Hi all,

2002 Accord EX F23A.

Awhile ago I developed a sudden and hard misfire. I replaced the spark plugs and spark plug wires, and this made it 90% better (I had replaced the cap & rotor last year, and both look good still). But it still occasionally dipped into a very low idle and once even conked out while I was coasting to a stop. Also I have a CEL that my cheap ODBII has never been able to figure out.

So I ran my boroscope into the intake, and...yikes. It was caked with carbon and grime. Yesterday I pulled the intake off, cleaned out the EGR passage which was at least 50% blocked, cleaned out the throttle body and butterly valve, and the entire manifold etc. Basically removed every trace of carbon and gunk and have a perfectly clean intake manifold and throttle body. I also removed the EGR valve and gave it a quick clean (it didn't seem too bad) and ran a flexible wire through the EGR passage from the intake to the EGR mounting plate to make sure it wasn't blocked or clogged. Buttoned everything back up.

On first startup, the CEL was immediately gone, and the car hunted a bit for an idle before settling nicely around 800 RPM. I let it idle for 5 minutes to reset the computer, but as soon as I gave it throttle, it struggled and then conked out.

I undid the negative terminal for 30 seconds, started it again, and the same thing happened, tho this time the idle was low, around 500 RPM. Instant conk out the moment I gave it throttle after 5 minutes. A third try, and when I tried to hold the RPMs at 2000, they went up and down to 3000 multiple times, despite me not moving the gas pedal.

There were a lot of vacuum and coolant lines I had to disconnect to do all this. Is it possible I just forgot to replace one, or there's a leak? What else should I look for? Many thanks!

 

Today while idling I sprayed carb cleaner on all the vacuum lines I'd removed, but no change in throttle to indicate a leak (I realize that is not foolproof).

It coninues to hold an idle, but either conk out or surge when the accelerator is pressed. Here's a video from today, showing that:


Maybe I got carb cleaner into the electrics of the TPS, and screwed it up?

 

I'm an unbelievable dumbass, lol

I had switched the plugs for the IAC valve and the TPS.

Switched them back, reset the computer by running at 3K rpms for 5 minutes, and everything is fine now.