Escort P0171 code

CraigE

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#1
I have a '99 Escort ZX2 with the DOHC 2.0 liter. Recently did a timing belt when the lower idler pulley failed.

Now I am getting a P0171 ( too lean ) code occcasionally. I can reset the codes and it may not come on for twenty minutes. No other stored codes but the Snap -on scanner did show a P1000 system check incomplete.


Any ideas on what may cause this? The Throttle position voltage was changing but did not seem real responsive. O2 sensor voltages varied with acceleration from 0-800. Any input is appreciated from any Ford guys Thanks CRAIG
 

Transman

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#2
I have found most of these come from the PCV hose sucked inside out and gooey, check for a vacuum leak on both ends not just at the PCV. Very common on any FFFord vehicle but for some reason the excorts happen more. The last one was the hose between the firewall down low under the intake. Good Luck & post results, Transman
 

wap

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#3
i agree with transman. pcv system on escorts is a very likely culprit. just curious, but when you get a too lean code is it sometimes accompanied with a too rich code as well? if so, check and clean mass air flow sensor. use only electrical parts cleaner to do this. a company called Gunk/Radiator specialty also sells a chemical call 'Mass Air Flow Cleaner.' fancy name for electrical parts cleaner. if the sensor wire of the mass air flow sensor is coated in a waxy/greasy buildup, the air flow is not sensed properly, and the ecm will freak out going from reich to lean to rich to lean....you get the picture. PCV hose assy may need to be replaced. oh boy, here we go, this is an OE part, usually around $30 dollars. if hose/rubber pieces feel all gooey and soft, the only fix is to replace them. let us know
 

CraigE

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#4
Thanks for the info guys. I know I did some PVC work on this same vehicle about a year ago. I will check it out and let you know. CRAIG
 

Transman

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#5
Good point on the MAF, Wap. I see so many of them with the pcv hose that it never occurred to me. Transman
P.S. did ya' notice I let the OE thing go right by? LOL
 

CraigE

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#8
I checked the PVC system and all seemed fine. I also cleaned the air flow sensor. Any other ideas? Thanks CRAIG
 

Transman

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#9
Check the pcv system closer, down the engine on the firewall side. It's hard to find the first one, fat hose like a pcv hose. Sometimes it is easier to see from underneath. I found the first one with my smoke machine. TransmanCrunch is probably still looking for his Bazooka, ROFLMBO! Transman
 

CraigE

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#10
I will look again. The only hose/tube I found before went from the front, (PCV) back to the intake phlenum. Thanks CRAIG
 

autodr

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#11
The problem with trying to fix a fault code without scan data avail, is you are trying to find the "answer" without getting to read the "question" ;D

Bring up your "Short term fuel trim" (may read STFT) and Long Term Fuel trim (might read LTFT) on scanner.

Bring up the MAF volts and/or grams per second (however your tool reads).

And bring up your IAC percentage.

At idle. what are the numbers on each of those.

Then, raise RPMs to about 3000 and hold steady in park. What are the STFT and LTFT at those RPMS?
 

CraigE

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#12
It may be fixed. I did find a vacuum hose off on the back by the intake. A good size ( 1/2") so I am surprised I did not here a vacuum leak. Hopefully the light will stay off now. If not I will start another thread. Thanks for the right direction to search. CRAIG
 

autodr

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#13
Cool, glad to see you've found it.

For future diagnostic information: With a vacuum leak, your fuel trims would have read very high at idle, like 20% or 30% positive trims that would tend to go close to zero at cruise RPMs.