[RESOLVED] Idle Is Low When Ac Is On ( Solution)

[razey]

Hey guys,

I am having some trouble with my AC, i am not to sure what the problem is so any help is greatly appreciated. Basically, when i turn my AC on and put the car in drive, my RPM's drop to about 625 and slowly rise up to 700ish RPM's. Some times when i put it into drive the the AC on it stays at around 625 RPM's. It seems to be intermittent mabey...
Also i have a good size boost leak in the car, i dont think this will cause my AC problems, but i am fixing it this weekend.
Also my car was shipped to Puerto Rico about 2 months back, i ended up having to replace the Battery that died on the way over here. Could something be jacked up with my alternator or AC Compressor?

Thanks,
Steve

 

[rush2252]

thanks Rush

here is what i did exactly :

did a boost leak and found leaks in the shaft seal ( throttle body and idle screw) i fixed them both and i bough a new idle screw with o ring

cleaned the throttle body
cleaned and changed several times the ISC
i restarted my ECU several times by unplugging the battery ( i left the car idles for 10 minutes before i start the AC )

NOTHING is fixing this problem if the car idles at 800 rpm without ac then i switch on the AC it dies. i have to make it idle at 1500 rpm in order for her to idle down at around 700 rpm but again between shift it stalls and sonetimes it reaches to 200 RPM ( BAD BAD vibration)

for the performance i am sure its beacuse its very hot the ecu is pulling timing and make it slower ( its fine with me this is not my issue )

vaccum with ac is on is 14 and sometimes 12 , when ac is off the vaccum is at 18-20

Have you check the intake manifold gasket or ever changed it? The reason I ask is because I dont recall my leaky gasket ever showing up on a BLT. From my experience my 2g would not idle and would constantly surge before I fixed the intake leaks. The ISC to my knowledge opens and closes to raise or lower idle depending on engine load IF and only IF you have a sealed environment with the Throttle Plate closed. I may be way off in left field but this is from my experience and from what I gather just looking at how its designed. If im wrong which I have been in the past somebody correct me. The ISC is set and once you turn on the A/C it opens or retracts so to speak allow air to enter the intake through the port in the bottom of the TB whenever idle raises the ISC if functioning properly is supposed to close and lower the idle.

If your still getting idle surge with a good ISC you have a leak somewhere or the FIAV isnt functioning properly. The FIAV is in the lower half of the TB. Read how it works in the VFAQ, also how often is the idle surge and have you checked base timing on the car?

 

[steve]

Idle surge is caused by the ECU seeing the engine speed being higher than the limits set for that ECT.
The most common cause is air leaking past the throttle butterfly either through the throttle body, one of the several other ports into the manifold, or like was pointed out from bad gaskets between the head and intake or throttlybody or injectors. A misadjusted BISS can add enough air to cause surging.

I ruined my original TB doing the seal replacement by over cleaning the butterfly. Their is a sealant around the outside edge on the back side of the butterfly and if you remove it the butterfly may leak too much air. You also not to touch the IPS on a 1G or the fixed SAS on a 2G (the stop screw) both of these control how far the butterfly closes in the bore.

The ISC and FIAV can allow more air than designed to bypass the butterfly. They are meant to be the primary paths during warming up so when people block them off they remove quite a bit of air and they "fix" their surging.

The failing to correctly manage the idle speed when the ECU should be in control continues to be unresolved. I should be sleeping so I won't post all the diagnostic steps that I've posted many times before on the site.

 

[RayBan GST]

Thanks rush and steve


i have made a BLT found some leaks on the gasket but only with soapy water , and those leaks were fixed, i did not change the gasket but i seal it with silicon and i did the BLT again and there was 0 leaks

As for the FIAV i am not sure if this is my problem as on cold start my car is fine and does not have any issues

i really suspect my ISC i will go today and ask my friend to let me borrow his ISc for a while just to make sure its not the porblem ( did i mention before that i changed it so many times) however i did not mention that all the times it was used but tested good 28 ohmp

i need to do this today so i will not give you more headache iam sorry for that but i believe that you feel with me its HELL here without AC

Thanks

 

[steve]

The ISC/IAC is only a small part of the idle speed control circuit. There in no point to changing it yet again. Assuming you measured the resistance of the 4 coils and they were all between 20 and 40 ohms it should be good and you have to look at the other parts of the system like the IPS, wiring, and ECU.

 

[roni-wan]

well seems we have different problems my main problem its the a/c cycling on/off and the car feeling really slow and heavy even starts to charge boost sooner without been at WOT on a b16g

 

[foxfan88]

I'm going to drop in here....

Can i get an Exact location on this expansion valve? And is it hard to get to? (like is it a chore to get it out?

My 91 talon has some symptoms similar to some listed in this topic.

My car idles great with AC OFF. when i turn it own, car idles down real low to around 5-600. And the car feels really loaded down while driving with the AC on, almost like the car is pulling something behind it.

 

[roni-wan]

any news? got the expansion valve will replace ir next week maybe it fix my problems

 

[roni-wan]

see the title changed to resolved what was the fix?

 

[dsmconifer]

I'm going to drop in here....

Can i get an Exact location on this expansion valve? And is it hard to get to? (like is it a chore to get it out?

My 91 talon has some symptoms similar to some listed in this topic.

My car idles great with AC OFF. when i turn it own, car idles down real low to around 5-600. And the car feels really loaded down while driving with the AC on, almost like the car is pulling something behind it.

i am going to second, this mine does the same exact thing to the dot. but i have a 92 eclipse n/t.

 

[RayBan GST]

hello again

well you are not gonna believe what was the fix of my problem , as you know ive been fighting this problem for so long and nothing seems to help so i decided yesterday to start all over again step by step , i worked on the car for almost 4 hours non stop rechecked everything but still the problem is there. i hated myself and the car and i made a decision to sell it, i was so furious that i floor it so hard until redline with no mercy until i busted the steering wheel pipe i dont know why it got busted ???? the steering fluid was all over the place it was a huge relief for the car and the car felt so fast

i pop the hood and fix the pipe and wiped the oil and start the car again GUESS WHAT ???? my idle is back to normal and i switch off the AC to find that my rpm is going up again responding to the AC my problem was the steering pump having to much fluid and pressure and i was so blind not to see it. flooring my car so hard with no mercy showed me the way for the great fix. dont do it


MY PROBLEM IS SOLVED AND I CAN DECLARE NOW THAT THIS THREAD IS RESOLVED.

 

[paultheninja]

I did a search and nothing was really answered. When I turn my ac on the second notch, The idle starts to really bounce, sometimes as low as 200rpms. If I turn my AC on full blast, my car will die at a stop light.

 

[BlueTurboSpyder]

If you have a vacuum gauge handy, I would check to see if your car has a normal vacuum at idle between 17-20 inHG with the a/c off. If you do the test and it's much lower more than likely you have a small to moderate vacuum leak somewhere. If this is true, that could cause your car to stall out when the a/c compressor operates once the a/c is on. If you can't do the test, does your car feel like it has the power it should while acclerating. If not, this could be a sign of a boost leak somewhere which in turn could be related to the problem of your car stalling. Good luck.

 

[jstgon]

Yes. I would agree with spyder, do the boost leak test. You could also check your grounds, that could have a slight role as well.

 

[RayBan GST]

just go to my old thread and you will find your answers there in details , i have been fighting this issue for a while now .

go to search and write idle is low when ac is on


good luck

 

[BlueTurboSpyder]

I did a search and nothing was really answered. When I turn my ac on the second notch, The idle starts to really bounce, sometimes as low as 200rpms. If I turn my AC on full blast, my car will die at a stop light.

RayBan GST, I know the problem described above sounds similar to yours but the solution to fixing your car is actually a very rare fix when dealing with those symptoms. The symptoms described can appear in some various issues that dsms experience. I very strongly suggest that paultheninja do the test for the most common problem first. A vacuum or boost leak can cause those symptoms and its beneficial to check that every once in a while anyway with our cars.

paultheninja, perform the test and if you are unable to find any issue there then do a little more research. Check out RayBan GSTs post. Also, if you have a question like that in the future just post a new thread in the problem diagnosis section. Good luck!

 

[roni-wan]

hello again

well you are not gonna believe what was the fix of my problem , as you know ive been fighting this problem for so long and nothing seems to help so i decided yesterday to start all over again step by step , i worked on the car for almost 4 hours non stop rechecked everything but still the problem is there. i hated myself and the car and i made a decision to sell it, i was so furious that i floor it so hard until redline with no mercy until i busted the steering wheel pipe i dont know why it got busted ???? the steering fluid was all over the place it was a huge relief for the car and the car felt so fast

i pop the hood and fix the pipe and wiped the oil and start the car again GUESS WHAT ???? my idle is back to normal and i switch off the AC to find that my rpm is going up again responding to the AC my problem was the steering pump having to much fluid and pressure and i was so blind not to see it. flooring my car so hard with no mercy showed me the way for the great fix. dont do it


MY PROBLEM IS SOLVED AND I CAN DECLARE NOW THAT THIS THREAD IS RESOLVED.

No way!!! couldn´t have imagine that ever!


but don´t see why steering pump its related to the A/C, if it would be a bad pump you should have that problem all the time not just with a/c on.

with the steering fully functional now and a/c ON, problem its completely gone?

with a disabled steering wheel engine will see less load and any extra load caused by the a/c its compesated with this absense