Hey all, I just bought my first mazda (2003 protege). It has a CEL on and my reader says P0171 - Lean Mixture. The funny things is that a week before, I test drove another mazda protege on a used dealer lot and it came up with the same error.

Since i've only driven 2 mazda proteges and they both have the same error, it seems like this is a common problem? or else it's just a coincidence?

I know what a lean mixture means, but I'm just wondering what people do to fix this. I searched a bit, and didn't find a lot of useful input. Here's where I am at this point.

I reset CEL to see if it was a stale code. it just stayed pending for an entire 200-mile trip, then the code and light came back after a little city-driving. I tried spraying some starter fluid around the MAF, the throttle body, the intake manifold, and the vacuum hoses and the revs didn't pick up, so I don't think it's a vacuum leak. Are the MAF sensors known to by flaky on these cars? I'd rather not buy a new one, but has anyone rectified this by buying a new O2 sensor?

The PO said the light would turn off and on for years and he just put some injector cleaner i've never heard of (it's in a box in the trunk) in the gas and hoped that would clean it out.

a little more info, in case anyone has encountered this: it seems to do fine in accelerating and driving at constant speed, but at idle it will be fine for several seconds and then occasionally shudder (the rpms will momentarily drop to 500 or below) and then i'll get a pending P0171 error code.

sound familiar to anyone?

what is your experience with this? any ideas on things i can do to troubleshoot?

 

The lean fuel condition could be caused by a dirty mass airflow sensor, vacuum leaks in the intake manifold or vacuum connections, or a defective DPFE sensor. The fix may require cleaning or replacing the MAF sensor, or using a smoke machine to find elusive vacuum leaks in the intake plumbing. To clean MAF disconnect negative terminal of battery, and remove MAF spraying it liberally. Wave it around to dry it. Re-install when dry, re-connect battery and let idle for 10 minutes before driving.
Other things to look out for: cracks in intake tube before throttle body, cracks in vaccuum lines, PCV line, and the dreaded internal leak in brake booster. To rule out brake booster, you must pinch off the vac line that goes to it from the engine and see if idle drops. When it is bad, you will notice poor braking power the odd time as well.
Another cause may be fuel pump and/or regulator is old and not putting out necessary psi and also fuel lines could be clogged or cracked (hence the fuel system cleaner). Driving around with fuel level below 1/4 tank puts extra strain on the fuel pump shortening it's life
An exhaust leak around or before the O2 sensors could also trigger it.
Let the FUN begin! Do the small stuff first.

 

thanks for the reply. i bought MAF cleaner and hosed the MAF sensor good. I also got new spark plugs (the elements were worn down quite a bit)

I thought the problem was gone after I drove it around a few times (it normally would have thrown the light by then) but after a 45-minute trip on the highway, the light came back on when i got back to stop signs and lights.

 

I'd move to the next cheapest step and check for vaccuum leaks, leaks around intake tube (after MAF, before throttle body). PCV Valve.
Good video: explanation first then actual test with a leak found: How To Find A Vacuum Leak - YouTube
Another Video with a Cigar: Finding Engine Vacuum Leaks With A Cigar - YouTube

 

OK, Im new here an ive looked over an over where an how to post a new thread, I can not figure it out, so...Maybe someone will see this an help me out.
I have a 1996 Mazda Protege that when I got the car the org. owner cut the wire to my idle sensor an I can not locate it anywhere on the car, or where it should be at.
If anyone knows where to locate this please email me.... (Angie)

 

[quote=razeldazelmi;129058]OK, Im new here an ive looked over an over where an how to post a new thread, I can not figure it out, so...Maybe someone will see this an help me out.
/quote]
When you first sign in, scroll down to "Mazda Protege" section or "New Member Area", click on it, you get a new page, at top of page click on Black button "New Thread", now you make your thread up: put a title and describe your situation.

Can't help you with wire though.

 

I looked at the videos. I already tried it, but thought "what the heck," i might not have gotten around the manifold gasket very well.

I used MAF cleaner and ether (starter fluid) since i'm clean out of brake cleaner. I hosed down everything on the intake and the manifold and connected hoses. I heard absolutely no change in idle.

I checked all clamps for the CAI to make sure they are tight.

I'm thinking of making a homemade smoke machine...

 

Dogg,

If you checked everything that noggin suggested, and I mean checked them thoroughly, then take a real close look at the hose that connects the brake booster to the intake manifold. By this, I mean take it off and check the ends where it slides onto the connections. Bend the hose and look for cracks. Do the same for the hose that connects the air filter to the throttle body. While you're at it, double check the other vacuum lines as well - same procedure. It's there somewhere....

J

 

i'm pretty sure i found the problem.

it's on the back side of the CAI near where it meets up with the throttle body. I could never have seen it if i didn't remove it. It looks like it was cut out with a tool by a previous owner (don't ask me why). I closed it off with several tightly-wound layers of tape and I think it's fixed now. I drove it around for about 5 miles and my long term fuel trim went from about 10% to around 0%, and the idle stabilized again. I want to drive it around a bit more to make sure, but i can't imagine it wouldn't fix it.

p.s. i have no idea why the revs would not have increased when i sprayed around it with brake cleaner and instant start. i was sure because of that that I didn't have any leaks in the piping. oh well.

 

Glad you found it. VERY BRUTAL!