Code P0171 on a 2001 2.0 liter Protege

[HAILERS]

I have this code P0171.

The engine idles fine in Park. The engine idles rough/low in Drive at a stop sign. And only when in Drive.

If this was caused by an idle leak at the intake manifold, I would think it would also idle poorly in Park and not just Drive.

Any suggestions other than clean the MAF wire? Or spray for air leaks using starter fluid etc?

I figure when you put it in Drive from Park, you make a switch with the shift lever and that switch tells the ECU that your in the drive mode and *something* gets energized/de-energized when you do that. EGR solenoid(s)?

Thank you. It's my first post on this forum and the car is a neighbors car. Both 02 sensors were replaced last summer (shop wired 'em backwards/upside down and I had to rewire 'em. Work fine when observed on the scanner while driving).

 

[Wagonbacker9]

wrong section. most of the MSPers in here pretty much check out at the word "drive"... seeing as we're all manual trans.

I'll have a mod move this for you...

and so there is content in my post, the problem will be more apparent at idle in drive because there is load on the engine. thats basically the difference, nothing to do with the EGR necessarily. though cleaning that and checking for vac leaks probably won't hurt.
i believe that code means you're running lean, which says vac leak to me... could be wrong though..

 

[fishdonotbounce]

Pull the spark plugs and check them out. Also check the boots on the coilpacks. If any of them look burnt, replace them. The coil packs and wires will run you about 50 bucks from autozone and quality spark plugs will run you around 20 bucks. You should also clean your EGR valve.

Use this how to to clean your EGR valve. EGR How-To

Good Luck!

 

[HAILERS]

Thanks for moving the thread.

Just a remark: I would have thought that the Idle air control valve (BAC on RX-7), would have upped the rpms when the PCM saw the load put on the engine when put in Drive. I

Thanks for the EGR cleaning thread. I need to find out what makes the EGR solenoid work/get energized. Like mabe it is not used at idle but is used when driving or the car put in gear.

I'm off to find out where the thread went to.

 

[HAILERS]

In idle or neutral the idle is just fine. Put the car in rev or drive while holding the brake results in a bad idle. But I noticed when it is initially put in Drive or Neutral, it will drop in rpms a bit but idle as well as you could expect seeing as it's now under a load. But after a minute or so, the idle goes to truly crummy.

I watched the STFT and LTFT after putting the car in drive with brake on. The LTFT initially was low as in -5 or +5, but as time went on the LTFT gained on the add side and went to +25. THAT'S when the idle goes to the crummy condition.

So that means the engine is running lean alright, and the PCM is trying to compensate for that by making the injector duty cyle longer until it runs out of head room to compensate anymore.

Sprayed starter fluid over all the hose/tubes/fitting/head gasket area and there was no change in the idle rpms, so it appears to not be a cracked duct or hose/fitting.

Leaves me wanting to check the fuel pressure but the FPR/PD fittingS seems (to me) to be Mazda peculiar, so my normal fuel pressure gauge won't fit.

Guess I'll spray the wire in the afm with starter fluid or ?? other cleaner.

Seems if it was a misfire, I'd see a misfire code come up and or it'd be misfiring in neutral or Park also. Plus it wouldn't have the trait of idling normally in Drive for a minute and then go into the crummy idle mode.

Just thinking out loud. Not my car. Not in a hurry.

 

[Wagonbacker9]

the idle is likely changing between open and closed loop.... when the ECU is able to manage it, it is running better, when it switches to the predetermined program (and things are in the predetermined configuration due to whatever the issue is) it gets worse.

 

[HAILERS]

It was just another cracked duct b/t the MAF and the throttle body. Where the convoluted ridges are. Fabricated a piece of pipe and clamps to replace the cracked part and it's back to normal. Thank you for the responses.

On one of my RX-7, if it had a crack in the TID like that Protege, the car would have died. Or if you take the elect plug off the Protege's MAF, it still runs. Do that to a 25 yr old Rx and that sucker will flat die right then and there if you remove its AFM plug.

I'll always wonder why, when I sprayed that intake duct on the Protege, the rpms didn't respond either up or down. Odd. On any other car I've owned the rpms would have gone up when sprayed.

 

[sporty111]

2001 Mazda protoge DTC P0171. Symptoms were engine ping on warm days, slight loss of power, hesitation on acceleration and the CEL. This too turned out to be a cracked intake air duct between the MAF and the throttle body, right in between the "accordian style pleats". I temporarily taped it up with a seal-all tape, until I get a replacement.

 

[43975]

even though this is in the wrong section it got me thinking many of us have this damn CEL and can't figure it out. The probrem is that I have no plastic on the pipes from the MAF to the intake mani?? maybe my coupler is leaking

 

[speed1585]

i have had this CEL for awhile now, along with the vac lines I bought to replace sitting in the garage. I have checked alot of things I am sure that for me its a vac leak. I have nylon tape all over the t-connectors as one was broke. I just clear the code with my reader. I got it way less in the winter, but when the day warmed up or like now in the heat I get it 5 mins after starting up

 

[43975]

I leave it on cause the car runs better with it on. When I turn it off the damn car stalls out and acts like a b****

 

[speed1585]

it amazes me that one code affects us all so differently

 

[HondaEat-R]

even though this is in the wrong section it got me thinking many of us have this damn CEL and can't figure it out. The probrem is that I have no plastic on the pipes from the MAF to the intake mani?? maybe my coupler is leaking

If your MAF relocated ? If so, remember how this affects troubleshooting leaks and things of that nature.