Unsafe engine revs between gears 3&4, 4&5, and shifting out of 5.

OK thanks...it just seemed weird.

 

Thanks for agreeing with me. Toyota is making me feel like I'm the guy in the movie who's seen the alien but everyone thinks he's crazy. Okay everyone, here's everything that's happened.

1) I connected a ground wire (12awg stranded) to the throttle body. Previous to that, the resistance between it and the neg battery terminal was "infinity" and with the engine running, the voltage was bouncing around at about .3 vdc (floating). Afterwards, the resistance was 0.000 and the voltage was also 0.000v. Unfortunately, this didn't change anything that I could detect.

2) I got a call from the regional "master tech" who tried to convince me that a) the reving was intended by design for emissions reasons, and b) that it was safe. I don't believe either one. No one seems to want to, or know how to, bump this to the engineering level, where they won't just be reciting what they've been taught. The tech also claimed there were no other "complaints" about this, another thing I do not believe. He claims he reads this forum, Hey C., take a look at some of the above posts: they've seen the alien too.

So from the time air & fuel molecules enter the TB to the time they pass through the (2) catalytic converters is what? 2 seconds I'd estimate. So it makes perfect sense to me to *hold* (not increase) the throttle in position up to 2 seconds between shifts until the "rich" mixture (engine under load) passes the converters, OR the next gear is engaged.

Claiming that *increasing* the amount of fuel, and holding it for 10 seconds, lowers emissions is bullshit in my not so humble opinion. Oh, and claiming that engaging 5th with the engine at 3000rpm (when it should be at 1900) wasn't going to wear the clutch out prematurely was also bullshit. Excuse my French.

3) I had another "truck doesn't slow down" episode, this one rather serious. One of the local highways has two lights about 1/4 mile apart, speed limit 50mph. I got stopped at the first one, and as I got started again, I saw the next one turn green and wanted to make it. So I was accelerating about 75% of full throttle in 3rd and then 4th (about 2400rpm) when the light turned yellow. I took my foot off the accelerator without touching the clutch and expected to get engine-braking, but NO! The truck continued on as if I still had my foot on the gas! I could feel that the engine was still driving, I wasn't slowing down and used the brake and stepped on the clutch: the engine rpm popped up to 3000 or so for its usual "emissions" cycle. Safe my ass. (C. I hope you're reading this.)

So my current thoughts are: If Toyota claims this is normal and intended by design, I don't want a Toyota truck. As much as I like just about everything else about it, I will not suffer having a truck that I cannot control. If, in the above incident, I had had less stopping distance there would have been a crash and I would blame Toyota for their design. You other guys up for testifying?

So I'm going to test drive some other Tacoma's of the same vintage ('07-'10), 4 cylinder, 4x4, manual transmission, and see if they do the same thing. If they do not, then clearly something is wrong with mine and I will demand Toyota step up to the plate and fix it. If they all do the same thing, I'm heading down the street to Nissan.

 

Obviously this is not normal. Your recent description sounds even more to me that something in the throttle is sticking. I had an old Toyota pickup that did the exact same thing. The throttle in the carb would get stuck in the open position for a bit. Yours doesn't have a carb, but there are many throttle components that could cause this. If it were me I would test all the sensor resistance values.

 

OP, try this.

Go to an autoparts store and buy a throttle body, or hell buy one from toyota (just make sure they have a return policy) and try it out, if it solves the issue document, and either get toyota to reimburse you or have toyota replace it after you return yours.

Sometimes its easier to just try to fix it yourself then shove it in their face.

 

Yes, but the Toyota techs have, twice, cleaned and checked the TB. In addition, the computer (ECM) confirms that it is holding the throttle open! At least, that's what I've been told. The tech who called me merely was trying to justify the ECM holding the throttle open.

 

But if Toyota isn't lying, and this is by design, then I've wasted my time and money. I'm going to test drive some other similar Tacomas and then decide.

 

This isn't by design. Plain and simple. They aren't figuring out the problem. Either switch shops or look into it yourself.

 

Just because they looked at the throttle body doesnt mean they have done anything with the sensors.

 

I would contact Toyota Corporate with the complaint and establish a case number. They should be very, very, interested in any type of undiagnosed "sticking throttle" situation given their fairly recent history.

 

Bad news, guys. I test-drove a 2009 2.7l 4-cylinder manual Tacoma yesterday, and while "it" wasn't as bad as mine, it did the same thing. Shifting from 4 to 5 resulted in the rpm's hovering around 2700 for about 5 seconds. I got it to repeat consistently.

So C. is correct, this IS by design, as ludicrous as that seems. My respect for Toyota engineering has reached new levels, since they can't find any other way to pass emissions. And since it's programmed to do it whether or not the clutch is engaged (re: my incident above), they've programmed a safety concern into the vehicle.*

I don't live in an area where emissions are checked (and I doubt a routine check would even find it). Can anyone give me advice about doing a "Volkswagen" solution? I.e. reprogram the ECM to not rev in this situation, or limit it to 2 seconds, like in the other gears.

I don't think I can tolerate this over the long term. It'd be like a stone in my shoe, assuming I don't crash into something first. And since I really like the truck in just about every other way, it's really a gut-punch to sell it. As well as a complete hassle, that I just went through buying it. ;-(

* My understanding is that the ECM doesn't know if the clutch is engaged, or what gear it's in.

 

Can you take a video of this happening? My rpms drop like a rock when I let off the gas. Sometimes I have to blip the throttle if I can't shift fast enough into gear because it's already at idle. 2011 4cyl 5 speed. Also it engine brakes very strong when I let off the gas on the highway.

 

Sounds like a Tacoma isn't for you.

 

@Lord Slime , make a video please.

 

An aftermarket EMS can alleviate the issue, such as the UCON, from URD. Since it controls the throttle.

This might be a repeat question, but have you disconnected your battery for say 10 minutes, to let the ecu relearn parameters?

 

Rpm hang and uncontrolled acceleration are 2 entirely different things. Like I said before, when I had a manual 6 speed it had rpm hang, but never once did it accelerate the truck without me doing it.

 

TRADE YA!

Sounds like your truck is NOT doing the "good" 2-second throttle hold. Can I copy your software ;-)

I could take a video, but since you can't see my feet (clutch in, accelerator at idle), I doubt it would be all that convincing just to see the tack hovering at 3000.

 

If I said I had "uncontrolled acceleration" then I misrepresented it. What I have is "continued speed" in the sense that when I take my foot off the accelerator pedal, the truck continues at the previous pedal position, which means it's "controlled" by the ECM, not me. If this was a mechanical linkage, pedal to throttle, it would clearly get "stuck" somewhere in between.

 

I know the battery has been disconnected at least twice (pre-sets gone on the radio) when the techs did that, but it made no difference. I can easily try it again, I'll get back to you on that.

To all of you who posted links, thanks!, and give me some time to look at them and see if they can solve my problem.

Since Tacoma4's 2011, with the same engine, does NOT do what mine does it's possible Toyota has changed the ECM code for 2011 (C. said only the '07-'10 did the rev) but not published it as a service note for earlier models. Maybe that's a path I could take?

 

With the exception of a lack of codes, this sounds to me kind of like a vacuum leak. Normally the RPMs would remain high because of the constant additional air provided to the engine by a vacuum leak. But modern engine computers can adjust for many conditions (including lean fuel mix that would result from a vacuum leak). Maybe the computer is adjusting various things to bring the RPMS down after 10 seconds (which must seem like an eternity), instead of after only 1 second which would be normal. These motors are not known for developing vaccum leaks, and I've been wrong before... but wanted to chime in anyway.

 

Update:

I have done more road tests on empty roads and I can consistently repeat the truck-doesn't-slow-down scenario I've described above. To wit, if you have loaded the engine in either 4th or 5th by one of the following methods* and leave it in gear, then taking your foot off the accelerator pedal has no effect for up to 10 seconds; the engine continues to push the truck as if your foot was still on the pedal. Braking is severely compromised, as you would expect. Stopping distances are greatly increased since, not only is the engine fighting the brakes, you are not getting any engine-braking.

As of this writing I have had two near-misses due to this problem. The first one I documented above (two lights) and recently I had someone fail to yield and make a left turn in front of me.

* Method a) accelerating at >50% of full throttle, b) maintaining consistent speed going up a hill, c) cruising at ~70mph in 5th.

Today I spent about an hour with the Toyota Customer Experience Center (CEC) speaking with their representative "Jackie" at (800) 331-4331.

She called the Dealership to see if they would look at the truck again. They refused, and I don't blame them. I estimate they've spent 8 hours via two good techs trying to diagnose the problem. Also, the first time it was in, C., the regional master tech, happened to be there and was consulted. They have exhausted all the options available to them. The "intended by design" explanation (earlier post) is as far as they can go.

What I've asked for is for someone at the engineering level to address the problem. Someone who can look at the software and find the place where it's doing this, and perhaps decide what can be done. (C. told me that the 4-cylinder manuals all do this from 2007 to 2010. And we have a post above where a 2011 owner says his truck doesn't do this. Also, this reving couldn't be done with an automatic transmission (any owners here?), it would certainly be a problem and totally blows the "for emissions" explanation out of the water.

So my conclusion, since the engine hasn't changed much, and the emissions regulations haven't either, and you can't do this with an automatic, is that this problem was FIXED in the software for both automatics (from the start) and manuals after 2010. So a software solution exists, it just needs to be tested in the older versions and then made available.)

Even though I've emphasized that this is a safety issue, Jackie's management refuses to do anything besides wish me a nice day. Welcome to red tape and by-the-book desk jockeys! I asked Jackie to have Toyota put their stance that this is normal and safe in writing; her management has refused. I've asked to speak to her supervisor, and I'm waiting on the call, but I don't have much hope of convincing him to do something outside the box.

One thing she did tell me is that their inaction is due to a lack of a certain number of complaints from other owners. When I asked how many was enough, she didn't know.

So I encourage those of you who own 2007-2010 2.7L 4-cylinder manuals, and have this reving problem and would like to see it fixed, please call the CEC and refer to case #1610030909.