Toyota RAV4 '06 starting issues

toyota
rav4

#1

2006 Toyota RAV4 with 4-cyl 2.4L Camry engine, 138k miles. I have four problems. They may be related.

  1. P0171 code – lean mixture. I have checked for the intake air leaks under the hood, and can’t find any. I have introduced Sea Foam into the intake twice. I have replaced the oxygen sensor, air filter, PCV valve and hose, MAF sensor, maybe something else. Didn’t help. The code is still there, and comes back after reset consistently.

  2. The car starts badly in the morning. This problem has developed slowly over many months. It turns and turns but does not start. Then I wait a little, try again. After some coughing, it starts. I have replaced the battery and spark plugs (were worn out badly, running better now!), used Techron a lot in the gas. Didn’t help.

  3. After long fast drive on the highways the car won’t start. Cranks and cranks, but it won’t start for up to half an hour no matter what in hot weather, maybe 15 or 20 min. in cool weather.

  4. Almost always, after it is fully warmed, the engine hesitates quite a bit at the stop lights clearly due to the idle RPM too low, well under 500. It feels as if it is about to die; however, it never did. If I shift into neutral, the RPM rises to 600-700, and it idles perfectly. This hesitation slightly improved after I have replaced the spark plugs, but it is still bad.

What do you think can cause these things?


#2

Clogged fuel filter, weak pressure regulator (or damper) or fuel pump can all cause a lean condition. Check the fuel pressure idling and running down the road - duct tape it to the windshield so you can read it.

That said, it sure sounds like an un-metered air leak. Check all of the intake system between the MAF and the engine. Flex the piping and hoses to make sure you don’t have a crack or split that can let air into the system past the MAF.

3, may be a symptom of the first problem (if its a fuel pump) but may be a second problem. It acts like an electronic problem affected by heat. Sounds like a sensor, crankshaft or camshaft position sensor.


#3

Thank you, Mustangman. The car does feel a little sluggish sometimes, although rarely.

Can I rent the fuel pressure meter at the car parts store?

I have checked the intake but didn’t flex the hoses. Would it be safe to flex them with the engine running while spraying a little bit of starting fluid at the flexing points?

Where are the crankshaft and camshaft position sensor located? I am thinking, maybe it’s possible to spray a little water on them, wait two min, and see maybe the car will start right away.


#4

As far as hooking up a fuel pressure gauge, that’s going to be quite difficult

Toyota typically does NOT have a fuel pressure test port on the fuel rail, so you’d have to tee in the gauge, and that would require some skill and knowledge on your part, and a “master” fuel pressure gauge kit, not just a simple $30 gauge

Do you hear any hissing noises when the car’s idling and the hood’s open?

Here’s something you can do, and it’ll answer a few problems about your fuel delivery system. Tomorrow morning, slowly cycle the ignition key a few times, BEFORE attempting to start the engine. If that results in the engine starting much sooner, then you definitely have a fuel delivery problem. If that is the case, then somebody with a fuel pressure gauge set and knowledge of the proper specs for your car . . . factory fuel pressure specs, for one . . . would need to diagnose it and determine exactly where the problem is

As far as your #3 issue, here’s an idea. The next time it doesn’t start after that “long fast drive on the highways” pour a cup of cold water on the crankshaft position sensor, and then immediately try to start the engine. If it briefly starts, the sensor is suspect. Note that a faulty crankshaft position sensor is just as likely to generate a fault code as not. Probably more than 1/2 of the faulty sensors I’ve replaced never generated a code or check engine light.

Have your ever cleaned the throttle body? If not, that is one of the first things I’d do. A can of throttle body cleaner is only about $5. Be forewarned, though. After you perform this procedure, the engine may run a little rough for a few minutes, until the throttle body learns its new end stops and the idle stabilizes.


#5

Thank you, db4690. Except the fuel pressure gauge, everything is pretty easy to do.

Where can the crankshaft position sensor possibly be?


#6

This may help

http://share.qclt.com/丰田Toyota%20RAV4%20Repair%20Manual/2AZ-FE%20Engine%20Control%20System/Crankshaft%20Position%20Sensor/00500510.pdf

If the sensor is faulty, it’ll probably read infinite resistance . . . or at least several million ohms . . . when it’s hot


#7

Best way to find the problem is to take them off and inspect them. It should be obvious if cracked.

As for the fuel pressure and crank and cam sensors - what @db4690 said.