hugo2648

I bench cleaned the throttle body. The IACV is absolutely clean.

Yet, upon the first start of the day, the engine stumbles before settling down to a steady idle. Then rest of the day, start ups are fine.

I am thinking the fuel system drains down to the the tank overnight so the first start does not have enough fuel. Agree? Or what could be the reason?

What is the component which maintains fuel system pressure and/or prevents fuel draining back? A part number would be appreciated. If the cause is something else, please let me know.

salimshah

The valve has tubing to provide air passage. Make sure the tubes/pipes are also clean.
After a change, the system needs to re-establish the new normal. You can provide a quicker start point by battery disconnect of about 20 min [you may loose some settings is the drawback].

Regarding fuel pressure, the insertion of the key ignition [even before turning to ACC] the vehicle primes it self up. Exception would be if you do all this at lightning speed,

Salim

ricco750

How do you know the IACV is "absolutely clean" ? Is it new ? Did you disassemble and clean it ?

JacobsDad

I agree...... If the fuel has drained back into the gas tank overnight it will definitely be difficult to start first thing in the morning.

The component which maintains fuel pressure overnight is called a "check valve". The check valve does inot last forever and it's very common that the check valve fails in its performance.

Try this the next time you start the engine after it's been sitting overnight..... Without starting the engine..... turn the key back and forth from off to on from off to on from off to on...... Doing this will cause the fuel pump to turn on multiple times to generate fuel pressure...... Then after the third or fourth time of turning it on/off, turn the key to the start position so that the engine fires up and it should fire up without any hesitation. After doing this on/off routine it starts up without any hesitation you know that the check valve is bad in the fuel pump module.

To fix the situation you could either replace the entire fuel pump module for $300 (USD) or simply install an aftermarket check valve on the fuel line which will only cost 20 bucks.

hugo2648

Where is this check valve located? I would want to go for an aftermarket checkvalve. What kind do I get? And where do I install it?