Argh...P0171 code!!!!

TegoXR

TegoXR

New member
I've been trying to get rid of the dreaded P0171 and P0171P code, replaced both sensors on the exhaust, I've cleaned the MAF and no luck! Could it be the MAF sensor? Where can I get MAF sensor for a good price? It does have 136k on it. Any input would be greatly appreciated.
 
I don't even know where to begin with checking the vacuum leaks, and I'm mechanically inclined. Should I take it to my mechanic?
 
Use an unlit propane torch. Start the 4runner up and when you blow the propane on the leak the engine note will change. I've used this method with success on old motorcycles for years.
 
Personal experience with a friends 99... had the P0170, did everything I could imagine to fix it... turned out that we needed to buy a new MAF and it fixed it. The newer style MAF (I think changed in 99), isn't quite as durable as the older ones.

Check FSM for testing procedures for MAF...but you might have to buy a new one. Toyotapartsales.com is my favorite for buying OEM Toyota parts.
 
Hate to sound like a noob but I wouldn't even know where to begin to look with the propane torch.
 
So I might've found the issue with the code, the bracket holding my aftermarket intake broke right off and left a hole about an inch big. Unfortunately there's a hole in my stock air intake box as well when I purchased the truck.
 
You can bench test the MAF with a multimeter to see if its still within specs before you buy a new one. Last time I had a P0171 code it was the MAF and I had to buy a new one. Make sure you clean it with MAF cleaner too.
 
P0171, code has me scratching my head

My truck is throwing 0171 code, once it is warmed up. Once it goes to idle AFR climbs to 17, 18, 19 then off the scales and trips the CEL. Sprayed throttle body cleaner all over intake, 7 injector, meth injector, pcv etc nothing
Cleaned MAF, nothing
Replaced MAF with one that is known to work. No difference.

Seems like most people report P0171 issue under load, mine only happens at idle. If I put the truck into nuetral and give it some gas the AFR goes back to 14.6 range.

Going to try a DIY smoke test to see if I can find a vacuum leak.
Any other ideas? Truck is due for smog and need to fix this before I can smog it.
thanks Josh
 
bikerjosh said:
Seems like most people report P0171 issue under load, mine only happens at idle. If I put the truck into nuetral and give it some gas the AFR goes back to 14.6 range.
Click to expand...

Josh,

I would almost guarantee yours is a vacuum leak... It's EXACTLY like mine was. Generally I am skeptical when people tell me they have the same problem- yours matches mine to the t.

Let me know how that smoke test goes, it's an interesting idea. Did you check your TB gasket? I've heard that's a common leak source. Start at the intake, and work your way deeper into the intake manifold, etc.

Hope you get it figured out man... I chased mine for months.

Alex
 
A.Wilson013 said:
Josh,

I would almost guarantee yours is a vacuum leak... It's EXACTLY like mine was. Generally I am skeptical when people tell me they have the same problem- yours matches mine to the t.

Let me know how that smoke test goes, it's an interesting idea. Did you check your TB gasket? I've heard that's a common leak source. Start at the intake, and work your way deeper into the intake manifold, etc.

Hope you get it figured out man... I chased mine for months.

Alex
Click to expand...

Alex, what method did you use to find your vacuum leak?
thanks
 
bikerjosh said:
Alex, what method did you use to find your vacuum leak?
thanks
Click to expand...

Is luck a method?

I was tightening something... Throttle cable I think? And noticed a strange noise when I passed my hand over the supercharger. I could wave my hand back on forth and hear a change in the sound. I traced all the seams with my finger and found where it was whistling when my finger would pass over it.

Good luck man... I had given up when I found mine, haha.
 
I am having the same code pop up, but only when I stop at idle!! Just put on the supercharger without any fuel mods so I know it's running lean. I've got a 5 speed so it's easy to drive around the very little pinging that can occur and I've been babying it until I put the 7th in. All vacuum hoses are good but I do have quite a bit of air coming from the L shaped piece of the supercharger on the bypass valve. Could this be the reason the code is popping up at idle? Any suggestions on getting a better seal on that thing??
 
found the vaccum leak

Think I solved it. While prepping the vehicle to do my own DIY smoke test, checking all the hoses again found a crack in the underside of one of the vacuum lines going to the SC. From the top of the car everything looked fine. Just need to disconnect the meth injection, hide a few things in the engine compartment and try and smog it.
Thanks to A.Wilson and the other members for the suggestions.:phone:
 
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