95 jimmy 4.3 knocking and spuddering

i read one entry similar to mine but i wanted to post my own.

about 1000 miles ago i started up my jimmy after picking up my son and it started sputtering and having damn near no power.

its all about the same now but its worse. it started knocking when i step on the gas, sounds like pinging but its only one or two knocks, its really bad when i first start it up. but it goes somewhat away, when i rev it up alittle more the power is more stable but i'm having to use alot of pedal to get anywhere. my gas mileage went down to about 14o miles per tank!!!! sucks that gas.

the check engine light flashes i checked the code its po3oo (multi cyl misfire)

and like alot of other people my idle is punchy, as though i would be lightly pushing the gas then letting off.

i took both heads off and my 1st and 4th cyl. are carboned up really bad. i'm thinking its the injector but i wanted to get some feed back from a more respected person. thanks for any advice given.

oh and how do most of you guys remove the 3rd cyl. plug.

Injector, nut kit probably has to be replaced.

EGR vlave has to be cleaned and reinstalled with a new EGR gasket.

Remove the upper plenum cover and look for washing.

ok i changed the cpi and i cleaned the egr.

i didnt get the nut kit since my gmc dealer doesnt have it in stock.

my truck still runs like shit, althou there is an inprovement.

still knocks and still sounds like crap at idle up untill 2500 rpms.

HELP

thanks

Check your fuel pressure.

i havent checked the fuel pressure yet. but i noticed i forgot to mention some of the other conditions.

my jimmy backfires alot, at idle it chugs, it pings alot. i dont understand why my engine would ping and backfire.
i did take the heads off and i was thinking maybe i am a tooth advanced on the dist. but i wasnt sure if that was an issue because timing is comp controled.

any more help to this lame brain.

oh and merry xmas.

Did you remove the distributor ever in the past? If not, I don't think it jumped a tooth.

This sounds like the injector or the nut kit has sprung a leak. Check it before you do anything else.

Remove the IMTV valve under the vortec top plate and look down with a flashlight and look for golden washed spots and pools of gas.

Also, if you smell strong fuel when you remove the valve, that will be your problem.

Also, take a whiff of your oil and see if it is thinned out alot from excess gas.

Also,

thanks again blazerlt.

yes i did remove the distributor in the past.

i know that the manifold has washing, i did replace the injector, there was an improvement, i did see all the black crap on the fuel lines. and there was the golden color on the drivers side and wet on the passenger side. basically the intake is pretty dirty.

so can the computer adjust the timing enough to compensate for a tooth being off, if that is the case.

no, the timing has to be set properly for it to adjust from base zero.

Also, did you replace the nut kit and use a new upper plenum gasket?

Gas and washing on the driver's side means your internal fuel line kit "nut kit" is bad also na dit leaking.

so how do i set the dist. or even know if i'm close with out a referance.
( timing marks )
i'm used to manual timing with a timing light this is all waaaay new. this is my first comp controled car. everything else was carbureted with lots of vacuum lines.

you will have to remove it and move it a tooth clockwise and counter clockwise to see if the problem gets better.

ok finally got the nut kit installed. its running SO MUCH BETTER. still has a rough idle. but its got power. the check engine light came on again and is blinking agian. so i'll see what code it is some other time. for now i'm relieved that it is working better. i love this truck.
thank you blazerlt.

What about the cpi injector?

i replaced the cpi a few weeks ago. i had to wait to get the nut kit, dealer didnt have it. and i ended up ordering it from gmpartsdirect.com.
its still got lower rpm problems. but its got power. nothing like before. it got so bad that i was manually shifting the tranny, because the power was so unstable i had to wait till around 4000rpm to shift it. and it was knocking really bad. i changed out the plugs. all the plugs were running really lean exept cyl1. cyl1 was really rich. the plug was all wet and black. but i didnt let the engine idle in gear. and i ended up forgetting the vacuum line in the rear of the plennum. i noticed because i test drove it at night and decided to put the heater on. but i put it back. i'll disconnect the battery and let the code clear and drive it around again. then i'll take it to autozone to see what code comes up. i cleaned the iac and the sensor that is right before the plennum ( in the intake hose)

when i first started it. it ran like shit. but i let it warm up and it started to mellow out. i really appreciate your help.
let me know if you got any info or ideas.

Did the problem start right after you removed and replaced the distributor?

Have you checked the fuel pressure yet?

no it originated about 2000 miles ago. i thought it was a head gasket. so i changed em. i got pissed off and frustrated. after it did nothing. finally got on this forum. talked to you and got to fixing.

havent checked the fuel pressure. yeah i did take out the distributor.

but i've driven my truck till the whole time its been screwed up. so i'm hoping from other posts that i've read that i didnt fup my cat. when it idles the exhaust out the tail pipe sounds, bad. like rapid puffs of air. but as soon as i give it a little gas its normal sounding. i was gunna get some sea foam and see if i can get the carbon build up taken care of. i know its loaded. when i took of the heads cyl1 and 4 were cokd up bad. and the intake egr passage ways were almost blocked up. i've cleaned the egr.
i've had alot of problems with this truck. and i've only had it since late june04.

so far i've
replaced the headlight switch
waterpump
heater core
head gaskets
cpi
nut kit
plugs twice
serpentine
front brakes

hmmm i'm forgetting something, but i've done alot of work for the last six months. i'm in love with this car. everyone makes fun of me but i love it. its purple, but its factory and the paint looks blue sometimes.

anyway i've driven this thing even though i know i shouldnt have. so i'm hoping i can fix what ever else might have gone bad from drivin her while hurtin.

thanks again blazerlt

hey my jimmy is a sls what is that i know its not the best one.

fuel pressure.

cap and rotor

coil

Also, what plugs are you using?

autolite platinum. they were like 3 somthing a pop.
my first time buying plat. plugs

And the rest of the things I asked?

Also, did you gap the plugs properly?

Did you check the general condition of the engine, compression test, vaccum test, fuel pressure test, or leak-down test? This would be the first thing before shot-gunning parts into it.

Did you check the general condition of the engine, compression test, vaccum test, fuel pressure test, or leak-down test? This would be the first thing before shot-gunning parts into it.

Due a tuneup is not considered a bad thing to do in any situation.

True, tune up is not a bad thing, I agree.

ok, i took my jimmy to a shop, and they told me the reason it idles and has poorer low rpm power is because the tps is bad. so i'll report back when i change it.

thanks to all, you're guys help is why i'm where i am, BETTER.