first off, great forum, lots of usefull info, been searching for answers and still have as yet to find one so thought I would try this.
Fisrt off I have a 2000 Blazer LS, 2 dr 2 wheel dr, 4.3. Here is my problem...The Blazer runs great for about 30 min, after that when ever i stop at a stop light, still in gear, just stoped with foot on brake it starts to cut out. Like it is going to die, but it doesn't, once it starts this it does this this wierd thing when I accelerate, it sputters and hardly goes. Once again it only does this if it has been running for about 25 to 30 min.
I have replaced fuel pump, rotor cap wires plugs got new cat conv, recentley had intake gasket replaced, I'm to the point where it seems like i just need to start replacing bit by bit? and was wanting to avoid this since I'm not sure where to start, Pcv Egr Map O2 or all the above? anyone else with this same problem?

 

Any codes? Stored or pending?

 

no known code but then I've only had it checked at auto zone, wouldnt a bad 02 sensor or maf or the others put out a code and kick on the ses light?

 

yes it would spit out a code and kick on the light.

 

Well I think I may Have figured it out, I noticed that the blaz only does it wierdness when the air or defroster is on? Don't know why this is any thoughts? I do know that my heater will only blow out the defr and the vents not on the floor, so maybe there is a vacume issue?

 

Your heater is a different issue and with the parts you were asking about there should be a code if they are bad. Not to say anything bad about Autozone but I would have it checked by a more reputably place with a lot better diagnostic capability. I had a similar problem and it was my distributor and I had a po300 night mare code. This is a easy check I know you said you change the cap and rotor but pull the cap off and grab the rotor and pull up on it a little bit and see if it will moves around if it does it is a bad distributor. Just a though.

 

I second the, Has anyone figured it out yet? Mine does this with or without the air or defrost. and I have noticed that it gets worse as it gets to running temp. I just picked up a dist. gear, timing set, intake gaskets, fuel presure regulator. Figure I"ll bite the bullet and start replacing stuff and see if I get it. without a code I have no real clue. We did a running scan and my timing was floating around so that's the call for replacing the timing components. Three day weeken lets see what happens. I'll post the results!

 

Dan I think you just wasted a lot of money I don't mean no disrespect but buying all them parts and not knowing whats wrong is like playing Russian roulette. For one your timing can not float around it is either on or off and if it is off it does not run or something is broke (Timing chain,gears, etc). Your Computer controls your timing and when it is set you can not or your engine can not change it (Unless there is a timing issue and if there is you would not be driving down the road), Intake gaskets would not cause this problem (You would have a problem all the time) Fuel Pressure Regulator might, put a fuel pressure gauge on it and drive it while watching the gauge. Point is you could of saved yourself a lot of money and time if you took the time to diagnosis it before buying the parts and doing a crap shoot.

 

I agree that it seems I'm just throwing money and hoping to get lucky but like I said without a solid code to go by I can only respond to what the symtems seem to tell me. I did get a lean bank 1 & 2 code and I suspect that's the fuel pressure regulator, because at the time it shot this code the fuel pressure was holding steady at 50psi. It didn't matter if you let it idle or revved it to over 4,000 rpm. It was stuck at 50psi.
Later the next day it was up to 58psi at idle and raised to over 60psi as you revved the motor??? Just to act back up again once at running temp., holding at 50psi but no code this time. Got to be the regulator, the pumps new.
As far as the floating timing. I know that its either on time or out of time. We had it on a scanner and was whatching the timing and it was floating or bounching between 12-17 degrees retarded,(am I allowed to say the word retarded?), it should be steady at 0. That tells me it's either the chain and gears or as I'm learning a posible worn distributor gear. With 100k on the motor it's not a bad idea to go ahead and replace the timing components.
The intakes been apart a few times looking for this's and that's and figured if I'm getting into it again I'll put new seals in the top half of the intake to rule out vacume leaks. I'm not pulling the lower intake frome the block and heads just the top plastic components and I'll check them real close for cracks, ect.
I've read quite a few posts and only seen one where someone found their true problem, it was the dist. gear, being the easiest and least involved I'll start there. If it works I can return the rest of the parts.
Ended up spending time with the family all weekend and probably a good idea, this thing is driving me crazy also!!! Wish me luck and good luck to those battling this gremlin.

 

well Sounds like some are having worse issues than me, this is the break down on my end, PROBLEM SOLVED, had the cat conv replaced problem still was previlant, so started taking things apart and looking at them, turned out the stuttering was coming from burnt out plugs, 2 to be exact, from what I can figure when the cat finally pluged almost all the way up, it caused a few of the plugs to foul up?, well I put all new in and we just drove the blaze on 600 mile road trip without a stutter or hiccup, not to mention it went from getting 18 mpg to almost 28 mpg highway of course and that was with ac on almost entire time! So as far as I,m concerned this was all a result of messed up cat conv. By the way thanks everyone for the replies there was a lot of time spent just reading through the forums and letting the blazer run and stutter to try and pinpoint this