Perplexed and need some help! 1990 F250 5.0. Bought it used and fixing it up. Pulled a code 33. Took EGR off and it was horribly gunked up. Cleaned it up good along with the EGR tube and port. Works with vacuum pump on it and holds vacuum. Replaced the EGR sensor. Replaced the vacuum canister the EGR system is hooked up to and replaced all the vacuum lines for the EGR system. EGR Solenoid checks out as far as I can tell going by Chilton and Haynes manual. After resetting the PCM and taking a drive I am still throwing Code 33!

 

Give me a little help here...do you have a EVP sensor or a DPFE sensor? And you said you replaced some of these parts, but did you test any of them for proper voltages or resistance?

 

Well I got fed up and went out and got a new EGR Solenoid and EGR Valve. I will see tomorrow if it still throws the code.

 

The OP's 1990 model year truck uses an EVP (EGR Valve Position) sensor. DPFE did not come into play until 1995-1996.

 

Well I replaced both the EGR and the solenoid. Problem solved! Don't know which was the culprit but now I have piece of mind that the entire EGR system is good. Now on to replacing the ICM to get rid of code 18 and life will be good.