Engine I need the help of toyota Guru's!

I need the help of toyota Guru's!

Ok, my fuel system is spitting codes at me reading p0171 fuel system too lean.

I drive a 01 corolla my current mods engine wise are only a rai and a trd exhaust.

I was thinking its my MAF but im not entirely sure cause the obd has a seperate code for that, if thats it why wouldnt that code trip and tell me its the maf acting up?

its really weird though cause when its humid outside my engine is fine, but when its really dry it seems like through the rpm band up till about 4k the engine kinda studders and doesnt wanna push any power, but after that it starts to move, forget about any power before 3k rpms (unless its humid) it never did this before untill about 5 months after the intake was added. any suggestions on what could be tripping this code and possibly causing my low rpm horse power to suck?

I appriciate any input!

oh also in the lower idle speeds the engine knocks, but i assume and hope this is all related to the same problem...

it could be... try cleaning it...

I doubt seriously it's you're MAF sensor. You're correct that you would be seeing a code if it were the culprit. However, the previous suggestion is a good one - definitely try cleaning it with some electrical parts cleaner.

My guess - your problem is the intake. MAF sensors are really sensitive to air flow dynamics and anytime you change that, you're going to have other changes. My 2003 Corolla ran WAY lean with an AEM CAI. I never got a fault code, but got lots of lean detonation.

How is your fuel mileage? If it's better than with the stock intake, then it's probably because you're using less fuel (lean mix).

Trav

This intake? is it the type that requires oiling the filter? if so then you MAF has become covered in oil and is no longer reading as it should. It is still functioning properly so it won't throw a code itself.

another thing you might want to check is the fuel pressure or a possible blocked injector. A lean condition is usually fuel related.

Just don't blame the filter for being over oiled... I had one before and it says all over the documentation not to over oil when cleaning it. But the oil can mess with a MAF sensor.

theres a diy at vvt-i.net... here's the link... he used an electrical contact cleaner...

http://vvt-i.net/forum/showthread.php?t=1952

check maf o2 tps and post o2 sensors with a volt meter check plug wire resistance

im so sick of talking about fuel air issues and maf issue, i don even wanna bother anymore......... my lexus, my baby needs a new maf

the rai intake pipe diameter is the same as the stock pipe, just a healthier bend and it doesnt scrunch up at the end like the stock intake, the maf is almost right after the filter, and the filter has a end on it that goes partly into the pipe which straightens out air flow, its a very nicely designed intake, especially for being generic. however i did try cleaning the maf with just a cue tip and a little water and i noticed a huge preformance upgrade, and the light hasnt come back since i reset the ecu, so hopefully that was it. my throttle is alot better now but it still isnt great.

I'm telling ya...it's the intake.

Widening the tube size will cause the MAF sensor to get a proportionately smaller sample of the incoming air resulting in a lean mixture. Removing the mesh from the air tunnel causes turbulence and incorrect MAF sensor readings resulting in a lean mixture. The closer the MAF sensor is to the throttle body, the more noise it receives, which causes a lean mixture. If the sensor is located directly after a bend in the tube, then it is receiving a more laminar airflow and this will cause a lean mixture.

Unless you have some way to get into the ECU and alter the MAF sensor voltage definitions, then a wider intake tube is going to cause a lean mixture and detonation. The remedy for this is not cleaning or checking anything - it's an S-AFC or some kind of fuel management piggyback unit or returning to the stock intake size. Measure the inside diamter of your intake and then do the same for the stock MAf sensor housing. If the RAI diameter is larger than the stock size, then you've found your problem...end of story.

Trav