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The Dreaded P0171

C

CSVT985

CEG'er
Joined
Nov 22, 2004
Messages
109
Location
Roanoke, Texas
It has been far too long since I logged on here and posted. The site changed...wow, its very modern. Good job~

Well I bought my car in 2002. Ever since then I have had P0171 - the too lean error. But Every year I have pulled my battery overnight, driven it the next morning to an inspection station about 8 miles away and have passed with flying colors. My car still runs great at 158,000 miles (need to change my sig).

Well I ran out of inspection On Nov. 1st. I did my same routine and pulled the battery and drove down there the next morning..here is the shocker. My ECU stated not ready and they failed me.

2 questions.

1) Can a car take longer to reset its computer as it gets older?

2) I am going to rent a OBD-II diagnostics tool from Autozone and am going to reset my computer 1 mile from the station ( im gonna pull over at a gas station right down the road), will this keep my computer in 'ready' status in order for me to pass?

Again, there is nothing wrong with my car, just some screwed up sensors or something. I still get 26 miles per gallon on the highway and it idles at 500 rpm, and has done so the past 4 faithful years.

Thank yall, hope to be on more often.
 
MAF - Mass Airflow Meter right?

Thats not the throttle body but the shiny tubing right after the airfilter?

Whats the best stuff to use? Thanks!
 
yeah

CRC has a MAF cleaner you can get it at autozone. Just remove filter and maybe screen and spray the MAF, don't take it apart.
 
CSVT985 said:
Thank you, I will let you know if it removes the code.

Has this worked for anyone else?
Click to expand...

Yes, it has many times. Note that P0171 could be many things. Most of the time it is a vacuum leak. Check for broken hoses, leaky clamps, etc.

From TSB,
P0171 - System Too Lean (Bank 1)The Adaptive Fuel Strategy continuously monitors fuel delivery hardware. The code is set when the adaptive fuel tables reach a rich calibrated limit.

Fuel System:
· Contaminated fuel injectors
· Low fuel pressure or running out of fuel (fuel pump, filter, fuel supply line restrictions)
· Vapor recovery system (VMV)
Induction System:
· MAF contamination
· Air leaks between the MAF and throttle body
· Vacuum leaks
· PCV system concern
· Improperly seated engine oil dipstick
EGR System:
· Leaking gasket
· Stuck EGR valve
· Leaking diaphragm or EVR
Base Engine:
· Exhaust leaks before or near the HO2S
· Secondary air concern
Powertrain Control System:
· PCM concern
 
Thanks guys

Thanks guys

Thanks guys for the input, it is very appreciated.

One last question, and its in my first post, do yall think resetting the codes and then driving 1 mile to the inspection place would do the trick? I will definately do the MAF and brake cleaner around the engine bay ( to see if the engine stumbles = vacuum leak)

But if nothing works, that would be my last ditch efford before taking it to an emissions place.

Thanks
 
You're probably overdue for an UIM & LIM rebuild anyways, but by all means go the easy route first. Hopefully the CEL will go off and you can have some breathing room after passing inspections. Currently your car isn't happy and as a result it's ignoring the Bank 1 PRE-CAT O2 sensors because it can't use this sensor in closed loop mode. If the chemical cleaner on the MAF doesn't do the trick then you might want to look at the list I compiled before I eventually did the UIM & LIM rebuild.
Clicky
 
CSVT985 said:
One last question, and its in my first post, do yall think resetting the codes and then driving 1 mile to the inspection place would do the trick?
Click to expand...

No, you must go through OBD monitor programs before the inspection station computer will permit testing. Usually the PCM will post a P1000 code stating not all the low level monitors have completed. I'm not positive about the P1000 number, but without completing the OBD driving cycle the ECM won't be ready and the inspection computer will recognize this "not ready" state. Summary: Even if your emissions are perfect and CEL is off you might not pass. At least in CA it works this way.
 
In case yu hadn't noticed, the emissions testing program changed. They go strictly on the PCM now for OBD2 vehicles instead of running a treadmill/sniffer test.

Previously, the treadmill/sniffer test was the primary means of testing and the OBD2 check was secondary. Now, the PCM has to "do its thing" in order to pass.

Steve
 
I read through your checklist, and most of that was done on my 120k maintenance.

It has new spark plugs, PCV and air filter

The re-torquing of the UIM bolts caught my attention though. While they may need it, I remember posting a question on here that I forgot about.

Several times when I am stopped and the radio is off and its all quiet around me, I can hear a tap-tap-tap-tap-tap-tap-tap coming from under the car. Someone told me its my exhaust leaking.

If my exhaust is leaking out from the manifold, could this cause a too lean error?

Thanks for the checklist yapper, im gonna take it down one by one till I get the problem fixed. By the way, what was it for you? The gaskets?
 
projectSHO89 said:
In case yu hadn't noticed, the emissions testing program changed. They go strictly on the PCM now for OBD2 vehicles instead of running a treadmill/sniffer test.

Previously, the treadmill/sniffer test was the primary means of testing and the OBD2 check was secondary. Now, the PCM has to "do its thing" in order to pass.

Steve
Click to expand...

Oh, dont get me wrong, I know of the emissions testing program. My car has never been on a treadmill with a probe up its butt. But my little plan worked the past 3 years. Its just getting the computer in a 'ready' status without it flagging a CEL. I must have just been extremely lucky the past 3 years because this is the only time I have failed due to the computer not being 'ready'.

Im gonna do the MAF thing and then try to reset the PCM and drive for 8 miles to get the car ready.

Does anyone know how long it takes for the computer to come back up into 'ready' status? Thanks
 
CSVT985 said:
If my exhaust is leaking out from the manifold, could this cause a too lean error?
Click to expand...
I don't think so. It would have to be a large leak and it would probably create a condition where exhaust gases got into the cabin.
CSVT985 said:
... By the way, what was it for you? The gaskets?
Click to expand...
I believe it was a cracked PCV hose. I can't be postive, because I put all new parts in (i.e. UIM & LIM gaskets, fuel rail seals, fuel injector O-rings, etc.) before I saw the cracked hose. That's why I had both codes, not just P0171.
 
yapper said:
I don't think so. It would have to be a large leak and it would probably create a condition where exhaust gases got into the cabin.

I believe it was a cracked PCV hose. I can't be postive, because I put all new parts in (i.e. UIM & LIM gaskets, fuel rail seals, fuel injector O-rings, etc.) before I saw the cracked hose. That's why I had both codes, not just P0171.
Click to expand...

Hmmm, I think my dad and I stumbled onto it. I dont know what it is, but he was spraying the carb cleaner and the engine accelerated a little. So we started to jiggle stuff at the back of the engine bay (at the firewall) and he grabbed a green tube going from the EGR to a dual input plug. It had the green tube and a tan tube going into. The moment he touched the green tube it cracked into 3 pieces. We hooked some fuel line up to it, cleaned the TB and MAF with cleaner, drove it 20 miles and no CEL.

Tomorrow I take it in to be inspected, wish me luck guys..
And thanks again to everyone who helped.
 
CSVT985 said:
.....Several times when I am stopped and the radio is off and its all quiet around me, I can hear a tap-tap-tap-tap-tap-tap-tap coming from under the car. Someone told me its my exhaust leaking.

If my exhaust is leaking out from the manifold, could this cause a too lean error?
..... By the way, what was it for you? The gaskets?
Click to expand...

The tap-tap-tap sound is the metal contracting and nothing to worry about.

Per TSB, if the exhaust is leaking, yes, you could get a P0171 code.

I had a broken vacuum hose.
 
Well it wasnt it, about 35 miles driven and the CEL came back on. Same codes. I have given up, my parents offered to help me out and are taking it to a shop that repaired my sisters emissions problems. I will let them deal with the problem. I was going to buy an MAF sensor and try to see if that was the issue, but honestly it could be 60 different things and I dont have time to diagnose each one.

I tried to reset my codes via the OBD-II sensor and sure enough, all 4 sensors were not ready and so the place just said come back for your free testing when you get the problem fixed. So at least I didnt use up my free re-test.

Thanks yall for all yall's help, but I think Im gonna let someone else do the hard work now, I just dont care anymore. The SVT is getting sold next year anyways for a car that doesnt have crap engine issues.
 
Fixed

Fixed

Well, I dont really know what to say.

Auto shops scare the crap out of most people, including me. Most people see $$$

But a local shop here in town that my Dad referred me to, diagnosed it down to the source.

MAF - OK
O2's - OK
EGR - OK

So, they found 2 hoses in the engine bay that, from age, hard started to let air into them. They RTV'd the crap out of them and let it dry over night....50+ miles later the mechanic reported no CEL and my dad is taking it to get inspected now.

So, thats that. Check your hoses!! Spray the carb cleaner!!

Total Cost: $126.97
 
Last edited:
CSVT985 said:
...So, they found 2 hoses in the engine bay that, from age, hard started to let air into them. They RTV'd the crap out of them and let it dry over night....50+ miles later the mechanic reported no CEL and my dad is taking it to get inspected now.

So, thats that. Check your hoses!! Spray the carb cleaner!!

Total Cost: $126.97
Click to expand...
You should consider changing the hoses.
 
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