2000 Grand Am 4-Cyl shuts off when A/C turned off

Hello,

I’m having a very strange issue with my 2000 Grand Am 2.4 L 4-Cyl (88,000 miles). Whenever I turn off my A/C the engine begins to idle out and sometimes it just turns off. I don’t think it’s related to the A/C directly because it also happens when the headlights turn on. The scenario with the headlights is that I’ll come home from work and put the car in the garage, the light sensors will cause the headlights to turn on (no light in garage) and when they do the engine stutters and the rpms drop below 500 like it wants to shut off. It happens when the engine is warm and it’s very consistent. Does anyone have any idea what could be causing this?

Any help would be appreciated.

Thanks,
David

have you had your alt. checked or battery,fuel pump? sounds like something might be drawing your fuel pump down or battery but you may want to change gas filter first if you haven't yet?

have you had your alt. checked or battery,fuel pump? sounds like something might be drawing your fuel pump down or battery but you may want to change gas filter first if you haven't yet?
I haven't had my alternator or fuel pump checked but I have replaced both the battery and fuel filter within a year.

I'm not sure if it's the fuel pump since I don't have any issues with my car while I'm driving, it's really only an issue when it's sitting idle.

Have you checked for trouble codes ??

Sounds more like a TB issue, maybe your IAC is clogged or bad. You can test and clean it, something simple and cheap to try.
Here is a test procedure..
Idle Air Control(IAC) Testing Replacing for 99+ (http://www.automotiveforums.com/vbulletin/showthread.php?t=663849)

Have you checked for trouble codes ??

Sounds more like a TB issue, maybe your IAC is clogged or bad. You can test and clean it, something simple and cheap to try.
Here is a test procedure..
Idle Air Control(IAC) Testing Replacing for 99+ (http://www.automotiveforums.com/vbulletin/showthread.php?t=663849)

I've actually fully replaced the IAC before, probably about a year ago. It was for the same issue which always magically disappears in the winter and reappears in the summer (that's why I'm trying to fix it again this year). What is TB?

I've also replaced the MAF sensor hoping that had something to do with it but the issue persists.

Something else I wanted to add, I just took the IAC apart and cleaned it a little bit (had quite a bit of carbon) and put it back on. I did a little test by letting the car just sit there and warm up to 200 degrees, at which point I noticed that it was trying to idle out on its own, had nothing to do with the A/C. At random the RPMs would drop to 100 and the hole car would shake, then they'd go back up to 5-600. So it looks like it's not directly related to power consumption but it is still affected by it.

I'm at a complete loss. Are there any other parts that can affect a car while it's sitting in idle?

Did you set the IAC before installing the new one ?

TB is the throtle body.
Thier isnt much else that controls idle. If you havnt had a tune up, plugs & wires, you might try that for the rough idle and wanting to die when idling.

Just a shot in the dark here. . . I know the TPS failing often causes the cars to idle too high. Is there any way it could be causing the car to drop RPMs during idle? Wouldn't really explain the whole A/C and headlight thing though.

Did you set the IAC before installing the new one ?

TB is the throtle body.
Thier isnt much else that controls idle. If you havnt had a tune up, plugs & wires, you might try that for the rough idle and wanting to die when idling.

If by set you mean making sure it's shorter than 1 1/8 of an inch, then yes it's set. Was there another step to the process?

Also, I see that in your pictures your IAC has a spring leading up to the tip. My original IAC and my replacement did not. Is this normal?

you set it correctly then, you did cycle the key on for 10 seconds & off for 10 secs. to reset the new IAC ?

I'm pretty sure they all hav a spring but maybe the 2000 2.4 didnt..

You may also want to pull the throtle body off and thuroughly clean it.

you set it correctly then, you did cycle the key on for 10 seconds & off for 10 secs. to reset the new IAC ?

I'm pretty sure they all hav a spring but maybe the 2000 2.4 didnt..

You may also want to pull the throtle body off and thuroughly clean it.

I don't know how to cycle the key, would you happen to have instructions for that? Your instructions on the IAC were very helpful BTW...

Like hungrycat7 suggested, I replaced the TPS sensor. I also replaced the MAP sensor, but still no luck. Is the throttle body the plastic top that surrounds these sensors? If it is then I just barely cleaned it yesterday.

Now that I've replaced any and all possible sensors related to idle time or fuel deliver, I'm going to have the fuel pump checked out. I've been wanting to replace it anyway since my fuel meter doesn't work anymore and the only way to fix that is to replace the whole damn thing :mad:.

I don't know how to cycle the key, would you happen to have instructions for that? Your instructions on the IAC were very helpful BTW...

Like hungrycat7 suggested, I replaced the TPS sensor. I also replaced the MAP sensor, but still no luck. Is the throttle body the plastic top that surrounds these sensors? If it is then I just barely cleaned it yesterday.

Now that I've replaced any and all possible sensors related to idle time or fuel deliver, I'm going to have the fuel pump checked out. I've been wanting to replace it anyway since my fuel meter doesn't work anymore and the only way to fix that is to replace the whole damn thing :mad:.

Cycling the key you just turn it on for 10 secs then off for 10 secs. but it should have been done when it was replaced.

Your throtle body is the silver aluminum piece the IAC goes into, and the TPS is attached to. Probly full of carbon on the back side, thier is also a tiny hole in the TB butterfly that can get clogged and it can effect idle.

If your fuel filter hasnt been replaced in the last 20-30k miles you might change that out.

Yeah both my GAs have that floaty gas gauge, and Ive been waiting a long time to replace the whole unit but my fuel pump seems to just keep going and going. :rolleyes:
My Se is creeping up on the 200k mile mark, it should be going any time now.

Hope that helps

Hello everyone,

I just wanted to give a status update on the issue. I had my fuel pump switched out and so far so good. I don't have any issues when the car is in idle and I feel a little more horsepower from it too. I do still have the issue (occasionally) where the car struggles to start and I have to actually hit the gas to have it turn on. Once it turns on though I no longer have any problems. Anyone have any ideas what that could be? I'm thinking faulty spark plugs but they were switched out less than a year ago so I'm not sure...

Anyway, I hope my somewhat expensive adventure will help someone save some money when he/she has this same issue.

Thanks,
David

I don't know how to cycle the key, would you happen to have instructions for that? Your instructions on the IAC were very helpful BTW...

Like hungrycat7 suggested, I replaced the TPS sensor. I also replaced the MAP sensor, but still no luck. Is the throttle body the plastic top that surrounds these sensors? If it is then I just barely cleaned it yesterday.


Cycling the key simply means to turn it on and off, but I can give you a link to instructions if you need it :)

The throttle body is the aluminum piece that sits on top of the intake manifold. The TPS bolts directly onto the TB, as does the IAC.

Cycling the key simply means to turn it on and off, but I can give you a link to instructions if you need it :)

The throttle body is the aluminum piece that sits on top of the intake manifold. The TPS bolts directly onto the TB, as does the IAC.


I think I covered this in post #11 (http://www.automotiveforums.com/vbulletin/showpost.php?p=5791565&postcount=11), thats ok tho! :cwm27:

Just to give an update to my issue. The problem is back again, exactly as before. I turn the A/C off and the entire car turns off with it. I did notice that the car is more prone to doing this when it's running hot and the temperature gauge was probably at 230 F. today. My dad suggested that I get the computer checked out, he thinks that the coolant isn't being delivered soon enough causing the engine to overheat. Would anyone here agree or disagree with that statement? Anyone have anymore suggestions?

yeah it sounds like you're gonna need to get it scanned.
Hard to say if the engine shutting off when the AC is shut off are exactly related, coiuld be something altogether different.
230 deg is pretty damn hot ! Might also have your cooling system pressure tested to see if its a leaking or if you have a bad gasket(s).

try this unplug your wires going to air pump and see if it shuts down like that..

yeah it sounds like you're gonna need to get it scanned.
Hard to say if the engine shutting off when the AC is shut off are exactly related, coiuld be something altogether different.
230 deg is pretty damn hot ! Might also have your cooling system pressure tested to see if its a leaking or if you have a bad gasket(s).

Just an update on the overheating. I had my mechanic replace the thermostat (again) and it turns out that NAPA had originally sold him one that had an open termperature of 195 degrees. My car should have one that opens at 180 degrees. Now that I switched that out my car doesn't ever go over 200 degrees. So that's one problem solved! YAY!

My mechanic suggested that I try having my fuel injectors cleaned to take care of the rough idle problem. He's willing to do this at a pretty reasonable price but he isn't sure if it will fix the problem. What do you guys think? I use 44k fuel injector cleaner once a year, every winter to keep those things in good shape. I don't know if that's really the issue here...

Also, I might have the onboard computer checked out at my local dealership. My question is have any of you ever had work done on the computer and what have you been charged in the past for it? I just don't want to get ripped off but I have not idea what a reasonable price for this is.

Thanks again,
David

Yeah the 195 is a little hot fo rth e2.4. I think all these GM engines just run hot sometimes. Glad you got that resolved!

Injection cleaner should probly be used more often IMO a good cleaning by a good shop wont hurt anything tho.

Stealership will set you back close to $80 for diagnosis, might be more might be less just depends on your area.

Good Luck!

Hello everyone,

One more status update and hopefully my last on this topic. I just returned from the dealership and it turns out I had a faulty fuel pressure regulator. I was leaking little bits of fuel from it which was causing my irregular idle. They replaced the part and my car now runs great.

I know I replaced a lot of parts that didn't need to be replaced for this issue but hey, at least those parts won't be breaking anytime soon. :licka:

Thanks everyone for all your help,
David