Gas pedal unresponsive on Rav4

Yesterday while driving my 99 Rav4, the gas pedal became unresponsive and RPM immediately dropped from 3000 RPM to 750 (typical idle status) RPM ... I pulled over and brought the vehicle to a stop and then all of the warning lights came on. During this time everything else seemed to be working fine, the brakes, engine, all the electrical stuff was working normally, it was just that the gas pedal was completely dead. I turned off the vehicle and after a few seconds restarted it and it was running normally again. From there I brought it in to the dealership and they found no problems with it (and there was no code stored). They basically said they had never heard of this problem happening before and had no idea what the problem was.

I was hoping someone out here may have experienced this issue before.

A little background, a few weeks ago I was having an intermittant problem getting the car started. It took multiple towings to the dealership but they were finally able to replicate the problem and found that the fuel pump relay was faulty. That was replaced and since then the vehicle has had no issues starting.

Reply to
chris
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It sounds like you had a fault in your throttle position sensor; I'm surprised that it didn't throw a code.

I don't believe your fuel pump relay had anything to do with it but you might want to find a different dealership/mechanic if that's an option for you. It doesn't sound like they're the sharpest diagnosticians around.

-- Mike Harris Austin, TX

Reply to
Mike Harris

There are many possible causes for the condition the OP described. Besides the fuel pump relay and throttle position sensor, other possibilities that should be checked and tested are bad gas, loose electrical connections, badly clogged air filter, badly clogged fuel filter, badly clogged fuel pickup, bad fuel pump, bad MAF sensor, and clogged injectors.

Reply to
Ray O

Ray,

Correct me if I'm wrong but - while all are possible, most of those conditions would result in poor idle as well, nor clear themselves upon a restart... wouldn't they?

-- Mike Harris Austin, TX

Reply to
Mike Harris

Very true. I was trained to check everything, and as Sherlock Holmes used to say, if you have eliminated all of the likely suspects, then whatever is left, however unlikely it may be, is probably the culprit.

The clogged fuel pickup is highly unlikely due to the large surface area of the screen, but if it is clogged, it could conceivably cause the engine to only run at idle, and after the engine is shut down, the suction action on the pickup is relieved somewhat and so allows more fuel flow for a while. I have heard of this condition but have never run across it myself and so would be low on my list of suspects.

I would think that more likely possibilities are a contaminated MAF sensor or an air leak in the plastic tube between the air filter and throttle body.

Reply to
Ray O

Thanks for all the responses ... it hasn't happened again since but I'm sure it will again someday ...

A friend of mine said that it was possible that after hitting a bump it would be possible for a sensor to go out of alignment temporarily ... I did happen to hit a bump and this happened right after ... any validity to this theory?

Reply to
chris

No. The chances that a bump will knock a sensor out of alignment, and then having another bump knock it back in perfect alignment are practically zero.

It is possible that there is a loose connection to a wiring harness or sensor that is causing an intermittent problem.

Reply to
Ray O

It died again yesterday. It's happened 3 times in the last 48 hours. I hit the gas pedal the engine dies and I have trouble starting it for a bit. I had it towed in again, they couldn't start it either but according to the computers everything was working as it should. They took apart the trottle body and there's some motor in there that they want to replace. They said carbon builds up in it over time and there's this little door that opens and closes and if it sticks it could result in the symptoms I'm seeing. They warned me they're not positive this is what the problem is but I don't see that I have any choice to try it out.

Reply to
chris

Who is "they"?

Reply to
Ray O

The dealership.

Ray O wrote:

Reply to
chris

Spray a mist of water into the air intake every day for around ten days, WBMA ;)

mike

Reply to
Mike Hunter

The part they replaced is the IAC ...

I know nothing about carsother than very basic stuff like changing the air filter, seems like from what I've seen while searching the net, is that based on my symptoms, it's one of these issues:

1) air/vaccuum leak somewhere 2) IAC valve/motor is faulty 3) EGR problem 4) ignition coil 5) distributor

Doesn't exactly narrow it down but at least the IAC is on the list.

Reply to
chris

Idle Air Control Valve - a little flapper valve controlled by a stepper motor, replaces the idle bleed air adjustment on a carburetor. If it sticks or the little passages to it get clogged your engine will run fine with the throttle open but won't idle right.

The dealer usually says "Replace the valve and everything else that can be wrong" because if they touch it they have to guarantee that the fix works or they have to fix it again for free. So they hit the car with a 'Parts Sledgehammer' to make sure that whatever it might have been they changed it. And you paid for it.

If you have an independent mechanic or you want to DIY it, you can take the IACV off and apart, clean the valve and passages, and see if that solves the problem before you spend big bucks replacing it.

For vacuum leaks, the old unlit propane torch trick - crack the valve open a bit and wave it over all the hoses and valves, if the idle jumps suddenly and then smoothes back out as the computer compensates, and when you move the torch away the RPM's dip and then recover, you just found a vacuum leak.

If the Airflow Sensor is on the fender and there's a big corrugated plastic air inlet line over to the intake manifold, they crack and the un-metered air bypassing the MAF will cause all sorts of fun with "runs but won't idle." Check on the bottom with a mirror, too.

-->--

Reply to
Bruce L. Bergman

Thanks I appreciate the detailed info ...

They already replaced the IAC valve/motor. I just got back from test driving it for a about 45 minutes. I have noticed a few minor differences so far.

When in park, the engine now idles at 800RPM where as before it was

700. When in drive and stopped, foot on brake, it idles at 700 and before it was at 600.

I drove through areas that required me to stop often, as the trouble (ie engine dying) usually occurred when I hit the gas from a stopped position. I encountered no problems (where as it happened 3 times in 30 minutes worth of driving between thursday and friday)

I'm hoping these are good signs but it will be a while before I trust the vehicle again.

Reply to
chris

Hi,

That bites!

Just curious about the year and trim/model

Reply to
Esmail Bonakdarian

Unfortunately it died again tonight, after about 10 minutes of test driving. Much like the first time it went bad. The gas pedal just went unresponsive, engine didn't die this time. Turned it off and restarted and it was fine again.

For the person that asked, it's a 99 Rav4 4-door with 100K on it.

Reply to
chris

Since my last post it has died on several occasions. This last time the dealership replaced the Throttle Position sensor for free but it didn't solve the problem.

The symptoms keep changing slightly every time something's replaced. Now the vehicle stalls while in motion and I lose power steering. The power steering aspect is new.

I read an older posting for a Honda that said this latest symptom I'm experiencing was a "classic sign of a gummed up EGR valve", is there any validity to that?

Reply to
chris

I should mention one other thing. The last time I was able to reproduce the problem for the mechanic , he hooked up the diagnositc machine and it showed something with the throttle.

There were 2 values, one was a simple on/off and the other was a percentage. When the mechanic pressed the gas pedal the percentage went from 12% to

78%, however the on/off setting stayed "off" regardless of the position of the gas pedal.

My current guesses are either the EGR or perhaps an O2 sensor. What kind of symptoms would I be seeing if I had a faulty O2 sensor?

Reply to
chris

Checking to see if the EGR is causing the problem is not that difficult. Just unplug the vacuum hoses from the EGR valve, block the hoses, and see if the problem goes away. If it does, then the EGR is stuck open or something is wrong with the EGR control circuit.

A faulty O2 sensor rarely causes noticeable drivability problems, and I've never heard of one causing the engine to die at idle.

Reply to
Ray O

One piece of correction, the engine predominantly stalls while the vehicle is in motion not when in idle. As you can imagine losing power steering when you're going 40 mph can be pretty dangerous.

Reply to
chris

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