This is topic engine codes 41 and 91 in forum Tech Talk at Northern California Ford Owners  .


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Posted by z pyro (Member # 3745) on :
 
my 89 fox's engine light comes on after driving for a little bit, and turns off if you restart the car. I pulled the codes and got 41 and 91 in the stored codes, which means it's running lean. this makes sense cuz it gets really bad gas mileage cuz the computer would be dumping fuel to richen it up. what should I check first? the fuel pump is really loud, should I replace that?

edit: upon further searching it seems 41 and 91 are the o2 sensors...guess i get to spend a shitload of money on new ones [Frown]

[ August 09, 2005, 03:28 PM: Message edited by: z pyro ]
 
Posted by menlo pony (Member # 4301) on :
 
Or Buy these???????????

86-93 O2 Sensor Harness $35.00

86-93 O2 Sensors $25.00/pair
 
Posted by 90GT (Member # 3) on :
 
My car would throw those codes sometimes when going up hills. I would just clean the egr valve and it would go away for a quite a while.
 
Posted by z pyro (Member # 3745) on :
 
I sometimes get the code for the egr position sensor not giving the right voltage (34 IIRC) would that cause it?
 
Posted by Quick 88LX (Member # 1950) on :
 
I pulled codes the other day KOEO (o) and got code 34 in stored memory (c). Same EGR hoopla. But code 34 stands for 3 different things so it could be any one of them! They all have to do with the EGR, so, I am going to run a KOER (r) test tomorrow to see whats up and go from there... I will let you know [Big Grin]
 
Posted by Quick 88LX (Member # 1950) on :
 
Also, if I read my Haynes manual correctly, if you don't have the coolant lines hooked up to the egr spacer then the PSV on the EGR will not work properly. I forget what it stands for at the moment but it senses when the coolant has reached operating temp. and signals the EGR. That could be something worth looking at IF you disconnected those lines. If not, nevermind [Wink]

I disconnected those lines and I am getting 34 from continuous memory. SO, like I said, I will run the KOER test manana. Everything else checked out perfect.
 
Posted by z pyro (Member # 3745) on :
 
well I have a cobra intake so there's nowhere to hook those lines up...


Im also getting a code 29 now
 
Posted by h8louzn (Member # 1075) on :
 
quote:
Originally posted by z pyro:
I sometimes get the code for the egr position sensor not giving the right voltage (34 IIRC) would that cause it?
Here ya go hope this hels!


Code 34 Or 334 - EGR voltage above closed limit - Failed sensor, carbon between EGR pintle valve and seat holding the valve off its seat. Remove the EGR valve and clean it with carbon remover. Prior to re-installing see if you can blow air through the flange side of the EGR by mouth. If it leaks, there is carbon stuck on the pintle valve seat, replace the EGR valve ($85-$95).

If the blow by test passes, and you have replaced the sensor, then you have electrical ground problems. Check the resistance between the black/white wire on the MAP/BARO sensor and then the black/white wire on the EGR and the same wire on the TPS. It should be less than 1 ohm. Next check the resistance between the black/white wire and the negative battery post. It should be less than 1 ohm.

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.

Let’s put on our Inspector Gadget propeller head beanies and think about how this works:
The EGR sensor is a variable resistor with ground on one leg and Vref (5 volts) on the other. Its’ resistance ranges from 4000 to 5500 Ohms measured between Vref & ground, depending on the sensor. The center connection of the variable resistor is the slider that moves in response to the amount of vacuum applied. The slider has some minimum value of resistance greater than 100 ohms so that the computer always sees a voltage present at its’ input. If the value was 0 ohms, there would be no voltage output. Then the computer would not be able to distinguish between a properly functioning sensor and one that had a broken wire or bad connection. The EGR I have in hand reads 700 Ohms between the slider (EPV) and ground (SIG RTN) at rest with no vacuum applied. The EGR valve or sensor may cause the voltage to be above closed limits due to the manufacturing tolerances that cause the EGR sensor to rest at a higher position than it should.

This will affect idle quality by diluting the intake air charge
 




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