5.0 Idles irratic sometimes and die when I pull out or tap the gas.

[Blue71]

Hello,

I have a '91 5.0 EFI motor (all stock with new injectors) in the '74 Bronco that dies when I pull out into traffic occasionally or when I am stopped and tap the gas while it is in gear to move forward or in reverse to back up. When I stop rapidly it tends to want to die too sometimes. It has a miss in it at idle and the idle kind of goes up and down in RPMS a little. Not sure if that would cause it, but it is annoying non-the-less. At most all other speeds it does great. Anything I need to check for to help improve this?

Thanks,

Blue71

 

[surfer-b]

Andy, the 3 sensors I would start with are....
1. MAF - take it out and clean it good with iso-p alcohol
2. check the TPS - should be set somewhere around .98 volts
3. IAC - these tend to get carbon build up and will not open or close as should

I would start with those then work with the miss, you may also want to check the fuel pressure. From the description you are giving it sounds as though when you stomp the peddel the computer is not getting the signal to send more fuel to the injectors which tells me I would make sure the TPS is working correct, after you have it set, with your meter still attached you should be able to work the butterfly and the voltage change should respond, as the butterfly is open the voltage should go up.

 

[scsm76]

Do you have a VSS hooked up?

 

[AZMike]

Check both the Idle Air Bypass and the TPS. Once you've verified that both are working, set the idle:
- Warm up the motor
- Unplug the IAB
- Set the idle to the desired base idle (600 - 700 RPM or so) using the idle adjust screw
- Set the TPS to read between .8 and .99 volts at idle.

Cleaning out the MAF with some good electrical cleaner won't hurt either.

After all this, you might want to re-set the computer by disconnecting the battery for a few minutes.

That should help with the hesitation. Not sure what the miss is - maybe you've got some mechanical problem going on (valve, fouled plug, etc). Have you done a cylinder balance test?