My CEL is back.... opinions please!

[tyr0981]

So i've been "battling" this P0171 code for sometime with intermittent "wahoo it's fixed" to the "WTF!?!? why is this back!" moments for along time now... Even though this recent P171 code fest started after i did the ISR mod, it isn't the first time i've been in the "battle", but in the past cleaning the MAF always "fixed" it until now.

I read allot of threads on here about vacuum leaks being the problem of many 171's on here, usually involved with a SC 7th injector (i have neither) but i took a look with my trusty Cigar smoke and found a few small leaks (at joints) and fixed them, no change....

So after cleaning my MAF a few thousand times, i finally replaced it with a known working MAF, all was good for ~1 week, then the 171 came back....

Basically I've decided the intake system is okay, so i'm moving onto the fuel system, i've always had long cranking starts when she's been cold, turns over for ~6 seconds (like ~15 cranks or so) before the engine starts. Now the 171 come on and off with apparent randomness....

so does that sound like a Fuel Pump on the fritz to anyone else?

 

[tyr0981]

One vote for the fuel pump...

out:

 

[allwheeldrive]

Fuel pump will do it.

 

[ajonesnv]

I would check the simple stuff first...Have you checked the PCV Valve and hoses leading up to it?

 

[ajonesnv]

Here is the FSM page for it.

EDIT: The fuel pump is always an option, but when my pump went (not to say it will be the same) it started getting super loud and then actually caused the truck to sputter, but I never got the 0171 CEL.

Good luck

 

[tyr0981]

could the fuel pump been 'limping' for this long though? ~8 years

no leaks from the intake system (Cigar smoke test), replaced several old / cracked vacuum lines on the manifold made no difference....

 

[Doc2012]

Have you changed out the O2 sensor with a known good one?

 

[tyr0981]

Have you changed out the O2 sensor with a known good one?

i replaced the downstream 02 sensor, maybe i should try the pre-cat sensor first eh....

 

[awpsome]

yea pre cat is the one to determine your air fuel ratio the one after is to make sure your cat is working. thats about it.

Ive seen this code a few times with my SC as well, thinking about it now its never come back for a very long time.

Ive done too many things to give you an direction, but what about fuel filter?
i cant image a fuel pump "limping" that long.
plus fuel filter is cheap, easy, fast to change. but then again im not the type to throw money at somethign till it fixes, i am the type to test and make sure its working or broken and change as needed.

 

[tyr0981]

Fuel Filter is about time to replace also.... i thought i'd be getting codes for the 02 sensor if that where the problem?

it makes sense to change the from 02 just based on age alone.... and it's time for a fuel filter also... been a couple years.

i wish test Fuel Pressure was an easier test!

 

[19963.4lsr5]

it be worth spending 20 dollars at Harbor Freight and getting their fuel pressure tester and make sure your pressure is OK.

But a pre-cat O2 sensor can cause it...its the checks and ballances for the entire EFI system and if its bad and failing to produce proper voltages AKA low it can be read as being lean....And you I believe have a wide band sensor.......

 

[ppnkxsaultss]

Fuel pump will do it.