2012 toyota tacoma stalls under heavy acceleration *SOLVED*

Hey guys, I have a 2012 tacoma with the 4cyl 2.7l 2tr-fe. It fires up easily, idles really smoothly at 700 rpm, it will even drive around fine, if you drive like you have an egg under your foot. If you press on the gas hard, once the RPMS hit around 2200 and up it stalls, it does not sputter and die slowly, it dies immediately. It does not matter the speed, or incline. It will fire right back up easily like nothing happened and will drive, until you give it too much throttle again, then it dies. The MAF sensor is brand new, the upper O2 sensor is brand new, I have checked the fuel pressure and it is within spec, and it holds pressure within spec after engine is turned off. The most annoying part is it will not throw a check engine light, or pending codes. Has anybody experienced something like this? Does anyone have any insight on what could be the culprit?

 

Couple of wild-assed theories, though the instant cutoff with no sputtering is weird..are you gradually giving it throttle and trying to milk it past 2200ish? or is it stalling only with sudden throttle input? if so maybe a large vacuum leak.

Clogged cat maybe? or intake filter?

Fuel pump/filter going out? I know you said the fuel pressure is within spec, i assume at idle. maybe it can't keep up with demand at heavier throttle?

Could also be a bad MAF. Are you able to read any real-time data and/or check voltages from the sensor?

 

I've tried to ease it past 2200, rpms but it won't, it will just die.

I haven't thought too hard about MAF sensor only because it is brand new, but that's not to say it's faulty or premature failure.

I have also suspected fuel pump/filter, I was only able to test the pressure at idle with a kit rented from oreillys. I would like to watch it as I drive/engine dies, but I don't have access to live diagnostics software.

I forgot to mention it only stalls when under load, such as in gear driving down the road or up a hill. In park or neutral I can redline the RPMS and it will not stall. I am absolutely stumped

 

My initial thought was crank position sensor, but then saw that it was a load based problem, so that is unlikely. Next guess is limited fuel flow, but that would fade off then sputter. If the engine just drops off a cliff and dies, that usually means the ECU says “we’re done” and just shuts everything down. Therefore I would be looking at a sensor giving the ecu bad data. CPS can do this and rarely throws codes when it does, but can’t resolve the difference in behavior under load with that problem. Also stumped.

EDIT: duhh, just realized you have the 4 cyl engine. The first place I went with this problem was map sensor, but the v6’s don’t have them, so I disregarded it. Yours does. That would be my next step. This explains why it only dies under load. The failing map is not telling the ecu about the drop in vacuum so it doesn’t enrich the mixture. Then it senses knocks from too lean of a mixture that it can’t get rid of with timing retard, then shuts down to avoid destruction. Bad map sensors tend not to throw codes either. Map sensors are known to be one of the more notorious sensors to fail.

 

Only thing I can think of is maybe a wire somewhere that's shorting or going open circuit or a coil or something that is spiking the PCM and causing it to shut down.

Do you have a scan tool that you can connect to it to view data and see if you lose communication when it dies?

 

I will check the MAP sensor next! Do you know if there's a way to diagnose it?

 

4 cyl doesn't have a MAP sensor either, both the 4.0L and the 2.7L are MAF engines.

 

Well, i am not going to say you are wrong, but rock auto sells about 13 different map sensors for the 2.7 engine. Not saying i have never seen an error there, but they are usually pretty accurate. They do not list any for the 4.0. Many maf based engines also use a map sensor. Ecu needs air density data. Some use discrete ambient barometric sensors (4.0 has one in the ecu itself) and others use the map sensor. Some of these will rely more on map data for acceleration data over the tp sensor. Many ways for the designers to arrange fuel metering. Maf does a poor job in telling the ecu about acceleration, so they use tp and/or map data or both.

 

Only way i know is with a scanner observing the live data. Should be a selection for manifold pressure.

 

What they list as the MAP sensor is actually the pressure sensor for the Secondary Air Injection System, the 2.7L has a remotely mounted pressure sensor where the 4.0L has them built into the switching valves.

The engine only uses the MAF sensor for metering airflow, the pressure sensor is only there to monitor the Secondary Air Injection System.

 

Thanks for the clarification. Clearly that is not going to help the op. I return to being stumped on this one.

 

Yea it's definitely a strange one, someone with an oscilloscope and knowledge on how to use it could probably diagnose it pretty quickly but without that it could prove challenging to figure out especially without being hands on with it.

 

UPDATE

It was the fuel pump, the filter that is integrated into the fuel pump to be specific.

There was small debri stuck to the filter and at the bottom of pump housing. it was just enough to restrict the pump of fuel during high fuel demand, but not enough to effect performance at idle or low rpms. I hope this helps someone.

Additionally, I thought I would have to drop the fuel tank, to access the pump, but if you have an access cab and a short bed, you can simply unbolt the bed from the chassis and slide back a foot or so. I added a picture to show. The 6 T55 bolts were a PITA to get out, but with a propane torch, wd40, and half inch impact, they all came out without breaking. Truck has 206k miles so was time for a new fuel pump anyway

 

Interesting find, glad you figured it out