RPM drop at idle with A/C on or other load on engine.

[gump1976]

Hello everyone. Well I've done some searching around and everyone is quick to say 'ISC' when the problem of RPM's dropping when the A/C is turned on. For most people maybe that is the problem, but I dont think it is my ISC in my case, which leads me here. I have changed mine out with one I bought from Crebotech and it seems to be working fine. On my TMO readout, at idle, I can watch the "Idle Steps" readout go from single digits, all the way up to 130 after I turn the A/C on and still just drops about 200 rpms. I turn off the A/C and the Idle Steps number returns to single digits. I have taken the tb off and cleaned it well, changed the tb and tb elbow gaskets.

Is there anything else in TMO i can look at that might help me determine what the problem may be? My TPS seems to be fine as it goes from .51v at idle to 5.00v at full throttle.

When I pressure check my intake path, I can hear a leak from what sounds like the throttle body shaft seals, can that leak cause this problem?

This is really bugging me, I can't even try to run the A/C and have the headlights on at the same time because it will stall out when I stop. Is my throttle body just shot? Please help, and suggestions.

 

[95gster]

I recommend you do a boost leak test that might cause the weak idle with a/c on. Also unplug the iac then run the car and see if that fixes your problem......

 

[DiamondStarCar]

Does yours surge while idling? I have the same exact problem as you and i got around 33ohms of resistance on each pin of my ISC, therefore I don't believe my ISC is out. I unplug it and it does nothing....really confusing. Im extremely frustrated and I too would like to know what is wrong.

As for you, a vaccum leak could also be it. Check the wire on top of the TB to see if it is worn. I spliced on a new connector hoping it would fix my problem but it didnt. Maybe it will work for you. Good luck and have fun!

 

[v2ner]

do ur headlights dim a bit when u step on the brakes or use ur power windows?

 

[gump1976]

do ur headlights dim a bit when u step on the brakes or use ur power windows?

I do not drive enough at night to know that right now. The rpm's do drop a little when I use the power windows but not a lot, maybe 100 rpms, same goes for the brakes. I put a bought a new battery a week ago just to eliminate that as a possibility, but that didnt change anything. If I put my headlights on I lose 100-200 rpm. My idle is rock solid otherwise. No surging.

I know the switch on the top of the tb works fine, according to TMO. I know I need to get a boost gauge that reads vacuum as well. I'd hate to blindly dump more money into things that might not need to be replaced... alternator, throttle body... etc.. just to figure this out!

 

[philly5eagle]

I do not drive enough at night to know that right now. The rpm's do drop a little when I use the power windows but not a lot, maybe 100 rpms, same goes for the brakes. I put a bought a new battery a week ago just to eliminate that as a possibility, but that didnt change anything. If I put my headlights on I lose 100-200 rpm. My idle is rock solid otherwise. No surging.

I know the switch on the top of the tb works fine, according to TMO. I know I need to get a boost gauge that reads vacuum as well. I'd hate to blindly dump more money into things that might not need to be replaced... alternator, throttle body... etc.. just to figure this out!

Did you every figure out what was wrong? I am still having the same problems.