Bucking And Surging Help
- Thread starter slow5ohgt
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*UPDATE*
I have verified that the car has 19lb injectors, autozone replacements. I cleaned up ecu grounds inside engine compartment and inside vehicle. Ran KOEO and KOER test, KOEO resulted in code 11 (normal). KOER resulted in 21 (ECT out of range) 41 (passenger side o2 lean, no switching), 91 (drivers side o2 lean, no switching). I ohmed out ECT cold and hot, in spec on both checks. 4.65 volts with KOEO at ECT connector. Ran KOER test again and codes 41 and 91 persist, but code 21 is gone. This led me to believe that the connection at ect may be bad, so i replaced pins inside the connector and rechecked voltage, all good. Test drive, problem still persists. Unplugged o2 sensors (this should put the car into open loop right?) and car runs exactly the same, no change. If it has the same problem in open and closed loop, doesnt that eliminate the possibility of the ECT, ACT, O2 sensors, and so on? Am I correct that the car only reads from the tps to adjust the fuel map in open loop? I tested tps just to verify the new one that is on the motor is good, and it reads .97 volts at idle and maxes at 4.7 volts at WOT.
Im at a loss of where to go from here.
I have verified that the car has 19lb injectors, autozone replacements. I cleaned up ecu grounds inside engine compartment and inside vehicle. Ran KOEO and KOER test, KOEO resulted in code 11 (normal). KOER resulted in 21 (ECT out of range) 41 (passenger side o2 lean, no switching), 91 (drivers side o2 lean, no switching). I ohmed out ECT cold and hot, in spec on both checks. 4.65 volts with KOEO at ECT connector. Ran KOER test again and codes 41 and 91 persist, but code 21 is gone. This led me to believe that the connection at ect may be bad, so i replaced pins inside the connector and rechecked voltage, all good. Test drive, problem still persists. Unplugged o2 sensors (this should put the car into open loop right?) and car runs exactly the same, no change. If it has the same problem in open and closed loop, doesnt that eliminate the possibility of the ECT, ACT, O2 sensors, and so on? Am I correct that the car only reads from the tps to adjust the fuel map in open loop? I tested tps just to verify the new one that is on the motor is good, and it reads .97 volts at idle and maxes at 4.7 volts at WOT.
Im at a loss of where to go from here.
No. I unhooked the egr and it runs the same regardless of whether its hooked up or not. Otherwise smog system is still intact.
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twistedwankel
Member
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.
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.
twistedwankel
Member
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.
Ok, I removed cap, rotated motor to TDC using balancer as a guide, then removed #1 plug and rotated back and forth to verify that motor is in fact at TDC on the compression stroke. Rotor is almost pointed at #1, which since timing is set to 12 degrees advanced makes sense.
A friend of mine suggested that this might be a vacuum leak. Does anybody know what vacuum is supposed to be at idle?
A friend of mine suggested that this might be a vacuum leak. Does anybody know what vacuum is supposed to be at idle?
ratio411
Founding Member
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.
twistedwankel
Member
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.
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.
That makes alot more sense to me as my understanding was the only reason for retiming the teeth is if you are so far off on tooth count that you cant rotate the distributor far enogh to get the correct timing without the plug wires stretching or the tfi hitting the thermostat housing.
Regardless, I have verified with a timing light against the balancer (as well as preadjusting the light to verify the balancer has not spun) that the car is set to 12 degrees, netting 36-38 degrees final. When the car runs good (cold right after start) it runs absolutely awesome. I mean, its the meanest stock 5.0 ive driven, and ive been in alot of them. Once it starts acting up as it warms up, it keeps up. As stated before, im getting 15psi vacuum at idle. From the research ive done, these motors stock should have closer to 20 at idle, so im leaning towards this being whats causing the motor to go lean. I have a buddy who is going to help me out with a smoke machine to try to trace down the leak.
Regardless, I have verified with a timing light against the balancer (as well as preadjusting the light to verify the balancer has not spun) that the car is set to 12 degrees, netting 36-38 degrees final. When the car runs good (cold right after start) it runs absolutely awesome. I mean, its the meanest stock 5.0 ive driven, and ive been in alot of them. Once it starts acting up as it warms up, it keeps up. As stated before, im getting 15psi vacuum at idle. From the research ive done, these motors stock should have closer to 20 at idle, so im leaning towards this being whats causing the motor to go lean. I have a buddy who is going to help me out with a smoke machine to try to trace down the leak.
ratio411
Founding Member
If the balancer spun, you would know it.
The vibration of the engine will shake out your fillings.
The vibration of the engine will shake out your fillings.
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.
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.
*Update*
Following jrichker's guide, tested o2 sensors and they are good. I started scouring the engine for vacuum leaks. I did not directly identify any, however, i did notice some lines that were hardened and dryrotted. Just for kicks, I went through the entire engine bay removing vacuum components (making sure not to damage them so that if necessary I could put them back). Now the only thing hooked up is supply to tree, a/c line direct to passenger compartment bypassing a/c tree, brake booster, MAP, and cruise control. The rest of the vacuum components are gone and all nipples on manifold plugged. Cranked car and idle surging was gone, car also accelerated smoother, but seemed to still be down on power from what it should be. Just for fun I decided to play with timing again. Instead of dicking around with a light I just pulled spout, increased timing until rpms stopped increasing and then reinstalled spout. Took car for test drive and it ran EXTREMELY strong and smooth. Continued increasing timing and test driving until I experienced pinging, then backed off to previous adjustment and test drove one final time. I can honestly say the car has never run this strong. It pulls as hard as my 89 with 3.73's did and its got stock gearing. After all the trouble ive had getting it running right, im hesitant to say its fixed, but if it runs good cold in the morning, then I think its fixed. Ill be putting about 200 miles on it tomorrow on a fresh tank of fuel, ill report back with results.
Following jrichker's guide, tested o2 sensors and they are good. I started scouring the engine for vacuum leaks. I did not directly identify any, however, i did notice some lines that were hardened and dryrotted. Just for kicks, I went through the entire engine bay removing vacuum components (making sure not to damage them so that if necessary I could put them back). Now the only thing hooked up is supply to tree, a/c line direct to passenger compartment bypassing a/c tree, brake booster, MAP, and cruise control. The rest of the vacuum components are gone and all nipples on manifold plugged. Cranked car and idle surging was gone, car also accelerated smoother, but seemed to still be down on power from what it should be. Just for fun I decided to play with timing again. Instead of dicking around with a light I just pulled spout, increased timing until rpms stopped increasing and then reinstalled spout. Took car for test drive and it ran EXTREMELY strong and smooth. Continued increasing timing and test driving until I experienced pinging, then backed off to previous adjustment and test drove one final time. I can honestly say the car has never run this strong. It pulls as hard as my 89 with 3.73's did and its got stock gearing. After all the trouble ive had getting it running right, im hesitant to say its fixed, but if it runs good cold in the morning, then I think its fixed. Ill be putting about 200 miles on it tomorrow on a fresh tank of fuel, ill report back with results.
Ok, ill be picking the car up tomorrow night and dragging it home, Then tearing into it on sunday to figure out wtf is going on. Im no expert on oil pressure issues on these motors, BUT, this is my understanding, someone please correct me if im wrong. There are only two major components that can cause this, the shaft, and the pump itself. If its a broken shaft, i can replace it through the distributor hole as long as both peices are still accessible to pull out with a magnet. If its the pump, ill have to pull the motor to get the pan off so I can replace the pump. Is that the best way to approach this? I know its not a guage issue because i pulled the oil filter and cranked the car when this happened, and not a drop hit the ground. The lifters are also deflated causing alot of rattling, so its definitely zero pressure.
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