speedo lags and my car won't go faster than 120 kph

[CdTriX]

i'm having a little trouble with my 97 4runner SR5 Automatic 3.4L V6

I juts got my alternator changed and it was driving fine. After about a day, it started to act up. I started to notice that my speedo would lag when i'd accelerate.

i'd be going 30 kph already but it'd be stuck at zero. After maybe half a second it would catch up.

if i let go of the gas, the speedo would hover at whatever speed i was going and after a while ( like 30 seconds ) it would fall on it's own. If i press the break it would fall faster.

at 100 kph i'm reving at 2k RPM. trying to maintain the speed feels like i'm constant accelerating and it feels like it's pushing really hard.

at 120 kph i am always on the gas trying to maintain the speed. it's at 2.5K RPM and it will not go higher than that.

I recently had a misfire late last year, ended up being a bad sparkplug, but i don't hear the engine skip, or anything this time. It's fine for acceleration at low speeds, but the speedo lags. The tach is fine, it's very responsive.

Any help would be grateful!

right now i'm going to try and reset the ECU, i'm going to let the battery sit for about 10 minutes unpluged from the car. and then let it idle for about 20 minutes. This should reset the AF ratio and whatever the car needs to reset and adjust.

 

[YotaFun]

The issue you are having sounds very similar to what my 95 olds was doing.

I was leaving a hardware store one day and all off a sudden acceleration would be gone.

The culprit ended up being the speedo cable.

IIRC on the runners if it is an Auto, the tranny retains its shift points from the speed to which the car is going.

And if the speed says that the car is only doing zero, it gonna sound like its trying to push itself till that speedo indicated to the tranny that the car is in fact moving and it is time to switch gears and go faster.

I could be completly wrong on this but it sounds like it is a speedometer cable issue.