Check Engine Light & Rough Idle Problem

Help.....

I am wits end....

I have had my truck to two different mechanics in the past year...

Here is the problem...

I have a 1997 Mazda B4000 Pickup that the check engine light comes on all the time and it runs rough and stalls intermittently. Especially in the winter when the outside temperatures are colder, it seems to be the worst time... The codes say Bank 2 lean and Bank 1 lean. I have replaced the Mass Air Flow, bother upper O2 sensors, completed a tune-up (plugs and wires), cleaned the injectors and the check engine light still comes on and it still runs rough and stalls at stop signs and lights.

Anyone have any suggestions?

Could the problem be the EVR vent solenoid, DPFE sensor, or the Evap Emissions Control System Canister? How do check this system?

Al

That can be a very complicated problem depending on what the problem is or was originally and what has been repaired and how it was repaired. For instance the truck goes without a tune up for a while and the air filter gets severly plugged, the lack of air causes the fuel mixture to richen. The computer tries to compensate by leaning the adaptive learning fuel trims. Later you give it a full tune up and it runs like crap and the check engine light comes on, you take it to a mechanic and he can't find anything wrong with it but he looks that the sensor outputs and it says both upstream O2 sensors are reading lean. He doesn't know what it is so he tells you to replace the MAF sensor and it still has the problem. The mechanic could have very well not even looked at the fuel trims or possably not known what the heck they mean, as many mechanics don't and therefore didn't know what was going on. If he did know what was going on he would have reset the adaptive learning and taken it for a road test to run it through a drive cycle. Problem fixed.

I don't know what has been done to the truck or if the mechanics you took it to knew what the where doing. I think the first thing I would do is have the ECU reset and drive it through the relearn procedure and go from there.

Thanks for the note and information. I am not a mechanic, but a novice that does not like being taken for a ride. Where can I get more info on Fuel Trims and resetting the ECU? I am taking the B4000 to another mechanic and want to suggest they look at these two possible issues. Also I have reset the check engine light by clearing the codes. After a while the cleared code appears again and check engine light comes on. The idle issue is when I stop at a light or sign the idle appears to be OK, then it start to "lope" then stalls. I notice the tach fluctuates between 1100 rpms and 800 rpms....

Again thanks and any input is appr....
Al

Have you checked out the EGR valve? This could cause a rough idle, but appear normal during higher RPM's.

Hey Man sorry I didn't catch this before. My 2001 did the same thing, the dealer said it would be $375 worth of parts and labor to fix. Turned out to be a ruptured rubber elbow that comes off of the large intake that connects to the air filter box. Sorry for the crappy description I am no mechanic. Any way there is a plastic tube with rubber elbows that runs around the back of the engine, one of the rubber elbows had ruptured and it was sucking air. The part was $50 and I put it in myself. Hope this helps.