Code PO 171

For about the last 3-4 days I have had this code. SES light came on, had it read by Advance Auto, they cleared it out, and the following day it came right back. Symptoms are unusually high idle at cold start (1800 vs 1200-1300), runs smooth until idle drops below 1000 then car starts loping. It sometimes acts like it's going to stall but doesn't except for last night it did when I pulled in the drive way. Regular maintaince is up to date and only thing I've done recently is having to replace the ECT sensor. Kind of hitting a wall on this one at the moment and appreciate whatever input or suggestions you may have. Car is a V6 with 162000 miles.

Now I have code PO 101 in addition to 171. Still have the same symptons as mentioned above. Did some one say inspection time :screwy:

What was the code(s) exactly ?

That usualy point you in one direction or the other.

171 = System too lean
101= Maf circuit, range or performance problem

Check your IAC for the low/high idle. Could just need to be cleaned and its port inside the TB sometimes gets clogged.

The p0171 could be an injector not opening or clogged. But the MAF sensor might cause the lean condition also.

Check the wires right where the plug in is, very typical for this to get damaged and give inacurate readings or none at all.

We have many test procedures for these things in the Tips and Maintenance (http://www.automotiveforums.com/vbulletin/forumdisplay.php?f=2148).

Keep us posted on your findings, and I hope that helps!

Check your IAC for the low/high idle. Could just need to be cleaned and its port inside the TB sometimes gets clogged.

The p0171 could be an injector not opening or clogged. But the MAF sensor might cause the lean condition also.

Check the wires right where the plug in is, very typical for this to get damaged and give inacurate readings or none at all.

We have many test procedures for these things in the Tips and Maintenance (http://www.automotiveforums.com/vbulletin/forumdisplay.php?f=2148).

Keep us posted on your findings, and I hope that helps!

totally agree with the above mentioned, also would like to add this - check for vacuum leaks, check injector O rings, low fuel pressure (leaking fuel pressure regulator), replace pcv valve, clean injectors,

Cleaned the MAF & made sure the wires were OK as well as the TB, unfortumately, that didn't help. Probably look for a vacuum leak next. I don't know if this would make a difference, but fuel filter has about 20000 miles on it and FPR is still original.

this causes lean conditions:

vacuum leaks,
leakig fps regulator
clogged fuel filter
dirty injectors, shorted injectors
clogged air filter
engine misfires
air leaks in the exhaust manifold before AF O2 (O2 reads more air)
lazy o2
dirty or bad MAF
TB dirty
IAC stuck or clogged passages

Because of the age + mileage, I would suspect bad plastic, rubber, gasket, or a seal on the PCV or EGR system.

1) Try plugging the air duct work were the PCV systems connects, this will isolate the PCV system for the short and block any unmetered air.
2) Reset and clear code.

How doe's she runs?

A handy tool for finding vacuum leaks is a can of carb cleaner. Spritz it around the intake and vacuum lines. If the engine smooths out, try and pin it down to a specific spot and go from there.

I do have some carb cleaner around the house. I'll try that. Also, had the codes checked one last time yesterday morning and PO 131 & PO 300 showed up as well. O2 sensor is fairly new(July) and plugs, wires, and coil packs were replaced in Mar/Apr. On the highway its fine and sometimes at idle its good but more often than not it runs as described in post 1.

3) You can isolated the EGR system by making your own EGR gasket to block the EGR port from unmeterd air.

Listened to car run earlier and it alnost sounds like a vacuum leak. Just need to narrow it down, couldn't locate it today. What would be the symptom of a leaking FPR?

When I first start the car of the morning, the idle goes up and down for about 1-2 minutes like someone is revving the car then backing off tho I'm not touching the accelerator at all.

replace pcv valve and idle up and down will stop. So you have internal vacuum leak that you can not hear. Then reset codes and see what happens.

Sorry for the delayed response, I haven't has access to a computer recently. The problem turned out to be a loose EGR valve. That was the last thing I was suspecting because of the other codes (101,131,171,300). It's been fixed for over a week and it's running like it should, best of all no SES. Gas mileage is better also(29 MPG).