Bucking when accelerating, surge at idle.

When the 02 sensor on my 2001 AT acted up, the check engine light would come on and the truck wouldn't always restart after a warmed engine shutdown. Resetting the ecu would clear the code and check engine light but it would return once engine warmed up.
You can try soaking it in gas overnight and cleaning it. I put a new sensor on and problem persisted. I'm think the cat was plugged but I traded it off before I could find out.

 

I would still check the cat to see if its plugged.

The correct way is to use a vacume gauge. But if it's severe enough you might be able to tell by starting the truck put your hand by the tail pipe and have somebody rev the engine to about 2500 rpm, let off and repeat. should be able to tell a big difference if it's clogged or not.

 

I would try gapping your spark plugs to like 0.25 and see if the problem goes away

...after you try all the other things that is

 

So just to give a reference for what I'm looking at, both cats appear to be new as well as the O2 sensor (afr sensor whatever you want to call it) one bolt on the upstream O2 sensor is partially stripped from whoever installed it. And the sensor appears to have no brand markings on it.

 

Yeah your exhaust is definitely leaking, if there’s only one stud that’s torqued down on that sensor. That bubble gum weld looks sketchy too.
The AFR sensor is probably reading lean as hell due to the leak, and the ECU is adding unnecessary fuel to compensate.

 

You should be able to double nut that and still get a bite...
get the high temp thread lock and lock the two nuts together...

You could also back that stud out a little.

Then I'd clean that weld up with some jb weld.


And yep....toyota ecm's like all the sensors to be toyota oem, so worth the extra investment....for sure.

 

I think your right, I was able to get the stud with the striped bolt off and flip it around and resecure it that way until I can replace it. But I'm now thinking I may have other exhaust leaks around these shady welds.

 

UPDATE:
So I went to the auto parts store and dished out a good chunk of change for a denso o2 sensor. Disconnected the negative battery terminal and removed the old one which was not torqued down all the way. Installed the new one properly and hooked the battery back up.
Went for a quick 5 mile drive and so far no issues.

Although I'm not 100% that is solely due to the new o2 sensor. Wouldn't disconnecting the battery make the truck relearn all the fuel trims and stuff anyways causing it to drive normally for a bit?
I will update tomorrow when I have time to drive longer.

 

I will definitely be looking over the full exhaust now and trying to find any leaks. I think I am detecting a somewhat sweet smell coming from under the truck when at idle so must be another leak somewhere.

 

Your exhaust looks almost new....and you dont have the dreaded cast iron headers.

Win win there.....

 

The entire exhaust is new, I was mainly referring to the weld points as they look suspect.

 

Ya. Came back to say even a small pinhole can throw that sensor off.
Likewise a bad mounting.

Get someone on the throttle and you should hear any leaks.

 

UPDATE:
So just when I was thinking the problem was solved a whole new set of problems popped up.
May have to make a new thread to discuss this but we'll see.

CEL: P0420, P0440, P0441, P0446
all popped up at the same time after the new o2 sensor was put on.
I've been doing nothing but reading forums and troubleshooting for the past week, now this. Seems pretty daunting but that's where I'm at.

 

My first thought is that the O2 sensor isnt deep enough into the exhaust stream, that will cause problems. I couldn't find a decent picture of a factory front pipe to do a comparison.

 

So just to update Incase anyone else is trying to diagnose a similar issue, replacing the upstream O2 sensor (air to fuel ratio sensor) has so far fixed the "bucking when accelerating" issue. Air to fuel ratio is now sitting right around 14.7 as it should and fuel trims look more normal. Yes I now have a bunch of other issues but I think I'll address that separately in another thread.

 

I also have the p0440 code, and have some "sweet smells" at idle. When accelerating (particularly in 3rd gear), the truck does hesitate in the 2-3k rpm range. When i bought the truck the dude did tell me it had an exhaust leak, and upon my inspection had suspect connections to what appeared to be new o2 sensors along the exhaust system. I used JB weld and my local mechanic straightened out a fuel leak (which i could've done on my own in hindsight after hearing the problem was a loose connection), and my CEL cleared and I passed PA emissions. However, a week later my truck began throwing this code again and some of the JB weld fell off at the cat and muffler. I have also noticed a bad gasket around the fuel pump. Right now I'm thiking ill try to patch the exhaust 1st (as this is the easiest remedy), then if the CEL stays on a while longer pull the bed and replace gasket. Just figured ide tell my story as I have 1 code and at least 1 symptom in common.

 

Have you checked that your throttle position sensor is securely connected? That could cause lurching. Experienced it a few times. Comes loose over time. Make sure that connection is snug.

 

So I think the new o2 sensor fixed the bucking issue. However I also have 3 evap codes p0441 p0440 p0446 which I assumed to be the charcoal canister above the fuel tank but I had the dealership smoke test the evap system and they said that the gas tank needs to be replaced, has a bunch of pin holes on top and also the filler neck. So maybe that's the cause of the codes.

 

Gas tank time. Cool.

 

Did they show you a video or picture or the leaks? It is the stealership that your at. Lol. I doubt your fuel tank has pin holes.

On top of the fuel tank there's rubber grommet that seals the fuel tank vent, when mines was leaking I kept smelling fuel after a long drive.

This is where mines was leaking from.