I have a 1992 f150 with the 4.9l. recently, ive been trying to figure out why my check engine light comes on randomly. I tried to see if its a specific time it comes on, but it seems completely random to me. a lot of times when it happens, it will be under a lot of load or going up a hill, and i feel like there is a slight loss of power. it gets slower and then once the light is off, it acts normal again. after running codes with engine on, i got code 225 and 332, being for the knock sensor and EGR system. there is a decent misfire on the truck so that might be whats triggering the knock sensor. since i got an egr code, i did some tests to make sure i was getting vaccum to the solenoid. it was getting vaccum, but it was not sending vaccum out to control the egr valve itself. for this test i was sure to let the truck get really warm, and rev it up to trigger the egr but did not get any vaccum. i replaced this solenoid, but it did not change anything. i was also sure to check the egr sensor to make sure it was getting a signal. also the egr valve moves freely and is not stuck. i just keep getting the egr code and i am not sure why. ive previously had SPOUT codes come on, which made me replace the sensor and correct the base timing with the sensor unplugged. so im not sure if that is still affecting the truck. it just still misfires a lot and i havent been able to figure out why. plugs and jets are also replaced already. i daily drive this truck and the light has been coming on for a couple months but it still runs fine. the light just bothers me and i would like to have it off. anyone have ideas?

 

You need to verify that the solenoid coil is being fed a signal from the ECM to activate.. If the solenoid has both and good vacuum, it has to work. I would also make sure the EGR valve is not stuck partially open from carbon.I would also check to make sure the diaphram for the EGR valve holds vacuum and not leaking. If you apply vacuum to the valve when the engine is idling, the engine should almost stall out.Finally, make sure the EGR position sensor which sits on top of the valve is in good working condition. It's just a variable resistor similiar to the TPS sensor.

 

Thank you, the solenoid was getting 13 volts at idle, and reving did not change it. So I’m assuming that is good. It still won’t let vaccum out the other side. The EGR appears to be completely free, but I have not vaccum tested it.

 

The only test I did on the sensor was resistance which it passed

 

What do you measure on the other leg of the solenoid when the valve is supposed to open? The ECM should pull down the other leg of the solenoid to ground to complete the circuit when its supposed to energize. I don't think the activation signal is reaching the solenoid for whatever reason.Probably because of a wiring/connection issue.