how do you know if a Iac valve is bad or not, I need some help please My car still runs rough and dies with the map sensor plugged in and way better without the map sensor. Could it be the IAC valve going bad????

 

If you dont have any Check Engine Light on I would say the IAC is okay.You might pull it off and clean the inside bore and reinstall it..clear the codes.If you remove the MAP connector...the ECM will substitute a fixed MAP value and will use the TPS to control fuel.Try and replace the MAP and see how that does.Good to see a girl in here...

 

I have replaced the map sensor its brand new and i also tried with the old one and its still acting the same way.... no difference i went ahead and replaced the tps too but the problem is still there i am so lost right now!! but thank you for your help

 

The process of elimination begins...If you have no codes I wouldnt be replacing sensors hoping it fixes it.It appears like most people in here have been down that road including me.The other items of concern would be fuel pressure/engine vacuum(vacuum leaks) and the engine itself.Plugs/wires..
does it have a lot of miles?...maybe a run a compression check.If one cylinder is dead ..your wasting your time/money on sensors?Hook us up with more info?when does it run rough?..all the time?when warm..when cold?...when your in drive at a light anything?.narrow it down ..

 

When it idles its really smooth just like it always did, but when I plug the map sensor back in it surges a little bit and dies, and have also put it in gear and it surges and dies but it's not missing or making any other engine noises that would be a problem. Just won't hold idle with the sensor plugged in, a very annoying problem!!! I really appreciate the help

 

Are you sure you dont have a check engine light on ? or service engine soon light ?.on the dash.

 

No check engine soon light comes on at all thats why this soooo weird!! and I feel lost because there is no codes being flipped!! very very weird!

 

When the MAP sensor is unplugged...the computer will go into a default value for the MAP and take its readings from the TPS.If you replaced the MAP...and tried a different ECU(computer) and still have the problem ,I would say the wires from the MAP to the Computer needs some inspecting.Or find someone who has a scanner to check that wiring circuit.I think getting a scanner will do you some help.Without it your just throwing parts at it..

You can also do a simple check...this will check the voltage from the computer to the MAP sensor remove the plug and there should be 3 wires(connector off the MAP sensor) ...my manual says the gray wire should have a half a volt or .5 at that wire with the key on.if theres no voltage there or very little that wire needs some inspection back to the computer.if it looks good try a known good computer?..You will need a voltmeter to do this check..good luck

 

Thank you very much for all the help and the time you have taken to help me figure this out! I will defintely try the test of the map sensor and hopefully find my problem and be able to drive my car again!! I will let you know how it went thanks again