Rough Starting

[artbuc]

99 Avalon. I am getting a momentary rough idle at start-up. It only lasts for a second or two then the engine ramps up to fast idle speed and runs well. It is getting worse. Now it may not start at all unless I stroke the gas pedal. It is behaving as though the fuel line is empty and it is taking a couple seconds to build pressure. I don't think it is the fuel pump because it runs fine after the 1-2 second rough start.

Is there a check valve in the fuel system which keeps pressure on the injectors? I wonder if I have a leaky injector?

I thought I had some bad gas and added Seafoam. Within a day or two the car started up fine and I thoght I had solved the problem but it has come back. Maybe more bad gas?

Thanks for your help.

[Jack Deth]

based on how my old t-bird worked, the fuel pump runs for a couple of seconds when the key is turned to the on position (before the start position). maybe just hesitate in the on position for a couple of seconds, let it pressurize, then try to start it.
maybe try drygas. if you have water in the gas, i don't think seafoam will do anything for it.

[pmesfun]

Try cleaning the Throttle Body and IAC valve. Also make sure your battery terminals are tight and clean.

[Jigg007]

I'm not sure if its time or pressure sensitive, but when you first turn the car to the "on" position the fuel pump will kick on for roughly 3 seconds to build pressure. Now if its time based, then you're probably not building the pressure in that 3 seconds required, but in the run mode it probably stays on constantly and eventually builds the pressure needed. If it monitors pressure, well then my statement is irrelevant.

Maybe the fuel filter or the fuel strainer restricting some flow? Filter is 30 dollars or less, the strainer is under 10.

[comwiz]

I had same symptom of my 97 avalon xl.
I cleaned the throttle body and Idle Air Control motor and whole thing of the part.
You can buy throttle body cleaner around $5.
When we use car for several years, TB slightly get carbon around the valve.
Which makes the valve stick and air flow badly. It makes rough start and unstable idling. Also you gotta check the wire cables around the TB.
The copper conductors get rust as time goes by. If you have smooth brush, just brush inside of connectors to clean the conductors.

[pmesfun]

^+1
I decided to go a little overboard.

[Jigg007]

Wow, that is clean! I'm also baffled how you removed that egr pipe

[pmesfun]

21" Breaker Bar, I basically used it on every nut/bolt. Wasn't planning on rounding off anything. Although speaking of the egr pipe. I almost rounded off one of the lower nuts, until I noticed the socket wasn't completely on it. Parts aren't coming in till Wednesday, so tomorrow the intake manifold is coming off to clean, and remove the bypass hose for replacement.