More friggin codes

[Hi-Po]

Right.. My car hesitates under acceleration, and fuel consumption seems high.
It starts easily enough when both cold and warm, but has a very low cold idle 400-500 rpms compared to 720-760 when warm.
During ordinary cruising everything seems fine though, but when trying to accelerate nothing happens despite going into boost

Codes as follows:

KOEO: Code 11 - System Pass

Continous Memory: Code 64 - ACT or VAT sensor fault, or circuit grounded

KOER: Code 94 - Secondary Air Injection system inoperative (left side)
KOER: Code 44 - Secondary Air Injection system inoperative (right side)

I am reasonably sure I don't have any vacuum leaks, and a visual inspection of the Thermactor system doesnt reveal any faults.

Any input please? Jrichker?

 

[jrichker]

Code 11 The computer's internal self test passed. The computer thinks it is OK and any problems present are in the external sensors.


Code 64 – ACT (Air Charge Temperature) signal low or grounded. Bad sensor,
sensor wiring on pin 25 shorted to ground, or bad computer.

Note that all resistance tests must be done with power off. Measuring
resistance with a circuit powered on will give false readings and possibly
damage the meter.

The ACT is located in the #5 intake runner on Mustangs built from 86-93.
Disconnect the sensor by removing the sensor wiring connector. Measure
the resistance across the sensor pins.

Ohms measures at the computer with the computer disconnected, or at the
sensor with the sensor disconnected.
50 degrees F = 58.75 K ohms
68 degrees F = 37.30 K ohms
86 degrees F = 27.27 K ohms
104 degrees F = 16.15 K ohms
122 degrees F = 10.97 K ohms
140 degrees F = 7.60 K ohms
158 degrees F = 5.37 K ohms
176 degrees F = 3.84 K ohms
194 degrees F = 2.80 K ohms

If the sensor resistances read good according to the table, remove
the passenger side kick panel and disconnect the computer connector.
A single 10 MM bolt secures the connector in place. With the sensor
connector still disconnected, measure the resistance between pin 25
(lt green/pink wire) and ground. If you wish, you can make your
measurements at the ACT sensor end. This will save you from
counting the computer connector pins to locate the correct one.
However, you will still have to disconnect the computer connector.
You should see 100K Ohms or greater between pin 25 and ground.
Less than that indicates wiring problems with the pin 25
lt green/pink wire shorted to ground. Note that the following
diagram on the connector displays the pins viewed from the
computer side.

See following website for some help from Tmoss
(diagram designer) & Stang&2Birds (website host) for
help on 88-95 wiring Mustang FAQ - Engine Information
http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif

Diagram courtesy of Tmoss & Stang&2birds

Codes 44 & 94 - AIR system inoperative - Air Injection. Check vacuum lines for leaks, & cracks.

The computer uses the change in the O2 sensor readings to detect operation of the Thermactor control valves.
When the dump valve opens, it reduces the O2 readings in the exhaust system. Then it closes the dump valve and
the O2 readings increase. By toggling the dump valve (TAB) and switching the diverter valve (TAD) flow from the
back of the heads to the air pipe, the computer tests for the 44/94 codes.

Testing the system:
Disconnect the big hose from smog pump: with the engine running you should feel air output. Reconnect
the smog pump hose & apply vacuum to the first vacuum controlled valve: Its purpose is to either dump
the pump's output to the atmosphere or pass it to the next valve.

The next vacuum controlled valve directs the air to either the cylinder heads when the engine is cold or
to the catalytic converter when the engine is warm. Disconnect the big hoses from the back side of the
vacuum controlled valve and start the engine. Apply vacuum to the valve and see if the airflow changes
from one hose to the next.

The two electrical controlled vacuum valves mounted on the rear of the passenger side wheel well turn the
vacuum on & off under computer control. Check to see that both valves have +12 volts on the red wire.
Then ground the white/red wire and the first solenoid should open and pass vacuum. Do the same thing to
the light green/black wire on the second solenoid and it should open and pass vacuum.

Remember that the computer does not source power for any actuator or relay, but provides the ground
necessary to complete the circuit. That means one side of the circuit will always be hot, and the other side
will go to ground or below 1 volt as the computer switches on that circuit.

The computer provides the ground to complete the circuit to power the solenoid valve that turns the
vacuum on or off. The computer is located under the passenger side kick panel. Remove the kick panel &
the cover over the computer wiring connector pins. Check Pin 38 Solenoid valve #1 that provides vacuum
to the first Thermactor control valve for a switch from 12-14 volts to 1 volt or less. Do the same with pin
32 solenoid valve #2 that provides vacuum to the second Thermactor control valve. Starting the engine
with the computer jumpered to self test mode will cause all the actuators to toggle on and off. If after
doing this and you see no switching of the voltage on and off, you can start testing the wiring for shorts to
ground and broken wiring. An Ohm check to ground with the computer connector disconnected & the
solenoid valves disconnected should show open circuit between the pin 32 and ground and again on pin 38
and ground. In like manner, there should be less than 1 ohm between pin 32 and solenoid valve #2 and pin
38 & Solenoid valve #1.

If after checking the resistance of the wiring & you are sure that there are no wiring faults, start looking at the
solenoid valves. If you disconnect them, you can jumper power & ground to them to verify operation. Power &
ground supplied should turn on the vacuum flow, remove either one and the vacuum should stop flowing.

Typical resistance of the solenoid valves is in the range of 20-70 Ohms.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91eecPinout.gif

See http://forums.stangnet.com/attachment.php?attachmentid=50636&d=1180923382 for a very nice drawing of the Thermactor Air System (smog pump) plumbing

If you have a catalytic converter H pipe, you need to fix these codes. If you don't, then don't worry about them

 

[Hi-Po]

Jrichker,

Thanks your advice.

Right now I hate my car with a passion, and I am not sure when I will manage to start working on it again.

I tried to disconnect the wiring from the ACT sensor today but didnt succeed thanks to the location of the supercharger. Just broke one of the plastic clips on the connection - can't get to the other one.

Anyhow, regarding the Thermactor codes - since I didnt get code 81/82 during KOEO (circuit failure on the diverter and bypass solenoid) can I then assume these two solenoids are ok? I.e. that I can focus on the airpump itself or the two valves?

 

[jrichker]

Do the tests to apply vacuum to the diverter valves and see what happens...

 

[Hi-Po]

I am definitely struggling with this.

Code 64:

I measured the resistance across the sensor pins and got 48.4 Ohms - temperature was around 18 degrees Celsius or about 64 Fahrenheit.

Is that a bit too high?

I also measured the voltage circuit and got 3.27 volt at same temperature (this as per page 275 in "How to understand, service..." by Probst).
So circuit voltage should be good.

Then I tried to measure circuit resistance twice, first from the ACT side and then from the computer connector side but I couldnt get any results. My voltmeter didnt react at all - which feels a bit strange...?
So... no resistance at all, does that mean there is a short somewhere between the sensor connector and the computer connector?
But if so, how come I get good circuit voltage?

What to do now?



Code 44/94:

Checked the air pump - ok.
Checked the bypass valve - I believe it is ok. I dont have a vacuum pump but the valve works fine by just sucking on the vacuum connection...
Same with the diverter valve.

One thing I thought was a bit strange when testing this a few days ago was that I could feel vacuum going to the air bypass valve when the engine was idling, but I couldnt feel any vacuum at all going to the air diverter valve - is it supposed to be like that?

Then I measured solenoid resistance - got 72.4 Ohm on the solenoid nearest to the fender and 71.9 Ohm on the other.

Next I checked for VPWR (KOEO) as per page 299 Probst - got 11 volts on each solenoid.

Will try to find a garage on Monday who can check the solenoids for vacuum.



So...

 

[jrichker]

ACT problem:
Check the end to end resistance of the ACT sensor to computer wiring. You should see less than 2 Ohms on each wire. Put one probe on the ACT sensor wire and the other on the computer pin it connects to. Use the diagram I posted to find the wire colors and pin numbers.

Code 94/44 problem
Use a vacuum gauge to check for vacuum at the solenoid valves with the engine running. Tap into the vacuum system at the vacuum tree and apply vacuum directly to the bypass valve and then the diverter valve to be sure they change the airflow through them.

 

[Hi-Po]

ACT problem:
Check the end to end resistance of the ACT sensor to computer wiring. You should see less than 2 Ohms on each wire. Put one probe on the ACT sensor wire and the other on the computer pin it connects to. Use the diagram I posted to find the wire colors and pin numbers.

jrichker, thanks your last.

I tried to measure this today but couldnt get any readings.

Soo... I am starting to wonder if I am doing something wrong here?
I put one DVM probe to one of the female contacts/'pins' in the sensor connector and the other to probe the female 25 'pin' in the computer connector.
My DVM was at the lowest Ohm selection - 200 Ohms. It didnt react at all - and sake order I tried all the other Ohm selections as well but no reactions. And of course I tried the other contact in the sensor connector - no reaction/result.

This is basically the same result as when I tried to measure pin 25 to ground the other day (and I tried again today) - DVM registers/measures nothing.

I checked resistance over sensor pins again today and got 55k Ohms - ambient temperature was about 16 degree Celsius/61 degree Fahrenheit.

From what little I can inspect visually of the lt green/pink wire it looks ok - and I have never messed with any of those engine harness wires before.

So what does this mean that I am getting no resistance readings on both the circuit/ground check and wire end to wire end check?


I havent done anything further with code 44/94 - it can wait..

 

[jrichker]

General advice when using an Ohmmeter:
Always have the power turned off on a circuit when you use the Ohms function on your meter. Have the ignition switch turned off, or remove the fuse (if there is one) or disconnect the battery negative terminal. This protects the meter from damage and helps prevent inaccurate readings. Keep your fingers from touching the probe tips when making the measurements because it will often cause inaccurate results.

The failure of the end to end resistance check means the wiring or connections for the ACT are bad. Try wiggling the wires when you do resistance checks to spot intermittent connections.

Use the diagram of the 10 pin connectors and try measuring between the engine side white 10 pin connector pin 6 and the LT green/pink wire on the ACT. There should be less than 2 ohms.

Do the same with the ACT black/white wire and pin 1 of the engine side white 10 pin connectors. There should be less than 2 ohms.

Do an end to end resistance check from the computer connector pin 25 to pin 6 on the body side of the white 10 pin connector. There should be less than 2 ohms.

Do an end to end resistance check from the computer connector pin 46 to pin 1 on the body side of the white 10 pin connector. There should be less than 2 ohms.

If all the resistance checks are good, then the 10 pin connector contacts are not making a good connection. Clean the 10 pin connectors with non-flammable brake parts cleaner and try to reshape the pins and sockets to make a better connection. A small jeweler's screwdriver is useful for this job.

 

[Hi-Po]

jrichker, I think we are on to something...

Use the diagram of the 10 pin connectors and try measuring between the engine side white 10 pin connector pin 6 and the LT green/pink wire on the ACT. There should be less than 2 ohms.

Do the same with the ACT black/white wire and pin 1 of the engine side white 10 pin connectors. There should be less than 2 ohms.

Do an end to end resistance check from the computer connector pin 25 to pin 6 on the body side of the white 10 pin connector. There should be less than 2 ohms.

Do an end to end resistance check from the computer connector pin 46 to pin 1 on the body side of the white 10 pin connector. There should be less than 2 ohms.

If all the resistance checks are good, then the 10 pin connector contacts are not making a good connection. Clean the 10 pin connectors with non-flammable brake parts cleaner and try to reshape the pins and sockets to make a better connection. A small jeweler's screwdriver is useful for this job.

I got approximately 0.4 Ohm resistance on all the above checks.
Didnt have time to clean the 10 pin connectors today but will get on with it tomorrow.

Shall let you know!

 

[Hi-Po]

jrichker,

This has been a confusing and frustrating day.

I started off with cleaning and adjusting the contacts in the 10 pin connectors.
Then I tried to measure resistance between the lt grn/pink wire and ground - and couldnt get any results. I tried measuring both at the sensor connector side and the computer connector side.

Then I measured end to end resistance from computer connector to sensor connector - both the lt grn/pnk and the b/w wire checked out at 0.4 Ohms resistance.
So obviously it helped cleaning the 10 pin connectors - but I am baffled why I cant get any readings for lt grn/pnk to ground.

Anyhow, not knowing what to do I decided to hook everything up and go for a test drive -

The car started up right away but with a rough and low idle, not really surging but running roughly at around 450 rpm to 600 rpm.
Not easy to drive while warming up, but when warm it idled nicely at around 700-740 rpm.
However it was just as before, hesitating and stuttering when accelerating or under load - not all the time but now and then... Sometimes it even accelerated as it should, but it basically felt like it got worse the longer I drove.

When coming back I scanned codes again - and I got 11 on KOEO, then I got 11 on continous memory - and 94/44 on KOER.

So code 64 - ACT - has disappeared, despite me even failing to measure resistance to ground.

Not really knowing what to do next I just cleared the codes, and pulled the spark plug on no 5 - it looked perfect.

I went for another test drive - and the symptoms were the same.

Back again I scanned codes again, and lo and behold now I got the two OK codes for KOEO and continous memory - and codes 94/44 KOER had disappeared.
Instead I got a new one, code 91 - HEGO (H02S*) circuit indicates system lean (left H02S)

So continous memory code 64 and KOER codes 94/44 has disappared all by themselves - the car feels exactly the same and I have got a new code 91 KOER.

One thing I havent mentioned before - my temp gauge has always been indicating very low - despite engine being at normal working temperature (I am running a 190 or 195 degree thermostat), however ever after this problem started it has basically acted as it should with the needle in the middle of the scale. Before it was at the bottom...

Can code 91 also point to fuel problems? My fuel pressure is around 41-42 psi when idling, going up to just below 50 when under boost.
O2 sensors, fuel pump and injectors and MAF are all new with around 3,000 miles on them now.

I am frustrated and depressed.

Any ideas please? You are pretty much the only thing between me and complete insanity now.

Thanks...

 

[jrichker]

Code 41 or 91 Three digit code 172 or 176 - O2 sensor indicates system lean. Look for a vacuum leak or failing O2 sensor.

Revised 22-Jun-2009 to include 3 digit code and wiring for 94-95 5.0 Mustangs

Code 41 is a RH side sensor,
Code 91 is the LH side sensor.

Code 172 is the RH side sensor
Code 176 is the LH side sensor

The computer sees a lean mixture signal coming from the O2 sensors and tries to compensate by adding more fuel. Many times the end result is an engine that runs pig rich and stinks of unburned fuel.

The following is a Quote from Charles O. Probst, Ford fuel Injection & Electronic Engine control:
"When the mixture is lean, the exhaust gas has oxygen, about the same amount as the ambient air. So the sensor will generate less than 400 Millivolts. Remember lean = less voltage.

When the mixture is rich, there's less oxygen in the exhaust than in the ambient air , so voltage is generated between the two sides of the tip. The voltage is greater than 600 millivolts. Remember rich = more voltage.

Here's a tip: the newer the sensor, the more the voltage changes, swinging from as low as 0.1 volt to as much as 0.9 volt. As an oxygen sensor ages, the voltage changes get smaller and slower - the voltage change lags behind the change in exhaust gas oxygen.

Because the oxygen sensor generates its own voltage, never apply voltage and never measure resistance of the sensor circuit. To measure voltage signals, use an analog voltmeter with a high input impedance, at least 10 megohms. Remember, a digital voltmeter will average a changing voltage." End Quote

Testing the O2 sensors 87-93 5.0 Mustangs
Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. You'll have to pull the passenger side kick panel off to gain access to the computer connector. Remove the plastic wiring cover to get to the back side of the wiring. Use a safety pin or paper clip to probe the connections from the rear. The computer pins are 29 (LH O2 with a dark green/pink wire) and 43 (RH O2 with a dark blue/pink wire). Use the ground next to the computer to ground the voltmeter. The O2 sensor voltage should switch between .2-.9 volt at idle.


Testing the O2 sensors 94-95 5.0 Mustangs
Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. You'll have to pull the passenger side kick panel off to gain access to the computer connector. Remove the plastic wiring cover to get to the back side of the wiring. Use a safety pin or paper clip to probe the connections from the rear. The computer pins are 29 (LH O2 with a red/black wire) and 27 (RH O2 with a gray/lt blue wire). Use pin 32 (gray/red wire) to ground the voltmeter. The O2 sensor voltage should switch between .2-.9 volt at idle.


Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter. Do not attempt to measure the resistance of the O2 sensors, it may damage them.

Testing the O2 sensor wiring harness
Most of the common multimeters have a resistance scale. Be sure the O2 sensors are disconnected and measure the resistance from the O2 sensor body harness to the pins on the computer.

The O2 sensor ground (orange wire with a ring terminal on it) is in the wiring harness for the fuel injection wiring. I grounded mine to one of the intake manifold bolts

Make sure you have the proper 3 wire O2 sensors. Only the 4 cylinder cars used a 4 wire sensor, which is not compatible with the V8 wiring harness.

Replace the O2 sensors in pairs if replacement is indicated. If one is weak or bad, the other one probably isn't far behind.

If you get only code 41 and have changed the sensor, look for vacuum leaks. This is especially true if you are having idle problems. The small plastic tubing is very brittle after many years of the heating it receives. Replace the tubing and check the PVC and the hoses connected to it.
A secondary problem with only a code 41 is for cars with an intact smog pump and cats. If the tube on the back of the heads clogs up the driver’s side, all the air from the smog pump gets dumped into one side. This excess air upsets the O2 sensor calibration and can set a false code 41. The cure is to remove the crossover tube and thoroughly clean the insides so that there is no carbon blocking the free flow of air to both heads.

 

[Hi-Po]

Thanks yours - I am also starting to believe I might have a vacuum leak somewhere, though I cant for the life of me figure out where it may be...

Anyhow, do you have any thoughts on how come these other codes just disappeared? And that I can measure resistance on ACT lt grn/pnk to ground?

Somehow I have a feeling there is nothing wrong with my O2 sensors, they are both literally brand new...

And why didnt I get code 91 when all this misery started last week?

I am very confused...

 

[liljoe07]

Code 91 takes control over the thermactor codes. If the Thermactor problem wasnt fixed, once you fix the Code 91 the Thermactor codes will show back up. The 02 sensors cant detect check both problems at once.

It sounds like the 02 went bad while all this was going on. If you wanna rule out a bad 02 sensor, just remove the drivers side 02 and put in the passenger side. Same for the passenger 02. If code 41 shows, then the Driver side 02 is bad. If 91 shows, then its a wiring Issue or an actuall LEAN Code.

If you get this code 91 solved, and 94 and 44 show back up, you may need to check the Crossover tube on the back of the heads

 

[Hi-Po]

liljoe,

Thanks your explanation, thats good to know!

I have found one vacuum leak which perhaps may be the reason for code 91 and the idling problems.

Will try to fix it tomorrow and see what happens then...

 

[liljoe07]

Cool.....good luck

 

[Hi-Po]

Ok, so I fixed the vacuum leak (PCV hose had jumped out of the lower intake) and code 91 has disappeared.

The car has a much better cold idle now, though not as good as I would like but that may have something to do with running 30 lbs/hr injectors. Maybe.

Anyhow, I let it idle for a while checking for other vacuum leaks and other stuff but couldnt find anything so I took it for a test drive.
Initially it felt very good, did a couple of acceleration tests and everything seemed fine - for a few minutes.
Then it started to hesitate when under load/accelerating and basically running like crap. So I stopped and it was idling poorly for a while (less than 15 vacuum), then it got better for no obvious reason and vacuum increased to around 17/18 (which I believe is normal for this POS car).

Drove home, checked codes and got 11 system ok for both KOEO and continous memory - and then codes 94 and 44 KOER.

Took it for another test drive and everything was basically the same. And same codes afterwards.

So... can really codes 94/44 affect the drivability in this way? The only thing left in the Thermactor system that I havent checked is the air pipe going from the cylinder heads (and that the solenoids actually opens the TAB and TAD).

Any good ideas please? jrichker? liljoe?

Could something be wrong with my ignition system?

 

[liljoe07]

Id say it could be an ignition problem. Under load is when a ignition problem will show its face the majority of the time. Id be checking the simple things first. Plugs, Wires, cap and rotor. Hows your fuel pressure? And to be accurate the Fuel pressure would need to monitored while the symptom is present.

Check the crossover tube for being clogged like i mentioned earlier. Ive never seen it affect drivability though

 

[Hi-Po]

Id say it could be an ignition problem. Under load is when a ignition problem will show its face the majority of the time. Id be checking the simple things first. Plugs, Wires, cap and rotor. Hows your fuel pressure? And to be accurate the Fuel pressure would need to monitored while the symptom is present.

I have an in-car fuel pressure gauge and a vacuum/boost gauge.

My fuel pressure is slightly higher now than it used to be before these problems started (at least I think so - its in the low/mid 40's depending on idle rpms).
And it goes up whenever the engine starts to loose power/hesitate under load/acceleration - but I thought that was an indication towards a vacuum problem, which I hopefully have managed to fix now. At least I didnt get code 91 today.

My ignition system is stock except for an old Crane ignition box - and I am starting to wonder whether this ignition box gets too hot or something since these problems seem to occur only a few minutes after the engine has reached normal working temp.
The ignition box is placed where the battery used to be.

Except for the air tube I am not sure what to start checking tomorrow.

I have pulled one spark plug - no 5 - and it looked just fine.

Spark plugs, wires, cap and rotor are all new with approximately 3,000 miles on them.

 

[liljoe07]

If there is any way you can bypass the Crane box and run the stock set up, Id try that. You said the vacuum went down a tad, and that can be caused by an ignition problem.