trickyrabbit

Several months ago I replaced the engine in my 2003 Civic EX sedan 5-speed with a 50K mile junkyard engine that was originally paired to an automatic transmission. So the CEL came on Friday. Code came out P0505. Got on here and did some research... idle air controller. Called the dealership to see how much one was just in case I couldn't fix it. While on the phone they told me the IAC was different between manual and automatic transmissions. I also looked at Majestic Honda for part numbers. Turns out the throttle body was also different between auto and manual (news to me... maybe not to most of you though). So I drove the hour to where the old engine is at and pulled the whole throttle body, cleaned it up (including the IAC) and installed it. Reset the ECU. Started the car. CEL was still on. Plug the intake temp sensor back in. Reset the CEL again. Started the car and no CEL. Great. I fixed it.

Is there that much of a difference between the auto and manual IAC and throttle body to cause this kind of problem, or was it was a fluke that it failed at 51K miles? Or am I the only person that didn't realize I should have swapped the throttle body out when replacing the engine with one from an automatic?

gearbox

iTrader: (95)

yeah the throttle body and sensors for auto and manual are completely different. my auto would barely run on a manual tb. using an auto tb on a manual is not as bad, but still the sensors are giving the wrong readings. you just dont feel it as much. the major difference is in the TPS sensor on the tb i believe, but the other sensors are different as well. just find a used manual tb with all the sensors and swap it over. usually $50 on ebay.

also the year should not matter, 01-05 has the same tb for all the engines. only differences are auto and manual.

trickyrabbit

Thanks for the reply. No need to buy a tb on ebay. As my original post said, I removed the one from the original engine. So is the IAC on the tb I removed actually bad or just not cooperating with the ECU? Basically can I sell it on ebay as a working part?

gearbox

iTrader: (95)

ah okay. yeah iac valves hardly ever go bad. they can get clogged up with carbon and work incorrectly, but nothing some carb cleaner wont fix.

CiviStang

wanna know the real difference between manual and Auto..

the photo below is our AUTO after driving to Jacksonville Florida from Orlando...

palsana

You are absolutely positively wrong about IAC valves going bad. I have had a very awesome carb cleaner used to clean up the IAC valve and it only lasted me 2 days before the CEL came on for it and no matter how good u clean it, once an IAC is bad it means replace. There is no other choice in it.
I have a 2003 honda Civic EX Auto trans with 1.7L VTEC engine.
BTW,i have had 3 different cleans for the throttle body and IAC valve. The IAC valve in my 03 civic ex auto is a DENSO brand which is no longer made by DENSO.

Nitrous1024

Embarrasing to say, I don't know what the IACV actually looks like.
I just did an auto to manual gearbox conversion, but my D15B's idle is fluctuating like crazy when I bring the car to a stop at traffic lights. The car idles nicely when I just start it and and even when I leave it running, but the problem is when I bring the car to a stop while flooring the clutch. I'm using the manual ECU, but I need to change the IACV as well. My car's mileage is now even worse because of this.