Hi Folks,

Your suggestion as to the cause and solution appreciated.

The truck:
1986 F 150
5.0L
Fuel Injection
Automatic
Driven perhaps 4 days a month

Symptoms:
(a) after warming up truck will sometimes die at stops;
(b) emissions too rich <fortunately now grandfathered out of compliance>;
(c) may suddenly lurch forward at stops when in Drive then die;
(d) expanding on (a) it may not hold idle after some driving about.

My thought was that it was time to go ahead and replace plugs / wires / distributor cap but I've got a feeling that is likely not enough.

While I enjoy working on it, my weekends get consumed pretty quickly with kids events and various "honey-dos".

Your suggestions as to further tests or likely causes most appreciated. If you think I need to get it to a trusted mechanic instead of my own work then that opinion is appreciated as well.

Thanks in advance.

-Robert

 

First thing I'd do is pull codes:

Fuel Injection Technical Library » How To Run a Self-Test

 

Thanks for the idea:

Good news is that I was able to find a reader on Amazon.

Not so great was I got no results other than the all clear: 11 / 10 / 11

I took the readings three times:
(1) - warm up truck, stop, take readings;
(2) - cold truck, take readings;
(3) - drive across town, highway and streets, stop, take readings.

All three read the same - 11 / 10 / 11

On the cross town drive it had a slight sputter at a stop sign but I did not let it die as I was in a hurry.

All thoughts welcomed.

Thanks,

-Robert

 

There are three types of codes that you need to pull:

1) KOEO - This tests basic electrical connectivity to the sensors & such.
2) CM - Continuous Memory - The computer stores codes encountered during the last several operational sessions
3) KOER - What the computer immediately detects and can report on with the engine running

Your code reader should have instructions for retrieving the three, unique, sets of codes (if not, the instructions are in the link I posted earlier); please be certain you're doing valid tests and retrieving all three sets.

 

I know this is shooting in the dark, but the EGR is a common failure point for these fuel injected trucks, causing the symptoms you describe. You can simply unbolt the EGR, make a flat gasket out of some aluminum flashing to block it off, and see if the problem goes away. If it does, you can decide on your next move.

 

Thanks - the sensor did a continuous memory test. But I did not do the KOER yet.

Will do it this week.

 

I have the same motor and had a similar problem where my truck would have a really rough idle and it would surge. I recently cleaned the idle air controller with carb cleaner and the idle was a little better. But a week ago I replaced the throttle position sensor and the rough idle and surging seems to have stopped. the throttle position sensor was like 35$. Hope this may help.

 

Update -

Went and got a timing light as the instructionsfor KOER testing insisted that I check that first. Looks like it was a good idea.

The timing oscillates between 20 BTDC up to 55 or BTDC every second it seems once it reaches running temperature. Also noticed for the first time what sounds like a clicking sound in the distributor area.

Thoughts?

Thanks,

-Robert

 

Finally found the time (and equipment - ie timing light) to get this done properly per my code reader instructions.

First things did not all go according to what was expected.

Did a timing light analysis and it turns out that the timing was varying every second from 20 BTDC to 55 BTDC. The code reader suggested that this would cause incorrect results potentially.

Despite that I pushed forward.

Did KOER tests with varied results:

If I performed the act of turning the wheel and pushing on break as instructed after the cylinder count came up I got no codes.

If I ignored those tasks I waited a while till a 10 code arose and then I did a quick mash of the accelerator. Then I got codes.

Codes:
41 - HEGO sensor voltage
34 - EGR control fault / EVAP control system fault
77 - Operator error during dynamic response test
25 - Knock not sensed during dynamaic response test

These last two suggest that I did not do the quick accelerator punch but again I don't really know.

The relationship with the code challenges has me suspicious and potentially no closer.

All thoughts and ideas appreciated.

Thanks again -

-Robert

 

As per the Ford 1986 Engine/Emission Diagnosis manual (called the Powertrain Control/Emissions Diagnosis manual in later years - also lots easier to use in later years, but it's the size of a small suitcase)

KOER code of 41 on a 1986 302 in a truck = HE11 = FUEL CONTROL - ALWAYS LEAN

HE11 says:

1. Check for vacuum leaks (vacuum actuator, (e.g. for thr A/C), engine sealing, EGR system, PCV system, unmetered air leak between air meter and throttle body, lead-contaminated EGO sensor)
2. Key off. DVOM on 20V scale, Disconnect EGO sensor from vehicle harness. Connect DVOM to EGO sensor and engine ground.
3. Disconnect ACT sensor
4. Start engine, run at ~2,000 RPM. Does DVOM read greater than 0.5V within 1 minute?

If no, replace EGO sensor and re-run test.

If yes...


HE12... Measure resistance in two circuits. Book says to use a Breakout Box, I really doubt you have that so it'll be harder... need to measure between:


- Pin 49 at the computer connector and engine block ground
- Between EGO sensor and Pin 29 at computer connector


Resistance should be less than 5 ohms. If not, fix your wiring and re-run test.



If so... HE13... Check EGO circuit for short to ground.


- Key off
- DVOM set to 200,000 ohms range
- Measure resistance between Pin 29 and Pin 40 at computer connector (breakout box if you have one)


If ohms reading is 10,000 ohms or less, correct the cause of resistance to ground and re-run test.


If reading is 10,000 ohms or greater...

HE14...

- Key off
- Reconnect EGO sensor
- Make certain ACT sensor is still disconnected
- Start engine, run at ~2,000 RPM for 1 minute, return to idle
- Perform KOER test (note - disregard any other codes at this time)


Is Code 41 still present? If so, inspect for corrosion or damaged pins at the computer connector; if OK, replace computer and re-run test.


If no, reconnect ACT sensor. EGO input circuit is OK. Goto Step 1 (we began at Step 11). HE1 is fuel pressure check, followed by fuel delivery test (output rate) followed by testing of injectors.


--


Codes 32, 33 and 34...

DD11 - OUTPUT STATE CHECK (sends me to the Appendix for more info what that is)

do not use a STAR tester... (code reader)

- key off, wait 10 seconds
- DVOM on 20V scale
- Connect DVOM negative lead to STO and positive test lead to battery positive
- Jumper STI to signal return
- Perform KOEO self-test until completion of Continuous Memory Codes
- DVOM will read 0 volts
- Depress and release throttle
- Did DVOM reading change to a high voltage reading?


If no... depress throttle to WOT and release. If STO voltage does not go high, goto Pinpoint Test Step Q40


If yes... DD12..

remain in output state and....
Check EGR solenoids for electrical cycling

- key on, engine off
- in output state check
- DVOM on 20V scale
- Connect DVOM between EGRV, VPWR and EGRV signal
- While observing DVOM, depress and release throttle several times to cycle output on and off
- Repeat for EGRC, VPWR and EGRC signal


Results...

If either output does not cycle on and off, exit output state and goto DD17


If both solenoid outputs cycle on and off.... remain in output state and... goto DD13



DD13...

Check EGR solenoids for vacuum cycling..


- key on, engine off
- in output state check
- disconnect and cap vacuum line from bottom port of EGRC solenoid and connect a vacuum pump
- connect a vacuum gauge in the common output (top) vacuum line to EGR valve
- Disconnect but DO NOT cap vacuum vent line from EGRV solenoid
- While cycling outputs on and off (by depressing and releasing throttle), observe vacuum gauge at the output. Maintain vacuum at source.


Results...

If vacuum does not cycle on and off in less than 2 seconds, check filter, replace as necessary; if OK, replace solenoid assembly, reconnect all vacuum lines, re-run self-test


If vacuum output cycles on and off in less than 2 seconds... reconnect all vacuum lines, goto DD14...

DD14:
- key off, wait 10 seconds
- vacuum lines reconnected
- check entire EEC vacuum line system per VECI decal for kinks, cracks, obstructions or leaks... if vacuum lines not OK, service as necessary and re-run test.

If they're OK.. goto DD15

DD15... CHECK EVP RESISTANCE WHILE APPLYING VACUUM TO EGR VALVE

- key off
- disconnect vehicle harness from EVP sensor. Inspect for damaged pins, corrosion, pins pushed out. Service as necessary.
- DVOM on 200,000 ohm scale
- Disconnect vacuum line at EGR valve
- Connect vacuum pump to EGR valve
- Measure resistance of EVP sensor between EVP Signal Pin and VREF Pin while increasing vacuum to 33 kPa (10 in. Hg).
- Observe resistance as vacuum increases

Results...

If reading gradually decreases from no more than 5,500 ohms to no less than 100 ohms, replace processor; reconnect EVP sensor and EGR vacuum line; re-run self-test.

If reading does not decrease gradually, goto DD16

DD16 - MANUALLY EXERCISE EVP SENSOR

- key off, harness disconnected from EVP sensor
- remove EVP sensor from EGR valve
- measure resistance of EVP sensor between EVP signal pin and VREF pin while gradually applying pressure to EVP sensor shaft
- Observe resistance as shaft is slowly pushed in and released
- Look for sudden changes in resistance readings

Results....

If both readings decrease and increase smoothly between 5,500 ohms and 100 ohms... refer to EGR system, Section 6 (I'd guess to check your EGR valve).

If either reading decreases or increases abruptly between 5,500 ohms and 100 ohms, then... replace EVP sensor... reconnect harness and vacuum lines, re-run self-test

DD17

MEASURE EGRV/EGRC SOLENOID RESISTANCE

- key off, wait 10 seconds
- DVOM set to 200 ohm scale
- Disconnect EGRV solenoid connector and measure solenoid resistance. Inspect for damaged pins, corrosion, pins pushed out (service as necessary).

Results...

If either resistance is less than 30 ohms or greater than 70 ohms... replace EGRC/EGRV solenoid, re-run self-test

If both resistances are between 30 and 70 ohms....

- reconnect solenoids, goto DD18

DD18: CHECK FOR VOLTAGE ON VEHICLE POWER CIRCUIT

- disconnect EGR vent and EGR control solenoids from haeness
- key on, engine off
- DVOM on 20V scale
- Measure voltage between battery negative terminal and VPWR circuit on both EGR solenoids

If either reading is less than 10.5v, service open circuit in harness and re-run quick-test

If readings are 10.5V or greater, goto DD19

DD19 - CHECK CONTINUITY OF EGRV AND EGRC CIRCUITS

- key off, wait 10 seconds
- EGR vent and EGR control solenoid disconnected from harness
- Disconnect processor 60-pin connector and inspect for damaged pins, corrosion, loose wires; service as necessary
- Install Breakout Box to processor connector; leave processor disconnected
-
- DVOM on 20V scale
- Measure resistance between test Pin 33 at the breakout box and EGRV signal at the EGRV solenoid vehicle harness connector
- Measure resistance between test pin 52 at the breakout box and EGRC signal at the EGRC solenoid vehicle harness connector

Results....

If either reading is 5 ohms or greater, service open circuit; remove breakout box; reconnect harness to processor; rerun self test

If both readings are less than 5 ohms, goto DD20

DD20: CHECK FOR SHORT TO GROUND

- key off, wait 10 seconds
- DVOM on 200,000 ohm scale
- Leave breakout box installed and processor disconnected
- EGRV/EGRC solenoids disconnected
- Measure resistance between text pins 33 and/or 52 and test pins 40, 46 and 60 at the breakout box

Results...

If resistance reading is less than 10,000 ohms, service short to ground and re-run self-test

If resistance reading is 10,000 ohms or greater, goto DD21

DD21 - CHECK EGRV AND EGRC SIGNALS FOR SHORTS TO POWER

- EGR vent and EGR control solenoids disconnected from harness
- key off, breakout box installed; processor disconnected
- DVOM on 200,000 ohm scale
- Measure resistance between test pin 33 and test pins 37 and 57 at breakout box
- Measure resistance between test pn 52 and test pins 37 and 57 at the breakout box

Results...

If any reading less than 10,000 ohms, then service open short; remove breakout box; reconnect harness to processor; re-run self-test; if code is repeated, replace processor

If all readings are 10,000 ohms or greater... replace processor; remove breakout box; reconnect harness to processor; re-run self test

Codes 77 and 25, I'm not worried about right now (user error caused at least one of them).

BTW it's pretty much SOP here that quoted text remains at the top and your new replies are written at the bottom - makes threading lots easier, thanks.

 

The first thing it should do is a KOEO test; it pulls & reports the CM codes from memory directly afterwards.

I don't recognize a Code 10 at all, I suspect it's a "separator star" as codes are shown twice - once, followed by a 4-second pause, then repeated.

The book is sometimes very specific about in which order codes should be dealt with (or ignored, as the case may be), so please be clear on what you're doing and reporting.

 

The '10 code is the separator code between the KOEO tests and CM dump. When getting codes with a test light I think you get 1 flash and then a long pause. The code reader interprets this as a 10 code. (There is no pause or separator between the repeated codes).

Also the code reader shows the repeated codes during the test (11...11...10...11...11) but later when you recall the memory, only the single set of codes are shown.
So memory recall of 11...10...11 means all good for KOEO AND CM.

 

I have never bothered with the timing light yet.

My '86 does not seem to respond to the PS and brake test. Does not mater if I do it or not. I think that may be for later years.

For the WOT test you need to wait for the 1st 10 code to appear then you have 10 seconds to complete the WOT test. Make sure the engine gets up to WOT... 2 or 3 seconds should be OK but a 'quick punch' may not work. The test must be done within the 10 second time period or else you get the 77 & 25 codes. If you have successfully done the WOT test and are chasing other problems then just skip it and ignore the 77 & 25 codes. (A 25 code without the 77 would be a real problem).

For more info see the code reading tutorial link in my signature.

 

'k, thanks; I don't have a code reader (count blinkenlights, instead) and end up teaching the kids at parts stores about OBD I and how to do it....