Rough Idle with A/C on

[curtie94]

I just fixed my ac, needed compressor and condenser, and recharged it on my 1991 Honda Accord. Now with the ac on the idle is rough, but if I raise the idle to 1000 it clears up and runs smooth. But at idle at 850, it makes a drone vibration noise that shakes the whole car. I have cleaned the IACV, and throttle plate before, and changed spark plugs, cap, rotor, and cleaned air filter.

Is this normal, or is it a issue that I should resolve.

The car has 176,000 miles but the compressor has 80,000.

[19dabeast85]

My cb7, before and after tune, shakes like crazy at idle with the ac on.

[oyajicool]

Perform compression check.
Check for vacuum leak.
Add fuel injector cleaner to see if improves.

[H311RA151N]

Check your engine mounts. Dont go jumping to conclusions yet. Vibrations change as the RPMs change. 850RPM and worn out mounts will do that. I know because mine does the same thing. A/C on and everything.

To check open your hood, prop it, put in D4 then nuetral then reverse (or slip the clutch with the E brake on) and see how much the engine moves. If it not twisting or floping bad then check for othe things. This is an easy, no tools test. Automatics respond more to this tactic. Or you can simply look at the engine mounts.

Second thought see how much it twists or bounces when starting.

[H311RA151N]

Perform compression check.
Check for vacuum leak.
Add fuel injector cleaner to see if improves.

I dont think he means it idles poor. Hes just saying its shaking. I guess we will find out when the OP posts again.

[curtie94]

Ya it runs good, the idle stays steady, it just shakes and drones. It seems like a lot of people have this issue. I've checked the sounds before, but it does't mean they are good. Thanks

[H311RA151N]

Ya it runs good, the idle stays steady, it just shakes and drones. It seems like a lot of people have this issue. I've checked the sounds before, but it does't mean they are good. Thanks

Good luck with it!

[oyajicool]

I dont think he means it idles poor. Hes just saying its shaking. I guess we will find out when the OP posts again.

With more load with A/C coming on during idle, the manifold pressure drops. If vacuum system is somewhat weak, it may be come evident there's leak, leading to ill running engine.

Also, #3 on my engine is low on compression. It vibrates a lot more with A/C coming on during idle. My engine mounts are not cracked.

Checking items i mentioned does not take much time and doing so eliminates possible causes for rough running at idle.

[Stoner51]

Mine does this when my IACV is dirty. Take it off and clean the carbon off the screen. There is a DIY on this somewhere. Also you may want to make sure your car is idleing high enough if mine is not at 900 it shakes bad.

steve

[curtie94]

Well I just had to replace the top radiator hose, it let go, so I bled the cooling system an now the idle is smooth with the ac on.

Just a quick question, when you check ac pressure do I check it at idle of 2000 rpms.

At idle I have 25 low and 150 high, it was 75 outside at the time.

[19dabeast85]

Is your AC still r12 or has it been converted to r134a? At 75* ambient you should be seeing about 35psi on the low side if it is r134a. I am not sure of the spec for r12 or if there even is a difference. You should be checking ac pressure with the ac on full blast cold at idle. If you have r134a just go buy a refill bottle with ac system leak stop in it. The stuff worked well for me and I just recently had to replace an ac line seal and the leak stopper was not evident in the lines....meaning in small amounts it won't cause clogging issues.

[Losiracer2]

cheap mounts can also lead to a shaky idle. I think that's what I have going on on my 4dr 90' EX 5spd. I replaced the rear mount, unique to the EX 5spds, with an aftermarket one and I think the rubber they used is too stiff.

When I go and unbolt it, it's smooth as butter. I'm considering replacing that with a Honda OEM one now since it shakes so bad. My damn glove box can be seen literally rattling against the dashboard.

[curtie94]

I retrofitted it to r134. There are no leaks in the system. I guess I'll have to add a little bit more.

I only added 2 1/2 cans of r134a so maybe a little more will fix it. I still have half a can of it left.

[H311RA151N]

I retrofitted it to r134. There are no leaks in the system. I guess I'll have to add a little bit more.

I only added 2 1/2 cans of r134a so maybe a little more will fix it. I still have half a can of it left.

2 1/2 cans? Even if your using 12oz cans thats 30oz. The system calls for like 26oz. You can blow your hand off overcharging an A/C system. Maybe you can add more id just be sure first. My 2 cents.

On the stop leak thing... I know its hard to find 134A with out it. I guess a little wont hurt anything. But thats like clogging your arteries to stop you from bleeding. Again IMO.

EDIT: The average temp in new hampshire is 84* right now.

80* F should be 30-40 psi Low side. 190-220 psi High side. 43*-48* F Vent Temp.
90* F should be 35-40 psi Low side. 190-225 psi High side. 44*-50* F Vent Temp.

EDIT Again: Make sure you have the recirculation button on.

[curtie94]

Ok I checked my pressures again I have 25 low and about 160 high. But I had about 40F vent temp before now I'm down to 36F after adding the rest of the can.

After adding the rest I now have 28 Low and high was closer to 200.

Ya I would never use stop leak in my ac, I added dye and I can't see any leaks.

It was about 70-75 out when I checked