cbr600rx7

So it's been a long project but I think we are getting there or maybe that's wishfull thinking.

So ever since we purchased the truck she has had a low throttle bucking issue. It seems to be most noticeable in 1st gear at low speeds and partial throttle. Today I leaned out the VAFM back to stock (previous owner had it turned 7 clicks CW{rich}) and the bucking seems to have gotten worse but the truck is idling smoother and no longer smells like fuel. I have base timing turned back to 12 degrees with +4 built into the cams and running 92+ octane and at highway speeds the issue does not present itself. I am pretty sure the issue is throttle body related and could be TPS. Any advice is welcome.

1995 4Runner 3VZE 5 speed 4.56 gears
Rebuild 3VZE
crower cams/LCE valve springs
7MGE VAFM With 3" ISR
2.5 exhaust
and so on.

Turtl3

Have u got a lunchbox locker in the rear?

cbr600rx7

Not that I am aware of. It should be factory open diffs (for now)

cbr600rx7

The issue seems more dominate when the vehicle is cold at low speeds in first gear. It's best explained as a low speed miss or stumble.

cbr600rx7

It will stumble considerably at 0-10% throttle at low RPMs. It's more noticeable when cold but also does it when warm.

fierohink

You can test the tps with a voltmeter to see if there are dead spots in the range. As well as check for smooth throttle plate movement.

cbr600rx7

Well we made a huge steep forward today. A friend had a extra manifold with throttle body attached and TPS. I swapped out the hole throttle body since it came off a running vehicle and sure enough the issue is gone. This throttle body had a toyota TPS sensor where the one that has been giving us problems was a cheap China made unit from rock auto that the old owner had installed.

fierohink

Knock off sensors do not work well in Toyotas.

As much as I hate paying dealer prices or factory prices, they never let me down when trying to eliminate gremlins. Bosch or Denso o2 sensors, denso MAF sensors, NGK plugs, etc.