P0171 Bank 1 Lean finiding issue

Broseph

Well-Known LVC Member
Joined
Aug 18, 2012
Messages
386
Reaction score
27
Location
Ohio
Title pretty much says it all. 02 v8 and I've been getting a P0171 code popping up. Interestingly enough, it has only thrown a CEL once, and I just happened to read codes off the car before taking my tune off yesterday

Anyway, it's come up ever since I had the Thunderbolt cats put in last March after they busted the gasket at the flange, but it was repaired and I also found out they put the rear 02 sensors I gave them on the same side, but I replaced those.

What I want to know is could this be cause by the timing slightly off? I did all tensioners and pretty much a rebuild last February. I haven't noticed any power issues, but I'm hoping it's not mechanically related.

That said, what am I looking at for Bank 1? Exhaust leaks, air leak at intake manifold gasket, fuel injector or bad O2? And what's the easiest ways to check all options? Also, if this has persisted for a few months without me knowing could that cause damage or will I be good if resolved soon. Thanks for any help
 
There are lots of possible causes, including marginal coils. I'd start with a smoke test of the exhaust and then the intake. An air leak at either place could cause that code. I doubt that you could have the timing off enough to cause that code, but still have the engine running smoothly.
 
Thanks Joe, that was my hope, I do have a ticking noise coming from the engine but many have said the injectors can be a little noisy and pulleys can cause the issue, the closest I could chase the sound was somewhere by the TB, maybe the ICV, im not sure.

I was wondering what would be a safe way to find a leak, Ive heard some use WD40, soap spray for small engine repairs, but for a car I wasn't sure.

Would marginal coils cause a lean condition and stumbling upon start up? I know every engine problem and low tire pressure is due to failed coils, but I attributed the stumbling start up to my tune since I have no issues with acceleration butvery time I start the car it stumbles out the gate for a second or two before the normal high idle kicks in.
 
Yes, it could cause a starting stumble.
You can use propane or similar to check for intake leaks while the engine is running, but that won't work for exhaust leaks. You can make a smoke machine with a fogger and a shop vac, for the exhaust.


AFAIK, all Ford engines (and apparently at least this Jaguar engine) make a clicking sound.
 
Whats the propane method? Leak a small amount out of a tank and see if it ignites?
 
Whats the propane method? Leak a small amount out of a tank and see if it ignites?

Leak a small amount out around where you think the intake may be leaking and listen for the engine idle to change momentarily.
If it ignites outside of the cylinders, you have much bigger problems.
 
Honestly Joe...do you iron your LVC cape before logging on or just wash n wear? :shifty:
 
if you dont think you have a leak or failing coils try cleaning your MAF. had my engine bay unsealed for a while and got stumble on start and lean on bank 1 code. cleaned the MAF with CRC MAF cleaner, cleared the CEL and problem has not come back.
 
Thanks for the tip. I did replaced my plenum/maf after getting a CAI. The MAF had actually cracked at the housing so it was leaking air, i glued it so it would hold up until the new one came in.

I notice that a lot of people refer to the MAF for lean issues. My only objection to that is if the leak is around that area or the senor is dirty etc. then the PCM should read a lean condition for both banks. Im not sure if P0171 is a generic lean condition that could refere to either bank or both, but if the leak is anywhere before the intake manifold I would imagine a different code for both banks being lean would pop up.
 
not sure about your argument, though what youre saying makes sense. i would clean it regardless tho, its a lot easier than checking for a mystery leak, and if it was cracked and you havent tried cleaning it i would do that first. the can says to clean the maf every time you switch a filter, every 6mos, etc, etc. mine did not look dirty, but it doesnt take much dust to get in there and fck it up.

worst case scenario is that you will have a can of fluid you are going to need for basic maintenance and a wasted 15mins..

oh and i read that some of those modified intakes use a filter with oil in it that can dik up your MAF. i dont have one, so i dont know anything other than that
 
I use starter spray for lawn mowers, but throttle body electronic injector spray works to find leaks when running. If you suspect O2 sensors, swap them as I did, different codes for each bank. The front sensors are the same. The rear sensors are the same. Front & rear are different. Good luck. I changed all four of mine, no more codes. The flange repair maybe suspect! JMO.
 

Members online

No members online now.
Back
Top