Hi Scotty,
I’m back again with another question regarding my 2007 Toyota Corolla. It of course has the 1.8l I-4. So, I’ve been chasing this issue for a while now. The car starts up when it’s cold 1-2 cranks no problem. Then after shutting the car off after driving and coming back shortly to turn it back over it takes 3-5 cranks to start when it’s warmed up…it always starts but it’s a very long crank time and when it cranks over it sputters to life a little bit. I’ve done my own research and I’ve replaced the following components in an attempt to resolve the issue. I replaced the fuel pump, all four spark plugs, coils, pcv valve and vacuum hose. Knowing your wife has a matrix with this motor im wondering if you could pass down some knowledge as to why this is happening. I cannot find a straight answer on my own and I don’t want to keep shooting in the dark and spending money on things that aren’t causing the problem. I’m thinking maybe a leaking fuel injector at this point but I really don’t know…let me know. Thanks
You can't rule out a leaking purge valve or a lying ect sensor.
A leaking purge valve on a Cold start, no big deal. The engine likes running rich.
Warm start, bigger deal. The engine doesn't like running rich.
Leaking purge valves have weird effects on fuel trims.
When the vapor canister is saturated with fuel vapors a leaking purge valve will cause a rich condition.
But when those fuel vapors are cleared from the vapor canister a leaking purge valve will cause a lean condition.
Grab a pair of vice grips and pinch one of the hoses going to the purge valve on a warm start. If it starts easier, well there you go.
Also, hook up a scanner and make sure the ECT (and the IAT) sensors temps look right during warm starts
Will do!! This is awesome! So much to learn!
Hi Scotty,
I’m back again with another question regarding my 2007 Toyota Corolla. It of course has the 1.8l I-4. So, I’ve been chasing this issue for a while now. The car starts up when it’s cold 1-2 cranks no problem. Then after shutting the car off after driving and coming back shortly to turn it back over it takes 3-5 cranks to start when it’s warmed up…it always starts but it’s a very long crank time and when it cranks over it sputters to life a little bit. I’ve done my own research and I’ve replaced the following components in an attempt to resolve the issue. I replaced the fuel pump, all four spark plugs, coils, pcv valve and vacuum hose. Knowing your wife has a matrix with this motor im wondering if you could pass down some knowledge as to why this is happening. I cannot find a straight answer on my own and I don’t want to keep shooting in the dark and spending money on things that aren’t causing the problem. I’m thinking maybe a leaking fuel injector at this point but I really don’t know…let me know. Thanks
Next time it does that, hold throttle wide open and start the car. If it starts more readily, you most likely have leaky fuel injectors. Back in the days of carburetors, you could flood the engine if you pumped the gas one too many times. The standard procedure was to hold the throttle wide open and crank. When they went to computers, they carried it over to not let the fuel injectors let fuel into the combustion chambers if the engine floods. They simply carried it over.
Thank you! That’s solid advice and I learned something today! I’ll give it a go! I can always use some knowledge from some experienced folks in this area.
I went ahead and did that test and it seems like it had no effect. Still a longer crank time than a normal cold start…
It takes a couple seconds to get the flooded air/fuel mixture out. Drive my 1979 Pontiac with a carb, sometimes I flood it out and it takes a couple seconds to clear.
So are you saying the injectors could be bad since it’s a longer start even with the throttle all the way down?
No. It takes a couple seconds for the flooded mixture to get out of the cylinders so it can start again. Air and fuel require the right combination, or the engine will flood out, or you could possibly be not getting enough gas.
Based on your symptoms, running from a cold engine requires slightly more fuel than that same engine at operating temperature. This is referred to as "running rich", it's normal for cars running from a cold start to run slightly rich. You say it had no problems starting from cold. Once it's at operating temperature, the computer subtracts some fuel, making it run stochiometrically at idle. When it's shut off, and the fuel injectors leak, the hot engine is no longer within the parameters to start (too much fuel). If it were running too lean, it would have a hard time starting from cold.
That makes sense. I have a lot of tinkering to do and I’ll get back to everyone with an answer! Thanks for all your help!
I replaced the fuel pump, all four spark plugs, coils, pcv valve and vacuum hose.
Did you test those parts first? How much diagnosis have you done? Scanned for codes? Checked live data such as fuel trims?
I don’t want to keep shooting in the dark and spending money on things that aren’t causing the problem.
Then you need to do a proper diagnosis rather than loading up the parts cannon.
There are no codes on the vehicle, I’ve monitored the fuel trims with live data before and the short term trim fuel trim at idle is close to 10% does that mean it’s running lean? Too much air? Additionally, I inspected the spark plugs and they looked like they need to be changed and the coils were for good measure. The pcv failed as the vacuum hose was clogged with residual oil. The fuel pump was a shot in the dark and had no effect. Maybe I should take it somewhere and have it tested for a fuel rail pressure loss or something. Or maybe there’s an intake leak that I can’t find and it’s sucking too much air…I don’t really know
short term trim fuel trim at idle is close to 10% does that mean it’s running lean?
It is a bit lean. Possibly you still have a small vacuum leak somewhere. When the engine is cold, extra fuel is added when starting so a small leak would not have as much effect as when the engine is warmed up.
Short term trims will always be fluctuating. Long term fuel trim is a better general indicator of overall fuel system performance.
https://www.youtube.com/watch?v=iYmOnXPBrB0
It's probably worth checking fuel pressure even though you've installed a new pump (OEM? Aftermarket?) . New parts can be bad all too often these days. You may be able to borrow a fuel pressure gauge at an auto parts store like AutoZone. (Typically they have you leave a deposit equal to the cost of the tool which you get back when it's returned.)
You can check for vacuum leaks using the time-honored method of spraying carb cleaner at suspect areas and listening for a change as the engine idles. The more modern method would be a smoke test.
You didn't mention if you've cleaned the MAF sensor and throttle body, but that's inexpensive maintenance that can frequently have beneficial effects.
I’ll look into fuel pressure tester and try tinkering with areas of suspect for vacuum leaks. I’ve cleaned the throttle body thoroughly recently and the MAF as well. I replaced it with an OEM pump and operated the same as the original. I’ll look into the long fuel trim as well. Thank you for all your advice and responses I think I’ll get somewhere with all this! I’ll leave a comment when I get it figured out!
Let us know how you make out! Here's another fuel trim video which I think is better than the one above:
https://www.youtube.com/watch?v=0FrOtKJR8Ac
Will do thanks again!