got codes and car wont idle right

[AUBURN1111]

Im getting codes 31, 87 Engine off. The car dies right after startup but runs fine on second attempt, idle will not hold steady at all. Ive done the usual new plugs, wires, cap, rotor with no luck. The fuel pump, regulator, and filter are new as well.

Any ideas?

 

[TheUser]

i'm in the same boat, but different codes. Have you pulled codes w/ the engine running?

31 is canister or EGR valve control system and 87 is fuel pump circuit. Maybe you have a short in your fuel pump wiring or something? I'm sure someone else will post w/ more help

 

[deftsound]

yup im in same boat as well, im getting codes 21, 41, 91, and 34, today i replaced the egr valve ($$$$ :damnit: ) no luck though so tomorrow i think im gonna buy the egr position sensor as well see if that fixes it, after i did the egr valve i got that code 21 which is ect sensor, wierd....so i guess now i have to check that out as well, grrrrr

 

[AUBURN1111]

I can hear the pump prime when I turn the key on so Im not sure what I would be looking for other than the obvious like cut wires.

 

[93tealstang]

I get code 31 all the time. It's the EGR system. I take off the sensor every now and them and clean it out and the code goes away.

 

[TheUser]

yup im in same boat as well, im getting codes 21, 41, 91, and 34, today i replaced the egr valve ($$$$ :damnit: ) no luck though so tomorrow i think im gonna buy the egr position sensor as well see if that fixes it, after i did the egr valve i got that code 21 which is ect sensor, wierd....so i guess now i have to check that out as well, grrrrr

my book says 21 is coolant temp/coolant temp sensor is out of range, so maybe if you fix that (new CTS?), then your O2's would work properly, fixing code 91 and code 41(lean cond), which is probably caused by 91. Either way, 91 and 41 are related.

 

[jrichker]

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 87 – fuel pump primary circuit failure. The fuel pump lost power while the engine was running. Check fuel pump relay, check inertia switch, wiring to/from inertia switch, red wire going to inertia switch for +12volts. Check other side of inertia switch for +12 volts.

To help troubleshoot the 87 code, follow this link for a wiring diagram for 98-93 cars [urlhttp://www.autozone.com/servlet/UiBroker?ForwardPage=az/cds/en_us/0900823d/80/19/59/5a/0900823d8019595a.jsp [/url]

For 79-88 cars use, http://www.autozone.com/servlet/UiB..._us/0900823d/80/16/71/3c/0900823d8016713c.jsp

 

[deftsound]

good point maybe before i spend more money on the egp sensor ill see about getting the ect sensor out of the way first, maybe that will fix code 91 and my car wont run lean, stupid o2 sensor, just got a new one not long ago

 

[jrichker]

yup im in same boat as well, im getting codes 21, 41, 91, and 34, today i replaced the egr valve ($$$$ :damnit: ) no luck though so tomorrow i think im gonna buy the egr position sensor as well see if that fixes it, after i did the egr valve i got that code 21 which is ect sensor, wierd....so i guess now i have to check that out as well, grrrrr

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.

Code 21 – ECT sensor out of range. Broken or damaged wiring, bad ECT sensor. Note that that if the outside air temp is below 50 degrees F that the test for the ECT can be in error.

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

ACT & ECT test data:

Use Pin 46 on the computer for ground for both ECT & ACT to get most accurate readings.

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.

Voltages may be measured across the ECT/ACT by probing the connector from the rear. Use care in doing it so that you don't damage the wiring or connector.

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

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

Code 34 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.

This will affect idle quality by diluting the intake air charge

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.

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

"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 .4 volt. 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 .6 volt. 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."
Charles O. Probst, Ford fuel Injection & Electronic Engine control