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I just replaced my EGR Valve, EGR Valve Position Sensor and MAP Sensor in my 88 F150 351W C6 with 135K. Before replacing the two sensors I was getting a 31 hard fault code and 33 memory code in KOEO tests and no codes in KOER test that I remember.
After sensor replacement I got 31 HF and 32 M code in KOEO tests.
In KOER tests the codes received were 44 and 31. However, they did not repeat immediately after each other. It gave 44 then 31 then 44 then 31. The CE light stayed on while driving.
After replacing the EGR valve the CE light is off while running and the KOEO tests show 11 and 11. However the KOER test is still showing the 44, 31, 44, 31. Aren't the codes supposed to repeat immediately. I'm not too worried since the CE light doesn't come one but am perplexed by the KOER codes.
I am new to this since purchasing the truck less than a month ago. It passed the Texas emissions testing before so I suspect it will be ok. I was only trying to improve the performance since I don't think tune-up maintenance has been done to this truck.
Maybe you are allready aware of this, but you need to have the engine completely warmed up before running KOER. The O2 sensors need to be working in closed loop or they will fail the test and set a false code. Also EGR is only turned on when engine is warm so it could also fail and be ok. Most instructions suggest running at 2000 rpm for 2 mins and then enter KOER.
Yes the engine was warm when I did the tests. I will probably check the codes again after driving for a day or two. I was really curious about the code 44 and 31 repeating as a pair instead of individually. According to all I have read I would expect to see 44, 44 then 31, 31 instead of the 44, 31, 44, that I am seeing.
Thanks. I thought it would repeat them individually instead of the list.
I put a vacuum pump on the new EGR valve. There is a slow leak of vacuum. Any suggestions on how to seal it. The EGR VP sensor is new also with a O-ring where it meets with the EGR valve. I tried using a thin film of gasket sealer. That helped some but there is still slight vacuum leak. I don't like to use that stuff but wanted to make sure the o-ring didn't move around out of the groove. Any ideas appreciated.
For anyone that cares, I finally decided to put the original EGR Valve Position sensor back on. This appears to have cleared up the code 33 where the system did not think the EGR Valve was opening. So I think the original cause of the code 33 and 31 was a bad EGR Valve and the Position Sensor was ok. Also looks like O'Reilly's gave me an incorrect EGR Valve Position Sensor. That's the first time I have had them do that as far as I can remember.