Hello all, my new to me 1987 Accord 3dr LXi - 166k miles (We had this type of car 21 years ago, so me and the wife just bought another to restore for her flower business).

Anyway, at cold start engine will rev high (1800 rpms), then drop down to 1200 after 2 mins or so, then go from 1200 to 1800, 1200 to 1800 rpms over and over again. Until I turn on the A/C switch, where the idle goes to 1200 without a lope while in either Park and Drive.

What do you guys think? Vacuum leak, Idle Air Control valve, leaky injector?

Thanks, Brently

 

might b the throttle positioning sensor , its a plastic piece located on the throttle body. you can get one for like 50 bucks

 

Sounds like a bad gasket in your intake manifold. Start the car and let it warm up, then take some starter fluid and spay it in short burst around the gaskets in the intake manifold, theres three of em on it. If it revs up while you are sparying then thats where your bad gasket is. If it a gasket just buy the set and replace em all, if you need a diagram let me know

 

I'll check manifold and ECU to see if any lights are flashing because the PGM-FI light is constantly lit.

Thanks... I'll report back

 

im a scrub in this area and i dont know if honda even has one of these.... but on my friends 300 he could adjust the rate of idling on the ICV (idle control valve) with a flat head screw driver.... do accord have em?

 

Solved!!

I took the long way to get there because I saw other problems. Therefore I did troubleshooting with other areas then ruled them out before getting to the Control Box, or to be specific (MAP Sensor - Vacuum Line #21). Here's what I did...

Swapped in a good ECU (No change)
Replaced the injectors with clean, used ones (no change)
Sprayed fluid around the intake gasket


Finally made the shift to the control box where hose #21 was pinched and surge disappeared. Opened box but was a pain to separate, so I swapped with known good used box.

Installed new spark plugs
Adjusted idle speed since someone had hosed that too.

Now it's almost purring like a kitten. Has a slight miss, so will need to investigate that. Plan on pouring a can of Seafoam in the tank since it's been sitting awhile.

Thanks for your help.