Random hesitation when accelerating

[Skibber]

I have been experiencing random hesitation / loss of acceleration in my 01 V6 when taking off from a stop. It sometimes happens in a straight line, but seems to happen more when turning. It almost seems similar to the VSC or Trac electronically cutting the throttle out, but there is no light indication or sounds that it is active. It's like there is no response when I'm on the gas or pumping it. After a short time it seems to comeback and starts gradually accelerating back to normal.

I have searched several posts and can't seem to find a definitive cause or solution. OBD throws no codes and the log is clear. Throttle cable doesn't seem to bind or stick and has little to no slack. I have changed the plugs and wires, but it still persists. I have a new fuel filter, but have not changed it yet as it doesn't really seem to be a lack of fuel flow causing the issue. I am also thinking about the AndyMod 2.0 to disable the VSC and Trac to see if that has any affect. I have noticed in 4WD/AWD that the trac does randomly come on briefly from a standing start even when I am not spinning the wheels.

Sensors at the wheels? Zero point calibration? Any thoughts?

 

[ThorInc]

Throttle Position Sensor?

 

[Skibber]

Throttle Position Sensor?

Figured I would get a P0120 or a CEL if it were a TPS issue. I will check the widget in the Torque app to see if there are any issues though.

 

[bike]

Curious what your min and max readings off your TPS are. I'm starting to get a hesitation as well on my truck.

Edit: My TPS reads 11% at closed and 73% at wide open. Only curious because I changed swapped it with a cheap Napa one at some point.

 

[octanejunkie]

If you are using Torque, what do the following values show when you are having an episode of lag:

-RPM
-MAF airflow
-Fuel trims, ST and LT
-timing
-engine effort
-coolant temp (for grins and giggles)​

Then compare the same values at the same RPM/effort when NOT experiencing this issue

Also when is the last time you cleaned/changed MAF and air filter, respectively, and how fresh are your plugs?

 

[Skibber]

If you are using Torque, what do the following values show when you are having an episode of lag:

-RPM
-MAF airflow
-Fuel trims, ST and LT
-timing
-engine effort
-coolant temp (for grins and giggles)​

Then compare the same values at the same RPM/effort when NOT experiencing this issue

Also when is the last time you cleaned/changed MAF and air filter, respectively, and how fresh are your plugs?

I will check the values during the next drive. I cleaned the MAF and installed new plugs and wires just a few months ago due to this issue. I also put on a K&N CAI that I had from my Tacoma (direct fit same part number for each vehicle) as well.

I experienced the same issue at about the same frequency before the work as well.

 

[octanejunkie]

No codes?

What plugs you running?

 

[ThorInc]

Figured I would get a P0120 or a CEL if it were a TPS issue. I will check the widget in the Torque app to see if there are any issues though.

My TPS never threw a code until a couple of years into hesitation issues, started noticing it while towing when cresting hills, etc. There was (?) a seller on this site selling Toyota OEM TPSs for less than $30 shipped a while back, 10 min install and MY issues totally solved(note the my ).

 

[Skibber]

no codes?

What plugs you running?

ngk (3967) bkr5ekb-11

 

[Skibber]

My TPS never threw a code until a couple of years into hesitation issues, started noticing it while towing when cresting hills, etc. There was (?) a seller on this site selling Toyota OEM TPSs for less than $30 shipped a while back, 10 min install and MY issues totally solved(note the my ).

I don't get the hesitation when I'm moving though...only from a standing or slow rolling start.

 

[19963.4lsr5]

I don't get the hesitation when I'm moving though...only from a standing or slow rolling start.

So pulling out and rolling on the throttle to get up to speed you have the hesitation? Or mashing the pedal to beat the turbo subie beside you?


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[Skibber]

So pulling out and rolling on the throttle to get up to speed you have the hesitation? Or mashing the pedal to beat the turbo subie beside you?


Sent from my iPhone using Tapatalk

Rolling on the throttle. It's like there's nothing thru the range of the pedal for a few seconds, then it gradually starts to accelerate back to normal. During this time that the throttle is "cut out", I can pump the gas pedal and not get any response. It doesn't really happen all that often, but it could be pretty dangerous if I tried to turn left thru a gap in traffic at an intersection and it happened.

 

[19963.4lsr5]

Rolling on the throttle. It's like there's nothing thru the range of the pedal for a few seconds, then it gradually starts to accelerate back to normal. During this time that the throttle is "cut out", I can pump the gas pedal and not get any response. It doesn't really happen all that often, but it could be pretty dangerous if I tried to turn left thru a gap in traffic at an intersection and it happened.

Pumping the pedal does nothing on a fuel injected engine.

Do you have a scanner that reads live data?

Do you have a friend with a 4Runner?


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[Skibber]

Pumping the pedal does nothing on a fuel injected engine.

Do you have a scanner that reads live data?

Do you have a friend with a 4Runner?


Sent from my iPhone using Tapatalk

I have a BT adapter and the Torque app to read/capture live data. I set up some graphing widgets per octanejunkie's suggestion in a previous post. So far the values look OK when idling, revving in park, and driving. The short term fuel trim seems to vary quite a bit and produces a choppy graph, but the long term trim seems very stable. I plan to export the log after it happens a couple times to see if there is anything that might point to the problem.

Note that if I "pump the pedal" when this issue is not happening, I experience the engine revs that relate to each press of the pedal....not so much when it is happening though.

 

[jgue467]

...

Note that if I "pump the pedal" when this issue is not happening, I experience the engine revs that relate to each press of the pedal....not so much when it is happening though.

Have you checked the trailer hitch wiring?

Mine had a touch of a miss only when throttling and using my blinkers for lane changes.

Discovered the trailer hitch had a short in it that would send a signal to the ECU when I used the blinkers. The short was between the blinkers and the stop lights, so the ECU thought I was braking while throttling up so it tries to cut power, ever so slightly yet enough to notice. Just a thought. Luck. :cowboy:

 

[Skibber]

Have you checked the trailer hitch wiring?

I haven't had the chance to get in a warm garage to troubleshoot any wiring yet. I have noticed that this problem is even worse when in 4wd though. Even though the wheels aren't spinning, the slip indicator lamp comes on almost every time from a standing start.

I can seemingly 'trick it" into not triggering if I hold the brake pedal lightly while accelerating...almost like feathering out the clutch on a manual trans. If I do this for about the first 5-10ft of the take off, then the throttle response is normal and the slip indicator does not activate.

I did a VSC calibration per Mike Thompson's blog but the problem persists. I am also planning the Andy Mod 2 with the Trac Off switch per MStudt's post to see if that can eliminate any electrical or sensor issues causing the problem.

 

[sugjavier]

I haven't had the chance to get in a warm garage to troubleshoot any wiring yet. I have noticed that this problem is even worse when in 4wd though. Even though the wheels aren't spinning, the slip indicator lamp comes on almost every time from a standing start.

I can seemingly 'trick it" into not triggering if I hold the brake pedal lightly while accelerating...almost like feathering out the clutch on a manual trans. If I do this for about the first 5-10ft of the take off, then the throttle response is normal and the slip indicator does not activate.

I did a VSC calibration per Mike Thompson's blog but the problem persists. I am also planning the Andy Mod 2 with the Trac Off switch per MStudt's post to see if that can eliminate any electrical or sensor issues causing the problem.

So I have the exact same issue and did the VSC Calibration as well and didn't seem like it helped much.

I do love the trick you stated and can confirm that works for me, just tap the brakes real quick and I'm on my way again.

I will actually try to schedule a visit to the dealership and just pay whatever the diagnose fee is to see what the root cause of the problem is.
Then I can just buy the part and either install it myself or pay my mechanic a lot less to do it for me

I'll update you guys of my findings!

 

[Skibber]

Note that the Andy Mod 2 is a verified work around for this issue as well. I believe this might be due to a bad/dirty TRAC sensor since disabling the system eliminates the issue.

 

[Myjar89]

Having hesitation while pressing gas, typically around 20 mph. Rough idle when starting. Replaced plugs, wires and a coil. My 01 4Runner ran great for a day, now it’s back to these symptoms. Ideas?

 

[Jidaran]

[MENTION=146626]Skibber[/MENTION] - did you ever resolve the issue? I'm having the same exact symptoms.

The TRAC issue (TRAC engages when accelerating from a full stop, but only while in 4wd) has been going on for about a year. I've cleaned the ABS sensors, done a VSC calibration... no dice. But I have the Andy Mod 2.0, so that's functioned well as a work around and I've learned to live with it.

On the way out of town this past weekend, throttle cut twice on hard turns from a stop, just as you described earlier. It hasn't repeated since.

On a possibly related note, my 4WD started acting up this weekend as well, it seemed reluctant to engage, also the dash indicator wasn't showing the actual state (indicating 2wd when it was in 4wd) and once it threw itself into 4wd with locked center diff while I was driving around 30 mph. I spent the rest of the weekend in unlocked 4WD (multimode) - I needed it to get up my friend's driveway and since the system was acting up, I thought it best to engage / disengage as little as possible. Drove home 6 hrs with no issues. Used the Andy Mod button each time I started the car to avoid the TRAC issue. Not sure if the use of the Andy Mod temporarily resolved the cut throttle issue over the past few days. I just put it back in 2WD today, no issues so far (but I've only done about 30 minutes of driving).

One more random thing - in 4-Lo (unlocked), I'm getting the TRAC shuddering hesitation *even after TRAC has been deactivated via the Andy Mod*. That's never happened before.

I did a visual check on the vacuum hoses and couldn't find anything amiss. Didn't have time to look into it more. Usually I'd do more trouble shooting before posting, but I'm about to head out on a week long road trip.