Question about 1990 Honda Prelude

1 Answer

RPM still a lil high after engine swap

Thanks for the help earlier. Now that I have the exhaust installed the rpm 3500 previuosly is now between 2500-1500 continuing to run as if it were cold, you know how the rpm rises and falls until it warms up. My car usually settled down to about 800rpm. I did find that the radiator is leaking and have one on order and decided to replace hoses and thermostat while I'm at it.
Could'nt find a vacum leak anywhere any tips on how to spot this problem, if it exist. Oh yeah I checked the throttle cable position it semed to be "normal" even took it off but still had the high idle problem.

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  • naflash_00 Oct 01, 2008

    Wow thats a wealth of info and I need it. I have a few more quetions, where are the EACV and Air temp sensor located. Before I check everything, are you saying pulling the back up fuse may possibly reset everything? I look forward to hearing from you again.



    Thank you in advance, "Slow trying to be sure"

  • naflash_00 Oct 04, 2008

    Where do I began, 1st thanks agian fo the info. I'm not sure I checked everthing right do to the position of the plug it didn't go to well. I put the new rad, hoses, and thermostat on today. The idle came way down no overheating this time. The idle still bounces between 1500-1000. I've did a lot of research latley, one person suggested I purge the system of air or take the EACV of because anti-freeze goes thru it and I may have an air pocket in there because of its position higher than the rad. I don't mind trying it just wanted to run it by you to see if you've heard of this. Also I noticed when I ****** the throttle control it slows down. But I didn't want to adjust that bolt in the middle of the throttle control because I thought it might take away the high idle all together.



    Thanks in advance you have been a great help.

  • naflash_00 Oct 09, 2008

    The verdict is in. After changing all previous parts still had bit of a high bouncing idle between 1000-2000 rpm. I don't recommend this for everyone seeing as how I just had a feeling about this. After the engine warmed to normal running temp, I put a wrench on the nut that holds the throttle in position,"the spring loaded part" standing on the driver side of the car I gently pulled the throttle to slow the engine. When it got down to 700rpm where it should've been. I pulled a little more and it stayed.

    Note: (the cable had plenty of slack and had been removed @ 1 point just to make sure that it wasn't the problem)

    The next morning I started it and it went into high idle about 2000rpm for about 2 min. and slowly declined until warm when it rested @ 700rpm. I'm not sure but think it may have been set different because I pulled the engine from an automatic and it may have been set to pull the vaccum line for that. Like I said in the beginning this was my first time doing something like this I'm just glad this web site was hear to help me along. The car runs great and I'm a happy camper.



    Thanks again everyone who responded I tried just about all suggestions that were given.

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With an idle control problem like this, you need to check for codes. One possibility is a code 14 Electronic Air Control Valve failure. Remove the connector at the valve and measure the resistance at the valve terminals. If the resistance is not 8-15 ohms, replace the EACV. Another problem could be with codes 1, 41, or 43, which pertain to the O2 sensor, which could have been affected by running the engine with no exhaust system. Try resetting the codes by removing the back up (Clock) fuse in the relay box under the hood for ten seconds. One more thing to check is for code 10 Air Temperature Sensor (TA). Resistance across the TA terminals should measure from 1000 to 4000 ohms.

Posted on Sep 28, 2008

  • Richard Schram
    Richard Schram Oct 01, 2008

    Pulling the back up fuse for ten seconds resets everything on the ECU. This allows you to run the engine again and check for active codes. If you receive any more fault codes, the check engine light should come on.



    The EACV is located on top of the engine near the firewall and has two wires going to it, one is yellow/black and the other is blue/red. The intake air temperature sensor is roughly beside the EACV on the intake manifold chamber and has three wires, red/yellow, red/white, and green/white.



    These are only the most likely possibilities. Proper diagnosis requires a scan tool and a good manual. I have access to Mitchell On-Demand for most of my information. It provides step by step testing procedurs as well as a good system overview.

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