Hello.
I have an 89 F250, 302, 4x4.

I replaced the Thermactor Air Diverter (TAD) today, thinking that was where my vac leak was and that should have dixed a lot of different issues I have with this truck.

Symptoms:
Vac Reserve canister on passenger side does not have any vac when engine is off.

cruise control does not work. It used to, intmitently.

Could these to problems be related? Does anybody have a digram of the vac lines for an 89 f250 302? The TAD was no good, the diaphram would not hold.

Not sure what direction to go here. Had horrible milage before I changed the TAD and the exaust smelled really strong... running to rich. Now that seems to have gone away since i changed out the TAD.

Just pulled the codes... 84 and 33 EGR vacuum solonoid circuit failure and egr valve not detected opening...

Any ideas as to what direction to go here in figureing this out?

Thanks,

 

Checked the voltage at the EGR Vac Sol. its 12v Key on Engine off. Checked vac line to egr valve, holds vac, no leak, and checked for vac at egr valve sol. and have vac there... I assume that I need a new EGR Vac Solonoid

 

Prob need the white sensor on top. As for the Cruise Control prob needs servo just had to replace mine for the same problem

 

The EGR valve position sensor? I will be checking that tomorrow.

Crusie Control Servo.... What does is look like? Where is it located? If its what I think it is (Has the large vac line going to it on driver side fender?) Is there a way to test it?

As for the EGR vac Solonoid, I'll be testing that also.... Sure hate to drop another 30-40 bucks on another one.... but I have to go to emmisions testing in mid march.... dont want to fail.

Thanks,

 

The servo is on the drivers side fender and a pain to replace. I did it by myself had to fight the spring in the throttle to release the cable.

 

Well, I replaced the EGR vacuum regulator solenoid today, still hasn't done the trick. Is there a way to test this? I get 12v on the connector, (red wire to ground) Looking at the Haynes book, it shows that one side goes to 12vdc, and the other side to the EEC pin 33.

I still get the 84 code (egr vacuum solenoid circuit failure.

I really don't know where to go here... I really want to get this fixed.

Any Ideas?

 

Sounds to me like the circuit may be open between the solenoid and EEC Pin 33. You actually answered your own question. Until it turns "ON", pin 33 should also have 12 volts on it. The outputs for solenoids on the EEC are actually inputs as well. You'll note that negative logic (switching LOW to turn something on) is used on all the outputs. This allows for sensing 12 V at the output to detect open coils or broken wires in the EEC. I prefer things to turn ON when ON and OFF when OFF, but I can see the advantage in this design for wiring design. The EEC outputs are all open collector outputs. If the output goes bad, it usually does so by failing shorted, and it usually keeps something turned on when it shouldn't be. If you plug up the EGR solenoid, with the engine at idle, the EGR should not open. If it does not open, chances are the output is OK, and the wire is broken somewhere.

 

Thanks for the reply. Today on my lunch break I checked the connector on the EVR to the connector that sits on the driver side wheel well and that rang through no problem.... didn't have much time to mess with it. Tomorrow I'll check from the connector on the wheel well to the connector that goes to the EEC on the firewall. I do have another EEC that I might swap in just to see if that makes the difference.

Also, I changed out the EVP today. Had a new one in the glove box. That didn"t help.

At least I have somthing to keep me busy LOL!

 

there is a couple of vacuum relays or sensors on a rail drivers side above the valve cover-one of them crapped out on mine and it kept throwing egr code-ran like crap mileage went to hell and cruise would not work-trying to find what is is called-dain bread!!!-it fixed mine quick-mine was a 88 f150-5.8 auto-gas smell was real heavy till she warmed up-reminded me of an old choke pull off valve gone bad

 

1 is a egrc-EGR control the other is a egrv-EGRvent both are vacuum and electrical-now I see a EVR ?? gotta love these new ones-well new to me-gimme a carb and points anyday!!

 

The valves are, front to rear, EVR (EGR Valve Relay), TAD (Thermactor Air Diverter), and TAB (Thermactor Air Bypass). My old 'Bird has twin valves for the EGR, one for vacuum and one for vent (4 in the assembly), but the truck has only one. To regulate position/flow of the EGR, the EEC dithters the valve on and off to pull it open a little, then vent when the valve drops back out.

The EGR code can be generated by a vacuum leak in the line from the valve to the EGR (green), the line from the reservoir to the valve (red), rusted out reservoir, reservoir full of oil/fuel/moisture, valve failure, bad connection from the EEC to the valve, bad diaphragm in the EGR, bad EVP (EGR Valve Position) sensor, or bad connection from EVP to EEC. Any of these things are subject to giving you an EGR code.