Mazda Protege 2000 P0171, P0442

I have a 2000 Mazda Protege, 1.6L with 5 speed manual transmission @ 150,000 kms. It is showing codes P0171 and P0442 which means system too lean and small EVAP air leak. The car performs well on cold start up but once warm it looses power. Idling is good and mileage is fine. I see from various forums that these cars have had some intake manifold and O2 sensor problems. I am formerly a mechanic and like to do my own repairs if possible. How can I test for these or other possible causes.
Doug

First step is to check fuel pressure and engine vacuum. These are the most common causes of lean engine codes. A vacuum leak that causes loss of power is bad enough to find fairly easily. Spray throttle body cleaner on a cold intake manifold and uppper plenum.. If fuel trims readnegative double digits, there's your leak.

Thanks, I can test the fuel pressure since I have a Snap-on FI pressure test set, but as far as fuel trims (?) are concerned I am at a loss. The best I can hope to do is to look for a blip in rpm on my analog tach or listen for change when I spray around the manifold joints. Will that work?

EGR's are another problem areas on Mazda's

Hurray! After more research I rememberd that this model year had a recall of Mass Air Flow meters and that I had not replaced mine because it was outside of the recall period and was running fine at the time. I bought one on-line from bugbarn for $75.00 + tax, free shipping and received a genuine part in a few days. I installed it, tested it and cleared the codes and am rocking in the free world again. Now I just need to fix the exhaust rattles, ball joint clunks and the rear door panel bulges..........

Thanks for the input,
Doug

Glad we could help out

what is bugbarn?

Mark's Bug barn is a Hamilton Ont.. company that does bug parts but they are linked to a company on the net called bestpricecarparts.com. There is a US or Canada link. I did a BBB search on them and they checked out. Part was genuine Mazda for $78.00 plus tax with shipping included. Got the part from a Vancouver BC warehouse in less than a week.

Doug

So at that price is it a used part?

....¡ Hi everyone ¡ First of all I want to send congratulations to these forum, because is very good to have a forum to discuss automotive technical failures and more in fuel injection system, These will keep us away from the bad technicians and high repairing costs that in most of the times they are not necessary and also they won´t resolve the failure ¡

.... So ok .. anyway. Responding to your code P0442:
I think you are having some problems with your evaporative system that is sensing a leak in line ports and these probably is making a lean condition in your combustion also.
I think you have to first chek, all the evap lines that goes from the evap cannister to your engine, chek if is there no leak, maybe the lines are blocked, loose or broken. Also you can check your filler cap maybe is not in a good condition. If u have already checked the lines for leakness, check the vacuum valves that are bolt at the end of the canisster, maybe the cacuum valves are nos sealing properly and that´s why the engine is drawing inproperly the vapor´s canister through the manifold.

I would respectfully have to disagree. Here's why:
P0442 indicates a small leak in the EVAP system, which can be quite small. The fuel system can add or remove fuel in order to compensate for aging parts, wear and tear, or small vacuum leaks. THis is to keep the air fuel ratio as close to 14.7 :1 as possible. A small vacuum leak indicated by the evap system would be a very small leak the the fuel system should be easily capable of adjusting out through the fuel trims. But, as you can see, P0171 is present, which we all know indicates the fuel system couldn't add enough fuel to achieve proper air / fuel ratio. THat indicates a Large, not small, leak.
To me, this indicates two problems.

Don't forget to look at the history of problems that manufactureres create. I used to work for a major motorcycle manufacturer and when they had a problem you could expect many occurances before they got it sorted out. The Japanese were famous for denying that they had messed up. Someone would lose face. In my search for a solution I came across MSN Auto and looked up my car. They listed the history of mechanical issues and I was reminded of the MAF recall that I had missed out on. The codes that I had didn't quite convince me that this was my only problem but I felt that I should eliminate this first. Testing components and tearing my car apart looking for ghosts is not high on my list of to-doos. Fortunately that was the problem and the $78.00 that I spent on a new genuine Mazda part and the $50.00 for a basic OBD-2 code reader and $20.00 for a manual proved to be money well spent. If I had given my car to the local dealer or shop I'm sure I could have spent alot more and still not have a proper repair. Fortunately I had time on my side and was able to keep driving the car while I considered the possiblities. If I could justify it I would subscribe to Alldata but that is for the shops that need to be on top of their game. I'm just trying to get by.

Cheers,
Doug.

My Mazda 2000 Protege had the Service Engine soon light come on. I read the code and found it to be the P0171 - system too lean. After reading a lot of posts I determined it was probably the Mass air flow sensor since mazda had a batch of defective ones and my car happened to have the VIN in the range of potentially bad Mass flow sensors. I called the mazda dealership to see how much one would cost. He suggested just checking the air intake hose that goes from the air filter to the engine. He said that it is very common that this hose will crack and give you this alarm. I went outside and took a look and sure enough there was a huge crack in it (I know I should have checked all the hoses first). I picked up the part and replaced it in about 10 minutes and the car runs great again.

Yep happens alot on mazdas.

Check Engine OBD code P0171:
More than 100K miles, and have this problem then do:
1- Clean MAF (use Brake cleaner),
2- Change Air filter
3- Big Air intake Rubber Hose, connecting Engine to Air Cleaner, may be separating/cracked from under. I found mine was cracked underneath (Hard to see but look at the ribbed are below). This hose is stiffer and may crack by time. Air leaks in and change the MAF reading.
If you take it to dealer then most probably he will tell you to change EGR, MAF, O2 or intake manifold gasket! Hey, they have to make money!