1994 Problem

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1994 Mazda B4000 V6

issue:
after driving for about 6-7 hrs straight with cruise control on or off the engine will slowly loose power. when pulling over the engine will idle very roughly and almost stall out. i will let the car sit for 10-20 mins and it will fire right back up again and run.

it will flash the check engine light intermittently throughout the drive, mostly when driving up hill or down hill. the light will start this behavior as soon as an hr into the trip or might wait a few hrs.


code:
i pulled code 335 Exhaust Pressure Transducer Sensor Voltage out of range.


i searched the forums and have come to the conclusion i don't have enough experience to make an informed decision. mind mind drifts to: egr, maf, O2 sensors, dpfe, cps, vacuum lines, and even the cat.

any help would be greatly appreciated

 

[arco777]

Fuel pressure issue i.e. relay getting hot, gradually increasing resistance until the pump has too little power to give enough fuel?

Just a thought.

 

[explorerguy89]

sounds like EVR code to me (dpfe)

 

[MrShorty]

My code list indicates that a KOEO 335 is for the DPFE sensor. As commonly as they fail, I'd probably check the wiring between the DPFE sensor and the PCM. If that checks out, replace the DPFE.

 

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are my symptoms related to EGR/DPFE malfunctions?

can i narrow it down to that?

*update*
checked the vacuum lines and they are all hooked up and seem intact with no leaks.

the EGR seemed to be in working order. i removed a vacuum cap and the engines idle changed for the worse, until i replaced the cap.

is that cap supposed to be there? there were only 3 lines hooked up out of a possible 4 connections.

 

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ok i referenced an older post about the VAC TREE.

the pic i found

the picture provided shows lines hooked up in a different order than my vehicle. my vacuum cap is on the front side (towards the bumper) instead of the rear (near the firewall).

does anyone have a diagram i could follow to double check my lines and their location on the VAC tree?

 

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bump

 

[MrShorty]

are my symptoms related to EGR/DPFE malfunctions?

can i narrow it down to that?

Possibly. In my opinion, you have identified a fault. I'd fix what you know to be wrong (in this case, there is something wrong with the DPFE circuit). If that doesn't fix all your symptoms, then continue diagnosis.

 

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Possibly. In my opinion, you have identified a fault. I'd fix what you know to be wrong (in this case, there is something wrong with the DPFE circuit). If that doesn't fix all your symptoms, then continue diagnosis.

thank you for your help. i needed a push to take the plunge.

i'm a poor graduate student and can't afford to throw $$ at this problem like i normally could.

i already tried to get the DPFE @ autozone, but they didn't carry it. maybe O'rileys will have it. i will check back in with the board once it is installed.

 

[arco777]

Ford dealers usually have the part, and I got my DPFE from a Mazda dealer for cheaper than what the Ford dealer asked. Ford wanted $135, Mazda $105, and with my friend's employee discount it was $75.

Keep in mind the part and its number has changed over the years but they can cross reference it. The one I replaced mine with was a different number, different material, and slightly different shape, but the mounting holes were the same. It included parts to change out the wire connector with the updated one and once that was done everything worked great.

 

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*UPDATE*
new DPFE did not correct the problem

im not sure what else to think now.

 

[arco777]

Next time it has trouble after a long drive, feel the fuel pump relay for excessive heat. Mine had a problem with not wanting to restart after a long drive and replacing the relay fixed the issue.

When I drove to the parts store to buy and replace the old relay, in only a 2 mile drive it was already very hot to the touch and I could see a burnt spot on the underside of the relay. It cost about $3.

 

[Tbars4]

..x-out...If you had your location under your name, maybe somebuddy locally could give you a hand...

 

[x-out]

i will check on the fuel p-ump relay....but where can you find it for $3.00?

the other threads stated it was $11-$30 at various stores

 

[medefries]

The trouble code shown says the sensor is out of range. It could be a physical exhaust problem and the DPFE was simpley telling you what it found.
Check for restrictions in the EGR valve, EGR tube, Small tubes and hoses to the DPFE. Any restrictions or leaks in these areas will cause an imbalance in the sensor. Also check the EGR switch, it gets it's signal from the DPFE and opens/closes the vacuum to the EGR valve. Is the EGR valve stuck. If you don't find the problem after verifying these areas, the I would look at the catalytic converter. It could be getting plugged up. Fuel problems don't make sense until the DPFE issues are fixed.