1991 Chevy S-10 My truck will start but will run till you h

  • 1 POST
  • 1991 CHEVROLET S-10

1991 Chevy S-10 6 cyl Two Wheel Drive Automatic? Miles

my truck will start and run till I hit the gas and I have changed the fuel filter and I put new plugs and wire cap and rotary button on its getting fire and gas. Why wont it run for long and its in time and the plug wires are in the correct firing order and its in time and it ran a week ago and it wont now! What can I do to get it to run?

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have the same problem?
Monday, November 17th, 2008 AT 3:39 AM

1 Reply

  • 17 POSTS

I had the same problem recently. I had to change my MAP (manifold absolute pressure) sensor, IAC (idle air control) valve and TPS (throttle possition sensor).

All are on the passenger side of your TBI;
the MAP senser is on the bracket to the left (facing the engine from the front)
The TPS is on the TBI towards the front. The IAC is directly behind the TPS.

For all of these, provided your engine stays on, let your engine run about ten minutes or to warm/hot idle temp. Your idle will drop slightly when it has reached temp.
Disconnect the negative battery cable.
Replace the TPS first (takes between 20 - 35 min); disconnect the wire assembly from the TPS, unscrew the 2 retaining screws, very likely a torx head. Follow the instruction sheet that comes with your TPS unit. Once replaced allow your engine to cool for about 2 - 3 hours. Reconnect the neg bat term start the engine, let it come to normal idle temp or to 700 rpm if you have a tach. Slowly increase your accelorator. If the engine "chokes" off, restart your engine and let it idle another 10 - 15 min. Again, increase the gas slowly. If the engine doesn't die, try to take your S10 around the block. If you are able to complete this without it dyeing take your ride for a short road trip, about 5 miles with regular stops at lights or intersections. While on the short road trip you still have no problems, continue your short road trip on a low speed hiway - 40 - 50 mph for 10 - 15 miles. Go home, let your truck sit for the night and do the same thing in the morning, short road trips ending with a freeway run 55 - 70 mph for another ten miles. These road trips will help the main chip reset to the new TPS.
After you have replaced the TPS and you have tried, but not succeded in the previous road trips and if while in gear or while idling and it chokes off or "chugs", you'll need to replace the IAC as well.

The procedure for the IAC is identical to the TPS.
The engine must be at running/idle temp before changing it out.
Once you have changed it out, let your engine idle for 10 - 15 min then, while in park, slowly accelerate untill the engine starts to "choke" or "chug" gently let off the gas untill the engine stablizes. If you have a tach, try to get the engine to 2000 - 2500 rpms, if not you'll need to go by sound.
It should sound as though you are at freeway speed. If the engine doesn't "choke" off or "chug" take the road trips as describd above. It will take about 100 miles at street speeds combined with freeway speeds for the main chip to reset for both the TPS and IAC.

The third "easy" solution is replacing your MAP sensor. Avgain, disconnect the battery, remove the wire clip/set and the vacuum line from the MAP sensor. Gently pull the retaining clips (there are no screws on the MAP) put the new one on in reverse.

If after you have done all three of the above, you may need to replace the fuel pump assy (this is in the fuel tank) and the fuel filter.

Each of the three main parts above will cost between $40 - $80 depending on where you go. You should consider getting the Haynes and the Chilton manuals both are about $25 each.

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Wednesday, November 26th, 2008 AT 9:32 PM

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