Revs dropping and rebound

[4runherpow]

I posted this as a response to an old 3rd gen thread. Any help is greatly appreciated!

I have a 2006 V8, when I’m coasting 40-60-mph if I press the brake the RPMs will drop fairly quickly and then rebound when my foot comes off the brake. This is also an issue when I’m coasting sometimes and I do not hit the break but the RPMs will sometimes jump down and rebound up. I first noticed this because at highway speed when I take my foot off of the accelerator and coast, then I put my foot back on to give it gas, it almost seems a little jerky as the RPMs jump back up.

At first, I thought it was my new muffler and exhaust maybe having less back pressure and thus having the RPMs drop, but I noticed I can re-create it with the braking and releasing of the brake. The RPMs will drop to below 1000 and then jump back up to 12 to 1400 RPMs while on the highway.

Is this a brake booster issue or vacuum leak that could create jumpy rpm’s and jerkiness when reapplying throttle? Anyone else have this before?

Thanks in advance!

 

[averyislost]

I posted this as a response to an old 3rd gen thread. Any help is greatly appreciated!

I have a 2006 V8, when I’m coasting 40-60-mph if I press the brake the RPMs will drop fairly quickly and then rebound when my foot comes off the brake. This is also an issue when I’m coasting sometimes and I do not hit the break but the RPMs will sometimes jump down and rebound up. I first noticed this because at highway speed when I take my foot off of the accelerator and coast, then I put my foot back on to give it gas, it almost seems a little jerky as the RPMs jump back up.

At first, I thought it was my new muffler and exhaust maybe having less back pressure and thus having the RPMs drop, but I noticed I can re-create it with the braking and releasing of the brake. The RPMs will drop to below 1000 and then jump back up to 12 to 1400 RPMs while on the highway.

Is this a brake booster issue or vacuum leak that could create jumpy rpm’s and jerkiness when reapplying throttle? Anyone else have this before?

Thanks in advance!

I think it is related to the exhaust. Both my 3rd gen 3.4L and my 4th gen 4.7L do this RPM drop after installing an aftermarket exhaust on them. Never did figure out why they do this, but both 4Runners exhibit this exact issue after exhaust installs. The 3rd gen was more intense than my 4th gen