Tacoma 2.7l bucking and stumbling MAF sensor

This is my third post about my trucks bucking and stumbling situation. My last two threads I strictly thought it was suspension related. Turns out maybe not after I read up on engine possibilities on thishttps://www.tacomaworld.com/threads/2-7-stumbles-and-bucks-under-load-solved.449971/page-2
My truck does not have a distributor to start with and I already replaced the coil packs not but 3 weeks ago. On the forum it was recommended to unplug the MAF sensor and see if it runs good. I did this and the truck ran excellent minus the 3k rpm redline and CEL. So assuming the part was bad I bought a brand new Hitachi brand MAF sensor, installed it and it didn’t change a thing. I know it’s in right with a good connection but again when unplugged the truck drives excellently. When plugged back in (old or new MAF) it bucks and shakes. I have no idea what else it could be, I didn’t check the codes that came up when unplugging the MAF but I can if anyone wants. Very strange why this would do this but I though I had it all figured out… disappointed. Any help would be highly appreciated!

 

What are the new CEL codes? That's a good thing to lead with. Changing out an older sensor isn't a bad thing, but there are LOTS of things that can cause bucking other than the MAF.

Mark

 

If unplugging the MAF worked then maybe it's being starved of fuel somewhere. When you unplug the MAF it goes rich to compensate.

 

These are the codes I got, I should mention that the truck ran great and the I parked it for 4 months, worked on it and now it runs bad. New O2 sensors to note as well as many other parts.

 

Your codes are not saying it's necessarily a MAF issue. They are saying that the MAF readings are out of range.

P0110 says IAT issue. Early years had an IAT, and newer ones don't.

If you don't have a separate IAT, then it's pointing (because you swapped the MAF) to a wiring issue.

Mark

 

The only reason why those codes exist is because I unplugged the sensor. There was no codes at all before I unplugged it weather it was the new or old sensor. That’s why I wasn’t sure if the codes would be useful.

 

Ahhhhh! Got it!

Are there any NEW codes since you reset and cleared? FWIW, sometimes it takes a little while for an issue to meet preset conditions to trigger an error. Worse, sometimes you can have an issue and not throw a code, or it throws a code for SOMETHING in the same feedback loop, even if that something isn't necessarily the cause.

Mark

 

Could it maybe be a combination? I never got a CEL or code in the first place but maybe something else that has something to do with the MAF is bad? On that forum I linked at the top the guy did a bunch of stuff to his truck to fix this problem but it ended up being him replacing the distributor with a junkyard Denso one. First, why would the truck run fine with the MAF unplugged but then you replace the distributor and it runs fine??? Second I don’t think he replaced the MAF sensor at all. Third, I don’t have a distributor so how does it even compare? I’m so lost hence why I’m here begging for help.

 

Any members nearby you can swap a MAF with?

 

My neighbor has a very nice nearly exactly the same truck but in white I could ask him. Do you think that would prove anything?

 

Prove you have a good MAF and it's a free to check.

 

I did some research and found the IAT is within the MAF, and not anywhere else like I thought. I still think the sensor is fine and there is a problem elsewhere but I have no clue what to say or where to start. Just looking for someone to start throwing ideas out

 

How many miles on the motor?

 

Just hit 190k

 

There's also an ECU temp sensor at the back of the head near the firewall. Sometimes those cause issues with idle and stumble.

 

As se7enine said, the Enine Coolant Temperature Sensor is at the back of the head. It's used as one of the inputs for fuel/air trim. It's at the backside of the engine a little towards the passenger side.

I'm not saying this is the cause, or even an issue. You can test the sensor if you pull it. However, it's zero extra labor to swap in a new one at the point that you have the old one out for testing.

To get to it you have to unplug the sensor first, because the wire is really short, and moving the main harness could damage the connector. Next, take off the black ground wire to the firewall, and then release the clips holding down the wire harness and move it enough out of the way to get to the sensor. You can get a deep well socket on it with a couple extensions.

Mark

 

Yeah that coolant temp sensor at the back of the engine gets pretty toasty back there...

When I pulled mine out.....it was burnt badly.....PIA to get to.....

 

My brother had a 2.4L Tacoma years ago. When it reached 235k, he was chasing a misfire issue for many months. In the end, it turned out to be a bent valve so he had to get the motor rebuilt.

 

That was my issue as well but OP has already done a compression check and all are 165 psi or there abouts.

 

Regarding the coolant temperature sensor is this what you’re talking about? Do you really think it could cause some sort of problem like that?