P0171 HELL

Hey guys First time posting here but I have been kicking around for a while just trying to soak up as much info as i can.

Im really struggling trying to figure out whats causing this p0171 i also had a p1130 and a p0125 at one point.

its an 02 taco 2wd with the 2rzfe 2.4 L with over 200k

its the owners brothers truck of course and hes sort of a cheap prick lol that being said the first thing i did was check the plugs, they looked like shit so i replaced them. I cleaned the MAF and both B1S1 and B1S2 found a vacuum leak and replaced the hose that runs along the front of the radiator to the air filter housing. cleared the code and told him to drive it.

so now its back and at first it was just a p0171 in stored and current
the second time i cleared the codes i got a p0171 in current and p1130 in pending
cleared them again and got p0125 and 171 and 1130 pending.. im assuming the 125 was from me unplugging the CTS and forgetting to plug it back in before i stared the truck

i was watching the MAF on the scantool and thought it looked a little funky so i replaced it.
did everything i could think of to try and find a vacuum leak sprayed CRC around all the hoses and intake and got no results
punched p0171 into prodemand and started running down the list - found a bad PCV and replaced it
checked fuel pressure at the rail and have right around 40psi

watched a couple videos online and im thinking maybe the booster or purge switching valve or whatever toyota calls it-just now i ran over and pulled the line off the intake to the check valve on the booster and couldnt blow or suck through it with the truck off - same with the line that goes to the evap valve-is there anything else i should be looking for that im not thinking of??

Oh the truck also has a pretty gnarly exhaust leak it has been cobbled together where B1S2 mounts
i dont see that throwing these codes though...?

HELP

Sorry for the format

forgot to mention before LTFT is 39 STFT 19 IAT seemed to be accurate and responding as the truck warmed up

 

Did you replace the MAF sensor with aftermarket or OEM?

 

aftermarket, couldnt get an OEM at the time.

 

A quick search here showed at least one resolution for a PO171 as the fuel pump. You said pressure was there. It sure couldn't hurt to change the fuel filter, maybe it's clogged enough to not maintain supply pressure during operation and cause a lean condition? The other codes I'd guess are related to the exhaust leak. That's how I'd proceed, do some online searching first then wrench it. FWIW, I recently changed the fuel filter on my 146k mile 2.7L just because, no real issues. Once I had it off, I bumped the old filter to see if anything came out from the tank side. There was a bit of sediment and the residual gas that came out looked like weak coffee.

 

Hey, bro. I had the same problem code and diagnosed it yesterday as an intake manifold gasket leak. Sadly, I don’t have time to fix it so I will have to pay someone else to do it for me. Just dropping in to wish you luck.

 

I will probably throw a fuel filter in it because the customer understands it should have been done already with 200 k miles and appears to be original.
I’m going to smoke the intake in the morning to see if I can find a bad manifold gasket or maybe where the EGR mates up I was hoping maybe someone had another idea something that wasn’t mentioned in Mitchell. I have heard people say maybe the orings that seal the spark plug tubes as well but who knows hopefully I will have some answers in the morning. Thanks all

 

just wondering how you diagnosed that intake i tried smoking this one and found nothing im going to replace it anyway

 

It can be really tricky diagnosing a bad intake manifold gasket. Heat causes the leak to grow and shrink. Also, the issue occurs with vacuum so looking for smoke with only about 0.5 PSI pressure is not likely to reveal anything.

I’ll be honest and say luck will need to be on your side. You might need to smoke test it multiple times and then warm the engine up and cool it down so that the leak appears.

Secondly, spraying starter fluid around the manifold can help; however, this too is an imperfect method.

I’ll also say that you should use the data from your ODB2 scanner to your advantage here. Ensure the front o2 sensor is working properly. Ensure the MAF works properly (it should be roughly equal in terms of g/s to your engine displacement). Ensure the fuel system works properly by seeing how the fuel trims change, as well as by measuring pressure at the rail.

Don’t be afraid to run a vacuum test with a gauge, too. Oscillations in vacuum will be a great clue.

 

Also, you can ensure the EVAP and or brake booster systems are not responsible by plugging those lines and seeing how the fuel trims change afterward.