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Jtc

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Discussion starter · #1 · (Edited)
In the last 5 months my 2007 rav4 (2.4) has been having trouble starting. It starts up fine when cold albeit a little longer and shorter at times but overall it starts up when cold. The problem comes after i take it out to drive long or short distances. After i drive somewhere getting the engine to running temp and I turn it off and I come back the car just cranks and cranks (strong cranks) but doesn't actually start. If I wait about 15-20 minutes it will not start but just crank and crank. It will start again given enough time like 45 minutes or so but that first start will be a little weak as in it just barely started after after cranking for a bit. But once it does that first relatively slow start, if i turn it off and try and turn it on immediately after it will start fast. If i wait for a longer time like a couple hours it does start up fine as it does when cold.

I'm pretty new to DIY car things so idk too much but i have done a few things and have gotten it checked it out by a mechanic and even they couldn't find anything

The stuff I've done include:
  • Replaced ignition coils (oem), spark plugs (oem), air filter (oem), Fuel injector O rings and grommets (from rock auto)
  • Checked fuses and relays (all seem to be okay and in good shape, replaced one main 20 amp efi fuse with a spare as it looked a little burnt but still no)

Stuff mechanic has done:
  • Cleaned throttle body, pcv valve (and replaced hose connected to the pcv valve), and maf sensor (I think, will double check)
  • Checked fuel pressure and they said it was fine
  • Plugged in obd scanner but couldn't find anything

Car drives fine when on and no check engine light although idle is a bit erratic at times dropping as low as 550-600 ish causing big vibrations and as a result the idle shoots up to 900ish to compensate (im guessing) then it goes back to where it should be stopping the vibrations. After some time the cycle starts again. idk if this is related to the no start but i thought i just mention it.
Battery is relatively new, starter and alternator have been replaced the last few years.

Please helppp with any suggestions as I don't want to keep replacing parts unless it is for certain as it can get expensive and money is tight rn, thank youuu
 
#3 ·
Possibly a leaking fuel injector is causing a rich condition and the “no-start”

Also look at coolant temperature sensor values.

If this engine has an idle air control motor, it may be operating erratically.

Try very slight pressure on the throttle pedal to open the throttle just a crack and see if that allows the engine to start.
 
#4 ·
Theory of engine, ...
When engine is cold, the ECU (engine control unit) will receive a signal from the ECT (engine coolant temperature sensor) that the engine is cold. The ECU will think the engine is in open loop. So, the ECU will use more gas to start the engine. Sort of like being an electronic choke. While in open loop, the ECU will follow a fuel map stored in its memory. When the engine is warmed, the ECU will think the engine is in closed loop. This is when it uses the air/fuel ratio sensor to determine how much fuel to use. It is commonly known as the upstream O2 sensor which is different from the downstream O2 sensor. Anyway, the amount of fuel is determined by ECU sending a pulse width modulation signal to the injectors. The longer the on time then the more fuel is sent to the cylinders.

Possible causes, ...
Electronics are sometimes heat sensitive. Meaning it can become flaky when too hot or too cold. The crankshaft position sensor (cps or cks) is used to help start the engine. The ECU which sometimes sits in the engine bay can also fail when hot. Cam position sensor can also cause starting issues. Fuel injectors can also develop issues when cooling down (rare). Air/fuel ratio sensor or O2 sensor can cause this crank no start issue. Leaky fuel regulator can leak fuel into the cylinders and cause long crank before start. If fuel lines are near heat then it can vaporize and cause vapor lock. Long crank before start.

Trouble shooting, ...
Mechanics use high level scanner to look at data PIDs to see if something is out of whack. Some use an oscilloscope to watch the inputs and outputs of the sensors. Personally, I have no experience with this because I do not have this equipment and the cost is prohibitively high.

When engine cranks but won't start, I would test for spark and injector pulse (Youtube videos on how to do these tests). If both no spark and no injector pulse then crank sensor is suspect. If fuel system issue then could try spraying some brake clean into throttle (avoid the MAF sensor). If ECU is over heat then would open hood and spray cold spray on it to see if it comes back to life. (of course, caution must be used when working with ECU.

Oh, almost forgot, use a code reader and check for DTCs (diagnostic trouble codes). I may give you a hint at the cause of your issue. Sorry for the long post. Good luck.
 
Discussion starter · #5 ·
ravenuer said:
When you said your mechanic couldn't find anything, was he able to look at it while having the no-start situation?
Click to expand...
The first couple times I brought the car in I didn't know about the time window that it doesn't start, I thought it was random no starts so I would leave the car and I guess they waited long enough before checking (helping customers before me) to the point that it does start fine and their diagnosis would be that theres no problem.
The last time I tried to bring it in (after having found that it doesnt start under certain conditions) I drove a little then stopped at the shop but waited 15 minutes before going in and having them try and look at it. They were a little busy at the time so it got extended to about 25-30 minutes before someone acutally looked at it. When they tried to start it the first start took a long time but it managed to barely start by a hair. But the consecutive test starts he did after were good. That's when they plugged in the obd scanner and found nothing. It's just annoying looking crazy even though I have seen first hand that it doesn't start.
 
Discussion starter · #6 ·
espos4 said:
Possibly a leaking fuel injector is causing a rich condition and the “no-start”

Also look at coolant temperature sensor values.

If this engine has an idle air control motor, it may be operating erratically.

Try very slight pressure on the throttle pedal to open the throttle just a crack and see if that allows the engine to start.
Click to expand...
Yeah I looked at leaking fuel injectors too, but when I replaced the fuel injector o rings and grommet I also went ahead and cleaned the fuel injectors with a $30 kit from amazon and a spray and it seemed to hold pressure from the spray fine so idk.
The coolant temperature sensor is actually what i'm looking at next but I want to be sure.
I don't think it has an idle air control valve on this generation sadly, although in honesty the idle has improved a bit but it still does go up and down causing vibrations i just dont know if its normal for this generation rav4.
Is the slight pressure on the throttle to help with a possible flooded engine? I looked at that but never really attempted it yet. Ive also seen to press on the pedal all the way though so idk to press slightly like you said or all the way down.
 
Discussion starter · #7 ·
Avisitor said:
Theory of engine, ...
When engine is cold, the ECU (engine control unit) will receive a signal from the ECT (engine coolant temperature sensor) that the engine is cold. The ECU will think the engine is in open loop. So, the ECU will use more gas to start the engine. Sort of like being an electronic choke. While in open loop, the ECU will follow a fuel map stored in its memory. When the engine is warmed, the ECU will think the engine is in closed loop. This is when it uses the air/fuel ratio sensor to determine how much fuel to use. It is commonly known as the upstream O2 sensor which is different from the downstream O2 sensor. Anyway, the amount of fuel is determined by ECU sending a pulse width modulation signal to the injectors. The longer the on time then the more fuel is sent to the cylinders.

Possible causes, ...
Electronics are sometimes heat sensitive. Meaning it can become flaky when too hot or too cold. The crankshaft position sensor (cps or cks) is used to help start the engine. The ECU which sometimes sits in the engine bay can also fail when hot. Cam position sensor can also cause starting issues. Fuel injectors can also develop issues when cooling down (rare). Air/fuel ratio sensor or O2 sensor can cause this crank no start issue. Leaky fuel regulator can leak fuel into the cylinders and cause long crank before start. If fuel lines are near heat then it can vaporize and cause vapor lock. Long crank before start.

Trouble shooting, ...
Mechanics use high level scanner to look at data PIDs to see if something is out of whack. Some use an oscilloscope to watch the inputs and outputs of the sensors. Personally, I have no experience with this because I do not have this equipment and the cost is prohibitively high.

When engine cranks but won't start, I would test for spark and injector pulse (Youtube videos on how to do these tests). If both no spark and no injector pulse then crank sensor is suspect. If fuel system issue then could try spraying some brake clean into throttle (avoid the MAF sensor). If ECU is over heat then would open hood and spray cold spray on it to see if it comes back to life. (of course, caution must be used when working with ECU.

Oh, almost forgot, use a code reader and check for DTCs (diagnostic trouble codes). I may give you a hint at the cause of your issue. Sorry for the long post. Good luck.
Click to expand...
Im actually looking at the engine coolant temperature sensor as someone also suggested that in the comments above.
I also mentioned the crankshaft position sensor and camshaft position sensor to the mechanic but he said that if that was the issue that it would cause a check engine light but there isn't one, I haven't looked at O2 sensors or fuel regulator though but i will now thank you, I did however think it was vapor lock so i wrapped the fuel line in the engine with some heat resistant covering but still no.
The mechanic did look for any codes at all but they sadly couldn't find anything.
Regarding the fuel regulator it does run fine though when its actually running but then again idk
 
#8 ·
Jtc said:
Im actually looking at the engine coolant temperature sensor as someone also suggested that in the comments above.
I also mentioned the crankshaft position sensor and camshaft position sensor to the mechanic but he said that if that was the issue that it would cause a check engine light but there isn't one, I haven't looked at O2 sensors or fuel regulator though but i will now thank you, I did however think it was vapor lock so i wrapped the fuel line in the engine with some heat resistant covering but still no.
The mechanic did look for any codes at all but they sadly couldn't find anything.
Regarding the fuel regulator it does run fine though when its actually running but then again idk
Click to expand...
If the engine coolant temperature sensor were faulty, ..
Say reading too high then when engine is cold, the fuel would be less than needed rto start a cold engine cause the ECU thinks the engine is warm
Say reading colder then engine would still start when cold or warm But would be running rich.

The check engine light does not always come on when the crankshaft position sensor fails. For instance, engine runs fine. Turn off. The ECU never sees a bad sensor. Then you come back and the CPS fails to work. The ECU does not know what the problem is because the engine isn't running so the ECU does not go thru its diagnostics. No check engine light. It really isn't unusual. It is a simple check for spark and injector pulse to determine if the CPS is faulty.

I would think the O2 sensor is faulty because the engine starts fine when cold and the ECU doesn't use the O2 sensor. When warm, the ECU uses the O2 sensor to start and run the engine. If you spray some brake clean into the intake (avoid MAF sensor) and the engine starts then could be O2 sensor or a fuel system issue.
 
Discussion starter · #9 ·
Avisitor said:
If the engine coolant temperature sensor were faulty, ..
Say reading too high then when engine is cold, the fuel would be less than needed rto start a cold engine cause the ECU thinks the engine is warm
Say reading colder then engine would still start when cold or warm But would be running rich.

The check engine light does not always come on when the crankshaft position sensor fails. For instance, engine runs fine. Turn off. The ECU never sees a bad sensor. Then you come back and the CPS fails to work. The ECU does not know what the problem is because the engine isn't running so the ECU does not go thru its diagnostics. No check engine light. It really isn't unusual. It is a simple check for spark and injector pulse to determine if the CPS is faulty.

I would think the O2 sensor is faulty because the engine starts fine when cold and the ECU doesn't use the O2 sensor. When warm, the ECU uses the O2 sensor to start and run the engine. If you spray some brake clean into the intake (avoid MAF sensor) and the engine starts then could be O2 sensor or a fuel system issue.
Click to expand...
Now that you mention it that statement with the cps does make sense, I just took my mechanics word because he said that if it were to be either crankshaft or camshaft that the check engine light would turn on. And I also saw video explaining that if it was the crankshaft that was causing the no start that if I try and start it while its happening that the tachometer or rpms would stay in 0. Is that true????
Ill look into that and spraying the intake with break clean to see if it starts.

With that though what do you think about possibly the cause being a bad fuel pressure regulator located in the gas tank or even the fuel damper located on the fuel injection fuel rail????
I appreciate the help so far though
 
#10 · (Edited)
Tachometer response, while cranking engine to start, is different for different cars. Not sure about the Rav4. If the signal is fed from the CPS to the tach then tach sometimes need to be going fast enough to get a response. Other times, you will see the needle move. Other systems, the signal from CPS goes thru the ECU and will not feed information to the tach until the engine is running. So, cranking will not show on the tach.

Usually, when the fuel regulator fails, the symptoms are a long crank before the engine huffs into a poor idle and eventually smooth out. I am no expert. Just a DIYer.
 
#11 ·
Also if you have a scanner and can look at live data, you should see somewhere around 100-200 rpm while cranking.

To the OP, did you ever check for spark during the hot “no start” condition?

A fuel pressure test would be helpful too, although I wouldn’t be surprised if there was no shrader valve to easily test fuel pressure.
 
Discussion starter · #12 ·
espos4 said:
Also if you have a scanner and can look at live data, you should see somewhere around 100-200 rpm while cranking.

To the OP, did you ever check for spark during the hot “no start” condition?

A fuel pressure test would be helpful too, although I wouldn’t be surprised if there was no shrader valve to easily test fuel pressure.
Click to expand...
Oh I haven't checked for spark yet while it wasn't starting. I actually just bought and are now waiting for obd scanner to come to at least point me to the general area before I do any more replacing. I did however ask my mechanic to check fuel pressure and he said it was fine.
 
Discussion starter · #13 ·
Avisitor said:
Tachometer response, while cranking engine to start, is different for different cars. Not sure about the Rav4. If the signal is fed from the CPS to the tach then tach sometimes need to be going fast enough to get a response. Other times, you will see the needle move. Other systems, the signal from CPS goes thru the ECU and will not feed information to the tach until the engine is running. So, cranking will not show on the tach.

Usually, when the fuel regulator fails, the symptoms are a long crank before the engine huffs into a poor idle and eventually smooth out. I am no expert. Just a DIYer.
Click to expand...
Ohhh okay I guess fuel regulator might not be the issue then. I was just trying to make sense of the fact that it doesn't start after 15-20 minutes but once it gets that first start any following attempts to stop and start is good meaning it might be losing pressure somewhere but it takes about 15+ minutes to actually lose pressure.
But I am waiting on an obd scanner to hopefully point me in the right direction. I will keep crankshaft sensor in my mind and will update once obd scanner gets here in a couple days to see what it says.
 
#14 ·
Jtc said:
In the last 5 months my 2007 rav4 (2.4) has been having trouble starting. It starts up fine when cold albeit a little longer and shorter at times but overall it starts up when cold. The problem comes after i take it out to drive long or short distances. After i drive somewhere getting the engine to running temp and I turn it off and I come back the car just cranks and cranks (strong cranks) but doesn't actually start.
Click to expand...
I've had the same thing happen twice with different cars. Both times it turned out to be the crankshaft position sensor. Best way to diagnose is have the dealer look at the wave form from the position sensor while the car is running; the wave form will sorta fade away when it gets hot. The position sensor is used for spark timing; no wave form, no spark.
 
Discussion starter · #15 ·
FKHeath said:
I've had the same thing happen twice with different cars. Both times it turned out to be the crankshaft position sensor. Best way to diagnose is have the dealer look at the wave form from the position sensor while the car is running; the wave form will sorta fade away when it gets hot. The position sensor is used for spark timing; no wave form, no spark.
Click to expand...
I'm waiting for an obd2 scanner too come in the mail. Would that be able to tell me if it was the crankshaft position sensor? Also wouldn't a sensor that fade away the hotter the engine gets cause the car to stall?
 
#18 ·
Jtc said:
I gotcha, so I would say your bet is it being the crankshaft sensor? What about camshaft sensor? Im only asking because I can replace the camshaft myself but not the crankshaft so i would be able to save money it is the camshaft.
Click to expand...
Some cars use a camshaft position sensor, others use a crankshaft position sensor. Both do the same job. Both the cars I had to replace was the crankshaft sensor, so yes, it was difficult. I did one myself, but had a dealer do the one for my Grandson's car. Fortunately, it was done under warranty.

But first, you should confirm the diagnosis by looking at the waveform out of the sensor. I'm not aware that that can be seen from the OBD II port, but I could be wrong.

If your RAV has the camshaft position sensor, then, yes, that would be easier to change.

On the heat issue: When you turn a car off, the sensor can get a heat soak and then won't start when you try to restart it. Other's, like my Grandson's car would die while he was driving it, i.e. the sensor got hot enough for the wave form to fade away; confirmed by the dealer when he looked at the wave form.
 
#19 ·
Jtc said:
I gotcha, so I would say your bet is it being the crankshaft sensor? What about camshaft sensor? Im only asking because I can replace the camshaft myself but not the crankshaft so i would be able to save money it is the camshaft.
Click to expand...
I’m not saying to guess on anything. Just speculating on a possibility. The best thing to do is drive it until it’s hot and won’t start.
Look at live data while cranking. See if any engine rpms are registering.
Then check for any trouble codes and test for fuel and spark.
Post the codes here and the results of your fuel and spark testing.
 
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