE
If you find the cylinder, then check for ignition at the cylinder, which is demo’d in this vid. It’s a no start video, but shows the basics:
http://www.youtube.com/watch?v=FBUYs539cy4
If you find you have ignition at all cylinders, then check compression:
http://www.youtube.com/watch?v=X_tbksFYhl4
Then we can go from there. Good luck.
You can use a test light to do a power balance test, just connect the one end to ground and hold the tip of the test light closer to the post where you removed
your wire from then the other hand you removed the wire with, then the spark will jump to the test light.
This is also easier on the coil.Quoted From Trcustoms719:
You can use a test light to do a power balance test, just connect the one end to ground and hold the tip of the test light closer to the post where you removed
your wire from then the other hand you removed the wire with, then the spark will jump to the test light.
This is also easier on the coil.I would be more interested in seeing the spark at the spark plug end now that I think about it. Autozone wires are notoriously crappy in my experience.
with the miss going away when you punch it. leads me to
believe vacuum leak. try searching for vacuum leaks
also spray around the carb base area. use a spray bottle and
water instead of carb spray. heres a video. if it was electrical
the miss would not go away under hard acceleration
unless the carb float not set up right. what was wrong
with the old carb?http://www.youtube.com/watch?v=9CPqbaSg … plpp_video
i dont know what was wrong with the old carb its been about 4 years since it was replaced i just know it was not allowing the vehicle to start after 4 different swaps to autozone we finally got a carb that worked so i know i need to get the carb tuned but i think the miss was there with the old carb aswell. vacuum is what i have been thinking but the car has seen so many different people i havent messed with it. ive been thinking of a 350 swap but cant afford to have it done i dont like the 305.
Quoted From college man:
with the miss going away when you punch it. leads me to
believe vacuum leak. try searching for vacuum leaks
also spray around the carb base area. use a spray bottle and
water instead of carb spray. heres a video. if it was electrical
the miss would not go away under hard acceleration
unless the carb float not set up right. what was wrong
with the old carb?http://www.youtube.com/watch?v=9CPqbaSg … plpp_video
You get the gold star man because that’s exactly what I was going to suggest for the very same reasons, well done!
the float not being correctly setup would not be a shocker i really need to have the thing tuned but im afraid of the price im going to be charged i dont exactly have a lot of money. vaccum leak i will deffinently look for. but now with soap and water for a vaccum leak amd i still spraying and listening for the engine idle to drop as it would with carb cleaner?
yeah, you would hear the engine rpm’s change and maybe hear a sucking sound if the vacuum leak is bad enough.
alright cool itll be a little whilr before i can do the test gotta a lot of busy days ahead of me but when i do the test i will let yall know whats up and if it helped
Quoted From deadclown:
alright cool itll be a little whilr before i can do the test gotta a lot of busy days ahead of me but when i do the test i will let yall know whats up and if it helped
Cool, We’d all like to know what you find.
Please keep us posted.
Thanks and good luck.Quoted From EricTheCarGuy:
You get the gold star man because that’s exactly what I was going to suggest for the very same reasons, well done!
Thanks for the gold star. Thats a keeper.
keep us posted on your progress
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