Has anybody had an3 issue with a CAI throwing a P0171 code? im dealing with the code now so the car can pass inspection and my mechanic told me he's hoping the intake didnt cause it, but hes not sure. Anybody has any experience with this. There is a lot info on the the code it self here so i know what it is and im gonna trouble shoot it.

 

Yes your intake can cause this. If you have an oiled filter then the oil can get on the MAF and the MAF can get ruined. Disconnect your battery for an hour. Clean your MAF sensor ONLY WITH MAF SENSOR CLEANER. Nothing else!!!!

Reconnect and try again.

 

yeah, he did that already, they cleaned the whole thing very meticulously. and then shut off the check engine light. It usually takes about 50 miles to come back on but it only too 10 miles and it came back on as soon as i got back in the car. I got 2 bottles of sea foam to treat it tonight. i dont think it will help but im gonna try it. if that doesnt work ill have to replace the top O2 and hope that works.

edit: my filter is just a cheap one i but i dont think it's oiled one.

 

I've had a recurring P0171 code. Mine went away for awhile after cleaning the MAF sensor (I used electrical contacts cleaner. Alcohol-based, dries almost instantly, leaves no residue. As far as I can tell, it's the same thing as 'MAF cleaner'. Couldn't find the MAF cleaner, but even Walmart has electrical contacts cleaner - in the automotive section. Do NOT use something like brake cleaner; it'll leave a residue and screw up your MAF sensor.)

I also replaced both O2 sensors, but that was more for preventive maintenance - they had over 150K miles on them.

The code has come back a couple times. Since then, I've run a couple tanks of Seafoam through the engine and the code went away again.

Seems to be a hard to diagnose problem when P0171 is thrown, but luckily not a biggie in terms of engine problems.

 

yeah, he did that already, they cleaned the whole thing very meticulously. and then shut off the check engine light. It usually takes about 50 miles to come back on but it only too 10 miles and it came back on as soon as i got back in the car. I got 2 bottles of sea foam to treat it tonight. i dont think it will help but im gonna try it. if that doesnt work ill have to replace the top O2 and hope that works.

 

anybody know the correct fuel pressure i should be measuring here? and do you measure before the regulator or after?

 

I tried checking the shop book for the fuel pressure and no luck finding what it should read.
Not that there are many vacuum lines, but have you checked them to ensure none are dry rotting and they are making good connection? Good check is to mist starter fluid around the engine while it's idling and see if you spray a location and hear the engine performance change (that means it sucked in the fluid).

 

I worked on the car last night and i got a couple of things done and finally get the inspection. First i replaced the fuel filter just to eliminate that variable when doing my fuel system test.
Second:
I put a can of seafoam on the fuel tank and a can in through the brake booster line that connects to the intake. There was not much white smoke at all so that should tell me that the engine was not so bad or it was pretty clean. Check engine light still there.

Third:
I checked for vacuum leaks. I sprayed all the vacuum connections and line with carb cleaner but the seem pretty solid. I mean i soaked then in that stuff while the engine was running but nothing. I wanted to test if the car cleaner would actually do something to the engine and i removed the intake pipe, sprayed a little bit in there and the engine studered right away. I even sprayed water on the whole thing to see if it would do anything but the engine was running nice and smooth. The MAF was already cleaned at the shop by the pros, so i doubt that that is the problem. Unless, the MAF is actually broken and not dirty. Which would mean that now i have a clean, broken MAF.

Then:
I used a mechanics stethoscope and checked pretty much everything and i couldnt spot any airflow out of the normal.

Last: I checked the Fuel pressure and im reading 30-31 PSI. At idle, It doesnt move much at all when i rev the engine. As soon as i shut the engine off, the pressure goes away down to zero.
This is pretty much where im stuck because i dont know how much i should be measuring at any point. I think that pressure sounds little on the low side so i might have a weak fuel pump or a bad fuel pressure regulator. I took some pictures of the fuel pressure test so ill make a write up when i fix my problem.
Any thoughts?

 

On a Series II 3800 engine, fuel pressure should be 48 to 55 psi with the key on and engine off. GM does not provide a fuel volume test spec but, as a rule, a good pump should deliver about a quart of fuel in 30 seconds.

 

any idea of what it Should be on the 3.4 LA1? I've been searching for this number the whole dang day and i cant find anything.