Hi! I'm new to this forum, and new to the world of trucks generally. this is my first post. I just bought a 98 Tacoma V6 4x4 5-speed manual trans with 100k miles. It seems in relatively good running condition, except that it has a high idle, and the RPMs seem to be high for any given speed/gear.

Starting cold, the idle RPMs surge up to around 2.5k, then drop to around 1.8k after ten seconds or so. Then after warming up for a few minutes, the idle holds steady at 1.1k. The engine tends to warm up fairly quickly. There also seems to be a slight "pulse", where the RPMs will very quickly surge and drop just a hair every few seconds, if that makes sense. Any idea what could be going on here? Is there more info I should provide?

As for the RPMs while driving, it seems to me that they are too high for whatever given speed/gear I happen to be driving at. Here are some figures: In second gear, I hit 3k RPM at 21mph In third, 3k at 30mph In fourth, 3k at 45mph In fifth, 3k at 52mph Also, in fifth I hit 4.5k at 75mph Is this normal?? It's been over a decade since I've driven a manual trans, but I used to drive my brother's 92 toyota pickup and I recall shifting INTO third gear at 30mph, not getting ready to shift out (although my memory could be skewed). Same for fourth and fifth. And doesn't 4.5k at 75mph seem high for fifth gear??

One thing worth noting: the original owner tricked this truck out in a number of superficial ways (fake naugahyde trim, barbed wire decal, welded a second tail pipe for symmetry, even though it isn't actually connected to the exhaust, just for looks). One thing he did was he put on a set of 31 inch tires and a set of aftermarket rims that have a high negative offset. This truck was manufactured to run 225/75R15 tires, so the ones on there now are 2.75 inches taller than factory specs. I am not sure if he had the speedometer adjusted to compensate, so is it possible that this could be messing with how I am reading the RPM/MPH? Also, is it possible that the tachometer is busted? When I hit 4.5k at 75mph, it doesn't really sound or "feel" like 4.5k, if you know what I mean. Thanks for any thought you might have, and thanks for providing such an awesome forum!

 

Welcome to the forum.

With this idle issue is your MIL on?? If so have you pulled the DTC to see what is going on.

Have you timed yourself over a few miles driving at 60mph to see how bad your speedometer is off.

It does seem your tach might be a little off on the high side With my 2000 3.4 very seldom do I get to 3000 rpm

The cold start rpm is normal but your warm idle should be under 900 rpm without looking that is only a guess.

Your so called pulse may be the AC idle up when the AC Compressor turns on and off. Could be the defrosters are selected or if the Charge is low causing it to cycle .

 

Thanks for the good advice! The MIL is not on. Will have to do a speed test. Going to go back to smaller tires anyway cuz the big ones rub the mud flaps on turns.

 

Did previous owner change the differential gears when they added tires? That would affect rpm.