Hi, New here but not new to cars.

I've been reading posts here and noticed some pretty educated answers to problems others have had so I'd like to present Ya with this lil problem Im having with My 85 F-150 FI (N) Pickup.

I have an 85 F-150 pickup thats dual fuel and Fuel Injected , Engine VIN series N . Ca will smog it on the fuel that you tell the smog station you run the most per a smog expert at a test only station.

Forget the dual fuel for now as Im testing it on Gasoline due to the fact that Im not sure how to test the impco propane controller. My First attempt to smog it was on propane as they told me propane runs cleaner , it failed gross polluter on HC and CO .

Now on Gasoline :

Key On , Engine Off gives me 11 11 , 11 11 or normal
Key On , Engine On gives me a 34 , EGR malfunction

Hand pumped Vacuum at 10in HG (mercury) or a little less to the EGR valve cuts the engine out at idle.


I've Hooked up 3 analog meters to measure the O2 , the Air Bypass Valve and the EGR Valve position, and 4 leds to monitor the relays that control the EGR Valve open and close solonoids, the Air Pump bypass Valve and the Air Pump Control Valve operation .. Heres what happens ....

At Startup Idle (cold) the O2 bounces nicely between about .2 and .8 VDC as refernced to either engine or frame ground.

When it warms up and is idleing the O2 raises to .9 , very rich.

(Timing looks good at about 20 BTDC , 10 with the Connector opened that the book says to disconect , which is book good.)

The EGR valve controls are very quiet here, no action.

When I gun it , in a moderatly ear tolerable level of RPM's the O2 sensor drops to about .3 and hangs there. Like its running lean. The funny thing is that the EGR Dump solonoid starts activating here . A little more throttle and the O2 sensor starts bouncing around nicely again .

With more throttle I see the EGR Valve Vacuum dump solonoid , the one thats supposed to bleed off vacuum to the EGR valve clicking away madly. Sometimes the EGR Pump Solonoid (the one that applies vacuum to the EGR Valve) comes on at this time , but I rarely see it come on. The O2 readings look good. The EGR postion hangs tight .

I pulled the position sensor and put it on a ohm meter and it tracks fine by slowly pushing the rod in and out, both sides of the pot , though they seem slightly differant from the slider (common) of the pot to the two ends.

I placed a vacuum pump on the EGR Valve and It responded by showing position changes on my Analog Digital Volt Meter.

I put a vacuum gauge on the EGR control solonoid output, the line that goes to the EGR valve itself while running the engine unloaded , between idle and about 1/2 throttle , I just see it trying to release the EGR valve while the engine is running very lean, around .2 to .3 on the O2 Sensor. Ocasionally while gunning it I see the EGR Pump solonoid Come on.

This seems backwards to me ? The EGR valve cools the cylinders to cut out NOX as I understand it. If the O2 Sensor shows lean , ala .2 to .3 then I would expect the EGR valve to try to open , not close. Very Rapid Accelaration will cause the EGR to open momentarily but it tries like crazy to close when its slowing down

I have a new Napa EGR Valve on the way , Can anyone tell me if Im on the right track here.

Any Help ?
TIA