Bucking And Surging Help

have you removed all the smog stuff?

Make sure your distributor is pointing to #1 at TDC on proper scale if more than one.
I thought my PIP might be bad so in process of replacing my 4 year old professionally installed unit I discovered the "pro" missed by one tooth making it out of time by 10deg? Ran amazingly well other then 4500rmp stumble. It's easy to do wrong. But it's easy to fix.
http://www.stangnet.com/mustang-forums/threads/breaking-up-86-aod-4200rpm-stock.862088/
Good luck.

slow5ohgt said:

Timing is set to 12 degrees with a light. Wouldn't that indicate that distributor is OK?

Sent from my SAMSUNG-SGH-I717 using Tapatalk 2

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No. If the base timing is off EVERYTHING is off that much. Then you add to it or subtract with your turning of the distributor. Actual rotor has to point directly at #1 plug with knowledge that #1 piston is at TDC. Some people actually remove the spark plug and watch a screw driver move up. (You can be off 180degrees on distributor just by cranking the starter.) Get it close with the starter and pull the belt to move it the rest of the way by hand. Or put a breaker bar with socket on the crank if you have one? Aftermarket distributors have 3 sets of timing marks. Make sure you are using the right set. I assume you know to remove the coil wire before hitting the starter!!

Most people make a mark on the distributor at #1 before they pull it so they don't miss by one tooth reinstalling. There is a good video floating around out there on how to do this. Google it. Easy to mess up but easy to fix.

twistedwankel said:

Make sure your distributor is pointing to #1 at TDC on proper scale if more than one.
I thought my PIP might be bad so in process of replacing my 4 year old professionally installed unit I discovered the "pro" missed by one tooth making it out of time by 10deg? Ran amazingly well other then 4500rmp stumble. It's easy to do wrong. But it's easy to fix.
http://www.stangnet.com/mustang-forums/threads/breaking-up-86-aod-4200rpm-stock.862088/
Good luck.

Click to expand...

Thing is that you can clock your distributor anywhere, and as long as the wire going to #1 plug is the wire getting the juice at TDC, you're fine. If your dizzy is put back 1 tooth off, all you do is rotate the dizzy or the plug wires, whichever works for you. So I don't follow the problem you had? If the 'pro' put a timing light on the car when he was done, 1 tooth or 10, it wouldn't matter. Sounds like the guy just marked the dizzy and put it back without timing it.

http://www.stangnet.com/mustang-for...t-0-on-damper-or-10-btdc.861778/#post-8664921

I just found this from Jrichker which says the same thing that ratio411 states. Can never learn too much about a 5.0!!
Jrichker also states: "There is no such thing as being a tooth off with a 5.0." I'll stand corrected.

Another thing I did find is that I had a defective "spout" which added to my issues. Replaced it with a new one and things got better once again. After 27 years I guess anything can go bad? Even a jumper.

If the balancer spun, you would know it.
The vibration of the engine will shake out your fillings.

my old 69 Mustang did that

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 06-Sep-2012 remove smog pump crossover tube reference

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.

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.

Backside view of the computer wiring connector:


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 (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.

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 (LH O2 with a Gray/Lt blue wire) and 43 (RH 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.


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. 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 Os sensor harness and the Dark Green/Pink wire on the computer pin 43

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 Dark Green/Pink Gray/Lt blue wire on the RH Os 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 Os 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

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.

good to hear!

That sucks, but your are correct, it is likely the shaft