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weird problem and i cant seem to fix it. Updated NEW PROBLEM NEED HELP

buffblazer

buffblazer

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ok here is the deal, my 86 k5 has a lugging problem. if im applying throttle more than half way the truck runs fine. but when im coasting and just holding the truck at a speed, it has random lugging actions, that almost feel like a misfire. and i know the first thought is misfire, or fuel. but ok im three months away from graduating wyotech, and i have been thru the automotive program so i kinda know what im doing. but anyway just to give you guys the run down to help narrow it down, i have check the entire ignition system and im getting proper spark everywhere. its carburated and i have check to make sure that there is no problem with fuel flow or if anything is clogged up and everything is ok. so then i went to the brakes to see if i was dragging. and my right rear was having problems not spinning freely so i cleaned everything up and disconnected the e-brake because it would not release. i test drove it and still no fix. my next area is the front right caliper because it froze up on me once and really warped the rotor, and my question is could that be doing it? and also i have a 4-speed manual and i was wondering could it be the tranny? i have been fighting this for 6 months and i need help. any ideas would be greatly appreciated.
 
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i know in a newer fuel injected vehicle we'd break out the scanner and start monitoring sensors and maf voltage along with fuel pump voltage... but....

is the carb running rich enough to make it lug at part throttle? i really dont know where else to tell you to look but i'll be keeping a watch as this will be a very informative thread...
 
luging has nothing to do with the brakes or transmission. Its all engine.

I agree with balterbuilt, sounds to me like its a timing issue or a carb problem. Hook up a vacuum gauge to one of the vacuum ports on the carb and a timing light, that'll tell you most everything you need to know.

Surprised Wyotech hasn't taught you about this stuff.
(I don't mean to sound like an ass)
 
well, he's still got three months, maybe timing is later on..do they still teach people about carbs?
 
I am having the same exact problem but with a TBI and today i checked the timing and all is well, could it be the fuel injectors or even the fuel pump
 
i agree that its not the brakes or tranny, if either locked up it would lag and hold until the truck stalled. it wouldnt be a come and go thing.

for a problem that comes and goes, its going to be an engine control problem, my guess would be a primary fuel delivery problem. above half throttle i believe your secondary circuits kick in, and seem to deliver adiquate fuel. i would adjust the primary fuel circuit at idle for the highest vacume reading and back it off an 1/8 turn. at least as a starting point.
 
my experience...

I had a few GM's that did the same thing--ran good if you floored it,but when "cruising" they would feel "jerky" like they were misfiring..one truck that did it was a 250 six with a one barrel carb that had the "Adjustible Part Throttle" screw inside the carb (the one few manuals even show or tell you about,and the few that do say "DO NOT TAMPER" with it!)..mine was evidently tampered with,it was open more turns than stock..fiddling with it didn't help a lot,but made it less annoying..I eventually got a V8 in it--end of problem..:D

Another 305 I had did that too..after trying different carbs,fuel pump,the distributor (had points and I suspected worn bushings letting the point gap change),and cleaning the gas tank out,I gave up and decided to live with it..


The guy who bought it from me pulled the heads off--one valve had a chip missing out of it,another was warped slightly,and after he did a valve job,it no longer "bucked" at bit like it used too..valve can do weird things--like make an engine misfire only when the burnt spot and the spot on the seat "line up" once in a while ,as they rotate while runing,and it'll only "skip" when that happens,not on every power stroke like you'd think..I've pulled heads and wondered how the hell it ran so GOOD with burned and otherwise "bad" valves!...and they had decent,but not perfect compression when I tested them--over 100 psi anyway..

A loose timing chain might do the same too...try using a timing light--see if the mark floats around, instead of staying steady...

Of course,it could be ignition too...any failing part like the pick up coil or module,or advance weights can cause similar symptoms..I'm just not that lucky I guess...:rolleyes:
 
ok lets start from the beginning the wires on the truck are 9 months old, and i did a resistance check and they were all within specs. plugs,cap,rotor are all only about 2 months. and i guess your all disapointed because it seems that i dont know as much as i should but really the reason i said brakes or tranny is because after 6 months of trying everything to fix it you kinda start think of other things like maybe the clutch is slipping or the brakes are heating up and sticking, or a warped rotor, so thats why i threw those other things out there, and i have taken the carb completly apart about 7 times getting the kinks out of it so i dont think its a carb problem. but the timing caught my eye, i timed the truck in class about 3 months ago, but i dont think i did it right but it was also doing that before so i was wondering can a truck just knock itsself out of time? i do know the dizzy seemed loose when i went to time it. but i have really not to bad of power or economy loss (except of the altitude change) and it idles nice. im sorry but wyotech is a good school, but they fly threw lectures so fast and cover so much in such a short time that some things you pick up on better than others. and no they do-not cover carbs which sucks and out of my 47 person class i was the only student that had even taken a carb apart. so i was kind of alone on this one. but thankyou for everything guys and i will check the timing and if you guys think of anything else i would appreciate it
 
10 to 1 says it's ignition related- probably a timing issue. Poor performance can be attributed to fuel issues, but your tailpipes would be telling you the story there. The fact that your idle is good shows us that your choke isn't sticking.

FWIW, I would re-check the wires and set the timing again.

By the way, don't get your panties in a bunch over a little teasing. The boys are trying thier best to help you out, but when you say stuff like this :

i have been thru the automotive program so i kinda know what im doing.
Click to expand...

and then ask for help, you're opening yourself up for a but of ribbing, don't you think?

Keep us posted, brother. Let us know how things work out.:thumb:
 
oh no when i wrote that i just ment that im not a complete retard, meaning im not like some people who just dont know me left foot from my right, i did not mean to sound like i know everything, sorry if it came off like that. but again thanks for the help and everyone keep the advice coming in my opinion, it doesnot matter how much experience you have or how much you know, advice is aways good to hear, and its you choice to do whatever you want with it
 
Check it out I just had the same problem as you remember i posted on this thread a few days ago, what fixed mine was timing. But i also changed the injectors and that seemed to help but those were 16 year old injectors they were a little due dont ya think. Tripple check the timing and let us know, if you need help give us a holler and some one will help you out. Hopefuly they dont rag on you so much any more.
 
ok new update on the problem. this one caught my eye and i was wondering if it could be connected to my previous problems. i was driving down 287 between laramie wyoming and fort collins colorado, and i heard a slight grinding noise. i pressed down on the brakes slightly and heard a popping sound, the truck shimmyed back and forth on the road and then another pop and everything was ok. i pulled over and checked everything out and everything was fine. i was closer to fort collins so figured i should try and make it to fort collins before it got dark. i turned off 287 and the same thing happened when comming up to a light. i then no more than get 4 blocks and i go to hit the brakes and i have not pedal. i mean it did not go to the floor and stay there but it was really weak pedal. the brake light came on, so i down shifted and pulled over. the next day i pulled off the tire and the hub assembly looked like a grenade went off in it. i figured out that the bearings were gone because of no grease (even know in march i had big O in loveland grease them and when i called them yesteday it says all they did was put new hubs on) so im trying to figure that one out to. but my question is, what caused my brakes to go out, and could this have any relation to the previous problem?
 
well when the bearings go and everything takes a crap on you the brakes will go with it. Did the hub (not the locking hub but the hub) have damage? If so you probably just need new hubs races and bearings. I'm thinking Big O didn't grease your bearings. Was the tire straight up and down (perpendicular to the ground) or did it look like it was just hanging off the truck?
 
and if "they just put new hubs on"... they didnt do the job properly, they probably never greased, and overtightened the bearings, so take pics of the odometer with todays paper next to it and pics of the hubs, fix it yourself and then go to the store manager and demand your money back and payment for the new parts and tow bill... you see, there is ALWAYS a tow bill...
 
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