Roger Mabry

I am trying hard to get the 1984 Ford F150 4X4 with 302 engine, Motorcraft 2 bbl
carb, dual cats and feedback solenoid on the carb to pass CA smog. It is currently
registered in Idaho where they do not have smog tests. It was a CA truck before
going to ID for the last 15 years. Has all the CA state needed equipment.

Getting codes now that I have a ODBI scanner and am trying to figure out what is wrong - codes are not helpful.

On the KEKO (key on test) - these codes are returned:

21 - Engine Coolant Temeprature (ECT sensor out of range)
22 - MAP (vacuum) or (BARO signal out of range
31 - EVP signal is/was low or out of range
41 - System lean
63 - Throttle Position Sensor (TPS) signal was too low

I have changed the ECT to a new one, changed the MAP to a new one and the codes remained on the next test. All the sensors and hoses are good. Cannot find any vacuum leaks. EGR tests out fine according to Haynes (when vacuum is hooked up RPM decreases as expected) and is clean in the passages below the carb to the actual EGR valve.

I have a new TPS that will arrive this AM and will install it at that time.
Engine has good overall compression, new timing gear, chain and harmonic balancer and the timing is correct at 10 degrees BTDC with the SPOUT off.
Dual Cats test fine with back pressure gauge and temps and vacuum is high at 20 and very steady.

Trucks starts, stops and runs good, idle is a little erratic (RPM's move about 100).

Need ideas of what to check or change next. Cannot get the truck registered in CA until I can pass the smog.

Last smog test showed very high NO, 15 MPH 3005 measured and 25 MPH 1482 CO was 15 MPH Measured .03 but got too high at 25 MPH 1.29 (need .77) and HC at 15 mph 150 MEAS (need 131) and 25 MPH MEAS 216 (need 103).

Will have to resort to a test station and pay their "open ended" diagnosis fees if I cannot fix this myself.

joshtowal

Which temp sensor did you change? By the thermostat housing or on the side of the block? Work in the order the codes presented themselves when you pulled them. Sometimes you get lucky and fixing one code fixes more of them. With the smog test reading high NO, I'm pretty sure that that means either the cat isn't working or it's running extremely rich. The lean code could be due to a vacuum or exhaust leak and it's trying to adjust for the extra oxygen there.

Roger Mabry

I changed the one next to the thermostat - on the intake manifold. It was the first code and the cheapest part.

I then tested again - no change. I installed the new MAP sensor and tested again - no changes. Will take it back this AM when I pickup the TPS.

Have checked pretty thoroughly for vacuum leaks and there are no exhaust leaks, will test more this AM after installing the TPS. Want to change the EGR gasket and make SURE, all is well in that area this AM.

Do not know what is meant by EVP signal code? What do I check there? If the manuals or codes gave "causes" it would help a lot. There must be Techs out there that have "written" down what they have found as "causes" over the years and they could share that information.

Thanks for the reply Josh!

GhostriderI

EVP
EGR valve position sensor(EVP) A potentiometric detection device used in electronically controlled EGR system. Sensor wiper position is proportional to EGR valve pintle position, which allows electronic control assembly to determine actual EGR flow at any point in time
This site might help http://www.motorera.com/dictionary/index.htm
Got it from 83fordf150, Hope this helps.

Roger Mabry

Ghostride:

Thanks, that will help a lot in understanding all the smog "lingo".

Changed the TPS this AM and managed to file the holes out enough
to get the .69V at idle, 4.99V on the reference line and a smooth higher value when the throttle was depressed. The sensors resistance checked out OK as well. The carb shaft is a little worn and getting decent repetitive voltage
results was the big chore.

Then had to re do the choke, fast idle and idle and adjust the mixture screws as well. I think I have them a little too lean and will go back and adjust some more later on after it cools down again.

Stopped to fix a few other things but need to drive it at least ten miles for
the new codes to show up in the "ECM/computer". Will do another scan or two this afternoon and see what codes are there/left to deal with.

Slow progress but I want to fix it myself. The smog test station guy said:
"You will never be able to get it correct by yourself". What a challenge that was!

Roger Mabry

Only these three codes are left to find the cause:

31 - EVP signal is/was low or out of range
41 - System lean
63 - Throttle Position Sensor (TPS) signal was too low

#31 - I cannot find anything wrong with sensors or vacuum in that area

On #41 - I turned in the mixture screws with no success. Cannot find any
vacuum leaks

On #63 - The TPS has .69V at idle and the idle is very rough and "hunts"

GhostriderI

I know you have checked everytinig but {41} have you thought about replacing the o2 sensor. It may check good and be plugged, also look at replacing the sensor for the egr {31} (EPV [Sensor wiper] just a fancy name for a reostat that changes restance as it moves) Also {63} reset your base idle and fuel/air mixture and start over with your adjustments, might fix the rough idle. Just some thoughts.

Roger Mabry

One of the first things replaced was the 02 sensor. Old one tested fine but I replaced it anyway.

I changed the EGR position sensor on top of the EGR, EGR checks out fine and open 50 and 100% with the correct HG. It is clean in there and has new gaskets.

Will reset the idle and mixture today, am chasing a possible bad fuel pump/flow problem. Front tank is not flowing fuel so am only using rear tank now. Will drop the tank and inspect when these problems are resolved.

Would like to find a new feedback solenoid (Ford calls it Mixture Control Solenoid) that sticks out the rear of the carb. Used in CA trucks in '83 and '84 only and I cannot find a new one anywhere (without buying a rebuilt carb along with it). It was not connected for years due to "someone" breaking off the locking tang and it falling out of the solenoid.

Roger Mabry

Truck started surging and dying on turns and stops. I tested the flow into a bowl and only got three tablespoons of fuel in 10-15 seconds cranking.

Replaced the pump and it squirts far and hard now, and in the same time
frame puts ounces into the bowl.

Will continue on with the smog passing quest now...

Roger Mabry

Barely failed the third smog test.
25 MPH HC MAX is 103 and it MEAS 158
25 MPH CO MAX is .77 and it MEAS 1.78

I ordered new CA approved Cats today and will try again after they arrive and are installed. A mechanic friend suggested the new cats since "he says" the back pressure test, banging on them for rattles and checking the temps does not work. Truck has 122K miles and it had been running rich for "years" due to the disconnected feedback solenoid. That will ruin the stuff in the cats and make you fail the testing process.