annointed

I have an '88 Civic hatch, base model fuel injected 1.5L, 4 speed manual.

The idle on the car is usually fine and normal at maybe 750-800 rpm when I start it up for the first time in the day (I'm estimating, since it has no tach). After the the car has been driven 10-15 miles and is completely warm, it starts idling at ~1500 rpm. If I blip the throttle, it'll usually try to settle back into a normal idle, but instead it starts fluctuating monotonously between 800-1500 rpm, like a roller coaster, up and down, up and down, like its trying to find idle. Every once in a while I'll come to another stop and it'll be back to normal idle. The next stop, it'll probably be back to either high or fluctuating idle, etc.

Another occasional phenomenon that I think is related is that the car sometimes doesn't want to start, usually after its warm and running earlier in the day, or if I happen to stall out (only happened once, lol). It will crank and crank, and finally throw the Check Engine light. If I hold the throttle wide open, it will crank 8-10 times, then barely start up, and immediately begin the roller coaster style idle hunt fluctuating like I mentioned above.

To me, this sounds like an idle air control issue. In April I let my friend, who is an auto tech, borrow this car for about 6 weeks, and he mentioned that he adjusted the idle air screw, which I was annoyed to hear, as those are generally set from the factory. Anyway, I parked the Civic for the past 3 months, and this week I just started driving it again, and this idle/hot start issue bothers me. The hot start problem happened to my friend a couple of times, too, but he felt it was an ignition issue, which I disagree with.

Last night I tried to find the idle air screw he mentioned, and I don't see any such thing on this motor. In fact, I see no way to even adjust idle, and he doesn't remember having toyed with the idle, even though I distinctly remember him saying that's what he did.

All I see is a vaccuum actuated plate that looks almost like a secondary throttle plate. It is situated just above the throttle body.

Although I doubt it matters, the muffler fell off the car back in May, too, so I'm mufflerless. I thought back pressure loss from being mufflerless may also contribute to the car's difficulty w/idling, but I think there's something else going on.

Anyway, sorry to go on so long. It really seems like the car is getting too much air somehow, except that the problem only starts after driving several miles. Anybody know what's the problem?

Do I need to replace that little vaccuum actuated mechanical idle controller? Is there something electrical that could cause this (sensor, relay overheating, etc?).

Thanks!

Mark

jhota

i had a similar problem. went nuts trying to find it.

it was simple in the end, though: the throttle cable was sticking.

how to check: wait until the car starts doing the "idle bounce," then stick your toe under the gas pedal and see if you can just pull it up a little. it may not seem like it moves, but if the idle settles out to where it should be, it's the throttle cable.

annointed

Yeah, my '02 WRX once kicked into a strange idle bounce mode, and it turned out to be a binding throttle cable. Subaru issued a recall for it a month later, too, lol, whcih I still haven't gone in for. Problem has never recurred.

Unfortunately, the Civic's bouncing idle doesn't seem to be the same cause.