I have an 89 Civic LX 1.5L Dual Point 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.
The car was purchased around March of '06, the tune up was done just before that

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 1750rpm then drops to 1000rpm and repeats) from 1000 to 1750 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 1750 and then a drop and repeat.

The check engine light has not come on.

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.

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 wire 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 in advance for all your help.

Joe

 

Does my car have a throttle position sensor I can check, and where is it?

 

Also, my coolant is kind of murky could that cause troubles?

 

fluctuating idle usually caused by EACV not working correctly, coolant level too low, clogged PCV valve or air in the cooling system - could also be a bad MAP sensor or a vacuum leak

 

Any idea what having that voltage between the black and yellow wire on the EACV harness and ground means?

What if I unplug the EACV, what should happen?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by shsesc &raquo;</TD></TR><TR><TD CLASS="quote">Any idea what having that voltage between the black and yellow wire on the EACV harness and ground means?

What if I unplug the EACV, what should happen?</TD></TR></TABLE>the black/yellow wire is the power wire - if you measure voltage between the black/yellow and ground, it should read the same as it does by measuring between pos and neg battery posts - if it doesn't, you have a bad connection somewhere in the black/yellow wire - it runs from fuse #14 in the under dash fuse box

if you unplug the EACV, which removes it from control of the ECU, the idle should drop to around 500-600 rpm and remain steady - if it does, you have a problem with the EACV - if it doesn't, then you have a problem somewhere else - if the idle is really high or still fluctuating, it can be a vacuum leak, a plugged PCV valve, low coolant level, air in the cooling system, stuck throttle cable or bad MAP sensor- once you unplug the EACV, you should get a Check Engine Light - you need to reset the ECU after you plug it back in





Modified by jlicrx at 8:55 AM 10/31/2007

 

I just got a check engine light, code 7 throttle angle sensor.

Also, what book is that from?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by shsesc &raquo;</TD></TR><TR><TD CLASS="quote">Also, what book is that from?</TD></TR></TABLE>that happens to be from the 90 CRX USDM Factory Service Manual