Rep Power: 0

Hi, getting a P0505, Idle air control on a 98 EX w/ 5-speed. Seems to be related to the IAC valve. The only symptom other than the code was a high idle, around 1200 rpm and constant suction (via a vacuum) that passes though the holes in front of the air intake. When I put my fingers over the hole, it idles right down and the instructions say, if that happens, it's a bad IAC valve. I took it apart, cleaned the screen and internals according to instructions found here, then replaced it. It did idle lower at times but now it really stumbles at times.

What I suspect happened is that the dirty screen was allowing the car to function half-way correctly and after I cleaned it the valve didn't really perform any better. It just allowed a bigger vacuum leak and the valve is still not functioning correctly.

So, does this seem logical? Should I try cleaning it some more? Could it be related to low coolant level (air in system) as I have read? How would I test this (the system if full as far as I know).

If I do end up replacing it, I'd like to try a yard part first. What is the range of models that it would fit this?

Sorry about the amount of questions!
Biederboat

 
Rep Power: 811

coolant is important for heating the iac and determining how it functions during warmup. if there is air in the system, it may cause a different reading and bad idle. so be sure you fix any coolant issues and bleed out the air. if there is still a problem after cleaning the iac, it is probably beyond repair. in which case, you need to replace the whole throttle body and sensors (its cheaper to buy the whole thing used). check ebay and be sure you get the correct model depending on whether you have auto or manual trans.

 
Rep Power: 0

Well, here's what I did. Went to wrecking yard and bought what I thought was an interchangeable unit. It wasn't, but I got the connector which was the same. I used the connector to power test it. I'm assuming this is an on/off switch powered by 12 VDC and it responded as such. The valve functions just fine and appears to seal fine when it's "off" and be open when it's "on" (powered). I wasn't able to blow any air through it when it was sealed. This leads me to believe that there is a problem in how it's controlled.

I'm confused as to why the whole "throttle body" might be bad. This appears to be just a valve tied into a vacuum port on the intake. If I plug the opening with my finger, the engine idles down just fine so I'm assuming the IAC valve is "open" when it should be "closed". There is no erratic nature to the idle, it's generally just too high.

Sorry if I appear to be questioning your assessment, I'm just trying to understand so I can more accurately determine the next step. I priced JUST the IAC valves and it was $204 at NAPA and I can't afford to buy what's probably a "no return" part.

Thanks,
Biederboat

 
Rep Power: 214

Gearbox pretty much summed it up for you. If you have a CAI or SRI that is the main reason why the IACV went bad, they normally dont go bad as much when you have a stock intake. And you can clean the IACV but that is not ussually the case. If you clean it and it still does the same thing you need a new one.

 
Rep Power: 811

what i said was, a used throttle body for $50 on ebay is cheaper than buying a new iac valve. the rest of the throttle body is probably fine. and the iac is not a simple on/off sensor, it opens and closes in increments based on the coolant temperature so you have a smooth warmup without idle surges.

 
Rep Power: 0

Okay, that helps. I appreciate the explanations. This thing does have an Ingen Technologies cold air intake that came from the previous owner. Sounds like I should be replacing it.

Thanks,
Biederboat