Trying to fix misfire '93 LX 5.0

[ni130597]

Hi, My '93 is misfiring horribly, codes are 34 continuous and 12, 34 KOER. Haynes manual suggests EPT sensor, EGR, EVP, and possible PFE (Pressure Feedback Electronic??? don't have a clue about this one...) . The EVP Haynes sensor test fails ( has @ 2.00V instead of less than 0.67V when it's hooked up, key on). The actual EGR looks pretty cruddy ( been in for 267K) on the manifold side....is there some cleaning I can do here b4 I reinstall the EGR...any EGR quick checks I can do before I put it back in or should I just replace the whole thing?... Right now I plan on trying a new EVP sensor to see if that cures the misfire..... btw already done plugs, wires, cap, rotor, coil.... still missing (cutting out completely on random intervals or throttle position then catching)...

TIA

Peace Out!

 

[MAC'n89Blckstng]

This is probably for tech.

 

[cenok is family]

subscribing...i drove through a pretty nasty puddle and got something wet, so now my car is kinda spittin and sputtering. i warrantied out my cap, rotor, and coil. my wires are fine. maybe my tfi module? i always thought that thing either worked or didnt though. my car doesn't die at all, just spitting at me.

btw, you can clean your egr with carb cleaner. i just did that actually, and it cured a surge/stall issue i was having at idle. if you have a vacuum pump, hook it up to the vac port on the egr valve and open the pintle up and clean up inside there too.

 

[GTOreturns]

Did you do any work to the car befrore it started to back fire?




Cenok give it a day to dry out in nice weather.

 

[Mustang5L5]

moved to tech

 

[jrichker]

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 1.5 ohm. Next check the resistance between the black/white wire and the negative battery post. It should be less than 1.5 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.

The following sensors are connected to the white 10 pin connector (salt & pepper engine harness connectors)

This will affect idle quality by diluting the intake air charge

Late Model Restoration has the Ford Racing M-12071-N302 kit with the EGR valve & sensor along with the ACT & ECT sensors for $45. See * * * N/A * * * 86-93 SENSOR KIT, 5.0L EFI, INCLUDES EGR VALVE & SENSOR, COOLANT TEMP SENSOR, & AIR CHARGE TEMP SENSOR MUSTANG for more details