95 chevy blazer problem

I have over 257000 miles on my blazer. It runs great. But It started to run rough. My wife took it to a (I hate the word !) mechanic. She has been before we got married. The truck had a hole new fuel system put on all the
way to the catylitc converter. mind you it cost a pretty pennie. Now every once and a while it will run rough. what should I look at first. I don't even know were to start.
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You've put on a "hole" new fuel system all the way to the "catylitc" converter (what ever that means) and a "hole" new airconditioning system on a vehicle with 257,000 miles? I'd imagine it did cost a pretty "pennie". I'd assume you've spent well more on repairs that the vehicle is worth.
My advice: Retire your 95 "blazer".
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Advocate wrote:

Did they change the fuel pump and filter, how bout the ignition/spark system, I would not say it is the end of this truck, I have a '83 Jimmy with 300k that I still play with, sill orginal engine and tranny. When the fuel system died I would have looked more at a long block instead of fixing the fuel @ 257K, but what is done is done.
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Advocate wrote:

Did they change the fuel pump and filter, how bout the ignition/spark system, I would not say it is the end of this truck, I have a '83 Jimmy with 300k that I still play with, sill orginal engine and tranny. When the fuel system died I would have looked more at a long block instead of fixing the fuel @ 257K, but what is done is done.
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What I would PERSONALLY check is the timing chain. with that many miles, when was the last time the timing chain was done? The chain inside the motor which connects the cam to the crank may be worn, and then the chain can get loosened by acceleration and deceleration and it suddenly runs rough, then all of a sudden the slack comes out of the chain and it runs a little better but not for long
Lots of ways to determine If this may be part or all of the problem some are hard, some aren't: Harder Check it by pulling all the plugs and the distributor cap, put a big wrench on the harmonic balancer bolt and move the engine back and forth with your left hand and hold the distributor rotor button (or watch it carefully) as you move the bolt back and forth, if every time you move the crank the distributor does not instantly follow, that is the slop in the timing chain. depends on how bad it is, but it really doesn't take very much slop to make it run really rough and throw the whole core engine timing scheme off.
Easy: New timing chains have NYLON impregnated into the top sprocket which bolts to the cam, the nylon gets brittle with age and starts to come off in pieces this creates, (yep) timing chain SLOP or loosening. If you change your own oil, run it down through a T Shirt or rag, if you find little chunks (or big ones too) of nylon, plastic stuff, Time to replace the timing chain. Another way to tell is put a timing light on the engine while its running, if the timing mark seems to wiggle back and forth and everything else is all tuned up, this can be your problem, you can be fooled by this one as it may do that for a variety of reasons, but if you have checked absolutely all the plug wires, cap, button, and fuel pressures and you still have a rough run, might be time for a chain
You can buy aftermarket chains which do not have the nylon, but even those eventually (about 125,000 mile ago for you) wear out. . So depending on how sloppy the crank to camshaft connection makes a huge impact on how a Chevy runs. Its fifty to 75 dollars worth of parts and will take you a day to do it, if your a good mechanic. If this is your problem, and the chain fails the engines exhaust values will be left to defend themselves against the pistons, usually the pistons win this fight, but they do a lot of damage to the pistons and can crack the head also. So any time I find a Chevy that has a mysterious "run rough" and it has a lot of miles on it, I like to figure out really quickly how good a shape the timing chain is in. If you try to get a mechanic to do this, it may cost you a lot more than the truck is worth, so choose your mechanic carefully, if you have a lot of deferred maintenance issues then you can expect them to want to fix all of it before they warranty the timing chain, as to do it you have to pull every belt and hose in it as well as the radiator, and move all that crap out of the way to get to the chain, you can easily expect to replace all belts, hoses, radiator cap or whatever else needs attention on the way in and out.
The other mysterious run rough is the Harmonic balancer, you didn't mention whether or not you heard any noise, if you hear any clanking, especially on gunning the motor, your harmonic balancer has a rubber insert in it, which could be worn out. If the harmonic balancer appears to wobble that piece of rubber on it may be worn out. (hope its this as this is a cheap fix.)
Hope this helps and Good luck figuring this out.
--
JAMES HAYES
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