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1988 K1500 silverado 5.7L 4x4

When I'm just cruising it rarely happens. Gets really bad when taking off and under load. Advanced the timing a little and that helped.

What I've done:
-Emissions system (EGR valve and SOL, MAP, PCV, air inj control valve)
-pick-up coil
-timing
-fuel filter
-cap, rotor, plugs and wires
-had fuel pressure tested and it was good (Around 12 if i remember correctly)


Any help would be appreciated.
 

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Clean the throttle body, and it sounds to me like your Distibutor may be shot. I had a similar issue and it turned out the be the Dist.
 

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Like murdog said it sounds a lot like a dist. I had a problem just like that and it was the dist. Only I had very low power and a terrable missfire. How about your compression? Is it within specs? Check that too.


Good luck, I would go with a dist. If it got better by advancing it id bet its a dist.
 

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Simple answer

If you have not figured this one out yet. Let me give you the easy solution. Replace the gear at the bottom of your distributor shaft. This problem is common on these trucks. What happens is the metal the gear on the shaft is a softer metal than the one on the cam it meshes with. This is one of those on purpose things, one of them has to wear faster than the other. The distributor is easier to remove and install, so chevy put the soft gear on the distributor.

The reason you are having problems is as this gear wears down the clearance between the meshing gears increases. This causes serious issues for your computer when it comes to timing the spark. You will probably notice that under acceleration, or deceleration things are well, but if you are trying to maintain lets say 70 mph, things are not so good. Misfires, surging, sputtering, all kinds of good stuff happens. this is because the gear on the distributor is in the free section which could mean quite a few degrees of pretty much instant advancement and retardation any time the speed of the engine changes when you are not speeding up or slowing down. To make it simple, there is too much play in the distributor.

The repair is simple, for 35 bucks or so you can purchase the gear from autozone. get a small punch. Pull the distributor naturally noting how you are removing it so you can install it the same way. Once ya get the distributor out wrap it in a few towels or something you can use to pad the distributor. If ya have a vise this is a good time to use it. When I did mine last I did not have a vice... So I used a beach towel and a brick (not reccomended im lucky I didnt bend the shaft or break the housing.) Push out the pin holding the dist gear in. be carefull do it nice and easy...dont damage the distributor. Pull the worn out gear off (oh yea you can tell if the gear is worn or not by looking at it. Look at both sides and the edges of the teeth in the gear, normally one side will be worn down more than the other and will be convex from more time spent accelerating than decellerating. At this point even if its not noticable go ahead and replace the gear. No matter what unless the dist is new its going to make a difference. Put everything back together.. gear on, tap the pin in. Install the distributor and all that.

Another thing you wanna look for, is in the cap. These distributors have a bad habbit of picking up any and all moisture, trapping it in the cap and never letting it go. Even here in south Texas where we might not see rain for a year or more at a time I have this problem. I have tried all the fixes. The new style distributor, The hack on the old ones...both of them. Drilling holes to allow ventalation, and sealing the cap to the body of the distributor with gorilla glue and sillicone to prevent moisture getting in there in the first place. Neither works... Not even in south texas.... its 105 outside... it hasnt rained really since like 09.. And just this past weekend I was fixing the result of this mess.

What happens is when moisture gets inside the cap, it creates 2 problems. One is immediate. The moisture if there is enough will cause a missfire. The second is more of a long term thing. The moisture mixed with the missfire (and I only vaugely remember the details and am not a scientist but this is the general idea) creates some kind of acid that corrodes the terminals inside the distrib. every few thousand miles....even in south texas...in the 105+ temp and like 35 to 40% humidity....and the last time it rained...blah blah blah...Still have to scrape what looks smells and tastes (dont ask) alot like corrosion found on a battery terminal... its thick too... thicker than my thumbnail some times..

Ideally you should replace your cap, but I just clean it with a knife (being carefull not to scrape off metal from the terminal dont want to open that up too much) sand paper, or steel wool to shine it up. Then coat the inside with wd40. and its good till the next oil change... i admit though i went almost a year since the last time i had to do it, and my truck was running fine. I just figured while I was messin with some other stuff. ya know

I hear that if you get a distributor and cap from Chevy it wont happen anymore..

the gear thing... thats a good thing... better replace a lil 35 dollar gear on yer distributor... than the whole thing. Or the camshaft...

Hope I made some kind of sense. I am sick, and its late and I am sleepy. I remember when I was trying to figure this same problem out, I was on 5 different forums, and after 6 months no one could figure out what was goin on. I finally did some research.
 
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