1998 Es300 Iac Valve After Cleaning?

[k_allison510]

Hi everyone. I recently bought my soon to be 16 year old daughter 1998 es300. After driving it on the highway for a while, we noticed the notorious rough idle. We shut the engine off for 10 or 15 minutes and all was good. It progresively got worse so I checked out the forums and read the one where the guy did a step by step on how to clean it so I did. We took it for a pretty long drive and again, all seemed fine until today. It started happening again and this time the check engine light would flash. We pulled over for about 5 minutes and then took off with no change until we got up to highway speeds where the cel stopped flashing and just stayed on. So my question is, can a faulty iac valve cause the cel to come on like the enigne was missing? I will probably take it off to clean it again and give it a spray of lube before I drop the $140 for a new but wanted to see if anyone thought it could be something else. Thanks for the help.

Kevin

[James Horning]

IAC ( idle air control ) .

Does it have a cold fast idle? ( 1200)

The check engine light flashing indicates there is a misfire, and that misfire can and will cause catalyst damage if you continue to operate the vehicle.

Determine the cause of the misfire.

See if a coil/ wire / injector has failed by isolating the cylinder that is misfiring at the time it is misfiring ... Diagnose .

Figure this out first, a IAC only controls idle speed . At hot idle it is open appox. 40-48 percent. If it fails you will have no fast idle cold, it will start, stumble, stall , and then maybe stay running.

If you have a data list from testing equiptment that would be great , fuel trim, key on maf, maf g/sec hot idle , would be the key.

[k_allison510]

it always starts up and idles smoothly. When its cold, it starts and idles around 900 with the ac on and about a 1000 with the ac off. But it always starts and idles fine. It only acts up after driving it for a while. Sometimes after about 50 miles, other times only after about 10 miles. Some times it doesnt act up at all. It never misfires unless it is rough idleing and only misfires while it is idling rough. After we take off or keep the rpm's up a little it stops. And sometimes it rough idles and does not misfire.