Rough Idle in Drive with AC on (1 Viewer)

[bmorgan]

With the engine running, in gear, and the AC on, the engine runs rough - steady but rough. It's only when it's under load, but I can tell the roughness is there with the AC off just not bad. EVERY once in a while, I'll stop at a light and it isn't rough, but maybe the compressor is cycling - I don't know.

I've replaced the engine mounts - that didn't do it. I did NOT replace the transmission mount so if that's possible... I recently replaced the AC pulley just in case. I'm wondering if it could be the compressor bearing. Does anyone have anything I should consider? This is my 95 with 180k. Otherwise it runs great - steady. In park, it is very smooth. Idle is steady.

Thank you in advance.

 

[Eicca]

Check your intake hose for cracks.

 

[Jgrauman]

Whats the RPM when in drive?

 

[bmorgan]

THe intake hoses look pretty good. I tried the spray with carb cleaner trick. I didn't hear any change. I should add it's been like this for over 2 years. No change.

The RPMs are about 650 / 700.

 

[bmorgan]

I'm going to give myself a bump... This issue has been going on for several years and I'm REALLY tired of it. I have searched and searched. I have asked local professionals - no one knows the answer to this.

181k 1995. Rough idle under load. Idle is steady. I've checked the vacuum hoses (but everyone knows how difficult a vacuum leak it so I'm happy to recheck them). I have replaced the engine mounts (but didn't change the transmission mount). The truck otherwise runs well. Idle RPM in drive is around 650/700. I have changed the AC pulley. I'm missing my idler pulley (took it off due to a bad bearing). Could this be the AC compressor bearing going out? Could it be the alternator bearing? I'm at a loss. Again - thank you for any help.

 

[inkpot]

There are 2 bearings in the front of the compressor that can wear/fail. Or, your compressor may be dying.

 

[bmorgan]

Could it be the compressor bearing for several years without getting worse?

 

[flintknapper]

Does the vehicle run rough at the same RPM with the A/C off?

With A/C on..the engine smooth out once RPM hit 900-1000 ?

 

[graham5david]

Mine does the same. RPMs drop when compressor kicks on and idkes rough .then compressor kicks off and RPMs increase and idle is smooth. I think it is either IAC valve or vcv valve .just haven't replaced either of them yet.

 

[bmorgan]

The rough idle is there just not nearly as bad with the ac off. When the rpms are up, it's smooth.

I'll run the checks on the iac and pcv valves.

 

[flintknapper]

The rough idle is there just not nearly as bad with the ac off. When the rpms are up, it's smooth.

I'll run the checks on the iac and pcv valves.

^^^^^^^ There ya go !

 

[Dave 2000]

Also, check your spark plugs, gaps, cracks leads.

Does the motor smooth out if you touch the throttle a little lifting the rpm a touch?

Regards

Dave

 

[bmorgan]

Thanks Dave - I'll check those but they are pretty new. It does smooth out with a little throttle.

A while back I had to thread in a new #6 injector wire. Is there any way that could do anything? Maybe at low power it isn't firing well so it's no getting gas in cylinder 6? I guess looking at the plug would tell me.

I can't get to these checks today. It will have to be tomorrow or Monday. I'll report back - thank you for the direction.

 

[Darb]

Mine does the same thing, it makes a vibration that can be felt as if the motor mounts are bad. I replaced motor and tranny mounts,and so so so much more!

I just replaced my head gasket and replaced everything else I could. Replaced every gasket/o-ring seal from the block up. I replaced all steering hoses and all cooler hoses to each cooler. Replaced the oil cooler gaskets, timing chain ,dampener,tensioner, timing cover o rings. All vacuum lines and hoses. Vcv, vsv, fuel pressure regulator all injectors serviced flow tested, head was completely gone through and so on and so on. All OEM everything and I can’t figure out why it still does this. I steam cleaned everything and the entire egr system is like new clean.

 

[graham5david]

Mine doesn't bother me enough to worry about. Just turn up the music and tune it out.

 

[bmorgan]

Darb - that is a LOT of work. I feel bad for this thought, but I'm kinda glad you didn't find it. 'Cause if you did, that means I would have to do all of that too. Eeesh.

Music is the fix for so many things...

I'll start the diagnosis. If I find anything, I'll be sure to post it. Thank you all.

 

[Darb]

My head gasket blew and that started me down the rabbit hole. I did every “while your in there” thing I could find because the labor to get back inside down the road for a leaking gasket or o-ring would be a ton of work. I thought that replacing all motor and tranny mounts would take care of it but nope. Maybe it’s in the compressor who knows!

 

[Dave 2000]

Injector spray pattern can affect idle, as can a leaky inlet/exhaust valve. I cannot remember as I rarely see the petrol versions but, is the TPS adjustable?

Regards

Dave

 

[bmorgan]

Quick update - IAC and TPS were not the fix. While the TPS was a little out of adjustment (now corrected) that didn't clear it up. Guess I'm on to the plugs etc.

 

[ATXnative]

I had this issue and the idle was really rough. New plugs helped a lot but rough idle is still there. It only happens when AC cycles in drive and at a complete stop. Any throttle whatsoever smooths it out. All my belts and mounts seem fine from a visual inspection. Keep us updated!