1227747 AMUR TBI Map surges

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01-27-2018
ChrisBama

1227747 AMUR TBI Map surges

88 K5/V10 Blazer 5.7 tbi 1227747 AMUR
Idle and Map sensor voltage both surging.

I can and did try adjusting TPS varying from .54 to .75, the best running was around .63 however it would dive, bog, falls on it's face or looses power when trying to go from 75% to wide open throttle.
IAC counts are 40-56 (depending on TPS) in park and are always 145 in gear.

BLM stays 128 most of the time.

The idle was set to 525 in gear with the IAC closed or fully extended and unplugged. The other readings were after re-plugging in the IAC.

I am kind of assuming that IAC 145 in gear means it wants more air? In which case a higher base idle would bring the IAC down? Is that correct?
Timing is set at 0. Engine is stock and has no modifications.
I did notice the MAP voltage goes up and down when the engine rpm surges up and down. Does that indicate a vacuum leak and if so how do I find it?
The only adjustable variables are base idle and TPS, so I am lost on what is out of adjustment?
I live at 5900 ft. above sea level, so it runs at high altitude.
Any help is very appreciated.
Thanks, Chris
01-28-2018
stew86MCSS396

Minimum idle should be set while in Park or Neutral and 100-125 rpm less than your target idle set in the bin. Oh btw...idk if it's just me that views this forum in the default "Black Gray Dark" but whatever font color you chose, I can't see any of the words you posted^^^.
01-28-2018
ChrisBama

Thanks for letting me know about picking the color, I thought it was my screen, I didn't know the default was unreadable. That explains the view reply ratio. What are the bin settings?
01-29-2018
ChrisBama

surging went away by unplugging the air pump and plugging its vacuum still bogs

I got the surging to go away by unplugging the air pump and plugging its vacuum.
It still falls on its face 75% throttle to full throttle.
01-29-2018
stew86MCSS396

Quote:

Originally Posted by ChrisBama

I got the surging to go away by unplugging the air pump and plugging its vacuum.
It still falls on its face 75% throttle to full throttle.

I realized that this more a "Driveability" issue rather than a "PROM Tuning" issue. Time to pull out a FSM, Chilton's, Hayne's etc. and run down the logic tree for the symptoms you're having.
01-29-2018
ChrisBama

Am I in the right range for TPS .63, IAC 45, MAP.67-.75? What are the bin settings and or ranges? I can't get the IAC count lower than 45 and are always 145 stopped in gear.