Need help with engine codes 41 & 91

The car is a 92 5.0 Mustang. Car ran fine prior to install of AFR heads and FTI cam. Since install, car ran great for about a week. Then I installed 24lb injectors and matching PRO M meter. I found that the lower did not seal so I installed it again and it is sealed. The car will not idle when I first start it. It revs up to 3000 then dies. I have to keep my foot on the gas. After a few minutes it will idle. Once I get on the road runs okay but it does buck slightly at lower RPMS (AOD with stock stall). However, once it reaches operating temp especially if I wait at stop light for long the idle drops from 900 to 600. Then I get a check engine light. The codes are 91 & 41 No EGO switch. The car then sounds rich and has no power when I drop the hammer. The car has O2 sensors that are less than one year old, new act, new egr, new injectors, new IAC. I have checked and set the TPS at.99. I have cleaned the IAC and also run a idle air control plate. I have swapped mass air meters and get the same result. I have also unplugged the 02 sensors and drove the car until it engaged the closed loops system with the same result with them plugged in. According to Pro M, this indicates the problem is not the Mass Air but probably with the close loop system. Can anyone tell me how to track down the problem? I know you can do this by checking the voltage output for all sensors in the closed loop system. However, I don't what the acceptable voltage level is for each component. I suspect it could be the ECT but I'm not get a code for it.

Help please! I have not been able to enjoy the heads and cam since they were installed. I may have to take the car to someone with the tech expertise to tell me what is wrong.
 
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Jrichker has posted values for ECT and ACT sensors before.

some IAC's are supposed to be installed upside down - not sure about yours (something i had to ask).

is the orange wire on the back of the intake attached? it is a ground for the HEGO's.

why are you so interested in closed loop components? it sounds like you have issues at all times? im just curious. :)

good luck.
 
it apparently is the design of the IAC. Rerun (IIRC) reported that the instruction he got with the IAC he got from AZ said to do that. i dont have personal experience, but would assume the instructions are there for a reason. :)

sorry, i dont know more about that particular unit.

good luck.
 
Code 41 or 91 - O2 indicates system lean. Look for a vacuum leak or failing O2 sensor.
The computer sees a lean mixture signal coming from the O2 sensors and tries to compensate by adding more 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

Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. 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 ground is in the wiring harness for the fuel injection wiring. I grounded mine to one of the intake manifold bolts