Cel = p0101 & p0171b

[Natural]

P0101 - Mass Air Flow performance problem
P0171B - Bank system too lean

The check engine light came on and both codes came up. Basically after the engine warms the idle will start bouncing up and down from 750 to 250. Give it a little gas for a second and it stops for a minute or so, then starts doing it again. The behavior is basically identical to pulling out the MAF plug. Tried another MAF unit and the problem persists. Thoughts?

Car is a 2001 ES 2.0.

 

[el_Don]

Clean the maf sensor and then reset the ecu by removing the negative terminal from the battery for a few mintues. This will allow the system to recheck itself. If that's not it and the CELs return, then the problem may be more serious, perhaps someone else can input.

 

[Natural]

I tried cleaning my old MAF, but it had no effect. Tried a second MAF and the problem is unchanged. I reset the ECU when I swapped them over, though the CEL returned just as the problem did.

 

[slavrenz]

Looking at my repair manual, these codes are completely unrelated (a bad MAF sensor cannot cause a lean condition, and vice versa). I suspect that you have some sort of short between your PCM and one or more of your sensors (especially for the MAF code), but the P0171 could also be caused by a bad O2 sensor, incorrect fuel pressure (caused by a bad fuel pump, injectors, etc.), a misfire, an exhaust leak, or a problem with your evaporative emissions system.

 

[Natural]

I decided to take the intake hose assembly apart just to inspect it, and it turned out the clamp at the throttle body was badly rusted and had a bit of play. Had to drill it out (screw head was stripped) so I picked up new clamps (one for the end of the filter housing too). Cleaned the area the best I could, put it back together, took it for a good hard run and so far no problems. No CEL and idle is longer erratic. Here's hoping *crosses fingers*. Appears it was a Vacuum leak.

Thanks for the replies.

 

[Bigblock73]

I had a lean code also on my car. Turns out the the factory intake boot had small tears in the rippled part. Built a FWI and BAM no more code, better sound, better fuel economy, and more horse power.(cabpatch)

 

[Natural]

bump

Turns out the problem wasn't fixed. After re-installing the intake system it was fine for a couple of days, then I got the CEL again, along with minor fluctuations in idle speed after the car had reached normal operating temperature. It would drop from 750 to about 600, trigger the CEL, and then return to 750 for a while.

It has gotten progressively worse, once again to the point where virtually every time the car is at idle it will begin fluctuating from 750-250rpm over and over again. It never actually stalls. Another thing I've noticed is that the rad. fan will cut out at the precise moment that the idle fluctuations begin. Also a new development, it will now occassionally drop to 250rpm and stay there until I give it a shot of gas, at which point it will return to 750rpm for a little while.

I'm going to re-confirm the codes again on monday at work, but since the problem has not changed significantly, I'm going to go under the assumption that the original 2 codes still apply.

Any suggestions on the next free or cheap test?

 

[prof15]

were you able to solve the problem? I am having the same problem in my car and have done a lot of things to the car and still nothing..

I first replaced air filter, then weeks later I replaced spark plugs and cables, and later I replaced the ignition coils. I also inspected all the vac hoses and the even replaced the pcv valve with no luck...

 

[Pyro-tege]

I am having a P0171 code also. Just popped up Friday, no engine or drivability issues however. I am subscribing to this thread. I like the handling of the Mazda, but the damn engine codes are driving me mad. I have never had a car throw so many codes. It has less than 64K too. My Sentra had almost 200k and only threw one code when I forgot to plug back in the MAF. This car is killing me. I am going to try run a can of Seafoam thru in case an injector is partially blocked causing low fuel output and a lean condition. Then if it persists maybe an O2 sensor since I am not having any drivability problems.

 

[slavrenz]

Guys, seriously, download the repair manual on this site (free!) and look through it. There are literally dozens of things that could be setting off a lean code and to explain them all would take a loooooooong time.

To the OP, did you check the accordion section of your intake hose? They're prone to ripping, and that may be causing a slight vacuum leak.

 

[Natural]

Thanks for the heads-up on the service manual, I'm downloading it now.

The problem persists, and is starting to annoy me. I could deal with this problem on its own, but now some other things are starting to pop up (including bushings) and this protege is turning into a real disappointment compared to my old first gen.

I've checked the intake tubing and even wrapped it up securely around the flex area. I've replaced the hose clamps on both ends of the tube, and even put small clamps on the connecting hoses to make sure no air is being lost there. I will try a replacement tube if I can find one cheaply.

Every time I take the intake apart to inspect and re-inspect it, it seems fine for the first day or so after, then gradually gets worse until it's back to the point where virtually every time the car is idling at normal operating temperature its rpm's are constantly dipping back and forth.

This really feels like a MAF problem, and though it is possible that the used MAF I purchased is also bad, I'm hesitant to go out and try yet another MAF without knowing for sure that it is the problem.

I was under the impression that MAF voltage problems (i.e. the connection plug and wires) had their own code(s) for voltage issues. Is there an easy (and reliable) way to test a MAF sensor and its connecting wires?

 

[Pyro-tege]

Guys, seriously, download the repair manual on this site (free!) and look through it. There are literally dozens of things that could be setting off a lean code and to explain them all would take a loooooooong time.

To the OP, did you check the accordion section of your intake hose? They're prone to ripping, and that may be causing a slight vacuum leak.

Where is he repair manual on here? Does it include 1.6 Proteges, because I can't find a paper one anywhere.

 

[Natural]

Where is he repair manual on here? Does it include 1.6 Proteges, because I can't find a paper one anywhere.

http://www.msprotege.com/forum/showthread.php?t=123744857

 

[Pyro-tege]

Thanks!