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Discussion Starter #1
i havea 95 blazer w/ the 4.3 cpi. @ 88,000 miles and 100% stock.
lately it has been running kinda slow. about 6 months ago, i did wires, plugs (platinum), cap and rotor. didn;t help any. the cap and rotor are cheap autozone parts, so should i replace these with ac delco?? should i replace the plat plugs with stock ac delco plugs? also i changed the cpi unit around the same time i did the tune up too, but i am still getting alot of black soot on the end of the exhaust pipe (running rich right).. one more thing, if the engine come near 200 degrees, it starts loosing power REALLY bad. that is not a problem now, cause of winter, but when summer hits, my blazer has a hell of a time pulling around my 17' boat.
i am going to replace the cheap stuff first like cap, rotor and plugs.. pull the upper plenum and check for leaks again. if its not any of that, then whats next O2 sensors? new cat? some help me and stear me in the right direction.
 

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Project: Sabriel
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id check the cat, especially as yu say it loses power when it gets hot. my 1995 CPI did the same thing, and it turned out the cat had gutted itself, and when the exhaust heated up the catalytic converter guts and they expanded, to almost 100% block the exhaust pipe, which allowed me to go about 15 mph down a hill. also, id switch all ignition back to AC Delco, it seems like S-10s dont like anything but stock for ignition.
 

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it wont hurt to check and clean your egr..... it could be working too much causing power loss or not enough and causing detonation thus power loss also.... it can go both ways depend on the engine

if its not a heated 02 sensor, i would just buy one and throw it on.... they are only 20 bucks or so

a way to check for a plugged cat is rev the engine around 3/4 throttle or where you notice the most power loss and shoot either into the intake...... if the motor revs, your cat is still flowing alright, if it bogs or stays the same, the cat is plugging up.

low end ussually isn't affected nearly as much as top end when a cat plugs up..

if the egr, fuel pressure, and all your other sensors are good, then ide start looking into the mechanical end of it...... compression check first

on my tbi, the map sensor was getting slow and not responding properly and getting sluggish...... kinda what your describing, i know its different FI but the map sensors do the same thing..... might need a new one

if you dont mind spending the money for a new cat, it wouldnt hurt though
 

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yea its probally the cat i just got mine replaced last week fixed teh problem.
 

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Discussion Starter #5
i was considering paying an exhaust shop to do a high flow cat and a flowmaster. they wanted to charge me like $330, is that a good price? but my exhaust pipe is really carboned up, and i don;t want the new cat to just crap out again. i want to fix it right the first time.

and a compression check is just a day or two away. i work two jobs, so my time is valuable..

new plugs, cap and rotor will be changed too.
 

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S-Clusive's Jester
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no thats a horrible price you cna buy a high flow cat for liek 70$. it mite be the cat if you get a rotten egg type smell when you accelerate quickly.
 

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Insane Network Engineer
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When you changed the CPI, did you change the nut kit as well? These are well known to leak as well... And as said above, pull and clean your EGR, try some ac delco rapid fire plugs, check your cap and rotor again.... Crappy plugs can help make it bad...In the dark, start your truck, lok at the cap and coil, see if you see any arcing... Check fuel filter again and run some seafoam through your engine...See if any of that helps you...Also just because you replaced your CPI doesn't mean it didn't go bad again.... Check for signs of washing in the upper plenum... If it's washed, then take it out and exchange it under warranty... Also check pressure at the shrader valve on the back of the intake, it should be running at 56-60 at start, and 61-65 at running... Check your 02 sensor, a bad one will cause your symptoms...And of course, as said above, check for a clogged cat....
 

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Discussion Starter #8
they wanted $330 for a new cat and and new flowmaster exhaust. i can get the cat replaced for like $125.

i bought the nut kit the same time i got the cpi, but didn;t replace it. :eek: yeah i am a dumbass. i will pull the plenum this afternoon and look for washing. i am also getting a puff of smoke when i accelerate like when the cpi crapped out.

i checked the egr, everything looked ok. no carbon chunks and it moved freely. i'm buying new plugs, cap and rotor today too. i checked into seafoam, and everyone tells me one of two things: either its illegal in the state of nevada, or they give me the autozone blank stare. and how would i check the o2 sensors??

thank everyone for all your help.. much appreciated..
 

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to check the o2 properly you need a scanner and watch the cross counts.

you can visually look at it to see if its fouled out like a spark plug, meaning all sotted up.. Generally they wont work properly when sotted up however that doesnt mean its the cause of your problem and alot of times, once you get the problem fixed and the proper mixed is acquired the 02 sensor will clean off with the leaner exhuast.
If its heated, they tend to be more problem proned when they get sotted up and unfortunatly the heated 02 sensors are alot more expensive.

if you dont have access to a good scanner I would go buy an 02 sensor and throw it on, unless its heated.... they cost too much to just do that.
 

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Discussion Starter #10
last night i checked under the hood while it was dark. and the coil lit up like a christmas tree when i revved the engine a little. bought a new msd blaster coil today, and what a difference. and it seems the harder i drive it, the better it gets.. maybe burning all the crap out??

i was also told that if your engine runs rich for any length of time, the cat should be replaced. so is it true that a car running rich for a while will clog the cat up??
 

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it can, but it depends on your definition of long time and how rich.... ive seen some pretty fouled out engines make a full come back........ even the cats.......... It may not be 100% but it still will flow plenty good for normal uses and pulling. Use your judgment with that, if you feel the power is dropping off at high rpms more than it should its probably from the cat... if it feels like it pulls smoothly and as anticipated and you dont want to spend the money i would leave it.
 
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