93 Silverado Idle and Stalling issues.

Asked by Feb 21, 2016 at 03:20 AM about the 1993 Chevrolet C/K 1500 Silverado Extended Cab 4WD

Question type: Maintenance & Repair

Hey, I have a 93 K1500 with the TBI system.
Ever since I bought it its had an idle issue. At
first it had great idle and had n o problems
when put into gear but you could not force it
to rev up in neutral. Good power too. I
decided to replace the throttle body since I
did the unheard of 4L60e to 700r4 swap
since the 4L60 grenaded before I bought it.
Problem with the new throttle body is it was
from a V6 this changed the problem. Would
rev up great but idled terribly all the time.
Worse idle in gear. Decided to put the V8
injectors back in it, rebuilt the throttle body
top to bottom with new TPS sensor, gaskets,
accelerometer, (everything but IAC valve).
Still had issues. Has new fuel filter, had a
system flush, and new plugs and wires, cap
and rotor. It ran a whiile with the EGR valve
unhooked from the MAP sensor but was
finally hooked up. Bo change. At one point
the block had gotten filled with gas but the
fluids had been changed and refiltered but
no difference still. Had to piece a couple
vacuum linea back together too. Basically
just searching for my idle issue. Timing has
been changed and checked twice, tps
sensor is new, and EGR valve wasn't hooked
up for the longest time. Any ideas?
Questions welcomed.

7 Answers


Ok, first I would check the EGR valve to make sure it is closed. The MAP sensor needs to be hook up. This may be part of the problem, a dirty MAP sensor. The IAC is another. But I think I would check the fuel pump pressure. It should be 9 to 13 lbs.

Valve was closed. But may be opening occassionally. MAP sensor was hooked up , i meant the box between the egr valve and tbi. Don't have the guage to check fuel pressure. But I adjusted timing and its idling well but it will occasionally stutter a bit and when dropped in gear it tries to stall. Like its bogging down. Not the torque converter though.


I still would check the fuel pressure, should be 9 to 13 lbs. The IAC can be tested at Auto Zone, and make sure that port is clean as that is a major source of vacuum.


Idk what autozone you go to but the ones down here won't test an iac valve. They only really do coils and ignition modules. But yes, make sure it's clean. Do you have a vacuum gauge? You should see what it looks like and rule out any vacuum leaks. These engines are dependant on vacuum pressure. Was your computer reprogrammed to use the 700r4? Pretty much it needs to think it's a manual trans truck due to no electonics in a 700r4. With the 4l60e the truck knows when it's in gear and adjusts idle accordingly. If the truck thinks it has a 4l60e and your running the 700r4 then it never knows it's in gear and has a hard time adjusting for load on idle.

I'm thinking autozone here isn't gonna check it either. But fuel pressure is my next check.Check the port on the inside or the tube its in? I dont have vacuum gauge either. The computer was never changed out or reprogrammed. Still wired for the 4L60e. Had to swap out the throttle body because it didn't have the piece on the throttle bracket for the tv cable. They make the tps sensor for a manual but if I'm correct it would have no change right? Since the computer wouldn't notice. And it brings the idle down when in gear. It recognizes the shift linkage is moving. The trannys are identical so it should have most of the electronics in it.


Tps won't make a difference. I'm pretty sure the 700r4 doesn't have a sensor to tell the pcm what gear it's in. It should have a speed sensor and tcc clutch connection. If you find a manual transmission truck in the junkyard it wouldn't be a bad idea to grab the prom out of it just to try.

Update is that the idles have been leveling out since I played with a few vacuum hoaes and set the timing again. Idles steady but occassionaly studders but comes back. Now also think my rings are worn as once it hots operating temp it won't hold pressure to save its life. Warm it barely holds 8 psi if lucky and the slight drop in rpms when shifting between drive and reverse drops it lower.

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