Honda Help

"Andy Sheehan, StreetsideStig" (AndySheehan-StreetsideStig)
03/31/2016 at 19:39 • Filed to: None

Okay, here it is:

98 Civic D16Y7. I just replaced the idle air control valve. Now the car bounces between 1100 and 1200 rpm at idle. All the time, any temperature.

Apparently, according to the forum professors, I’m supposed to go through the idle “relearn” process, as follows:

Disconnect/reconnect battery to clear ECU codes

Start car, hold at 3k rpm until the radiator fan comes on.

Restart car with no loads on engine, let idle.

The trouble is, it’s freaking impossible to hold the engine at 3,000 rpm when the ECU keeps adjusting the throttle. I was able to hold it at about 3500 for a while, but even then it kicked down before any kind of time passed.

I tried just driving it around and then restarting it, but it had no effect. I’m lost, here. Also, OBDII readers won’t connect to my ECU for some reason.

All help is greatly appreciated.

DISCUSSION (6)

LOREM IPSUM > Andy Sheehan, StreetsideStig
03/31/2016 at 20:30

First thing I’d probably do is unplug the iacv to see if anything changes. If it still runs the same while unplugged I’d suspect a bad replacement part.

I’d also probably check for vacuum leaks around anything you touched. A great method is to use an unlit propane torch. Open the valve and stick the nozzle around everything you worked on with the engine running. If the idle surges wildly, you found your leak. Carb cleaner, brake cleaner, ether starting fluid, etc can be sprayed around as well if you don’t have a torch. (Although if you’re spraying something non flammable the idle will dip instead of surge)

I guess I should also ask exactly why you replaced the iacv to begin with? Was the car behaving the same way before you swapped the valve over, or were you trying to resolve one issue and ultimately created another?

Was the iacv that you just installed a new part or a junkyard find or something?

Andy Sheehan, StreetsideStig > LOREM IPSUM
03/31/2016 at 20:36

With the IACV unplugged, it still surges, only faster and with a shallower range. I guess it could just be a simple vacuum leak. I’ll test for that.

LOREM IPSUM > Andy Sheehan, StreetsideStig
03/31/2016 at 20:46

Ok, the new valve is doing something then, and if it’s doing it quickly it’s probably not a gummed up used part I’m guessing.

I’m no tech, but I don’t think the iacv itself is at fault here.

How was the car behaving before you swapped the valve? I’m wondering what prompted it’s replacement.

Any water leaks into the interior? Sunroof perhaps? The non responsive Ecu could be an indicator of a bigger issue, but best to start with the easy stuff I guess.

Andy Sheehan, StreetsideStig > LOREM IPSUM
03/31/2016 at 20:54

No water leaks. I swapped the valve because was previously having idle issues. It would idle lower and lower until it died. I took the first valve off for cleaning, then put it back on, and this surging issue started. I learned that I might have damaged the valve in the cleaning, so I bought a refurbished one. While that was in the mail, I blocked off the first valve with a piece of gasket material. The surging stopped, but I had to take out the idle screw and adjust the throttle cable to get it to idle without dying. Once I did, however, it held the idle without issues.

Today I got the new valve, put it in, replaced the screw, and returned the throttle cable to its original position.

I think the old IACV was the problem (it was incredibly dirty and sticky), but now the computer is all confused because I had things disconnected. The ECU could be bad, but it hasn’t affected anything else.

SnapUndersteer, Italian Spiderman > Andy Sheehan, StreetsideStig
03/31/2016 at 22:00

Vacuum leak? hole in one of the intake hoses after the IACV?

Andy Sheehan, StreetsideStig > SnapUndersteer, Italian Spiderman
04/01/2016 at 08:15

I was thinking that there might possibly be a vacuum leak around the MAF, since I cleaned that the same time I first removed the IACV. I’ll have to check for that later.