Rough idle, more when A/C on

DEAN DEORTUBE

MEMBER
1992 HONDA ACCORD
2.2L
4 CYL
FWD
AUTOMATIC
475,000 MILES

Having a rough idle issue for several months now. Replaced spark plugs (NGK iridium ix), wires (8 mm Taylor), distributor assembly, coil, EGR valve (vacuumed most of the carbon after removing the original EGR valve), o2 sensor. Also, bought original second hand parts from eBay (map sensor, IACV, throttle body). Cleaned the throttle body and checked the throttle position sensor - voltages are okay. Installed all these parts along those many months of having the idle problem. Installed the throttle body, IACV, map sensor. Bleed the coolant. Disconnected the IACV wire to adjust the base idle (750 rpm). Reset ECU. Adjusted the timing. The car runs fine and has fast acceleration with minimal hesitation. If I am on stop light the car idles rough when the rpm goes down below 1000. Rough idle increases if A/C was turned on. Rpm dips down to around 500 then goes back up to 750-800 rpm. I think it is an electrical issue. But I cannot pinpoint where the problem is. Had Autozone checked my alternator, battery and both are fine. The rough idle stops when rpm is 1000 and above. Failed emission recently (HC was high) that is why I replaced the o2 sensor, EGR valve, spark plugs and wires. But the rough idle is still the main problem. Been searching the internet for the solution but with no luck. Hope you can help! Thanks!

Thursday, September 28th, 2017 AT 10:08 PM

5 Replies

JIS001

MECHANIC
3,412 POSTS

First check for any vacuum leaks like the intake manifold or broken vacuum lines. If that is okay then re adjust the idle in the same manner you did.

Here is the spec and use a tachometer:

Start the engine and let it warm up to operating temperature (the cooling fan comes on).
Connect a tachometer.

Disconnect the 2P connector from the EACV.
Check the idle speed in the no load condition in which the headlights, blower fan, rear defogger, cooling fan, and air conditioner are off.
Idle speed should be:
Manual: 550 +/- 50 rpm
Automatic: 550 +/- 50 rpm (neutral or park)

Adjust the idle speed by turning the idle adjusting screw. Turn the ignition switch OFF.
Reconnect the 2P connector on the EACV, then remove the "BACK UP" fuse, in the main fuse box, for 10 seconds to reset the ECU.
Restart and idle the engine in the no load conditions in which the head lights, blower fan, rear defogger, cooling fan, and air conditioner are not operating for one minute, then check the idle speed

Idle speed should be:
Manual: 700 +/- 50 rpm
Automatic: 700 +/- 50 rpm (in gear)

Idle the engine for one minute with the headlights on high beam and check the idle speed.
Idle speed should be:
Manual: 770 +/- 50 rpm
Automatic: 770 +/- 50 rpm (in gear)

Turn the headlights off, idle the engine for one minute with the heater fan on high speed and the air conditioner on.
Idle speed should be:
Manual: 770 +/- 50 rpm
Automatic: 770 +/- 50 rpm (in gear)

That procedure should bring you back to spec. Setting base idle at 750 is too high. If it is more of a vibration at idle then look for collapsed engine mounts. If surging look for vacuum leaks. If okay order a new idle air control valve vs. A used one.

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Thursday, September 28th, 2017 AT 11:39 PM

DEAN DEORTUBE

MEMBER
3 POSTS

What is a good OEM IACV brand? Tried replacing the original IACV with a new non-original IACV and my idle became worse, that is why I bought an original second hand IACV from eBay. The idle surge issue was fixed. By the way, I first replaced the four engine mounts prior to replacing several ignitions parts. It helped specially the rear engine mount (the main rubber got busted and had vacuum leak but still having rough idle after installations. The main problem now is the rough idling at idle speed. I will try your instructions step-by-step and will let you know. Thanks!

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Friday, September 29th, 2017 AT 11:27 AM

KEN L

MASTER CERTIFIED MECHANIC
54,272 POSTS

It could be low compression on one cylinder as well.

Here are a couple guides that should help:

https://www.2carpros.com/articles/how-to-test-engine-compression

and

https://www.2carpros.com/articles/engine-vibration-at-idle

Please let us know what you find.

Cheers, Ken

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Saturday, September 30th, 2017 AT 5:04 PM

DEAN DEORTUBE

MEMBER
3 POSTS

Thanks for replying! Why is the idle smooth out when the rpm is at 1k and above even if i'm not giving it a gas? If there's a compression problem with one or more of the cylinder(s), the engine vibration should be constant and less engine power. I don't have that. The car has a good acceleration from stop and has the power to climb hills. Anyway, ordered the compression tester from amazon because it only cost $20 and also curious why i'm losing engine oil (3/8" below the full line of my oil dip stick) after driving the car for about a month. Been using synthetic oil (mobil/valvoline 10w-30) for close to 20 years and regularly change the oil every 3,000 miles. No indication of coolant leak on the oil and no excessive smoke after replacing the o2 sensor, egr valve, etc. Adjusted my base idle following the steps you've given me. When I tried to turned on my high beam the rpm dips down to around 600 and slowly goes back up to 750 - 800. The same thing happened when I turned on my a/c. Is this normal? There should be something that equalizes the extra electrical load on a car (92 honda). Don't know what car part(s) handles that. Also, tried spraying brake cleaners on some of the tubings and parts while at idle hoping to locate any vacuum leaks but did not detect any idle change. I'll do it again following the guidlines you've given me. Thanks!

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Sunday, October 1st, 2017 AT 10:14 PM

KEN L