2000 B3000 skips at an idle

[mt_cyrus]

I purchased a 2000 Mazda B3000 several months back and have had no luck finding the source of my troubles, which are the CEL (code P0174- bank 2 lean) and the truck idles rough but smoothes out once the rpms increase. For the code, I’ve tried cleaning the MAF, replaced the air filter (is stock), new fuel filter, checked for vacuum leaks, and anything else that I could try based on what I could glean from various info sources. Took it to a local, trusted shop and he discovered that it has low compression in two of the cylinders in bank 2 while trying to fix the skip at idle. The motor idled fine when he put propane through the fuel rail. He replaced 2 injectors trying to cure the skip, cleaned the fuel rail and also checked for vacuum leaks but no luck. Anyone have the same problem and/or have a better idea what it could be?

 

[Rearanger]

I found this:

"Ford p0171 AND p0174 lean codes can also be set by a bad EGR differential pressure sensor. These sensors have a very high failure rate once a vehicle has more than about 60,000 miles on the odometer or is more than five or six years old."

"The DPFE sensor is mounted on the engine, and is attached with two rubber hoses to the tube that routes exhaust gas to the EGR valve. The original equipment sensor has an rectangular aluminum housing about three inches long. Corrosion inside the sensor reduces its sensitivity to EGR flow, causing it to under-report EGR flow. The PCM responds by increasing EGR flow, which may keep the EGR valve open longer than usual creating a lean condition in the engine. Thus, a bad sensor may set a P0401 code (insufficient EGR flow), or it may not set an EGR code but a P0171 and/or P0174 lean code instead."

 

[mt_cyrus]

Thanks for the advice but I also replaced the DPFE sensor. Read about it on this board and checked it out, had enough moisture in it to drip, so i replaced it. Couldn't remember all the correct letters last night, so skipped mentioning it. Only the P0174 code shows up, have never gotten P0171, have reset the CEL several times. Forget where I read it but read that low fuel pressure may cause the skip, have yet to check that. Would a faulty O2 sensor cause the code or would it come up as it's own code? Had a 96 Ranger (2.3 5 speed, 250,000+ miles) and never had any trouble with codes, other than occasional O2 sensor.

 

[Rearanger]

Problem on one bank says vacuum leak to me. I think an O2 sensor would show all banks unless there is one per bank. You could try replacing O2 sensor. How low was the compression on two cylinders?

 

[Rearanger]

Took the time to consult my manual. Here are expanded possibles to check;

Fuel pressure regulator malfunction, leaking - check pressure
Fuel Pump weak, leaking check valve - check pressure
EVAP canister purge valve leaking
Fuel rail pressure sensor (if you have one) incorrect
Air leaks after MAF
Vac leaks
PCV system leak
Dip stick improperly seated
Exhaust leaks before O2 sensor
EGR system leaks
EVR solenoid vac leak
Secondary air injection malfunction - if you have that

Don't forget that the system might be sending unburnt fuel to O2 sensor and sensor thinks system is running too rich so it leans it out.

 

[mt_cyrus]

There's one O2 sensor per bank, then one after the cat. Thanks for the additional info, I hope to get enough time to try at least a few of your suggestions this weekend