This is becoming very frustrating for me I cannot seem to get rid of this code 34 no matter what I do. Ive already installed a brand new EGR valve, replaced the position sensor with a new white one [truck had original white,] replaced the EGR vacuum solenoid, and replaced all the old plastic vacuum lines with new rubber, but again CODE 34! Even left the battery unplugged for 30 minutes

Truck is a 1990 F150 w/302

One thing i did notice is that the EGRs (both old and new) seem to be in a slightly 'open' position (see image) at idle where you can see just a about a quarter inch (or a little less) of the little shaft inside....Is it supposed to be like this or is this the reason i continue to get that code 34?

One thing I can say is that it finally seems to idle normally, 600-700RPM, however it idles a little ruff.. I figure this is also related to my code 34.

I would appreciate anyones input as I do not know what to try next I really need to get this truck SMOGed

 

EGR should never be open at idle. Pull off the vacuum line, it should close if the valve is receiving vacuum when it shouldn't be or the solenoid is not venting to atmosphere and holding vacuum. The EVP signal should be around 0.67v. What are you measuring at the EVP?
Are you getting a 34 engine off or on?
Possibilities include EVP wiring/ connector issues or possiby an issue with the ECU itself, capacitor issues.

 

Smog testing follows Federal guidelines but can be slightly different area to area. With that said that truck will be a tail pipe test in my area. The engine light needs to be working but it doesn't matter if it's on, now this is just for the truck you have. Other years have other rules. It might pay to check with a smog shop and see if the light matters. You still want to fix the problem but this would make it less urgent.

 

I live in northern California, i assume SMOG here is very strict but I do not know for sure. I do know that my truck runs some what rich and idles just a bit rough. It used to idle high.. i fixed that problem, now it just idles a bit rough. So far i have replaced the EGR, EVP, all emissions vacuum lines, fuel regulator, EGR solenoid, and IAC. I also removed and cleaned the throttle body very well.

Im going to replace the Coolant temp sensor and MAP this weekend, im hoping that this fixes the rough idle issue.

 

Im getting 34 engine off, however i did the engine off test after a 30 mile drive.. when i first replaced the EGR and EVP, I cleared the codes and did an engine off test and only got code 67, which im not worried about. So, for whatever reason, after i clear the codes and go for a drive, 34 comes back.

I know that there is no vacuum to the EGR at idle, i made sure of it. Today i am going to test the EVP voltage to see where its at. I also plan to apply a little bit of reverse pressure into the EGR to see if i can get it to close a little more, or to verify that it is already closed. Worst case scenario, i will just end up replacing the EGR and EVP with motorcraft parts.