Running rough with code

Hey guys I've got a head scratcher. I have a 2002 2.7l Tacoma. All of a sudden the engine started running real rough on me like it wasn't getting fuel. But i got a code for system too lean bank 1. Which there's only one bank of course. So i thought maybe o2 sensor or one of the cats were plugged. So i took the exhaust apart first to rule out the cats which there are two. Then i read that it might be the MAF sensor so i just changed that a few minutes ago. I've changed the spark plugs and the fuel filter as well but the other day the code for the system too lean went away and a code for the MAF and/or IAT came on. Nothing has helped and i need the truck back on the road because it's obviously my daily driver. So any help would be greatly appreciated. Thank you!

 

P0171 "System too lean bank 1" ....check for vacuum leaks in the engine bay. It's usually the cause if that's the only code you're getting.

 

^Yep, could be vacuum leak (such as leak in intake manifold gasket), which would allow more air getting into the engine downstream of the MAF sensor. If you have a scan tool or Bluetooth OBD2 dongle, you can watch the O2 sensor readings in real time. If the reading is too lean at idle but goes to normal (or rich) when you give it some throttle, it's a typically telltale of a vacuum leak.

 

Ive checked all over for vacuum leaks and havent seen any. I put a walker maf in. Got it from carparts.com

 

It wont even hardly run anymore. Every time i give it gas it just dies

 

I am leaning towards an EGR issue... Not there to look and see but follow my thinking. If the EGR valve is stuck open/partway open she is gonna run poorly, at the same time the additional exhaust gas is reducing, leaning out, the desired air fuel ratio that the o2 sensor(s) are looking for and popping the code. It has been a while since I looked at a 2.7 dont know if the EGR just dumps or has ports to put it at specific places in the intake.

 

Whats the EGR valve? Sorry im not very mechanically inclined

 

I mean it seemed to me like it would be a sensor. Its just really odd that it just happened all at once. Could it be the timing?

 

Truck wont even start now. So im think it might be a fuel pump

 

How are you checking for vacuum leaks? Smoke jar?

If you suspect it's the fuel pump, hook up a fuel pressure gauge and see...

 

I was checking for cracked lines or anything obvious. Like i said im no mechanic so i dont have the stuff needed to do a pressure check. What else could it be thats keeping it from starting?

 

I never heard the fuel pump kick on at all

 

Did the MAF code pop up after you put that aftermarket MAF sensor in it? I'm betting that's a big part of why your truck won't start now, I've heard you should always stick with OEM Denso MAF sensors. Aftermarket ones are a gamble at best.

Your truck should still run while throwing a P0171 'system too lean' code, might run rough depending on how bad it is but when I had it, my truck ran fine minus the code for several weeks until I finally found the vacuum leak.

I'm thinking it made matters worse when that aftermarket MAF sensor went in (if I'm understanding the timeline correctly).

 

no it popped up before. I disconnected the battery before I put it on and no engine light since but now I cant hear the fuel pump coming on and it wont start at all

 

the fuel pump only energizes when the motor is turning over.

 

Sounds like it could be the fuel pump. Better to test for fuel pressure first before replacing, but it sounds like you like to just throw parts at it without testing, so go ahead and replace the fuel pump and see if it fixes it!

The exhaust gas is almost all inert gases, nitrogen, CO2 and H20, so a stuck open EGR valve will not lean anything out because there is no (very, very little) oxygen in it. This is why the EGR works to lower combustion temperatures. The extra N, CO2 and H20 mixed with the fuel and oxygen slows the burn rate, so there isn't a spike in temperature.

 

Well i only replaced the parts that i could find cheap any way. As i said before im not a mechanic so i was just looking for advice on which route i should take next

 

I'd recommend you stop throwing money at a solution and take the truck to somebody who is a Mechanic. Paying the $100 diagnostic fee is going to be cheaper in the long run and you could be replacing perfectly working factory parts with junky Autozone specials. You dont have a particularly good track record of your home repairs: https://www.tacomaworld.com/threads/truck-chatters-when-i-hit-the-brakes.459333/

If you're really set on becoming the next ASE certified redneck then back up a mile and begin with the basics. Fuel, Spark and Compression.