lymeris

My engine started surging on my 90 civic and the check engine light came on. I shut it off and restart it and its all normal. The behavior is intermittant.
The code book pointed to the EACV as the problem.

I'm not a mechanic. From what I understand if it acts up its either in the wiring, or the valve as explained above AND it could also be a faulty ECU. I'm going to a friend's house (and fellow member) and he's going to run it through various tests. I'd rather try to replace the Valve then the ECU obviously, but I may end up doing both. If I put a used EACV in and it still does it, well, you know. Could be the ECU.

BUt now your saying if I take it off and soak it in a carburator cleaner it may fix the problem? That's worth trying first. Is there adifference between an EACV and an IACV? Would it be safe to soak an Electronic Air Control Valve?
Lymeris

Fliptard

try taking it off and cleaning the valve part with some brake cleaner, sometimes they get gunk in the and can't open/close properly, causing it to surge.

Tyson

[edit, thanks?]

lymeris, your issue is probably more of an intermittent leaky vacuum hose. the EACV compensates for changes in air into the engine, but if air is coming in thru a hose, then it can only do so much. so it can be working fine as it should.

do a normal water spray test while the engine is running to see if the water blocks the leaks, the engine will respond if it does. then you can pinpoint the leak.

if you DO take the EACV out, then you really ought to replace the gasket from the dealer. or else youll for sure create a leak.

i dont think it has anything to do with your ECU.

lymeris

If there is a vacuum hose leak causing this problem, what is causing it to be intermittent and not a consistent problem?

Tyson

[read the fine print?]

I can't answer why intermittent issues are intermittent. But I can tell you from experience it's probably a vacuum leak and not an ecu issue. There's nothing electrical that will rev the engine. It's all mechanical. If it's revving up, then it's getting more air than it expects. It could be the eacv sticking or being off, I didn't say it wasn't. But it's designed to react to situations. If the engine is getting more air than the eacv can compensate, it's not the eacv fault.

That's where my logic is.

jlicrx

several different things can cause a fluctuating idle - getting a Check Engine Light and code 14 doesn't necessarily mean that it is a problem with the EACV - any time the ECU can't control the idle, it assumes that everything else is o.k. and the problem must be in the EACV and throws a check engine light and code 14 - this is because the ECU has no way of knowing if you have some other problem which it has no control over

other things to check:

1. vacuum leak from broken, cracked or disconnected vacuum hose

2. stuck PCV valve - the PCV valve is controlled by vacuum from the intake manifold - when the engine is at idle, the intake manifold vacuum is at its highest - with the vacuum high, the properly working PCV valve should be mostly closed - if the valve is not mostly closed, you have essentially what is the same as a vacuum leak which is bypassing the valve

3. low engine coolant level or air pocket in the cooling system - the ECU reads the engine coolant temp in order to control the EACV - with low coolant or air pocket, the temp sending sensor may not be surrounded by coolant and sending the wrong info to the ECU

4. bad gasket (figure eight shaped 'O' ring) between the EACV and the intake manifold

5. wiring problem at EACV - we see a lot of engine swaps where the wrong connector is plugged into the EACV, particularly on swaps converted from DPFI to MPFI - the EACV connector has 2 wires which are: blue with yellow stripe and black with yellow stripe - on MPFI cars, the connector is white and on DPFI cars, the connector is green

if you have a fluctuating idle, one way to tell if the EACV is working or not is to start the engine and let it idle - disconnect the 2-wire connector from the EACV - the engine speed should drop down to around 500-600 rpm and remain steady - if it does, the problem is most likely the EACV - if it doesn't, the problem is most likely elsewhere

lymeris

Thanks.

lymeris

TO jlicrx
My thanks! Your explanation is clear and extremely helpful. It seems it would be understandable why it could be intermittent if the leak is in a place where it's irregular for some reason. I think your last point should be my first step. I have a friend who is helping me. I'll print this out for him and we'll check this out.

Lynne (aka Lymeris)

jlicrx

clear out your stored PMs and i will answer your PM