Rough idle PO122 & 507

[dguy]

Hi. Having problem with rough idle, poor gas mileage 1997 305 vortec
I have replaced plugs, wires, dist. cap, rotor, throttle position sensor
and have tried another EGR valve. I did a guick check for intake manifold leaks and found none. Seems to run fine other than at idle
Periodically on startup engine light will flash then go out
I have at times got codes 122 and 507
Don't know what else to try. Thanks for any help

[gfdcpt]

Originally Posted by dguy

Hi. Having problem with rough idle, poor gas mileage 1997 305 vortec
I have replaced plugs, wires, dist. cap, rotor, throttle position sensor
and have tried another EGR valve. I did a guick check for intake manifold leaks and found none. Seems to run fine other than at idle
Periodically on startup engine light will flash then go out
I have at times got codes 122 and 507
Don't know what else to try. Thanks for any help

have you checked your throttle body to intake gasket had that problem with an 88 gmc sprayed a little gas around the gasket and ran smooth only affected at idle also

[SpitAndDirt]

P0122 Throttle Position Sensor/Switch A Circuit Low Input
P0507 Idle Control System RPM Higher Than Expected

Sounds like you might have a problem at the Throttle Position Sensor. Did you set Minimum Air when you installed it? This means that if you did not set the Tps output voltage that the computer sees, the computer will think your foot is on the gas when it isn't and vice versa. You really need to have a scan tool that will allow you to look at what the compter is reading from the TPS. -Chris

[mphmilkman]

Originally Posted by SpitAndDirt

P0122 Throttle Position Sensor/Switch A Circuit Low Input
P0507 Idle Control System RPM Higher Than Expected

Sounds like you might have a problem at the Throttle Position Sensor. Did you set Minimum Air when you installed it? This means that if you did not set the Tps output voltage that the computer sees, the computer will think your foot is on the gas when it isn't and vice versa. You really need to have a scan tool that will allow you to look at what the compter is reading from the TPS. -Chris

How do you adjust for minimum air on the vortec system? The TPS will not adj. Do you ajdust the throttle blade?

[SpitAndDirt]

No, don't adjust the throttle blade. The TPS should adjust at least a little. If not, you could be looking at a bad ground for the sensor or.... not enough input voltage, which would lead to not enough signal voltage being sent back to the computer. Check that you have a couple of solid grounds mounted to one of the thermostat housing bolts. There should be two of them or at least two wires, on one connector. Hope this helps.