Truck lunging forward

Hey guys, whenever I stop and sit for a bit with my foot on the brake, the truck sometimes jumps forward as though someone rear ended me. I've gotten so much crazy advise. I've had the driveshaft balanced, transmission changed, brakes done, driveshaft completely rebuilt and balanced again, and it still does it. I'm so frustrated with this problem and can't afford to keep spending money like this. please help....

Also, exactly how many catalytic converters are there in a 2006 tacoma pre runner?

 

Stop spending. You’re gonna hate the answer.

The lunge is when the A/C compressor clutch kicks in and the engine revs to about 750rpm. Push the A/C button on the HVAC controls to shut off the light…no more lunge.

And, there is 4 cats on the V6 and 2 on the I4.

Oh, and welcome to TW.

 

Also, if you have defrost on, the AC runs.
And the light won’t be in. So it will do it in defrost too.

FWIW, mine does it too.
Always has, it’s normal.

 

You need to fire your mechanic for doing all the work to try and fix that problem. All the items you mentioned that were fixed would never cause a truck to lunge forward.

Mine does the lunge too. All v6 Tacomas do it. Just remember to keep a bit extra pressure on the brake pedal at stop lights.

 

Turd gen owner chiming in, yeah same here.

 

All V6 Tacomas do not do this. The only way mine would do this is if I was double footing it. Using one foot for braking and the other for the accelerator.

 

My 15 and 18 do it...

 

The slip yoke on the drive shaft binds from axle roll an then when it slips it feels like this truck lunges, there are a million threads about this issue. Grease it if you have a zerk , if not pop it off and drill it out for a grease zerk or just re grease it often.

 

Yikes, a quick search on this forum BEFORE doing all that crap would have been much easier and cheaper...

 

Maybe I'm confused here. Is he saying when he's stopped at a red light when he lets off the brake his truck surges or lunges forward? If so, I just drove home just now and tried this. My truck, an 08, didn't do anything like that. Maybe I need a tune up. Lol!
But I do grease every zirk I can find and have occasionally greased the drive shaft. Maybe that makes a difference?

 

Mine has never done it. Unless my foot slipped off the clutch in gear.

Score another one for the 6 speed!

 

No, he said - Stoped, foot on brake.

There’s been multiplayer posted on this subject.
And many with nearly the same description - “stopped, lunges, feel like rear ended”.

 

This is a new problem, and nothing I've ever experienced in my V6 Taco. Not understanding how the truck lunges while the brake is depressed...can someone explain?

My condolences OP if the AC is the issue when you spent all that money trying to find the fix

 

It should not lunge if the brake pedal is pushed hard enough.
The thing is, most people push the pedal just hard enough to keep the truck stopped.
I am/was guilty of this myself.

 

Ahhh got it. Maybe i've been doing a good enough job of keeping it depressed all this time lol

 

Does it happen more frequently or violently when you brake hard to a stop vs a more gentle deceleration?

And are you experiencing the truck actually lurching forward several inches after reaching a complete stop with your foot firmly on the brake (vs more of a shudder with no actual forward movement, which is how I’ve experienced the AC compressor kicking)?

If so, might want to look up “Axel Wrap”. I’m no mechanic, but roughly speaking it’s driveline angle related but caused by rear suspension. I had a ‘11 develop those symptoms (intermittently, but often quite violently in the event of a very hard stop) and replacing some seriously abused rear leafs took care of it.

 

Any chance that might have something to do with the torque converter?
Edit: Yeah, I know, grasping at straws, but still...

 

Completely normal. Usual cause is the idle, to meet mpg regulations, is low and when the AC compressor kicks in, the idle jumps so it doesn't stall and thus the surge. Sometimes it's more noticeable than other times.

 

No, highly unlikely.

 

We bought our trucklet new in 2005. It has always had the 'lunge when stopped', though it doesn't do it every time. I never bothered to track it down but I suspect it's the compressor engaging, just like several of you have posted. I hardly notice it anymore, but it sure was disconcerting at first. For the record, I hit all the driveshaft zerks at every 5K oil change.... and I'm quite sure that has nothing to do with the 'lunge'.