"The Parkway Stall"

my 2001 toyota camry is great but has an intermittent, annoying problem no one can diagnose or correct. If I drive for a while at top highway speed (say 65mph) and then have to come to a stop (to pay toll or stop light) I get a very rough idle and then the car stalls. Have had new plugs, wires, coil, radiator ($1000 repairs) already done to solve problem. Check engine light never comes on. Can also drive lengthy trip and it doesn’t happen. Anyone care to comment?

Has anyone looked at your IAC? (Idle Air Control valve)

At that age, it’s common for them to get dirty and cause the exact symptoms that you describe.
They can easily be cleaned, though many places will simply replace them.

I agree, its probably a dirty or bad IAC so just have the throttle body cleaned and the IAC inspected.

Wrong. It’s the egr valve. With the vehicle running, pushed up on the diaphragm. It should stall or run rough, but it should retract to its normal position. If it won’t start or runs rough after that, it’s carboned up and needs replaced. Very common problem. Easy to check. I’ll bet $100 and you can thank me later. Toyota tech with over 15 yrs experience.

If it was an iac, the car wouldn’t start unless gas pedal was depressed, and that’s almost always a cold start issue. Next time it happens, rap the egr valve with a hammer and the diaphragm will release back down. Another way to verify.

By the way, next time take it to a qualified Toyota dealer and you’ll save a lot of money in the long run.

If there were a problem with the EGR circuit the Check Engine light would come on with an EGR fault code.

Have someone look into the Idle Air Control valve. This can malfunction and not turn the Check Engine light on.


My vote is for an Idle Air Control valve problem.

Next time it happens, look at the coolant temp guage. Any sign of overheating? If not, I think the other comments here are correct, something to do with the throttle position at idle, the IAC most likely. It could be some corrosions elsewhere in the throttle body too. It only takes a couple minutes for a tech to verify that activating the EGR stalls the engine (it should), so it’s worth the time it takes to test that too.

I’ve seen the same complaint without a p0401 (egr flow insufficient) usually that code will pop if the vsv is inop, but not usually if the diaphragm sticks b/c it usually clears right up and a p. 0401 is a two trip monitor. Ok! A Toyota scan tool will be able to active test the Iac Duty ratio from low to high. It should be smooth and follow the command. Oh, check the egr valve for sticking!!!. Iac problems on Camrys are so far and few in between. But i suppose its worth checking. But test it, dont guess with pArts. Fords are very common.

Hello all who responded. I’m overwhelmed and grateful for your prompt attention to my stall issue. As expected, I drove down the Garden State Parkway yesterday to visit my mom and when I got off and slowed down the car stalled!! argggg…I will definitely check both the IAC and the EGR. When you (Mr. Tilted Tree…nice moniker by the way)) say "rap the EGR valve with a hammer, I don’t know where to find that. PLease advise! The other weird thing is when I am about to stall and the idle is very rough the gas pedal depresses “by itself” as if trying to correct the problem. Did you ever hear of this? And again, it can run for miles on end and purr like a new kitten at idle. Like a well-hidden cardiac issue. Why doesn’t the check engine light come on if it’s the EGR valve? And I agree with you totally that “guessing with parts” is the surest way to empty your checkbook and leave you feeling resentful towards your mechanic. I’ll get back to you guys on my progress and thanks again for all this superb attention. I feel like a debutante. :slight_smile:

One more thing Mr. Tilted Tree (I’m assuming your gender but please correct me if I’m wrong). If, as you say, this is an EGR sticking problem, why does this only happen after driving a long time at highway speed? The engine never over-heats either and I have a brand new radiator. Does this problem only show up with a hot engine or at certain sustained mph’s?

Question: Did this problem occur immediately after replacing the radiator? What was the reason the radiator was replaced btw?

Here’s a little EGR tutorial. Might help. EGR means Exhaust Gas Recirculation, is a valve which intentionally recirculates a little exhaust gas back into the engine intake manifold. That sounds crazy, since the engine is supposed to run on gasoline and air only, right? not exhaust gas, but this is required by federal regulations in certain operating instances to cool the combustion chambers enough to reduce nitrogen pollutants, which become a problem when the combustion chambers get overly hot. So the EGR is a valve which can open and close on command, and it routes from the exhaust to the intake manifold. But if it were open all the time, because the engine prefers gasoline and air as a steady diet and doesn’t really like to have exhaust gas put into it, if the EGR valve was open all the time, the engine would always run poorly, and pretty much always stall at idle. So by design, in operation, the EGR valve only opens during accelerations, and even then, only when the engine is fully warmed up. Theres a vacuum switching valve (vsv, which is also a valve, but a different valve than the EGR valve) which prevents the EGR from opening at any other time.

But valves are mechanical devices, and can fail to shut off when they are supposed to. Like when your kitchen faucet drips even though it is turned off. So you have to replace the seat washer. Same with the EGR. It may be turned off by the command of the engine computer, because you aren’t accelerating, but it could still be sticking open anyway and leaking exhaust gas into the intake manifold.

So what may be happening w/your car, is that you drive on the freeway, the engine is fully warmed up, and you accelerate from time to time, so that will cause the engine computer (on some cars the engine computer isn’t involved, but the same idea) to command the EGR to open briefly each time you accelerate, and it will open both b/c you accelerate and because the vsv allows it to open, since the vsv knows the engine is fully warmed up. The problem then may be that instead of closing like it should as you decelerate and stop, your EGR is sticking open, at least partially, and as you come to a stop after driving on the freeway, instead of a diet of air and gasoline, the engine is still getting some nasty exhaust gas recirculated, and it complains, coughs, and stalls.

It’s not that uncommon for an EGR to stick, because if you think about it, it is passing extremely hot and corrosive exhaust gas through it. That’s a touch environment, so it can corrode and start sticking. I should say the EGR valve on my 40 year old Ford truck and the one on my 20 year old Corolla are both original and still work fine. So they don’t always fail.

I always test my EGR valve every time I change the oil. It’s part of my oil change procedure. On the Corolla it is simple as pie. All I do is allow the engine to reach operating temp at idle. The EGR is closed at this point, right, b/c I’m not accelerating. Then I remove the vacuum hose that is used to command the EGR to open. I make sure there is no vacuum being applied there. Then I apply a vacuum (with a device mechanics have called a vacuum pump) directly to the EGR valve. If the engine stalls, I know the EGR valve is working correctly, as it opened, and the engine complained. Provided that the engine starts and runs normally once I remove the vacuum pump, then the EGR tests ok. If it didn’t stall, then the EGR is stuck. It might be stuck closed, or stuck partially open. If it was stuck partially open, I’d probably notice the idle being a little rough too. If it was stuck wide open, it wouldn’t idle at all, it would stall out.

So what you mechanic could do is the same test I just described. On your car the engine might correctly stall with the test vacuum applied, becuase your EGR valve does open when commanded, but when you try to restart the engine, it will then not not idle well, and may stall again. That’s an indication the EGR is sticking.

With all that said, there are other things that can cause the engine to stall out when coming to a stop, after driving on the freeway. But get the EGR tested. If it fails, you know that’s the probable cause, so replace it. EGR replacement is a fairly simple and inexpensive thing. If it passes, at least you’ve eliminated the EGR, and can move on to other possible causes.

hello everyone who responded to my “parkway stall” problem. We’ve checked the EGR valve and it operates correctly. Doesn’t seem to be the issue. So now we’re going with the IAC valve. My husband did a resistance test on it yesterday with an ohm meter and the resistance was too high. He’s thinking this is the problem, plus he found a sizeable hole in a rubber tube that goes into the mass air flow sensor box. Could that be a problem too? Anyway, he wants to replace the IAC. Mr. Titled Tree, you were a Toyota mechanic. Is this difficult to replace? I’m trying to save money but if the job is too difficult I will have to take it to the mechanic. Anyone care to comment?

If it was an iac, the car wouldn't start unless gas pedal was depressed

This is not always the case. You can have a bad IAC that doesn’t adjust properly when the throttle goes from open to closed, but does when it goes from closed to open.

@camry kar: usually IAC’s are just a couple of bolts and some vacuum lines. Not sure how they are mounted on your camry but on the ones I’ve worked on, they were on top of the engine with easy access. Should be easy. I’d first replace the rubber tube going to your MAF (Mass Airflow). That could very well be your problem to begin with. That could be a really easy cheap fix.

Here is 4 cylinder Camry IAC location picture.

Quote: he found a sizeable hole in a rubber tube that goes into the mass air flow sensor box. Could that be a problem too? "

Holy cow, details, details. details. Like I said before, you can’t assume anything. A hole in the air intake can throw the whole system off because the sensors are no longer reading the air pressure and temperature actually going into the engine. Replace or at least duct tape the thing up until the part is ordered and comes in and your problem should vanish.

On my 1989 Dodge Caravan, the IAC was an easy replacement.

On my 2002 Sienna, it takes some serious work to get at it. Just saying.