michael walker

hello everyone and thanks for looking at my thread..
I was wondering if anyone can help me figure out why my 95 k1500 from 600 rpms to exactly 2000 rpms has very little power or acceleration. it will also pop back through the tbi if i push it..
but once it hits 2000 rpms its almost like it has a power band. it hits 2000 and takes off with plenty of power... Ive owned afew of these older trucks and ive never ever seen this happen..
I checked all the sensors and they seem good (to me... i could have done something wrong while testing). I checked the timing .. I checked the fuel pressure..
Everything seems fine.. I didn't check the compression yet but i dont think compression would make it not have power but once it hits 2000 it pulls hard...
Does anyone have any ideas what would cause this truck to do this.. Im really stuck on this...
The truck idles pretty good also..
its just when i step on the gas it doesn't wanna go till 2000...
Im stuck on this one...
if anyone needs more information just let me know

Irish_alley

most common problem i believe is grounds. check your grounds and clean them up.

oilcanhenry

Yes. What engine and transmission do you have? Is it OBD I or OBD II? Can you run some codes? Back in the day, we would have put a vacuum gauge on it, but if its idling smooth, its likely not any vacuum leak. Have you down-shifted to a lower gear when this happens?

michael walker

yea i was reading something yesterday about the grounds in gonna look into that.. thanks

michael walker

im not sure on the trans its a 95 k1500 sub..3 speed auto with overdrive... i believe its a 5.7 tbi.. i havent manually dropped a gear but it has kicked down to increase rpm to gain power. i have tried manually going through the gears but no change... which like i said soon as the tach hits 2000 literally i feel like a huge bump in power an the truck takes off.. Ive checked all the vacuum lines and even switched afew that i thought werent perfect...oh yea n the computer is a 1 im pretty sure. check engine light is off n ive never seen it come on either..

Irish_alley

when you turn the truck to "on" without starting the truck the ecm runs a diagnosis. during this time the "check engine" light should illuminate for 3 seconds or so. does it light up when you first turn the key "on"?

Sabino56

sounds like something is putting engine in wrong BLM cell for the actual conditions and mapping is not close until you happen into some cell enabled by 2000 rpm & whatever. Normally you’d expect a check engine/code to give a clue, which, I assume why Irish is verifying that check engine light is actually working.
I think, but not sure, that cell is determined by MAP & rpm. After making sure there a no codes stored, grounds clean ( there are 3, I think) if I was making wild guess I’d bet on MAP being bad/flakey.

michael walker

Yup it does come on when i turn the key on but i noticed it comes on when in the on position but does not turn off after the 3 seconds.. This could be because i tripped the check engine light on my way home from work by unplugging the timing jumper wire under the dash to see if there was a difference.. which there definitely was.. im gonna go out and check to see what codes are stored if any and clear the cp... and try again to see if it turns off after the 3 seconds

michael walker

sounds good to me.. Im pretty sure when i tested the map with my vacuum pump it seemed like it was working good. If i remember correctly i think how i did it was measured the voltage at a particular vacuum..off the manual things seemed good although im no expert.. I think u definitely could be right... I hope so anyway.. this is a real bazaar problem ive never seen

Sabino56

Sounds like you have some codes to track down before shotgunning by changing the MAP. Post whatever codes you find..