Mechanics

89 HIGH AND ERRATIC IDLE OUT OF GEAR

1989 Honda Civic

I have an 89 Civic LX 1.5L fuel injected, 167k, with automatic transmission. When I bought this car the owner had just done a full tune up and replaced the transmission fluid and had all the service records to prove it and all previous maintenance however he would not let me keep the records because they had his credit card info on them.

Anyway, the car ran fine for a while, though it always idled at about 1000-1500 rpm, passed emissions with flying colors a few months ago and then just the past month or so it's been idling erratically when in neutral or park and warmed up. It will jump (actually more like pumping the throttle than a jump, it smoothly accelerates up to 2500rpm then drops to 1000-1500rpm and repeats) from 1000 or 1500 to 2500 rpm up and down as long is it's in neutral or park. When started cold it idles at around 2000 until it warms up then it acts as above.

When cold and in gear it surges when you first start out, it's about the same behavior as when in neutral and hot a smooth acceleration up to 2500 and then a drop and repeat.

Now, when I bought the car I was told that it needed a valve cover gasket and it leaks a little oil, presumably from the valve cover, when hot. I have not fixed this gasket.

I replaced the air filter and the pcv valve as those were the cheapest fixes in the Haynes manual, but they didn't fix the problem.

Could this be a vacuum leak from the valve cover gasket? That's what my dad thinks.

Or could it be related to the transmission somehow, why else would it only do it in neutral and park?

The Haynes manual also mentions the EGR valve causing idle troubles but I can't afford the buy one and try it out if it won't definitely fix the problem.

Can an auto parts store or mechanic pull codes for my car so I could tell if I have a sensor problem? I only know about the little trouble light under the passenger side floor mat because I checked one on my other 89 civic when the check engine light came on.

Thanks for such a wonderful site and thanks in advance for your help.
Sincerely,
Joe
Avatar
Shsesc
October 26, 2007.



Now it's more like a pulsing from 1000rpm to 1750rpm when in idle or park, but I remember it being higher before, I think.

Tiny
Shsesc
Oct 28, 2007.
Do you have a book for this vehicle?

When was the last major tune-up? Is the check engine light On or has come On and disappeared.

Okay start with the electronic idle air control valve and the EGR open it up and clean it

Rasmataz
Oct 28, 2007.
The car was purchased around March of '06, the tune up was done just before that.

I only have the Haynes manual for the car.

The check engine light has not come on.

The Haynes book says that special tools are needed for doing the EGR Valve.

I'll try the electronic air control valve test procedure tomorrow.

Thanks

Tiny
Shsesc
Oct 28, 2007.
The Haynes book says that special tools are needed for doing the EGR Valve. Are you talking about testing it or removing? All I want you to do is open it up and look for carbons.

Rasmataz
Oct 28, 2007.
To even check it on a fuel injected vehicle it says, requires special tools.

Tiny
Shsesc
Oct 28, 2007.
What a vacuum pump and a scantool? Okay then

Rasmataz
Oct 28, 2007.
I'm sorry I was looking under EGR system instead of EGR valve.
It only requires a vacuum pump to test it, but it doesn't say anything about opening it up, how do I do that?

Tiny
Shsesc
Oct 28, 2007.
Remove the EGR valve completely off the engine and inspect for carbon on its pintle and also the passages in the manifold.

Rasmataz
Oct 28, 2007.
The EACV has the right resistance ~12ohms it's supposed to be between 8 and 15ohms
I get voltage on the wiring harness for the EACV The voltage is 10.28 volts between the black and yellow side of the harness and ground.

Haynes Manual says See dealer service dept. Or a qualified repair shop. Any Idea what the problem is with having a voltage there?

The Haynes manual is not really clear, it says that if there is no voltage between that harness pin (black and yellow) and ground then repair the open circuit between the harness and the #14 fuse, if there is voltage see dealer service. Does that mean it's broken either way!

Also what is battery voltage, it said if the two harness pins had battery voltage between them then the ECU could be faulty, I assumed that meant ~12 volts It read.16 volts or thereabouts.

Also when I pulled the ecu fuse to reset the ecu before the procedure it said the check engine light would flash constantly when I started the engine after pulling that fuse, but it didn't, instead it idled around 3000 then when I unplugged the EACV harness it started doing what it did before, pulsing between 1250 and 1750. When I plugged it back in it idled at 3000 again.

I took off the battery terminal to clear the codes that I assume resulted from removing the harness on the EACV however I did not check for codes before doing this. After 30 seconds I put the battery terminal back on and started the engine, it was back to it's normal pulsing between 1250 and 1750 again, that's much better than idling at 3000.

I checked the little ECU light under the carpet and it did not flash at all in position 2 on the ignition. I drove it around to see if it would set off a code and it did not.

So I am guessing there is a problem with whatever connects to that EACV harness, would that be the ECU? Or am I way off?

Thanks again for all your help so far.

Tiny
Shsesc
Oct 29, 2007.
Also check the fast idle control solenoid could be coming On when its not needed.

Rasmataz
Oct 29, 2007.
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