CEL codes P0171 and P0440
 

Hello all!
Since a few days I'm the proud owner of a 2002 Protege ES. If I did things right there should be pics in my profile. The codes in the subject are what I'm trying to learn about. I've seen a few threads about EGR (what's that?) and MAF that may be the cause for one of these codes. I don't have the receipt with me but one has the description running too lean and the other says something about evap control system leak... (something with evap anyways). I'll post the exact text later. I know that the evap code can come up when the gascap isn't on right but I doubt that's the problem. I have a rough idle too. Not the whole time all the time. But I have it to where the RPM's go up and down between 550 and 850 I guess. Low enough to make the car shake a bit as if it will shut off when it goes any lower. Do all these things have to do with eachother? I was dumb enough to pay a shop to pull the codes and pay for it. I learned later that autozone and them do it for free. I've been thinking about buying one of those code readers myself. I know my car used to have a full exhaust system on it with headers and intake. Now it's back to stock. I see two wires coming from the MAF that have been cut and reconnected. I would like to know where to start checking or cleaning. I read that blowing smoke in the intake will show where any vacuum leaks may be but I don't know how to go about that if that's a good way.

Since this is my first post on this site I'd like to say hi to everyone and I look forward to getting to know you all. Thanks a lot!

Welcome to the club :) - Search! Best way to find lots of information. ^^^

Welcome to the Forum.

From the FSM
P0171: Fuel trim system too lean
Causes: misfire, malfunction of O2 front sensor, PRC solenoid valve, pressure regulator, fuel pump, purge solenoid valve; fuel filter clogged or resticted, fuel line leakage, fuel return hose clogged, leakage from exhaust system, insufficient compression.

P0442: Evaporative emission control system leak detected (small leak)
Causes: malfunction of purge solenoid valve, canister drain cut valve, pressure control valve, charcoal canister, catch tank, rollover valve; loose or defective fuel filler cap, cracked fuel tank, EVAP hose damaged or loose.

EGR refers to exhaust gas recirculation and MAF is the mass airflow sensor that measures the density of the intake air to provide info to the PCM that allows it to adjust injector pulse duration to maintain proper A/F ratio. If wires to the MAF have been cut and reconnected, I'd check that out also.

Good luck in finding the problem(s).

Thanks for the welcome.. and sure I'll search for as long as I live.

Thanks goldstar for the info. I'll have to check what FSM, PRC and EVAP mean. I'll check some stuff, clean it and reset the codes. Then see how it goes.

Is it true the ECU has to re-learn everything while driving after resetting it?

Welcome to the forum.
The wires to the MAF were cut?
It's possible whoever put the car back to stock just did a really lousy job. I would double-check all the conections and make sure the stock intake and header were put back together correctly.

goldstar, do you think it's possible that the stock header was replaced with a bad gasket or the sensor on the first cat isn't connected or connected properly? Would that cause the second code?

MiltonOS,
FSM = Factory Service Manual
PRC solenoid valve = Pressure Regulator Control solenoid valve located in intake manifold
EVAP = Evaporative Hose (connects between charcoal canister and fuel tank)

kargoboy,
I'm far from a competent diagnostician when it comes to engine problems but I would think that a bad exhaust manifold gasket or faulty O2 sensor would more likely cause the first code.

Thanks. I'd have to think that's at least part of the problem, then...

Thanks, I'll go over the things I know to find. For the EVAP Hose, where is it? Where is that cannister? How far from the tank? Or is it inside the tank? Would I have to drop the tank to get to it to check them?

A lot of these things mentioned I do not know where to find. I don't even know where the fuel filters are. I think I read there is only one near the tank but I'm not sure. What is a good manual to get? I don't even have a handbook or manual at all.

I appreciate all the info! The rough idle didn't happen much today. What octane fuel does my car need? I put 93 in, that's the highest we got. First time I filled the tank too. I wonder if my gascap is flaky. I think I'll start with that and a code reader so I can troubleshoot and reset it myself easily.

Also, make sure all vacuum hoses are connected and in good shape. A vacuum leak could cause the crazy idle, lean condition, etc. Vacuum hoses are the place to start, verify everything there first, then move on to troubleshooting the electronics.

No no no on the 93 octane! You are just thowing money away (gas isn't expensive enough?)
Use 87, that's what you engine is built to run on, in stock form, anyway.

Your idle will fluctuate between 500/850-ish if you are running the A/C compressor (that includes your defrost and dash/defrost setting).

Thanks, I read about the vacuum hoses too so they are on the top of my checklist with the gas cap and the MAF with wires. How can I be sure? Where can I get replacement hoses? Dealer only??

When I talked about the idle I mean that it was bouncing up and down constantly. Even with A/C off. Now you mention the A/C though, I've noticed the light in the A/C on/off button sometimes flickers, sometimes comes on steady, sometimes stays off for a bit. Is this the car regulating something or is this not working right?

https://www.mazda3club.com/showthrea...ht=a%2Fc+light - U R not alone... my '03 lx did that too.

You can get replacement vacuum hoses from the dealer or you can get silicone hoses, in various colors, from: www.hosetechniques.com

They have a car-specific kit to fit our models.

you say "did"... so what did the problem end up being? thanks for the link too!

dunno... i traded the car in on an '03 msp, which i promptly totaled.