Riddle Me This: Truck Won't Hold Idle

Greetings TacomaWorld friends . . . here's my issue: About a month ago, my '00 Tacoma (4x4, v6, 320k miles) threw the dreaded p0171 code. After some TW research, I pulled and cleaned the MAF with a can of choke cleaner, which was straightforward enough. 50 miles or so later, the Check Engine light went off ('wow, I actually fixed something for $5 and 30 minutes of my time!? that never happens') so I figured everything was back to normal. Fast forward about a week or so and I began to experience an issue where my truck won't hold idle when started. By this, I mean that as soon as the engine starts, the idle jumps to 1200rpms for about 2 seconds, quickly drops to zero then stalls out. If I feather the throttle as I get the truck going into 1st gear, it's ok. If I give the throttle a nice push in neutral (revving up to about 3500rpms), it seems to get whatever the issue is worked out as well. At present, this occurs roughly 50% of the time that I start the truck. So what I'm wondering here is, do I go the obvious route of replacing the MAF since that's what was most recently worked on, or do I chalk that up as coincidence and look elsewhere first? Curious if anyone with a v6 first gen has experienced this issue and what it was.

A bit of extra info that may or may not be relevant: since March I have been working as a hired hand on a remote property (2 hrs of 4x4-only to the nearest highway, another hour to the mechanic/parts store). I don't make the drive to town often, and when I do, I don't do it again for a few weeks. My job has me driving around the property about 5 miles per day, but it's mellow driving, so I wouldn't say that I've been thrashing on the truck too much lately. I can get by with the funky idle issue while out here, but my concern is that the issue might be progressive so I'd like to at least get an idea of what I'm dealing with so I can either buy parts or organize an overnight trip so the mechanic can do their thing with it.

All ideas welcome (unless you want to tell me to kick rocks and use the search function on this site ) Thanks all. -- Cass

 

Well first I would check the codes usually when it acts up it should store something (even before the check engine light comes on) now I know some MAF will be sensitive either because of type and sometimes age, so its critical to only use the actual MAF cleaner. But before changing it make sure the IAC(idle air control) valve is working (it should be under the throttle body green head with a plug) if you can get the truck to start and somewhat idle and you take a screwdriver and tap on It and see if the idle changes then it may be your problem you can get away with cleaning the valve and cleaning the port on the throttle body

 

Should only use MAF cleaner on the MAF sensor, good chance you may need a new sensor now.

Is the P0171 code back? I had an issue with that code on my last Tacoma where it wouldn't idle at stop signs and stall out, ended up the MAF sensor was bad and needed a new one.

If you go that route, make sure to get an OEM/Denso one...there are a few cheap aftermarket options but Toyotas don't take well to aftermarket sensors.

 

Another big cause of a P0171 code is a vacuum leak, would probably be a substantial one if it's causing the truck to stall but I'd check that first before committing to a new sensor

 

I am suspecting that the air boot between the MAF and the throttle body has a slight tear in it. The rubber gets old and brittle and I am thinking the extra vibration has cracked it. It takes maybe 3 minutes to take it off completely and then you can flex it around and see if there is a crack.

 

https://www.obd-codes.com/p0171

A code P0171 may mean that one or more of the following has happened:

• The MAF (Mass Air Flow) Sensor is dirty or faulty Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
• There could be a vacuum leak downstream of the MAF sensor
• Possible cracked vacuum or PCV line/connection
• Faulty or stuck open PCV valve
• Failed or faulty oxygen sensor (bank 1, sensor 1)
• Sticking/plugged or failed fuel injector
• Low fuel pressure (possible plugged/dirty fuel filter!)
• Exhaust leak between engine and first oxygen sensor

 

I just had this on Saturday. weird thing too. replaced CV, ITRE and never touched anything else. on test drive, couldn't keep idle.

limped it home from uncle's (mechanic) and let it sit overnight. started it on Sunday afternoon and fired up and held about 700 for a few, then 450 idle after 5 mins.

pulled EFI, cleaned TB and MAF. held a little above 500 so I just "cracked" the TPS and idle jumped to 700. secured it back tight and still runs fine today, go figure

of course mine is the electronic TB. you may have to adjust your idle pots? did you remove and clean the IAC valve?

 

I just dealt with it for a few months until I had a chance to take apart and clean the TB and IAC, which I did yesterday. Hopefully that fixes it, but if not, the TPS is my next target for inspection. How is your truck running now? Still going strong w/o the start up issue after loosening and retightening the TPS?

Also, by idle pots do you mean dashpot? Bc I noticed the cap on my dashpot is compromised and have another thread going to figure out if I need to replace.

 

other than my up/down idle, yeah no stalls