Im rich...(running :-/)

Make sure the o2's are switching from lean to rich and arent stuck in closed loop. From the symtoms it sounds like an o2 but you said you put new ones in you may have a bad computer? check out to see if they are switching correctly.

Yea I have a very similar problem, been trying to figure it out forever too. Never really see smoke but under partial throttle is feels like the motor is just flooding itself(hesitates but is still trying) and then finally backfires. As soon as I hit WOT in any gear it is fine but it seems to lose all low end torque. Same as above too, when not up to operating temp it has all the low end torque in the world, sounds like a sensor to me as it screws up once in the warmed up loop but which one???

What are your mods? Any monkey business with with the MAF sensor or injectors or are they both stock?

Edit: disregard... I see at the end of your post where you said it was all stock.

Do a little test and measurement before you spend your money...

Code 24 - Intake Air Temperature (ACT) sensor out of range. Bad sensor, bad wiring. The ACT for Mustangs built before 95 is in the #5 intake runner. It measures the air temperature in the intake to help computer the proper air/fuel ratio.

Note that that if the outside air temp is below 50 degrees F that the test for the ACT can be in error.

ACT & ECT test data:

The ACT & ECT have the same thermistor, so the table values are the same

Pin 7 on the computer - ECT signal in. at 176 degrees F it should be .80 volts

Pin 25 on the computer - ACT signal in. at 50 degrees F it should be 3.5 volts. It is a good number if the ACT is mounted in the inlet airbox. If it is mounted in the lower intake manifold, the voltage readings will be lower because of the heat transfer. Here's the table :

68 degrees F = 3.02 v
86 degrees F = 2.62 v
104 degrees F = 2.16 v
122 degrees F = 1.72 v
140 degrees F = 1.35 v
158 degrees F = 1.04 v
176 degrees F = .80 v
194 degrees F = .61

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.

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

Well got around to grabbing some codes tonite and it seems I have a bunch, some kinda scary ones too. Off of the hard codes I got 31 and 67, which dont seem to be readily related to my problem but who knows. For the second set of codes(continuous) I first got 85 and 43, I then replaced a leaky injector o ring and cleared the continuous memory codes. After I drove it for a while I check codes again and just 83 came up for continuous codes, which seems to have several different possibilites. Anyone have any ideas. I guess Im just waiting for jricker to come in with some testing procedures.

ttt

88-GT said:

Well got around to grabbing some codes tonite and it seems I have a bunch, some kinda scary ones too. Off of the hard codes I got 31 and 67, which dont seem to be readily related to my problem but who knows. For the second set of codes(continuous) I first got 85 and 43, I then replaced a leaky injector o ring and cleared the continuous memory codes. After I drove it for a while I check codes again and just 83 came up for continuous codes, which seems to have several different possibilites. Anyone have any ideas. I guess Im just waiting for jricker to come in with some testing procedures.

Click to expand...

I can't find a match on a 5.0 for code 83 - all of the code 83 listings point to other engines.

CODE: 31 (KOEO) - EVP circuit below minimum voltage. Vref (5 volt reference voltage supplied by the computer) missing or broken wire or bad connection in circuit. Use a DVM to check for 5 volts on the orange/white wire. If it is missing, look for +5 volts at the orange/white wire on the TPS or MAP sensor located on the firewall near the center of the car. Use the black/white wire for the ground for the DVM.
With the sensor removed from the EGR and still connected, press the plunger and watch the voltage change on the brown/lt green wire. Pull the passenger side kick panel and measure the voltage at the computer. You will need to remove the plastic cover over the wires and probe them from the backside. A safety pin may prove very useful for this task. Use pin 27, EVR input (brown/lt green wire) and pin 46, signal ground (black/white wire) to measure the voltage. The orange/white wire is Vref and should always be 5 volts -/+ .25 volt. Be sure to measure Vref at the EGR sensor to rule out any broken wires or bad connections.

Code 43 engine running - Heated O2 sensor not reading (run at 2000 rpm's for 2 minutes and retest - check for O2 switching). 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.
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.


Code 43 engine off - Was lean at WOT for 3 seconds or more - Fuel control

Code 45 AIR not Diverting (AIRD) - Air Injection. Check vacuum lines for leaks, & cracks. 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 wheelwell 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.


Code 67 - clutch not depressed (5 speed) or car not in neutral or park (auto) or A/C in On position when codes where dumped. Possible neutral safety switch or wiring problem. This code may prevent you from running the Key On Engine On tests. You can generally ignore this code, since it has no effect on engine performance.


Code 85 - CANP solenoid - The Carbon Canister solenoid is inoperative. Check vacuum lines for leaks and cracks. Check electrical wiring for loose connections, damaged wiring and insulation. Check solenoid valve operation by grounding the gray/yellow wire to the solenoid and blowing through it.
The computer provides the ground for the solenoid. The red wire to the solenoid is always energized any time the ignition switch is in the run position.

bad fuel pressure regulator maybe ???? put a gauge on it and check the fuel pressure , if you have had the tank or something back in the back of the car changed recently make sure the return line is not kinked

Well I swapped out my 160* thermostat for a 180* and wow did it make a difference. It has all of the low end torque it should and barely ever hesitates, still does it every once in a while so I will keep searching but it is definately livable. Gas milage has also increased ALOT. Maybe something to look into for all the others having similar problems.

Those Ford engineers, they're pretty smart, putting a 180* thermostat in by design. Do you think they might know something we don't?

Maybe we should think more about keeping some of the things the way they designed them. There just seem to be certain parts and designs that are hard to improve on...

I have learned that cleaning the throttle body will help a lot. I always clean the carbon off my TB if the car has over 50K. I have done this MULTIPLE times and there is much more bottom end and less restriction. You would be surprised what's behind that butterfly valve.


Just an idea.