idle issues on my 94

[DonnieFB]

my 94 XLT started running terrible. I pulled codes 121, 337, 558, 157, 158 and 416. I don't understand what controls these things .I just had the plugs and wires changed. I have also replaced the EGR valve, EGR Solenoid, EGR pressure feedbck sensor, PCV valve, TPS, IAC valve and a couple of vacuum lines. The idle goes up and down when the IAC is connected. When I disconnect it, the idle goes down and will cut off the car. or just idles low. Don't know what causes the low voltage readings on these codes etc.Can't spend much more on this. Any ideas would be welcome. Thanks

 

[974X4BLACKSPORT]

How many miles does the XLT have? Has the throttle body ever been cleaned? The ports for the IAC get clogged and restricts the air causing poor idle. How does the engine respond in the 1500-3500 RPM ranges?

 

[DonnieFB]

How many miles does the XLT have? Has the throttle body ever been cleaned? The ports for the IAC get clogged and restricts the air causing poor idle. How does the engine respond in the 1500-3500 RPM ranges?

It has about 215000 miles,
I have cleaned the throttle body with spray cleaner several times. It goes up and down in the 1500 - 3000 range. If I unplug the IAC it was running better but now if I do it it seems to bog down and cut off

 

[FR-425]

High voltage across so many different systems would indicate an open circuit.

Low voltage would indicate a short.

You likely have a broken, worn through, rodent chewed, wire that is intermittently shorting on something.

 

[DonnieFB]

High voltage across so many different systems would indicate an open circuit.

Low voltage would indicate a short.

You likely have a broken, worn through, rodent chewed, wire that is intermittently shorting on something.

Thanks I will look it over some more. Just trying to get an idea and direction to go.