i got a 2000 blazer 2 door 4x4 4.3 sfi
sometimes when i cold start it, the engine will idle normal then will sputter almost dieing. then idle up to 1800 rpms and stay there.
also i have manual shift and when taking off it seems kinda like a rubber band effect boggs out then takes off. and going down the road at highway speeds i feel it slightly jerking off and on.i got 4 codes, the throttle posision sensor(changed that) egr valve(cleanded that) map sensor, checked that,and low pressure in the gas tank. don't know bout that. also i have recently changed my plugs and wires, and checked all vacume hoses except the 4wheel which still engages. the check light goes away on its own. i'm unsure of what the problem is, and pray its not the fuel pump. very pricy.

 

i forgot to add that the problem gets worse when its really cold out. i am kinda leaning toward the egr being defective, but would be a slap in the face if thats not it.
so far my truck is running with no problem plenty of power and normal idle. i did notice tonite that when i had my defrost on when accelerating it would start changing back to vent, i think that is neutral if u disconnect the vacum correct? i 'm not 100 percent sure that -That mite be my problem. i was told to spray either(sp) around the fittings and if the engine idles up in that specific area
then thats where i have a leak. does that sound logical or don't try that at home deal?
Does any one have a problem or had one like this that just comes and goes?? Its Driving Me CRAZY!! I.E. Running crappy throwing code, then running good and codes clear without intervention..
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so far my truck is running with no problem plenty of power and normal idle. i did notice tonite that when i had my defrost on when accelerating it would start changing back to vent, i think that is neutral if u disconnect the vacum correct? i 'm not 100 percent sure that -That mite be my problem. i was told to spray either(sp) around the fittings and if the engine idles up in that specific area
then thats where i have a leak. does that sound logical or don't try that at home deal?
Does any one have a problem or had one like this that just comes and goes?? Its Driving Me CRAZY!! I.E. Running crappy throwing code, then running good and codes clear without intervention..

 

Have you cleaned the throttle body (specifically the IAC bore)? Did you verify that the new TPS sensor signal is actually getting to the PCM? Has the code for the TPS sensor popped back up? When was the last time a full tune up was performed? How is the fuel pressure?

Have you ran through the diagnosis of a vacuum leak? I use an unlit propane torch with a running engine. Trace along the vacuum lines. It definitely sounds like a vacuum leak from your description of a loss of HVAC mode control as you accelerate (low engine vacuum situation).

 

no i haven't cleaned the trottle B yet. and yes the same code apeared for the tps- not enough voltage, short circuit,or faulty.
i havent checked fuel pressure yet. i've noticed some v-lines colapse when pinched lightly, i plan on replacing all of them. and not to sound dumb, but how do u check to see if the pcm is reading the tps?

 

You would back probe the wires where they enter the PCM, either that, or monitor the TPS output through a scan tool.

 

ok sorry its been a while lost intranet for a minute. last time i posted i found a buch of vacum leaks and fixed them. and the truck ran fine. when the weather was warmer. now i havent had problems with power loss. oh and i did have the tps checked and it is running in conjunction with every thing. the pcm.. i also checked the fuel pressure, when it was acting crappy. when i turned the key on the pressure went to 58 and started bleading off after 5 seconds and went past 50. even after i turned the key off then on again, same thing. i started the moter and it held at 51psi. and throttled up it jumped to 60 and leveled back out at 51. so i turned it off again and tryed just turning the key on. it went to 60psi and stayed there for at least 15 minuted. and now my truck is running fine again. u think maybe its the pressure regulator, or fuel pump. cause sometimes it still will idle up, and when it does that it runs fine. but when its acting up i cant get it to idle up without it choking out. and recently i had to drive in 4th gear at 70 mph to just make it home cause the throtle was non respnsive. just kept jerking realy bad. thats when i tested the pressure again and those are my most recent results. when i checked it before it was 60psi key on and 51psi engine on. i'm sure ive got it narrowed down to the pump or regulator. also when its acting up i can hear the pump really loud. and now i don't. what do u think?? change regulator?

 

most of my problems was the fuel pump. i just changed the pump not the sending unit. i went cheap and got a new one from directauto.com. also my vacume lines wich i replaced all except the ones going on top of my trans. i'll get that later when i change my clutch. and wich is weird i seen one of the wiring harness's laying right on my front drive shaft. and sure enuf it wore a spot in it and ate thru a wire. fixed that and my service light has'nt ben on since. and its like drivin a brand new truck. and just from my experience the mechanic that checked my truck either was lying to me or that didn't show up on his test. either way i fixed it myself and special thanx to the forum. Helped me a great deal