Hesitation from Stop

[4runnerWiniarski23]

Hi guys,

So I’ve been slowly piecing together my exhaust with new parts back to front (rusted NY truck). I have a rusted thru hole on my secondary cat section, near the front flange. It’s a tough spot to try to patch or weld because it’s right on the flange seam. I am convinced that this leak has been my issue with the P0420 code that I’ve been driving with for months, tried cleaning maf, new rear 02 sensor.

I recently welded the hole as best I could and it seems to be holding really well. I reset my CEL and been driving for a few days trying to get my evap and cat readinesss complete. I only have a 8-10 mile drive into work on back roads so not much highway time to help with this. I have noticed one huge difference since clearing my CEL. My truck has a hesitation now coming from a stop, say at a light. It’s really weird because i never had it driving around with my CEL light on. Just to confirm i wasn’t crazy I unplugged my rear 02 started the truck to trigger the light and sure enough hesitation is gone.

I’m looking for some clues on where to start. Throttle body? Fuel filter? I just don’t see how the CEL is related to either of those. ABS sensor? Something with the teacher/vsc maybe?(grasping at straws here)

Thanks in advance for any input,

Al



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[4runnerWiniarski23]

Hi guys,

So I’ve been slowly piecing together my exhaust with new parts back to front (rusted NY truck). I have a rusted thru hole on my secondary cat section, near the front flange. It’s a tough spot to try to patch or weld because it’s right on the flange seam. I am convinced that this leak has been my issue with the P0420 code that I’ve been driving with for months, tried cleaning maf, new rear 02 sensor.

I recently welded the hole as best I could and it seems to be holding really well. I reset my CEL and been driving for a few days trying to get my evap and cat readinesss complete. I only have a 8-10 mile drive into work on back roads so not much highway time to help with this. I have noticed one huge difference since clearing my CEL. My truck has a hesitation now coming from a stop, say at a light. It’s really weird because i never had it driving around with my CEL light on. Just to confirm i wasn’t crazy I unplugged my rear 02 started the truck to trigger the light and sure enough hesitation is gone.

I’m looking for some clues on where to start. Throttle body? Fuel filter? I just don’t see how the CEL is related to either of those. ABS sensor? Something with the teacher/vsc maybe?(grasping at straws here)

Thanks in advance for any input,

Al



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Bump!! Anyone got anything


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[kolelt]

You could try and cleaning your mass air flow sensor.

 

[99problems]

Did you clear the CEL by resetting the computer by disconnecting the battery, or by clearing the code with a scan tool? If you cleared it with a scan tool, my thought is that the computer has a pretty slow adaptive learning curve and may be having to adapt itself from whatever it was doing to compensate for your exhaust leak. This issue may just work itself out in a few days time if that's the case.

 

[4runnerWiniarski23]

Did you clear the CEL by resetting the computer by disconnecting the battery, or by clearing the code with a scan tool? If you cleared it with a scan tool, my thought is that the computer has a pretty slow adaptive learning curve and may be having to adapt itself from whatever it was doing to compensate for your exhaust leak. This issue may just work itself out in a few days time if that's the case.

So I did clear the code with my scan tool.
Are you referencing that the truck will relearn my driving style, I think it only does that when you disconnect the battery.

I have to dig into this some more because I believe I do get a traction light in the morning when the truck is cold. (Possible abs sensor st the wheel busted or loose?)

I cannot think of any other reason why clearing the CEl would attribute to my hesitation other than when the VSC/TRAC light is on (CEL) the traction control is off and if the sensor is bad i wouldn’t have known.


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[99problems]

So I did clear the code with my scan tool.
Are you referencing that the truck will relearn my driving style, I think it only does that when you disconnect the battery.

I have to dig into this some more because I believe I do get a traction light in the morning when the truck is cold. (Possible abs sensor st the wheel busted or loose?)

I cannot think of any other reason why clearing the CEl would attribute to my hesitation other than when the VSC/TRAC light is on (CEL) the traction control is off and if the sensor is bad i wouldn’t have known.


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I was thinking that the condition in the computer software which triggered the CEL may have been caused by the exhaust after the software made attempts to correct the issue, and has not yet reset itself to what you would consider "factory normal". That is, if the ignition was attempting to change the air/fuel ratio to account for all the extra air it thinks is present by adding fuel, and then you take away the "extra air" you might be left with a very rich fuel mixture that hasn't been recalibrated yet by the computer. If you purposefully reset the computer I believe it will be forced to relearn the mixture from its base setting rather than adapt its currently stored setting.

 

[4runnerWiniarski23]

I was thinking that the condition in the computer software which triggered the CEL may have been caused by the exhaust after the software made attempts to correct the issue, and has not yet reset itself to what you would consider "factory normal". That is, if the ignition was attempting to change the air/fuel ratio to account for all the extra air it thinks is present by adding fuel, and then you take away the "extra air" you might be left with a very rich fuel mixture that hasn't been recalibrated yet by the computer. If you purposefully reset the computer I believe it will be forced to relearn the mixture from its base setting rather than adapt its currently stored setting.

Now I am following what you meant. It's been almost a week driving just to and from work, haven't been able to get readiness on evap or cat yet but hesitation feeling a little better. I'll give it the weekend to see if it goes away or I'll force reset by disconnecting the battery.


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[whyzee125]

You have a clogged cat / cats. With the hole, the exhaust gases had an easier exit but now that it must flow through all the way the restriction is more evident. Fairly common on these trucks as they pass the 200k mile mark.