Tacoma 2.7l bucking and stumbling MAF sensor

It's not impossible.

 

I would carefully check all your vacuum lines.....alot of time if you rule out everything else...
leaks can be tricky.......mine has a pcv grommet that crumbles....massive leak there....

 

Truth!!! Not only can they be tricky, but sometimes show up in unexpected places.

Troubleshooting is differential diagnosis a lot of times. Eliminate what it cannot be, check what you can (what's left) and hope for the best.

Mark

 

If you're gonna put in a new MAF, get an OEM one. Aftermarket sensors are a gamble at best with these trucks and you might just be compounding the problem with one

 

So I’m going to replace the temp sensor at the back of the head and see what happens. All the vacuum lines appear to be clean and not dry rotted but you never know. I replaced the MAF with an oem part # Hitachi part so there should be no issue there.

 

Yes, hitachi is basically OEM. I have one on mines and it's been running well for 2 years... but maybe the computer is glitching? Try disconnecting the battery for 30 mins, and then running it again for a full restart. Also, check your upper o2 sensor to see if it's dirty or something (have you ever replaced it? if yes, how long ago?). How's your air filter (clean? well secured?)

This is an interesting problem because you've mentioned replacing the coil packs, MAF, distributor, and checking for vacuum leaks. These would normally be the most likely problem areas, especially with the codes you pulled on the scanner.

 

So I just did a whole bunch of cleaning on my truck and hope to improve this problem of which it didn’t change anything as far as I know. I took some pictures of things that I have no idea what they do and was wondering if anybody may know. I couldn’t clean the rear oxygen sensor since it’s impossible to get to but I did clean the front one of which were both replaced with OEM only about 100 miles ago. I did the same thing by running it with the new MAF sensor and it still did its bucking, then I unplugged and it ran great. Plugged it back in and did the same bucking thing *to note I took the same roads with it unplugged*. I have no idea what to even do now

 

If the truck runs better with the MAF unplugged then it's because the truck is running in "limp" mode.

Rom your photos:
1/2. Your throttle-body looks OK, but gunky around the edges. This could cause issues since the plate may not close properly.
3. The throttle position sensor looks like it's original, and normally won't cause issues as you describe
4. The EGR CAN cause bucking and misfires.

EGR could be a culprit, and would be my focus in your shoes. I removed it years ago, and have no idea how to troubleshoot one on a Tacoma.

Mark

 

Yes that and difficult cold starting.

 

Not too hijack but new to the forum and came here because I bought a full OME lift setup for my 98' 2.7 and wanted to read up....
Now, last couple days I've been getting hesitation after shifting into 2nd at the bottom to mid of the pull in that gear. Has me searching for the culprit and happy to see this thread....stopping on the way home today to pick up some MAF cleaner and have my codes pulled. Seems like a good place to start and will be watching this thread closely, thank you!!!

 

Not to take the spotlight but I started a thread and I'm having the same exact problem with my 98 2.7L with 233K. I've replaced the MAF, Crank, and Camshaft sensors, and the MAF connector. I've also checked the vacuum and is fine. Starts great cold, but after a minute it dies. I can restart it and it dies again. Repeats several times until I can get it to start and keep into the gas pedal. Once I start to accelerate is bucks and lags. You can hear the engine trying to spool up with more fuel but nothing happens. Once the engine is warmed up, my truck runs fine. Here and there, there is a slight buck but nothing big. If it's cold outside, like below 55 degrees, it won't have any problems. Once it's about 60 degrees or more, everything happens. Hope this sheds some like that others are in the same boat, Thanks!!

 

I pulled the codes on mine today....p0102 throttle position sensor. Was bucking worse than ever in low rpms 2nd and 3rd as I was running around town today. Local dealer didn't have a tps in stock so I bought from Napa along with some MAF cleaner. Went home pulled the MAF sensor and used a whole can up and yes it was filthy... took it for a run and was still doing it mabey not as bad and went back down and bought another can cause I could still see some caked on the elements on the MAF sensor, while I was there bought 4 new iridium plugs and a can of TB cleaner.
Got home and spent more time on MAF with assistance of a very soft model paint brush and got it completely clean. Pulled plugs and replaced, old plugs looked nice color but all gapped at .043" and gapped new at 032". Decided not to install the napa TPS but hold out for oem if I need it and took it out on another run.
There it issssss...runs smooth once again no matter rpm range even if I try to lug it. I'll still pull the TB and give it a good cleaning when I have time. Also it had a K&N in it, shitcanned it for an oem dry air filter. Thanks for all the info on these pages!

 

Yeah those oiled filters are notorious for gumming up MAF sensors over time. The dry paper ones are definitely best

 

I’m getting misfires on my ‘02 2.7, need to check the codes again.

what’s the scoop on the iridium plugs?

just checked, P302. misfire cylinder 2.

 

I wouldn't use iridium plugs unless you're boosted. Theres no advantage other than a longer changing interval.

This is a good thread on spark plugs

https://www.tacomaworld.com/threads/the-truth-about-spark-plugs.152726/

 

Dang, I’d say that pretty much sums it up.

 

Tacosaucetoyoyo, did you ever figure out the problem?

 

So your saying that changing the spark plug gap from .43 to .32 fixed your bucking issue when accelerating?

 

The moral of the story is that even the iridium plugs need to be checked every so often...

They can last a really long time....however if that tip/whisker erodes, it does so very quickly past a certain point...

So in my book, any of these, I would swap and inspect every 30K or so....

You really want to see whats going on in your engine anyways....

See if its oily, or running white hot....


Save money by drinking water with your lunch.....not here....

There's a video out there where this guys double tip TT iridium plugs burnt up just past 50K........




A bad engine ground will cause pre-mature plug wear.....burns the tips up.....