Rough Idle in Drive with AC on (1 Viewer)

[bmorgan]

Also: bmorgan, I don't see where you ever answered the above question; did I miss it?

Oh - I'm sorry. Yeah - the idle reacts when the compressor kicks on. It idles with the compressor off set just above 650 - it seems to hover right around 670 / 680. Hell - let me go check.

Compressor off and in park: 650
Compressor off and in drive: 620
Compressor on and in park: 690
Compressor on and in drive: 650/660

That's pretty normal, right?

 

[CJF]

Hell - let me go check.

Compressor off and in park: 650

Compressor on and in park: 690

That's pretty normal, right?

Good data; thanks for checking.

That data is NOT normal.

Idle with compressor off is perfect, but:

Compressor on and in park should be ~900.

I think you should really focus on why the A/C idle up function is not working properly. Can't be a faulty EGR, undertorqued crank bolt, etc. since your idle with A/C off is perfect.

Really not many things it could be: IAC (which you said you checked?), or connection from the compressor/clutch telling the ECU that the compressor is engaged.

 

[CJF]

...

 

[bmorgan]

Good data; thanks for checking.

That data is NOT normal.

Idle with compressor off is perfect, but:

Compressor on and in park should be ~900.

I think you should really focus on why the A/C idle up function is not working properly. Can't be a faulty EGR, undertorqued crank bolt, etc. since your idle with A/C off is perfect.

Really not many things it could be: IAC (which you said you checked?), or connection from the compressor/clutch telling the ECU that the compressor is engaged.

I'm sorry - I fat fingered that. It should read 790 (not 690), but that's still not 900. Anyway - it's WAY too hot to go digging into the compressor right now. It's still working. I'll recheck the IAC later this week. I have check it and I replaced it a few years ago (idle was jumping from 1000 to 3000 over and over). Thanks for the help. It's good to rule things out.

 

[toyogi]

Update to idle issue -

My main battery / starting battery was going bad. Replaced it and idle issue solved. My guess is that my alternator was working hard to keep up with lack of charge acceptance and load. Coincidence??

I have a dual battery set up with a isolating/combining solinoid Both batteries now Optima Yellow Group 27F.

 

[ATXnative]

I tried tightening the belts and it made it worse; still rough when A/C kicks on in idle (not while driving) D or R (not in N or P) and engine load on the ultraguage kicks up. Idle kicks up to 950 when A/C kicks in. Any gas, though, when in R or D, smooths it out.

 

[jvazquez53]

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.

Are these the RPMs with the AC on?

 

[bmorgan]

Almost a year later and nothing has changed. So it's not a wear item wearing. To add to the list of symptoms: when I first start it up with the ac on, there is a very obvious tapping sound. It goes away with the ac off or when it warms up.

I'm going to try a more comprehensive testing log:

AC off idling in park/neutral: 650
AC off idling in gear: 820

AC on idling in park/neutral: 820
AC on idling in gear: 680

Its the last one that is the problem. It's pretty annoying at a light. I'm willing to try anything. I appreciate the help in advance.

 

[bmorgan]

Oh yeah - and I have a p0401 code, but don't we all...

 

[graham5david]

I might as well do this too while I have everything out of the vehicle. Can the IAC still be purchased

 

[bmorgan]

Well, I pulled my IAC and ran the full round of testing on it. Testing checked out. Luckily I have a couple 80s, so I swapped one just to be sure. It's not the IAC. What's the next thing to check? Like I said - whatever it is, isn't changing. It's exactly the same for a very long time.

 

[ATXnative]

I cant remember when I last commented on this, but I have the same issue - vibration in D idling only with AC compressor kicked in. If no AC, or in N, or with any throttle, it's completely smooth. RPMs are fine and kick up appropriately. I'm stumped as well...my only thought is actually the trans mounta or some sort of clutch issue since if im idling in D and compressor kicks in I kick it in to N and it becomes completely smooth. I dont know how to check for these issues without doing some major work though.

 

[bmorgan]

I'm with you, ATX, but I keep being told that I should be idling above 800 when in drive with AC on. I'm certainly not idling that high. I'm well below 700. If I lightly put my foot on the gas while sitting at the light so that RPMs are between 800 - 900, it's SO much nicer.

What about adjusting the throttle cables? Could that be anything to look at? I just trying to think back the work I have done. I have removed the TB before, but I didn't really go through the adjustment process. I just tried to put it back where it had been. But maybe I didn't get it right.

 

[graham5david]

I'm with you, ATX, but I keep being told that I should be idling above 800 when in drive with AC on. I'm certainly not idling that high. I'm well below 700. If I lightly put my foot on the gas while sitting at the light so that RPMs are between 800 - 900, it's SO much nicer.

What about adjusting the throttle cables? Could that be anything to look at? I just trying to think back the work I have done. I have removed the TB before, but I didn't really go through the adjustment process. I just tried to put it back where it had been. But maybe I didn't get it right.

Mine has done the same since purchased. Replacing the compressor in a few weeks when I reinstall the engine. Maybe that will help.

 

[Dave 2000]

I replaced both engine mounts on a whim. Turned out to be a good call after 25 years with the heavy six on them. Virtually no vibes at idle (Diesel) and the car generally feels smoother. I think I posed up pictures, you can only tell if the mounts are good by removing them, forget the put a bar in here or there.

One thing I do know is if the mounts are soft and a vibe sets in the engine rocks to and fro as it bounces back against soft rubbers.

I would also question that slow idle, I have not read the whole thread but has the rpm been checked with anything other than the stock rev counter? Something else, does the engine run fast at cold start up? Perhaps there may be a clue there, idle speed has to be increased to counter thicker oil ect.

regards

Dave

 

[bmorgan]

I'm afraid I've replaced my engine mounts. They are less than 2 years old.

I have been using my OBD2 readings for rev.

I have noticed that my wife's 80 idles higher at first than mine does. That's a really good catch, Dave. I only recently noticed it when I cranked hers up. That's something...

 

[bmorgan]

Checked today - my initial RPM is about 1100.

 

[ItsBavid]

How's it coming along? I read in another thread that bad O2 sensors were causing an issue with similar problems that you're having with the AC on. Seems like you've tried everything but hopefully not this.

I'm experiencing the same thing at Idle while in drive and at a stop. With AC on ill be at 780 rpms and it starts vibrating obnoxiously. I'll turn the AC off and the RPM's will drop a hair and be smooth and as quiet as a hybrid. I wish I could just tune it to move up or down a couple hundred RPM's when the AC kicks on.

 

[bmorgan]

Well, I think I MIGHT have finally found the culprit. Did some staring at it with a buddy recently and we were noting that the vibration seemed to be in the belts. So I just took the fan and pulley off. I laid a long screwdriver against the engine so it was steady and drug it along the flange of the water pump. It looks like my water pump shaft is either warped or out of alignment. It's a toyota OEM and I did replace it not long before this all started.

Funny thing, ItsBavid - I just ordered new O2 sensors. I guess I can do that after I verify a new water pump is the fix.

I just looked up my maintenance log. I replaced it about 3 years ago and that's about the time I first noticed this. That's right - I've been annoyed for 3 years but I can put up with a lot.

 

[Theguiltyspark]

I had this exact issue. Vibrations through the truck when in drive and the AC on, no vibrations when the compressor would cycle of OR in park or neutral. I tracked the vibrations we coming from the muffler, right where the catalytic converters and O2 sensor are at. There is a bracket in this area and I was able to zip tie the muffler to the body of the truck to stop the vibrations. Problem solved. Harmonic vibrations suck!