Hey guys. LO3 is idling like CRAP runs fine off idle but has a nice miss when just sitting. My plugs,wires,cap and rotor are all less then 10k miles old have Borg cap rotor and wires...ac delco plugs. The wires are the 7.5's...I was wondering what else can be causing this rough idle. I was looking at the EGR and the diaphragm moves freely (was told by someone to check it) recently seafoamed the car which helped with some throttle response but no luck on the idle. Any suggestions on where to start would be cool. I have the cash to do a tuneup on it but I don't think its time. A friend of mine said it could be a broken down wire. Thanks for any help guys...(by the way how often do you guys change your plugs wires etc.)\

**edit** And also sometimes when the car gets warm in traffic about the 200 range the idle will get better...

 

Morris,

I had a similar problem and it turned out to be a combination of a bad IAC sensor and a vacuum hose that had a hole / crack in it. I am assuming that you dont have any service engine codes? If not I would check; IAC and vacuum connections and hoses first.

 

Hey Heel...Nope no codes being thrown, Ill have to dig up the guide on how to clean the IAC, I haven't tried that yet. Ill also go over my vacuum lines again.

 

Moriss

You may want to check the TB to intake manifold gasket. Over time this gasket may turn to mash and create a vacuum leak causing idle issues.

IAC is not a sensor - it's an ECM controllable stepper motor which control amount idle air entering intake manifold when throttle is closed.

EGR valve is best tested using a vacuum pump. Applying vacuum directly to EGR inlet port while observing idle quality. EGR must hold vacuum.

Check plugs, sometimes a broken spark plug wire may cause idle issues.

//RF

 

Thanks guys gonna go over all this stuff...if there are anymore problem areas id gladly check those too. Ill check the IAC first since that seems like the easiest place to start. And also I hear it doesnt take much to screw those things up.

 

Morris, You can test the IAC with it installed too. I dont know the exact wire color coding for your application (do a search and you should be able to find the procedure or just post and ask) but all you have to do is backprobe the IAC with a multimeter and measure the voltage across it. It should be something like .5 volts closed throttle up to 4.99 volts wot with a gradual increases as the pedal is depressed. Its simple to test and only takes a minute or two. If it doesn't check out THEN you can remove it, clean it and test it again to see if cleaning helped.
Hope this helps

Brandon

 

Thanks alot Brandon. This is what im going to try first.

 

Update! woohoo. Finally figured out why its idling like crap. Went out there this evening (pitch black) My grandpa said to spray a FINE mist on the wires to see if they spark. Well I look down there and i dont even spray and I see a lazer light show. Gonna clean the IAC tommorow and probably get a new cap,wires etc. Thanks guys