[bnabors135]

New to site and have got a lot of info - pulled codes on a '90 and got #34 in the continuous memory. Do I need to replace the EVP and the EGR together or just the EVP.

 

[TTBlows]

You can try the EVP and see if it fixes your problem. That's the cheaper route. Good luck finding one that works, even new ones from Ford seem to be bad straight out of the box these days. Don't even bother with Echlin (Napa). Try to find a Parts Plus that carries Standard electrical parts.

 

[Steve83]

You don't need to replace anything yet. That code doesn't mean there's anything wrong with the sensor - it means the sensor is returning an unexpected value. The first assumption is that the sensor is working correctly and that there's something mechanically wrong with the engine or the vacuum system. Check the vacuum lines for leaks, especially the black ones & green one. Then check the vacuum reservoir on the R wheelwell. Then see if the EGR is opening & closing fully, and if the EVP's output varies smoothly as the EGR moves. The Haynes manual shows exactly how to test all that, and there are plenty of other resources that can help.

You should never buy parts until you know which one is the problem, and seeing "EVP" in a code definition does NOT mean the EVP is bad.

 

[Fireguy50]

CM 34 means EVP circuit has intermetantly failed above the closed limit of 0.67 volts
So you might have a EGR solenoid leak, or a wiring issue
Doubtful that the EVP is to blame, but it's possible.

 

[bnabors135]

I did nothing yet - got a code 32 today in the CM when I checked - a code 34 first and now 32 (high now low circuit failure in reguard to limits) - Fireguy, what is an EGR solinoid leak - how to fix? Could this problem be the reason I'm getting a lot worse gas milage than I used to? This is the only code I get - Is it important enough to fix or just let go? Seems a minor issue to me but may be causing problems I'm not aware of. Vacuum lines seem to be good - I'll get a Haynes manual to test the rest.