1999 Honda accord. Idles up and down. Will start cold, ru...

Q: 1999 Honda accord. Idles up and down. Will start cold, runs great. Try to restart warm, won't. Floods.

asked by on January 10, 2018

A lot has already been done to try to pinpoint this issue, but not by myself. I know fuel pump regulator, filter etc.. I was wondering if the main EFI relay could give these symptoms? Its only 50 bucks, but wanted to ask before I did it. Plugs are soaked. Runs excellent after it starts.idles up and down. Give a little gas and it purrs. If its shut off after running awhile it will not start until cooled down.

My car has 134000 miles.
My car has a manual transmission.

This problem of erratic idle speed is often referred to as "surging" or "hunting". The causes include a faulty idle air control valve or circuit (IAC), a faulty ECM (not common), faults in the fuel pump control circuit, defective spark plug(s) or ignition system components, faulty fuel injector(s) or injector circuit faults, and PCV system faults. Often, the application of a real time automotive scanner can find the fault as actual engine operating parameters can be viewed during the "surging". I would recommend that you request a rough operation/rough idle diagnostic and the responding certified mechanic will perform the required diagnostic steps to get this resolved. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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