Two issues on V-6; pinging under load with 91 octane and hesitating from idle (no load).

If my memory serves me correctly, when I was younger I had a car that had a carbureted engine that had a problem with the accelerator pump (which squirts pure gasoline down the venturis). It behaved the exact same way. You could bring the revs up slowly but it would hesitate badly when you stomped on it.

 

The accelerator pump has been taken over by the ECU which will open the injectors longer for a bigger spray of fuel when it detects a snap in the APP sensor. Go ahead and replace that MAF sensor and then rest the entire system. (Disconnect the battery for 30 seconds) This will allow you a faster learning curve for the ECU to recalibrate with the new MAF sensor. Then if the problem is still there, maybe you could take a short video of the gauge as it idles. I would like to watch the fluctuation in the O2 sensor as well as how the STFT and LTFT shift. Video is always better than snapshot. lol

 

I took some shots of the gauge this morning on my way to work, replacing the O2 #2 with the TPS. Steady-Eddie on the throttle, relatively flat freeway, close to 65 MPH. I'll do the idle ones (or a video) after I replace the MAF sensor.

These readings are about 2-3 seconds apart and they are in chronological order.

 

running way lean. this is weird. it's as though you have just an intake leak. either that or you're fuel starved (like having a clogged fuel filter )

 

I'm just looking at that lambda reading. According to that it's in a slightly rich condition, and trying to hold it there according to STFT.

Such a fun word to say.....Lamb-da..... Lamb-da

 

But not at idle, where the trim's at -18%.

 

I thought 1.000 was perfect? Average is darn close to that.

 

idle can be a little funny though. im not sure about the fuel trims while idling, or what im about to say. reason being, is mostly when your idling, it's right after turning on the vehicle. or it's warming up. during the warmup process, your engine runs hella rich until it's warmed up. the -18 at idle may just be from the learned warmup process.

 

Roger that. Without a reference, it's hard to know what's good and bad.

This is a good example of why you should get familiar with your numbers when your engine is running perfectly!

 

curious. what repairs have you done within the passed 3 years? i thought you posted the answer on the other thread you made but i didn't notice anything.

 

Posts 3 & 9 in this thread have that info. Nothing major though. Plus it's been a gradual decay in drivability... I would have totally noticed it if it happened the same day that the timing belt was changed or something like that.

I think the only non-scheduled maintenance/normal wear item repairs I've done on this truck are shocks and one coil. An O2 sensor was replaced in vain, so that doesn't count.

 

im giving myself a headache thinking about all this.... it may actually not be so much an air leak intake issue as it is either a bad rear o2 or inefficient catalytic converter.

so if im understanding fuel trims correctly, your computer is trying to keep your engine running as close to lambda 1, over stoichiometry, as possible. in doing so, it has to run your setup with more fuel. your 02 sensor voltage being around 7 with fuel trims being around 18% verified that. all this just to stay at/near lambda 1.

it may be just want I mentioned. either a bad rear o2 sensor (less likely in this case), or bad catalytic converter (more likely in this case). am i wrong?

 

and if it were an intake leak, the fuel trims would say +19% or so, but the o2 or A/F sensor would be around .45 and not .7 since it's running just fine while lambda is at 1....

 

I thought I read that the rear O2 sensor was all about measuring the efficiency of the catalytic converter. A code / CEL would indicate either a malfunctioning rear O2 sensor or catalytic converter. But failure of either one of those two items would not impact how's the ECM sets the air fuel mixture since the front O2 / air/fuel sensor already has that figured out.

I guess that at some point the catalytic converter could get so bad/clogged that it would impact performance, but I thought it was more about making sure that the emissions are in check.

If my presumptions are correct, disconnecting the rear O2 sensor would throw a CEL but not impact anything else. But as they say, when you presume, you make a prez out of you and me.

 

Mostly correct.

Might want to read this, they say the author is a total stud.

https://www.tacomaworld.com/threads/addressing-some-common-misnomers-of-the-p0420-code.396763/

 

Good info.

By the way, that guy's avatar bears a striking resemblance to yours. Another 'schvinger', I see. Toit like a toiger.

 

Hmm. lets say im wrong. Your o2 sensor still shows that youre getting too much fuel by showing around .7 volts. But your trims are saying they have to compensate by adding 14-18% fuel to achieve 14.7:1, and it thinks it's achieving it. But still reports .7~volts (rich). And all this while reporting perfect efficiency from the catalytic converter.thats what seems so weird to me.

Have you tried just clearing the fault codes/dtcs? maybe theres a glitch in the fuel trim matrix, and it needs to be cleared and relearned. Couldnt hurt i suppose.

 

Now I'm getting confused. I thought that the lambda O2 sensor at almost exactly 1.000 meant that the mixture was perfect. Not too rich, not to lean. The fuel trim adjustment is making it perfect.

The .7 V number is from the rear O2 sensor which measures catalytic converter efficiency more or less. Offhand I don't know what this number should be.

I haven't cleared codes because there aren't any codes. I have, however, disconnected the battery cable for several minutes. I did this after I cleaned the throttlebody just for the heck of it.

 

oh, the lambda (rear) sensor runs around 1v, with 1v being perfect. While the front o2 sensor runs around .45v where that value is also perfect. Above lambda 1v is lean, below 1v is rich. While on the front o2, above .45v is rich, and below is lean.