Hello. Ive had this problem ever since I got my accord. And I tried for a long time to fix it when I first got it, then gave up. Well several years later it still has the problem and Ive decided to try to tackle the issue again. Heres what it does.

When the car is idling and reaches the temp that kicks the cooling fan on the idle drops so low that it almost dies. (Engine shaking low), then it will return to almost normal, but still too low. It will continue doing this every time the cooling fan engages. Something I noticed that I wasnt sure was suppose to happen was that when the cooling fan came on, the A/C clutch also engaged and started spinning. I have asked mechanics and other accord owners if this is suppose to happen and I got mixed answers, so I didnt know if that had anything to do with it.

I have tried everything that I can to try to fix this, even replacing parts that I knew wouldnt help but did it anyway. Plugs, wires, cap, rotor, alternator, battery, high and low T stats. After alot of research I was lead to the idle air control valve. So I took it off, cleaned it thoroughly, and it didnt change it at all. Well they are very expensive so I decided to try one at a junk yard that pulls parts for you. I cleaned that one very good and installed, no change at all.

After all this my guess is either one or both of these reasons. That when the cooling fan and/ or the A/C Clutch comes on that the initial electrical load drops the idle because whatever is suppose to compensate for that additional load isnt working right. This is why I changed out so many electrical parts. And/ or that the same thing is happening with the IAC not controlling the idle properly when it needs the additional air.

Yesterday I took it to my local Honda dealer and asked them. One of the mechanics came out and took a "look" and it, and of course he didnt wait long enough for the car to warm up and reproduce the problem so he could witness it. But after me explaining it he told me that I need to start by getting the base idle right. He explained how to do it. And just to make sure I looked it up and found a forum thread about the idle adjust.

So today I tried to adjust it, and I think I may have found a related problem. Heres how I did it. I warmed up the car, disconnected the IACV plug, then tried to adjust the idle. Heres what I noticed. I was able to get the idle to drop turning clockwise, but it wouldnt raise any higher than it already was. Which was too low at about 500-550. (Under hood info says proper idle is 700 (+50). It didnt matter how much I turned that screw it would not raise any higher. Then I turned it off, put the IACV plug back on, and pulled the 7.5A back up fuse for 10 secs to clear the memory. Started it back up, and it was still too low, same as before.

So, this is either its own problem, or is related to why the idle drops so far down when the cooling fan and A/C clutch engage. I know this is a long post but I wanted to make sure I provided all the details I could to hopefully get some help. My next step is paying Honda $120 an hour to diagnose it, which at this point Im almost ready to do out of frustration.

Thanks in advance for any help.

 

When you unplug the IACV, the should be 550 rpm.

Read this post: https://www.hondaaccordforum.com/for...e-speed-38734/

For the idle problem, the a/c should not turn on when the cooling fans turn on. I suspect that someone messed with the wiring, or something is crossed. Have you owned this car since it was new?

Readjust the idle according to Jim's procedure, then unplug the a/c compressor. See if the car stops having the problem. I think the ECU doesn't expect the a/c to turn on when the cooling fans turn on and the extra load is messing up your idle.

 

Ok. I can confirm now that the ac compressor comes on at the same time the cooling fan kicks on. I can hear the same sound you hear when you turn on your ac inside the car. Hard to describe the sound. But also my idle did raise after I did it earlier. Its at slightly above the mark under the 1, so about 750. I guess the ecu hadnt "learned" yet. When the problem happens it goes from the 750 mark down to the mark right above the 0. So maybe 200 or so. I guess ill be taking it to Honda monday.

 

You cleaned the IACV, but did you clean the bleed air passage and clean bore of throttle body, and throttle plate (front and back)? The throttle bore and plate also contribute to base idle condition.

When base idle is correctly set, idle should only drop to around 700 +/-50 rpm w/ IACV disconnected. The first tach rpm mark is not 200, but 500 rpm. Your base idle setting should be near the intermediate 750 rpm mark between 500 and 1000 rpm.

good luck

 

Believe it or not the distributor has internal parts that need to all be functioning. If you pull up a schematic for A/C condenser fans you will see that the distributer is part of the controlling for A/C components. check it out.

 

Thanks for all the help. Can we confirm that when the ac is turned off that the ac compressor clutch should NOT engage? Cuz depending on who I ask I get yes and no. if the true answer is no then thats what I need to be concentrating on.

 

The a/c compressor should not turn on when only the cooling fans are needed to lower the coolant temperature.

You can verify the drag on your engine by unplugging the a/c compressor (one wire connection), then see if your problem goes away once the car heats up.

You will have to do some basic electrical tests using a volt meter to try to figure out the problem. Do you have a volt meter and know how to test for continuity (an open/closed circuit)?

 

Yes to both. I use to be a tech at sears on washers and dryers

 

What I would do is make sure the a/c switch is turned off inside of the car and the fan blower switch inside is turned off.

Unplug the a/c pressure switch. This is below the battery and is plugged into one of the metal a/c lines. It may be tough to reach from the top.

Test to see if each pin is open or closed to ground. I always use a valve cover bolt as the ground. The two wire colors on that connector should be blu/yel and red/wht.

 

Ok, Ive been working on it for hours and I have a lot more info to hopefully figure this out, which I think I may have. I ran several tests, one that PAHonda suggested and the rest were directly from my Honda Manual PDF.

1) After taking out the battery, and battery tray (which I broke a bolt doing because my car was previously owned by someone near the ocean, so lots of rusty bolts.) Anyway it wasnt easy to get to the a/c pressure switch just like you said PAHonda. Anyway I tested both pins to ground and neither had continuity so they arent grounded somewhere, so thats good.

2) According to the manual the switch itself should have continuity between the pins, which it does so thats good.

3) I tested the a/c relay by running power and ground to the B and D pins, then checked for continuity between pins A and C, which it had so thats good.

4) Heres where I think the problem is. According to the manual the red/white wire should have voltage when hooking one lead of the meter to the red/ white and the other to ground. So I guess this means that that wire is always hot. Anyway there was NO VOLTAGE.

So if I am right this is where the problem lies, but I dont know where to go from there. I ran out of light, and my hands are pretty beat up, but Im hoping that PAhonda can help me diagnose why this wire has no voltage. I checked all related fuses. The wire itself goes from the switch into the chassis so Im not sure where to test from there to figure out why. Im going to look at the wiring diagram in my manual, but I wanted to get this posted so anyone that thinks they know can reply.

Thanks again for everyones help, at the very least at least I know where to tell the Honda mechanics to start and maybe same a little money on labor, but it would be nice to figure this one out on my own.

PS: According to the manual if there is no voltage to the red/white wire it says" Repair Open in the red/ white wire between the AC diode and the AC pressure switch.