I have a 2000 4runner 2.7, 232k miles

About 2 weeks ago, car stalled at a red light, so after researching the threads, it led me to clean the throttle body, IAC and MAF.

I removed the TB/IAC from the engine and used TB cleaner to thoughly clean the TB and IAC. I used MAF clear to clean the MAF.

I also noticed the air intake hose was in bad shape so I replaced that too. After putting everything back together and ensured everything was tight and properly assembled, I took it for a test drive and it ran like a champ!

Couple days later, Check engine pops up, OBD reader showing code P0171. I cleared it but keeps coming back, However it drives fine. This past Tuesday I drove it 4 hours to drop it off with my daughter. no problems the whole drive up. Today she calls me telling me car keeps dying. Can't drive it more than a few minutes before it dies.

Not sure what else to do. Was the cleaning not enough? Any other parts that may be a culprit? I don't know any mechanics in central California so, trying to figure out next best step.

When I had 0171, it was the MAF, I absolutely blasted it with cleaner (until the cleaner started dripping out) and it eventually started working. However, I also had a massive vac leak that I'm sure didn't help.

I'd check your hoses, worst case you need a new MAF. Thankfully the 99+ ones are easier to find (and cheaper) than the ones for the 96-98 are

That's what I would start with. Especially if you can see the rpm gauage twitching. As if the engine doesn't sense that rpm. It will not turn on the fuel pump.

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Of course with my luck the car has issues after I came back home. I'm gonna make the 4 hour drive back up to install the MAF.

Question though, part number on my MAF is 22250-75020,
However when I look that up, it's the entire assembly, MAF sensor with metal hose assembly.

I found another part that is the MAF sensor insert, part number made by Delphi AF10133 or can I use the MAF for the 3.4 engine Toyota part number 22204-21010.

Can I replace just the insert with the parts above or do I need to replace the entire assembly?

Double and triple check your vacuum hose routing and tightness. Getting a P0171 after doing recent work on the engine is almost always, as close to always as could be, a mistake with routing or putting the hoses back on. Not saying you did a bad job at all, just reflecting on my own work over the years as well as helping others track down this code as well. Especially with superchargers installed.

I'll double check the vacuum hoses, but I should say I was already getting the P0171 error code before i took it apart to clean everything out. The error code is what prompted me to clean out the system hoping it would fix it.

Does anyone know...

My MAF part number is 22250-75020, However when I look that up, it's the entire assembly, MAF sensor with intake tube, priced at around $800+

I found another part that is the MAF sensor insert, part number made by Delphi AF10133 for about $76 does anyone know if I can use the MAF for the 3.4 engine Toyota part number 22204-21010? About $100.

Pretty big price different, if anyone knows would be super helpful.

How is the throttle position sensor??
Spray water via a spray bottle on vacuum hoses and joints and also to the rubber grommet placed between the injectors and cylinder head. If you see any drop in RPM, at any of these test, there is a vacuum leak.

Check whether the pins inside the MAF are straight (not bent) and tightness (grasping on the male pins) on the connector end.

my son, what seems to be a similar if not exact problem in his 1999 4runner 3.4L. Problem was it was never throwing any codes. Finally, after trying to fix the problem a few different ways, one being replacing the throttle position sensor, which didn't work...the car finally threw a code. Forgive me, I don't remember the code but it indicated a potential problem with the air/fuel sensor. Replaced that, fixed the problem and hasn't occurred since.

Its been a few months, but here is the latest update:

Replaced the MAF and the air/fuel sensor and the car ran much better but only a couple of days. After a complete diagnostic, it has low compression on cylinder 1. Not what I wanted to hear.

Cyl 1 - 120psi
Cyl 2 - 170psi
Cyl 3 - 160psi
Cyl 4 - 175psi

Registration is due in a few weeks and it wont pass smog until this has been fixed.

Any help/suggestion on next steps are greatly appreciated.

120psi on cyl 1 will make it run a bit rough, but it shouldn't stop the engine from running and shouldn't make it die. With a 2000 model year or newer, you don't need to pass tailpipe, just visual and OBD-II checks - so that should be your goal at this point.

Do you have any way of viewing/logging fuel trims? It might be a clue to check whether trims are off everywhere, near idle, under load, etc.

-Charlie

I was down to 90 PSI in a cylinder and mine never died. Loss of compression doesn't mean loss of engine function, just power as it doesn't push the crankshaft as forcefully and equally as the other pistons. Although you found an issue, it's not the issue, if that makes sense.

I replaced my IAC valve chasing a stall at idle that made it almost undriveable and it improved it but ultimately it was the TPS that failed with no code. You still have the P0171 code though or did that change? In case you are thinking it, 120 PSI does not trigger a P0171. You'd have to have a hole in your intake valves in order to get a lean code and near 0 PSI.