2002 Monte Carlo SS has lean code....HELP!!

S

smaldirt28

Well-Known Member
My father in law has a 2002 Monte SS with a 3.8L and it has a lean code that wont go away. It has had the code with two different motors bc the first one locked up. So far the computer has been replaced, intake gaskets replaced, fuel injectors replaced, checked for vacuum leaks, o2 sensors replaced. I am sure there is more but nothing is fixing it. After clearing the code it takes about 10 miles of driving for the light to come back on. Does anyone have any possible ideas that may solve this issue. Any help or ideas would be greatly appreciated. Thank you all in advance.
 
If you can get a fuel pressure gauge and test pressure on the fuel rail. Pretty picky on the pressures it needs. If its not up to snuff its either a fuel pump regulator or even a partially clogged filter. Some regulators run off engine vaccum too so id find where its at and ck for good vaccum as well if thats the setup it has. If you need any tech info theres plenty out there as far as specs. Good luck
 
Thanks for the reply Mike. The fuel pressure at the fuel rail has checked out good. We were going to replace the filter but since everything checked out good when testing the fuel pressure we havent done that. Should it still be done even if it tested good? Are there any other things that can produce the lean code? Need to have emissions test done and when the check engine light is on it is a automatic fail. So just trying to figure this thing out....LOL
 
Well i do know of a tech bulletin. Ck engine vaccum....should be around 18 inches. If its higher..........catalytic converter is plugged or is loose on the inside....and that can cause a lean condition. Let me ck some other things.....let you know.
 
There is a MAF sensor...big blox that is between air filter housing and throttle body. Those are known to get dirty and throw lean codes but yet the car runs ok. There is a cleaner that you can use........donot use brake clean. Its a very picky sensor. Try the vaccum reading..if it cks good id take the MAF sensor assembly off and clean it good. Very very common for those to get dirty and actually they say every 60000 miles to clean them. Good luck
 
here is some of the things we have done. replaced m.a.f ,fuel pressure reg,injectors,resealed intake,replaced upper inteke,new o2 sensors,new egr tubes,replaced engine,new bcm,new pcm, the vaccum i think is right about 15. tommy did cut out the resignater pipe which is well after the cat and post o2 sensor so i wouldnt think that would matter,although it is leaking there.we also did tune up,and replaced manifold gaskets and the flange gasket.I smoked the intake and the only spot i could get it to leak at was the hole where the maf sits. i replaced the oring and it still leaks a little. it does not surge when i spray around it with carb clean though.
 
Weird. Maybe since its different engines and such might be something like a bad gas cap? Never seen one cause a lean code but guessing it could. I'd drive it with cap off just to see. D
 
Po171

Only drive it 9 miles. Light will stay off!

These are tuff ones to do Tom:

Looks like the parts cannon has been shot at this.

Racin90 covered the usual suspects on the PO171. The MAF, however,
Chris says it has been changed out.

You have changed injectors.
You have changed EGR
You have checked vacuum
You have checked fuel pressure

You have not replaced the fuel filter.

I think there is a relationship between pressure and VOLUME.

There is usually a test that you can run for 15 seconds or so and usually pump
at least (x) amount of liquid into a 1 gallon container.

As you have suspected it is either fuel or vacuum in my opinion.....

Also...google is your friend....try some Chevy forums.....

As a last resort you might get Mike "Wahoo" Jones to come over a glue a
Ford Oval to the front......


Hope some of this helps.....Let us know....


John D. Stribling
 
i did a volume test as well. i think the solinoid for the air pump is stuck open. i havent had a chance to look at it yet.
 
air pump sol possible,plug it off and try. may set air code though. however, map? possible intake runner ****ing air from crankcase? pcv o ring? seems as if the 171 is bank 1 only if it has 2 pre cat o2 sensors. that would mean problem only affecting bank 1. problem would most likely be south of t-body. if driven much farther, will bank 2 lean code set 151 I believe? Greg
 
if plenum was changed, was pcv "straw" properly installed? have also seen plastic fitting where vac booster line connects leak.Has lower int gasket been replaced? We all know that is a plastic POS. The re design from fel pro seems much better, as well as the metal replacement heater tube elbows. Checking is cheap.When the diagnostic dice are rolled, you can usually have the car properly diagnosed and repaired for much less than all the parts one may throw at it...
 
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