jfmjr

Having an issue with rough idle on startup after car sits for a couple days. Car almost stalls and throttle hesitates until car warms up. ANY THOUGHTS?

sixonemale

I have an SC430, but based on experience from another car I owned with that same problem, it could be some sort of engine coolant sensor, or mass air flow sensor malfunction. Worst case, you have some sort of leak of coolant into the heads, which I highly doubt. Anyway, those two types of sensors are my best guess.

scorpio74

Make sure your air filter is clean. Check the throttle body for any build-up that could prevent the opening and closing of the throttle valve.

scdroptop

iTrader: (1)

I wouldn't call mine "rough" idle but it idles a little high and I feel a little shimmy before it gets warm and after about five minutes and a few miles it goes away. 36k on a 2005. My 2002 with 25k miles on it did something similar and so have about every other garage queen I've owned unless brand new. Seems like our cars are telling us to drive them more!!!

Nonetheless, mine is under warranty and I will have it looked at just to be sure. You should do the same if it is very rough and almost stalling. Air filter and perhaps even a fuel injector cleaning/intake cleaning might do you some good to get rid of all the carbon buildup.

I was told by a custom racing engine builder once that carbon buildup is a killer for plugs, filters, intake, exhaust, etc. He said it was the root of most evil. At the time he was rebuilding one of my four rx-7 engines that had low compression due to....guess what? Carbon buildup causing cracks in the rotor housing main seals! Fun stuff $$

sixonemale

Jfmjr,

Let us know what the problem is or was, once you get it diagnosed. Again, if it's anything similar to the problem I had, where I would start up my other car cold, it would idle rough and almost cut out when initially accelerating, then after five minutes it ran fine. Again, I think it's a sensor (engine coolant temperature sensor or the mass air flow sensor) allowing cool water or cool air to flow into the engine prematurely, thus causing a rough idle.

HVisone

The plugs will often go first and could be a problem esp with less than top quality premimum gas.....and sometimes the alcohol that is now stuffed into gas, can cause some issues as well; esp. since when it sits around, one might end up with some water in the gas over a period of time.

Without alcohol, gas could be stored much longer before going "bad"

Also if not driving the car, everyday or so, keep the gas tank filled to max (old airplane trick) to keep moisture out of the the tank and causing some problems

Bigredone

Give it a drink of Sea Foam additive. Works like a charm and only about $8 at Autozone or PepBoys.

jjbenzo

You should also check to see if the spark plugs and coils need to be replaced.