I have always owned Toyotas because they are the best on the road. I have a 1984 4 runner with 309,000 miles and no problems. I also have a 2000 4 runner with no problems. My wife drives a 2001 Sequoia and there is where my problem is. I need some help from someone that might know what is going on. When she is driving down the road it will stop running or drop down to a low rough idle. It might go a week without having it happen, but it might happen five to six times in one day. She has to get of the road and wait for 5 to 10 minutes before it starts to run again. I have had it at Cobb County Toyota in Atlanta, Ga. and Riverside Toyota in Rome, Ga. and neither could fix it because it didnÆt happen while they gave it a test drive. One would think you could tell someone what the truck was doing and they could trouble shoot it. Because it doesnÆt leave a code they say nothing is wrong. I called Customer relations "1 800 331 4331" at Toyota.com and they were no help at all. Here is what happens: After about 30 minutes of driving it will stop running and drop to a rough idle. If you floor the gas pedal it will slowly work its way up to 2000 rpms then drops off to about 800 rpms. Then it goes to 2500 rpms and back down to 800rpms, then up to 3000 rpms and so on until it is running properly. It might take 5 to 10 minutes for this to happen. Does anybody have an idea of what could cause this? It is a 2001 Sequoia 4x4 with 79,000 miles on it. It has always had the service done by the book. Thanks for the help

How is it running (e.g. very rough?, misfiring?, or (smooth...but just not following the accelerator) when it slowly climbs back up to 2000rpm with the accelerator on the floor and drops back to 800 rpm? If you slowly move the throttle as it's doing this, how does the engine speed change? Does the rpm ever start tracking the throttle movement while it's trying to recover?

Does this truck have the vehicle stability control (and the drive by wire throttle control)? If so, do you get any lights indicating the VSC is active? (i.e. erroneously thinking it's in a skid, and taking control of the throttle?

Puzzled that no codes are being logged into the computer.. that might be a clue that the VSC has gone crazy and taken over control of the throttle.

It runs great most of the time. It is just out of the blue it drops off. When it is acting up and I floor it I just keep it floor and it idles rough thin starts to climb up. When it goes up it revs smooth but then drops back off to a rough idle. I have tried to flutter the throttle and nothing changes. So I just keep the throttle to the floor and let it work its way out of it. It does have VSC but the light doesnÆt come on. It also has the drive by wire. Thanks for the help. Can the Toyota place check the VSC to see if it is working right? I believe it does because I can make the light come on when I am going up my gravel drive. The rpms never tracks the throttle until it has made a full recovery.

I looked over at www.alldata.com --that thing has quite a list of TSB's, some of which involve ECU programming. I agree; weird it's not throwing codes. If you want the dealership to give you some of the literature for the TSB's, make sure you have the VIN handy.

Yes, they should be able to check the VSC for you.

Thanks for the reply. I will have to go to another dealer and try to get the TSBs from them. When I picked up the Sequoia today from Riverside Toyota, I drove it right around the building and tried to trade it in on a 2005. They only offered me $12,000 for the trade-in price and was even going to keep the $1500 cash back offer from Toyota. Some people try to still you blind. It would be nice to get a fair deal from a dealer without going through the numbers game.

I don't know much about Toyotas, but I can tell you from experience that GM trucks will act just like that if there is too much alcohol in the fuel, or if there is water in the fuel.

The water floats/rolls around in the tank and sometimes gets a little sucked into the fuel pickup.

Since all new GM trucks have fuel deadheaded to the fuel rail, the result is a rough run condition that starts and ends with the rearmost cylinders.

This is expremely difficult to diagnose since it is dependant on the tech catching it in the act while in the shop. It's one of those things that is almost impossible to diagnose on the road since you can't obtain a fuel sample while driving 55-65 mph.

About the only reliable way to check [for water] is to remove the fuel tank and take a look inside.

If alcohol is the problem, there are electronic testers for that. The dealer should have one.

How many tanks of fuel have you gone through like this? Have you tried getting your fuel from another station?

One last thing, do you have a K&N air filter installed?

Clay

The first thing I thought of was bad gas. My wife said she was getting gas when the station had a fuel truck filling up one of the under ground tanks. I have been getting my gas from other places since the first time I had a problem. I did pull the in line fuel filter and change it just in case. I run a toyota air filter in the Sequoia. Thanks for the reply.

Y'know something? Just try to drive it with the gas cap loosened for a few miles and see what it does; they go bad sometimes; messes up the pressure in the tank to allow your fuel to flow smoothly.

Think of the glug-glug of emptying a gas can without taking the vent cap off.

Newer rigs I think toss a code for that, but I'd give it a whirl just to see how it runs.

If you drive too long with the cap loosened, that will turn on the check engine light and set error code P0440. The ECU via the evap system measures tank pressure and expects a slight vacuum to be pulled on the tank. The ECU will set the above error if the vacuum is not present after 20 minutes of engine run time.

The vacuum sound you hear when the cap is loosened is the slight vaccum pulled on the tank by using engine intake manifold vacuum via the evaporative emission control system.. This is normal operation.

Normal pressure developed by the in tank fuel pump is 38 - 44 psi per the FSM. A fuel rail pressure check to verify the fuel pump and pressure regulator are OK wouldn't be a bad idea due to the following.

Unless Toyota has added a fuel pressure (rail) sensor in later models, there is no sensor to measure and detect low fuel rail pressure.. So you could have this problem and error codes might not be set. OBDII codes P0190 - 194 are defined for this purpose, but not implemented on some (if not all) Toyotas. It would seem to me that it would at least set a P0171 (running lean) code however.

Had an '85 Cressida 5M that would occasionally loose power w/o explanation.. also experienced difficult starting in cold weather, which I later found out to be caused by low fuel pump pressure. The in tank fuel pump eventually failed..

One other situation I've experienced but haven't mentioned involves the ECU itself.. If for some reason the ECU memory were to be loosing its stored long term fuel trim value, it will definitely stumble and lose power similar to what you described..

I have experienced this occasionally, when I've been working on the vehicle and had the battery disconnected (thus erasing the long term trim values stored in the ECU).. I've done this many times (due to welding, numerous electrical mods, etc). Every so often when I restart the engine and attempt to drive off after having had the battery disconnected, the engine has no power even with throttle way down similar to your description. After the engine stumbles along for 15 seconds or so, it eventually gets enough info to recompute the long term trim and begins to run OK.

The following suggestions are easy to do, and probably not the problem, BUT worth checking....
Pull the EFI fuse (it's a 20amp fuse on my 2000 4Runner) and check just to make sure it's in good condition and reseat it a few times to make sure the electrical contacts are clean and making good contact. Power is always on to the ECU memory via this fuse (even when vehicle is not running) so the memory is kept alive with the long term trim values.

I have experienced low voltage fuses that have been overloaded and running hot to only crack the fuseable link instead of blowing the link metal away and they will continue to supply power, but cause strange, intermittent problems.. so while you have the fuse out, look at it very closely, looking for any imperfections or darkening along the link.

You might also pull and reseat the MAIN EFI Relay.. This relay supplies power (from the same 20amp EFI fuse mentioned above) to the fuel pump.. Any intermittent in this circuit would cause the fuel pump to lose power.

And check your battery terminal clamps to make sure they are clean and tight.

btw, if you want more info what the "long term trim" values mentioned above do, read this article...

Lastly, I'd start asking around and see if there isn't a dealer somewhere near you that has a hot shot OBDII guy that can figure this out..

Thanks for all the ideas. I did check the gas cap and had pulled the EFI fuses but I never did any checking of the EFI relays. I will do that today. I did disconnect the battery to clean the terminals and left it disconnected all night before putting it back. Thanks for the link to the article it was interesting.