Electrical Alternator (91 Mustang GT & 89 Lincoln Mark VII)

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The verdict is in....the Mustang did NOT pass emissions.

Told the idle was borderline high, just under 1,000 RPM. And, the NOx levels were too high.

Below are the readings for the different test points:
At 15 mph, it measured 1348 RPM. Emission levels were
--HC (PPM) : Actual 40 (max allowed 85)
--CO (%) : Actual 0.01 (max allowed 0.54)
--NO (PPM) : Actual 838 (max allowed 629)


At 25 mph, it measured 1158 RPM. Emission levels were
--HC (PPM) : Actual 30 (max allowed 67)
--CO (%) : Actual 0.01 (max allowed 0.45)
--NO (PPM) : Actual 785 (max allowed 686)

So, it looks like it failed because NOx were too high and the idle rpm were accelerated.
The technician suggested I look into vacuum leaks to lower the idle RPM, or possibly retarding the timing.

Looks like we have bit more reading to do to figure out the issue here.

Jhp & son (slightly disappointed)
 
Drop idle via the "baseline idle reset procedure" should be easy fix.

As for high nox, could be a few things. Verify the egr function. Set baseline timing to 10 degrees. Could also be bad/aged o2 sensors. Might be worth a pair of new motorcraft sensors.
 
Drop idle via the "baseline idle reset procedure" should be easy fix.

As for high nox, could be a few things. Verify the egr function. Set baseline timing to 10 degrees. Could also be bad/aged o2 sensors. Might be worth a pair of new motorcraft sensors.

Finally got some time to get back to working on the car. Changed the O2 sensors, and did a homemade smoke test to see where the vacuum leaks were coming from. Turned out that the gasket between the EGR spacer and throttle body was faulty. Went ahead and replaced the gasket, and followed recommended procedure for the base idle reset. Car is running like a charm. Will take it Monday to get it smogged again.

Also, decided to do something about the damaged radiator support, especially since it seems that the passenger front side is pushed in a tad. Went to the junkyard to see what we could find. Came across a 93 five-oh and removed the apron and support. Took a while because the sawzall broke down and we scavenged for anything to keep on the job (see picture). Passerbys were a tad shocked, but my son was determined to bring it home. Glad he didn't give, even after a long while.

Now we need to figure how best to proceed. After the car passes smog, we will likely remove the fenders and see if the lower frame is straight enough to use as is or if we need to replace. If the former, we may end up removing the spot welds on the car (and replacement piece) and drop in the aprons and radiator support and weld together. If it is damaged, we will need to figure out where we cut the frame to attach the replacement.

Either one will likely take us a bit of time. Any suggestions?

Jhp & son
 

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The verdict is in....the Mustang did NOT pass emissions.

Told the idle was borderline high, just under 1,000 RPM. And, the NOx levels were too high.

Below are the readings for the different test points:
At 15 mph, it measured 1348 RPM. Emission levels were
--HC (PPM) : Actual 40 (max allowed 85)
--CO (%) : Actual 0.01 (max allowed 0.54)
--NO (PPM) : Actual 838 (max allowed 629)


At 25 mph, it measured 1158 RPM. Emission levels were
--HC (PPM) : Actual 30 (max allowed 67)
--CO (%) : Actual 0.01 (max allowed 0.45)
--NO (PPM) : Actual 785 (max allowed 686)

So, it looks like it failed because NOx were too high and the idle rpm were accelerated.
The technician suggested I look into vacuum leaks to lower the idle RPM, or possibly retarding the timing.

Looks like we have bit more reading to do to figure out the issue here.

Jhp & son (slightly disappointed)
Drop idle via the "baseline idle reset procedure" should be easy fix.

As for high nox, could be a few things. Verify the egr function. Set baseline timing to 10 degrees. Could also be bad/aged o2 sensors. Might be worth a pair of new motorcraft sensors.
You guys are brilliant and your advice stellar. My son and I followed the recommendations and got results.

Car passed smog test yesterday. Here are the numbers from the test:

At 15 mph, it measured 1323 RPM. NOx emission levels (PPM) :
Actual 484 (max allowed 629)

At 25 mph, it measured 1129 RPM. NOx emission levels (PPM) :
Actual 391 (max allowed 686)

I will try to post a picture of the project car shortly. Need to track down the passenger window switch so we can open the windows. It gets hot inside with the windows up.
 
I will try to post a picture of the project car shortly. Need to track down the passenger window switch so we can open the windows. It gets hot inside with the windows up.

Motorcraft sw7062 is the part number for a window switch.

Don't bother with the aftermarkets...they suck.
 
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Motorcraft sw7062 is the part number for a window switch.

Don't bother with the aftermarkets...they suck.
Well, we tracked the problem to the power window motor. The brushes have fallen off the copper wires. I have searched far and wide for replacement brushes. Only ones I can find are attached to the copper wire on the bottom. However, the ones on the motor were attached on the side. The spring was underneath the brush, and the copper wire was connected perpendicular to the travel of the brush.

Anyone have a recommendation for a source for brushes? If so, would you know the dimensions?

Tempted to modify the brush in the picture so that the copper lead is coming to the side, but this would result in a small brush height (which would mean short life-span) for the brushes. I know they are carbon and can be shaved down.

Is there a preferred method for connecting the copper lead to the carbon brush? I don't know if a soldering iron would get hot enough to heat up the carbon to bind with the solder.

Thx, Jhp & son
 

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Well, my son came home about two weeks ago, barely rolling into the driveway. Said the car had died on him on the road. Restarted it and inched his way closer to home. Finally made it up the hill and rolled into the driveway, with the engine off.

I asked if he had run out of gas. He said, "No, my friend and I put gas in the morning."

Checked it out and it wouldn't start. As I was already dealing with a timing belt and water pump issue on my 99 4Runner. I told him we could get to it later in the week. After several unsuccessful attempts (using the Crank No Start thread) over the course of ten days, I snuck off and grabbed two gallons of gas, poured it into the tank, and voila the car started.

Now, after a few choice words mutter under my breath, I turned to him and said, "It doesn't sound right, seems to be idling high and stuttering." It smelled odd, not sweet just rich and burnt. So we started looking for vacuum leaks with our homemade baby oil/soldering gun smoke machine. No luck.

Looked in the forum for guidance and came across a thread that recommended using an OBD-1 code reader to try various tests (KOEO, KOER, and CBT). Here are the results:

KOEO: 11, 10
KOER: 41, 91
Cylinder Balance Test
Test 1: 70,
Test 2: 70,
Test 3: 60, 70

Don't have a compression tester and the ones at the local auto part store are already rented out. So unable to check on that tonight (we may end up buying one, so if you have any suggestions, please let us know. I'm trying to get my son a decent set of tools as we go along with the project car).

Looking at the test, I am assuming that there must be a leak, since we replaced the O2 sensors recently (when the car was emitting too much NOx). Need to work on putting together a better smoke test machine. Also, little confused why cylinder 6 only came on after the third test in the Cylinder Balance Test sequence. Shouldn't it have popped earlier?

Should we switch ignition wires and spark plugs on these two cylinders to two other cylinders and run the CBT again?

What are we missing? Could running the tank dry (we installed a brand new tank, fuel pump, and sending unit [which for some reason hasn't worked from day one so the car doesn't register any fuel even when we fill it to the hilt]) have caused a problem with the injectors (seem to be the original ones).

By the way, we made the mistake of running the tests in the garage, with the front of the car facing out. Good thing we have a side window and side door. We nearly succumbed to the exhaust fumes. We are working in the garage to avoid the heat. Will have to rethink that, I think.

Anyway, thanks for any advice and guidance. Nearly strangled my son for the empty tank, but giving him a pass because he did say upfront that the car was idling poorly and backfiring beforegand.

Thanks, jhp and son.
 
Check fuel. Misfire and o2 codes could be the result of fuel starvation
Really? By the time we were nearing the end of the tests, there was an awful lot of smoke in the garage. A smokey haze. Why would that be? It wasn’t noticeable at the beginning. By the end, we could see smoke in the engine bay.

I get the point of the O2 sensors. Maybe need to check for vacuum leaks again.

On the fuel issue, should we check fuel pressure on the rail? Or are we checking the injectors?

Why would cylinder 7 and then cylinder 6 pop up in the CBT?

A lot of questions, we know. But, on the bright side, we keep learning.

Jhp & son
 
Well, my son came home about two weeks ago, barely rolling into the driveway. Said the car had died on him on the road. Restarted it and inched his way closer to home. Finally made it up the hill and rolled into the driveway, with the engine off.

I asked if he had run out of gas. He said, "No, my friend and I put gas in the morning."

Checked it out and it wouldn't start. As I was already dealing with a timing belt and water pump issue on my 99 4Runner. I told him we could get to it later in the week. After several unsuccessful attempts (using the Crank No Start thread) over the course of ten days, I snuck off and grabbed two gallons of gas, poured it into the tank, and voila the car started.

Now, after a few choice words mutter under my breath, I turned to him and said, "It doesn't sound right, seems to be idling high and stuttering." It smelled odd, not sweet just rich and burnt. So we started looking for vacuum leaks with our homemade baby oil/soldering gun smoke machine. No luck.

Looked in the forum for guidance and came across a thread that recommended using an OBD-1 code reader to try various tests (KOEO, KOER, and CBT). Here are the results:

KOEO: 11, 10
KOER: 41, 91
Cylinder Balance Test
Test 1: 70,
Test 2: 70,
Test 3: 60, 70

Don't have a compression tester and the ones at the local auto part store are already rented out. So unable to check on that tonight (we may end up buying one, so if you have any suggestions, please let us know. I'm trying to get my son a decent set of tools as we go along with the project car).

Looking at the test, I am assuming that there must be a leak, since we replaced the O2 sensors recently (when the car was emitting too much NOx). Need to work on putting together a better smoke test machine. Also, little confused why cylinder 6 only came on after the third test in the Cylinder Balance Test sequence. Shouldn't it have popped earlier?

Should we switch ignition wires and spark plugs on these two cylinders to two other cylinders and run the CBT again?

What are we missing? Could running the tank dry (we installed a brand new tank, fuel pump, and sending unit [which for some reason hasn't worked from day one so the car doesn't register any fuel even when we fill it to the hilt]) have caused a problem with the injectors (seem to be the original ones).

By the way, we made the mistake of running the tests in the garage, with the front of the car facing out. Good thing we have a side window and side door. We nearly succumbed to the exhaust fumes. We are working in the garage to avoid the heat. Will have to rethink that, I think.

Anyway, thanks for any advice and guidance. Nearly strangled my son for the empty tank, but giving him a pass because he did say upfront that the car was idling poorly and backfiring beforegand.

Thanks, jhp and son.


Code 41 or 91. Or 43 Three digit code 172 or 176 - O2 sensor indicates system lean. Look for a vacuum leak or failing O2 sensor.

Revised 01 Sep 2019 1.) To emphasize do not attempt to measure the O2 sensor resistance. Disconnect the O2 sensor from the wiring before doing any resistance checking of the sensor to computer wiring.

Code 41 is the passenger side sensor, as viewed from the driver's seat.
Code 91 is the driver side sensor, as viewed from the driver's seat.

Code 172 is the passenger side sensor as viewed from the driver's seat.
Code 176 is the driver side sensor, as viewed from the driver's seat.

Code 43 is not side specific according to the Probst Ford Fuel injection book.

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 O2 sensor. Before checking the O2 sensor circuit wiring resistance, disconnect the O2 sensor from the rest of the circuit wiring. 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.


Disconnect the O2 sensor from the harness and use the body side O2 sensor harness as the starting point for testing. Do not measure the resistance of the O2 sensor, you may damage it. Resistance measurements for the O2 sensor harness are made with one meter lead on the O2 sensor harness and the other meter lead on the computer wire or pin for the O2 sensor.
Computer wiring harness connector, computer side.
88243.gif


Backside view of the computer wiring connector:
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87-90 5.0 Mustangs:
Computer pin 43 Dark blue/Lt green – LH O2 sensor
Computer pin 29 Dark Green/Pink – RH O2 sensor

The computer pins are 29 (RH O2 with a dark green/pink wire) and 43 (LH O2 with a dark blue/lt green wire). Use the ground next to the computer to ground the voltmeter. The O2 sensor voltage should switch between .2-.9 volt at idle.


91-93 5.0 Mustangs:
Computer pin 43 Red/Black – LH O2 sensor
Computer pin 29 Gray/Lt blue – RH O2 sensor

The computer pins are 29 (RH O2 with a Gray/Lt blue wire) and 43 (LH O2 with a Red/Black wire). Use the ground next to the computer to ground the voltmeter. The O2 sensor voltage should switch between .2-.9 volt at idle.


94-95 5.0 Mustangs; note that the 94-95 uses a 4 wire O2 sensor.
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. Using the Low Ohms range (usually 200 Ohms) you should see less than 1.5 Ohms.



87-90 5.0 Mustangs:
Computer pin 43 Dark blue/Lt green – LH O2 sensor
Computer pin 29 Dark Green/Pink – RH O2 sensor
Disconnect the connector from the O2 sensor and measure the resistance:
From the Dark blue/Lt green wire in the LH O2 sensor harness and the Dark blue/Lt green wire on the computer pin 43
From the Dark Green/Pink wire on the RH O2 sensor harness and the Dark Green/Pink wire on the computer pin 29


91-93 5.0 Mustangs:
Computer pin 43 Red/Black – LH O2 sensor
Computer pin 29 Gray/Lt blue – RH O2 sensor
Disconnect the connector from the O2 sensor and measure the resistance:
From the Red/Black wire in the LH O2 sensor harness and the Red/Black wire on the computer pin 43
From the Gray/Lt blue wire on the RH O2 sensor harness and the Gray/Lt blue wire on the computer pin 29

94-95 5.0 Mustangs:
Computer pin 29 Red/Black – LH O2 sensor
Computer pin 27 Gray/Lt blue – RH O2 sensor
From the Red/Black wire in the LH O2 sensor harness and the Red/Black wire on the computer pin 29
From the Dark Green/Pink Gray/Lt blue wire on the RH O2 sensor harness and the Gray/Lt blue wire on the computer pin 27


There is a connector between the body harness and the O2 sensor harness. Make sure the connectors are mated together, the contacts and wiring are not damaged, and the contacts are clean and not coated with oil.

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

Check the fuel pressure – the fuel pressure is 37-41 PSI with the vacuum disconnected and the engine idling. Fuel pressure out of range can cause the 41 & 91 codes together. It will not cause a single code, only both codes together.

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. The exception is that the 94-95 uses a 4 wire O2 sensor.

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

Code 41 can also be due to carbon plugging the driver’s side Thermactor air crossover tube on the back of the engine. The tube fills up with carbon and does not pass air to the driver’s side head ports. This puts an excess amount of air in the passenger side exhaust and can set the code 41. Remove the tube and clean it out so that both sides get good airflow: this may be more difficult than it sounds. You need something like a mini rotor-rooter to do the job because of the curves in the tube. Something like the outer spiral jacket of a flexible push-pull cable may be the thing that does the trick.

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.

Complete computer, actuator & sensor wiring diagram for 94-95 Mustangs
94-95_5.0_EEC_Wiring_Diagram.gif


Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs
91-93_5.0_EEC_Wiring_Diagram.gif


Complete computer, actuator & sensor wiring diagram for 88-90 Mass Air Mustangs
88-91_5.0_EEC_Wiring_Diagram.gif
 
Really? By the time we were nearing the end of the tests, there was an awful lot of smoke in the garage. A smokey haze. Why would that be? It wasn’t noticeable at the beginning. By the end, we could see smoke in the engine bay.

I get the point of the O2 sensors. Maybe need to check for vacuum leaks again.

On the fuel issue, should we check fuel pressure on the rail? Or are we checking the injectors?

Why would cylinder 7 and then cylinder 6 pop up in the CBT?

A lot of questions, we know. But, on the bright side, we keep learning.

Jhp & son


The CBT isn't like a modern engine misfire test. What it does is disable an injector and look for a drop in engine RPM and changes in o2 performance. They test isn't perfect, as it briefly establishes a baseline and then kills the injector. Most manuals state to run the CBT at least 3 times if cylinders are registering as dead. If you get one cylinder once, but the other time, then it indicated an intermittent misfire as opposed to a cylinder that is dead for all 3 tests.

For fuel pressure test, just check the rail. Should register 39psi with the vac line off and plugged. With vac line on it should drop to around 35psi. Revving the motor should spike it to 39psi.

If that checks out fine, the o2 sensor codes are likely a result of the misfiring. At that point, you should go back to the basics for misfire troubleshooting. You can test the injector with a multimeter. Should measure 14.4 ohms. With the fuel pressure guage still hooked up, cycle the key to pressurize the rail. When it's stable, Touch each injector with a 9V battery. It should click and you should see the pressure drop.

You'll want to verify spark as well.

After that...compression test time.

There's always the chance to that something electrical is damaged. 10-pin connectors are notorious for bad connections and these control the injectors. Wouldn't hurt to disconnect, clean and reconnect them.
 
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My son was rear ended this week while driving on the freeway. The other driver was 79 years old and had a Toyota 4Runner with an off road body package (heavy front grille).

Fortunately, it was during rush hour traffic in Los Angeles. So, traffic wasn’t going very fast. Nonetheless, his bumper sustained some damage. We need to replace it.

Saw an used rear bumper from a 1995 SN95. Can we put this on the 91 GT?

Thx, jhp84 & son
 
My son was rear ended this week while driving on the freeway. The other driver was 79 years old and had a Toyota 4Runner with an off road body package (heavy front grille).

Fortunately, it was during rush hour traffic in Los Angeles. So, traffic wasn’t going very fast. Nonetheless, his bumper sustained some damage. We need to replace it.

Saw an used rear bumper from a 1995 SN95. Can we put this on the 91 GT?

Thx, jhp84 & son
Nope,
sorry to hear about wreck. Kids ok and the car ain't hurt bad.
 
Nope,
sorry to hear about wreck. Kids ok and the car ain't hurt bad.
He is fine. A bit shaken up, that’s all.

Told him not to worry about the car. Just another opportunity to learn together more about his vehicle.

Btw, not related to the accident, he mentioned the automatic transmission seems to slip (awkward shifting) when in overdrive. Where do we start to determine if this is an issue or just him getting more familiar with the car?

Thx again, jhp84 & son