'88 Civic hatch high/unsteady idle problem once warmed up...

[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

[Darb 2k]

the car not starting is 9/10 times the main relay. 80 bones from honda.

[EF You]

the car not starting can also be a distributor problem. many times when the car is cold it cranks fine, but once that distributor heats up, the worn out crank sensor goes on strike.

the idle jumping is probably the fast idle thermo valve. if you cant find the idle screw, its probably because the little rubber cover is on it. look for a black rubber cap on your throttle body, the screw is under that.

[Setanta]

TPS and FIV (Throttle position Sensor and Fast Idle Valve which controls the motor when cold) are the first two things you should check, followed by the EACV.

Don't forget to check all of the vacume hoses - but the above are the most likely suspects and playing with the idle screw wont fix the situation.

[annointed]

These are very informative posts. I'm not sure what is what on this motor, as I'm more accustomed to Subaru motors.

I see a cylindrical solenoid thing mounted on the left side (driver's side) of the intake manifold. Is that the Electronic Idle Air Control Valve (EACV?). I've never heard of a Fast Idle Valve, but that sounds like its exactly my problem...where is this? And which connector is the TPS? I'm assuming its the connector on the left hand side (ie, driver's side), directly accross from the throttle butterfly itself, at the base of the throttle body. On the front of the base of the throttle body is a sensor that throws a Check Engine light if I unplug it while the car is running. Above it is a similar looking sensor that seems to do nothing when unplugged.

What is what on this motor?

Thanks for all your help!

Mark

[annointed]

I'm going to go outside and look around under the hood again to try to ID the parts mentioned above.

My AIM is annointedWRX for anyone who might be able to help.

Thanks again.

Mark

[annointed]

OK, it sounds like this is narrowed down to my FIV. With a considerable amount of help from incucivic via AIM, I have a good idea of what I need to do to remove that unit and retighten its internals, as they have probably come loose somewhere over the past 195k miles this motor has seen. I'm sure it'll all be common sense once I dig into it, as I have a pretty decent amount of car/wrenching experience...just kinda a newb to Hondas, though. I love this little Civic, and wouldn't mind a nice turbo b16 or something along those lines to get it moving a little faster, lol. I can't seem to get a car w/o modding it...but that's another story. I'll report back in when I find out more.

[annointed]

Oh, I have 4 codes blinking on my ECU:

7
10
14
16

But I had every connector around the Throttle body disconnected at some point today, so i will reset the ecu and drive around all day tomm doing my daily business and see if it throws any of the above codes again. Also curious to see which code it throws during the cranking/no start condition. Wierd thing is, if I let off and wait 10 sec, it'll usually start right up next time I crank...

Mark

[Setanta]

The TPS is on the side of the throttle body. EACV is where you stated it was, the FIV has hoses going to it and will be located on the block under the manifold somewhere.