Latley my car has started idleing rough. when I'm stoped at a light it seems like the car want's to die. The idle sounds low and it sort of sounds like it's chuging but the RPMS are where they have always been, about 450. I pulled into my freinds place last night and before putting it in park I left the lights on and rolled down both power windows at the same time. When I rolled them down the volts droped way low and the car really started chuging. This may be a common thing I don't know. The car seems to run fine when driving it's just when I'm stoped at a light or something that it starts to idle rough.

 

when my alternator went bad the windows got real slow, the radio started to go in and out, and the car lost alot of power, the blinkers didnt work as well, even though i had filled the blinker fluid tank

 

the belt may also be slipping... check it for loose tension or varnish

 

Does the car feel slower? If the alternator output is really low, it will affect performance big time. You should have a good 13+ volts cruising, and at idle it should not drop below 12.

 

yeah I have the volt guage and it reads around 13 to 12

 

Mine gives pretty good voltage readings at idle and at speed, but my idle drops every time the blinker blinks and is lower with the headlights on than with them off. I'm glad you guys posted this. Its the thing I think of when I'm driving but never remember to post.

 

I'm just curious what could be causing the rough idle. It's something that has just developed. I don't know what else it could be I've replace wires, cap & rotor, plugs, O2 sen., coil., timing is good. What else could cause rough idle?

 

a weak ignition cause by a weak alternator could cause these symptoms

 

Don't trust the stock guage for diagnostics, use a hand held multimeter (digital or analog).
Check your grounds and positive connections.

 

Your voltage at idle should be around 13.8 to 14.2. If it is near
12V, something is wrong.

 

The CS130 style alternators in 3rd gens are notorious for going bad. I've replaced the alt 3 times on my '89 Iroc, and only have 80K on the car.

 

my alternator is dying as well, i was planning on buying a new one, i am not sure whut the stock alt. has for amps but i was l ooking at either an 80 or 100...what do oyu guys think?

 

ok,
There are two things that cause a alt to go bad: one of the three diodes in the rectifier burning out, or the rear bearing. Of course the voltage reg could go to but is more rare.
If your alt experiances even ONE diode going out your car would not run past the life of the battery (about 15 miles max). Now your battery could be bad and your alt could be trying to pick up the slack, which makes it run at full capacity trying to keep the car running AND charge the bad battery. This could go on for a long while depending on the strength of your alt. A lot of times after people replace a battery the alt goes in about a month because of this.

The best way to test this is with an (true) AMP gauge. They run around $100 or most auto parts store will do it for you. Make sure the person using it knows what the hell they are doing. They should read the amps cold (without the car running) and while the car is running. This should tell you if it is the batt or alt.

What makes me cringe is your 450rpm idle. My formula does this and the charging system blows (at least by my standards). My iroc idles around 900-1000 and has NO charging problems. I will be rebuilding the Throttle Body on my Formula to fix this. (ChemDip, new IAC, and triple check the TPS). you might consider doing the same.
Your rough idle could be causing your charging problems, and a rough idle could have a lot of culprits.
but most are not to hard to handle

 

hey Val,

Well my guage does read around 13-14 while in drive I checked it again after my last post. Another suspistion of mine was maybe the TBS was not working properly. Is there anyway to check it? I know the tune up portion is fine everything has been replaced and it didn't have this problem prior to changing all the wires and plugs and so on, so I'm thinking it has to be some sort of sensor. I'm going to put up another post just to verify what my RPM's should be at.

 

The idle is probably due to a dirty IAC and IAC passages. You can clean it without disassembly, but is not as a complete cleaning as it could be.
If you take apart your Throttle body you will have to reset your TPS voltage. You will need a DVM or a scanner to do this.

Since you probably dont have these I would suggest removing the Throttle Body and then the IAC from the TB. Use a bottle of B12chemtool to clean out all the carbon. Be carful not to spray down the TPS sensor as it is sensitive to the sovlent. Clean it as best you can. Personally I would get a new IAC if you can, as this would eliminate it as a problem and considering the age of the car it won't hurt.

Make sure you spray down the TB blades with WD40 or something.

To be honest I've never heard of a TBS. I know of TPS, IAC and MAP that could be on or near the Throttle Body.

 

that was a typo, I meant TPS. What is the IAC?

 

when my altornator went it just stoped working. The voltmeter ion the car and a hand held read 8v while the car was running. I replaced it with a 108 amp altonator because that is what the car came with.The idle air control valve IAC is located on the throtlebody it is a valve that opens to alow more air flow to the engine under time of strain such as the air conditioning.