Need help diagnosing ’95 CEL codes

[6JStockCar]

I just joined this site but have found very useful information here for past problems. I have a ’95 Contour GL 2.0 that is real sluggish & bucks at less than half throttle, but runs fine once I get past half throttle and up to highway speed. This problem started last week and the check engine light came on. I ran the key on engine off & key on engine running diagnostics and found the following codes. I need some help determining what to fix. I live in Iowa and the temp was in the single digits when this problem started.

KOEO

181 – Fuel system at rich adaptive limit at part throttle, system lean (Bank # 1)
332 – Insufficient EGR flow detected (EGRP/EVP/PFE/DPFE)
335 – EGR (PFE/DPFE) sensor voltage higher or lower than expected during KOEO
336 – Exhaust pressure high/EGR (PFE/DPFE) circuit voltage higher than expected

KOER

172 – Lack of Heated Oxygen Sensor (HO2S-1) switches, indicates lean (Bank # 1)
326 – EGR (PFE/DPFE) circuit voltage lower than expected

 

[striker2]

i would start by replacing the upstream O2 sensor. reset the PCM and drive it. then see what codes come back. im betting you will also have to either replace the EGR valve or the DPFE sensor (or both)

 

[BrApple]

before replacing the egr valve of dpfe sensor pull the tb and clean the egr passages. once that is done test the egr by applying a vacuum to the valve, if the idle doesn't change then the valve is bad or the passages in the UIM are still plugged, if the idle gets worse and the car dies then you can try the dpfe sensor, its most likely a metal one and it has failed, get a new one and make sure it is a plastic one.

as a side note, the 95 will only have one O2 sensor, it will be before the cat in the exhaust manifold.

 

[projectSHO89]

Third opinion:

Replace the DPFE sensor first as it is toast. Probably got moisture in the sensor lines and it froze. Now, it sounds like there is uncommanded EGR flow due to the sensor.

Reset the PCM and then retest. You'll also likely end up replacing the O2 sensor, however, it's "failure" may be a side effect of hte DPFE's failure.

Steve

 

[striker2]

before replacing the egr valve of dpfe sensor pull the tb and clean the egr passages. once that is done test the egr by applying a vacuum to the valve, if the idle doesn't change then the valve is bad or the passages in the UIM are still plugged, if the idle gets worse and the car dies then you can try the dpfe sensor, its most likely a metal one and it has failed, get a new one and make sure it is a plastic one.

as a side note, the 95 will only have one O2 sensor, it will be before the cat in the exhaust manifold.

He has a zetec. the EGR doesnt go through the TB but directly into the intake manifold at the bottom of it. so no cleaning needed. you can test the EGR valve still however in over 240K miles on my zetec i never had an issue with it. its most likely to be the DPFE sensor

Third opinion:

Replace the DPFE sensor first as it is toast. Probably got moisture in the sensor lines and it froze. Now, it sounds like there is uncommanded EGR flow due to the sensor.

Reset the PCM and then retest. You'll also likely end up replacing the O2 sensor, however, it's "failure" may be a side effect of hte DPFE's failure.

Steve

the EGR flow is controlled by the PCM opening a solenoid to let vacuum reach the EGR valve. the sensor simply tells the PCM how much it is flowing. this does mean, however, that if the sensor was shorted to read no or low flow all the time that the PCM will open the EGR valve more than is really necessary. However the EGR only flows burned air/fuel so it will not effect the actual air/fuel ratio. it just delutes it to lower cylinder temps and reduce NOx emissions. the "failure of the DPFE" sensor should not effect the O2 sensor.

i still say start with the O2 sensor and then worry about the EGR faults.

 

[6JStockCar]

Thanks guys. I replaced the 02 sensor because it was in front and fairly easy to get to. It ran fine right away so I went on a 60 mile test drive. During the first 30 miles, the CEL randomly came on 2 or 3 times for about 5 -10 seconds and then went back off. I did not notice the light during the last 30 miles of the trip. The engine performance did not change when the CEL flickered on. I'll monitor the CEL during the next few days but it appears to be fixed now.

This site is awesome!

 

[Bradness]

If you're getting a lean code on only 1 bank, you likely have an air leak. Look for or replace any gaskets which are sealing up bank 1. The LIM/UIM w/b the 1st place I'd check.

If your code(s) were for both banks, then you'd check stuff like the accordian tube, t-body, etc.

 

[projectSHO89]

It's a Zetec (only one bank).

Since the CEL iluminated, there should be a DTC stored. Probably your EGR system running it's tests and failing. Your observation is typical for EEC-IV EGR faults that do not set a persistent CEL.

Pull the codes again to verify.

Steve