Almost dying when stopped
Thread Starter
Cruising
Joined: Jun 2009
Posts: 11
Likes: 0
Almost dying when stopped
Every time I come to a complete stop, my '94 does exactly the same thing:
The RPM's will come down, the volt's start coming down, and the car almost dies, but not quite. Then it will come back up to normal RPM's and volts for a second or two, then back down for a second or two.
It does not stop doing this until I move. The car has never died on me yet, but it is very annoying. I have never had this happed while moving at any speed.
The worst is at night, because the headlights dim very badly and then come back on full, so I am sure the person ahead of me is wondering "what in the hell...?"
Any ideas I can start with? This has been going on ever since I bought the car last June.
The battery is a 2 year old wal-mart brand. Every thing else is stock. No idea when the plugs were last changed.
The RPM's will come down, the volt's start coming down, and the car almost dies, but not quite. Then it will come back up to normal RPM's and volts for a second or two, then back down for a second or two.
It does not stop doing this until I move. The car has never died on me yet, but it is very annoying. I have never had this happed while moving at any speed.
The worst is at night, because the headlights dim very badly and then come back on full, so I am sure the person ahead of me is wondering "what in the hell...?"
Any ideas I can start with? This has been going on ever since I bought the car last June.
The battery is a 2 year old wal-mart brand. Every thing else is stock. No idea when the plugs were last changed.
Instructor
Joined: Jan 2010
Posts: 174
Likes: 4
From: Austin_Palm Bay_Houston Texas_Florida_Texas
You may have a couple of things going on here.
First, your battery may be on the way out, as it should hold most it's charge from the constant alternator charge. With that said, if your RPM's are dropping so low to the point of almost stalling, it is normal that the battery will drop a couple hundered milivolts or so. At very low RPM, the output of the Alt. becomes greatly diminished. At very low RPM, your voltage drop will become more pronounced if you have a lot of your accesories running.
Secondly, it sounds like you may have a "lazy" IAC. When you let off of the throttle, your IAC should respond quickly and open up to let more air flow through the idle passage in your throttle body. I would recommend removing TB, clean out the carbon buildup in the idle passage in the TB, and the IAC pintle.
First, your battery may be on the way out, as it should hold most it's charge from the constant alternator charge. With that said, if your RPM's are dropping so low to the point of almost stalling, it is normal that the battery will drop a couple hundered milivolts or so. At very low RPM, the output of the Alt. becomes greatly diminished. At very low RPM, your voltage drop will become more pronounced if you have a lot of your accesories running.
Secondly, it sounds like you may have a "lazy" IAC. When you let off of the throttle, your IAC should respond quickly and open up to let more air flow through the idle passage in your throttle body. I would recommend removing TB, clean out the carbon buildup in the idle passage in the TB, and the IAC pintle.
Le Mans Master
Joined: Mar 2004
Posts: 8,700
Likes: 298
From: Ft. Lauderdale Fl
Many times you get a hint from a code. Have you checked for codes.
Could be one of a few things...ie. an O2 sensor/idle air control motor or a dirty T/B.
These are cheap (under $50.00) and easy to install. Cleaning the throttle body also is not to difficult.
Could be one of a few things...ie. an O2 sensor/idle air control motor or a dirty T/B.
These are cheap (under $50.00) and easy to install. Cleaning the throttle body also is not to difficult.
Last edited by runner140*; Feb 10, 2010 at 02:06 PM. Reason: add
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
Team Owner
Joined: Jan 2009
Posts: 73,568
Likes: 33
From: Somewhere in Mo
St. Jude Donor '09-'10, '14
You may have a couple of things going on here.
First, your battery may be on the way out, as it should hold most it's charge from the constant alternator charge. With that said, if your RPM's are dropping so low to the point of almost stalling, it is normal that the battery will drop a couple hundered milivolts or so. At very low RPM, the output of the Alt. becomes greatly diminished. At very low RPM, your voltage drop will become more pronounced if you have a lot of your accesories running.
Secondly, it sounds like you may have a "lazy" IAC. When you let off of the throttle, your IAC should respond quickly and open up to let more air flow through the idle passage in your throttle body. I would recommend removing TB, clean out the carbon buildup in the idle passage in the TB, and the IAC pintle.
First, your battery may be on the way out, as it should hold most it's charge from the constant alternator charge. With that said, if your RPM's are dropping so low to the point of almost stalling, it is normal that the battery will drop a couple hundered milivolts or so. At very low RPM, the output of the Alt. becomes greatly diminished. At very low RPM, your voltage drop will become more pronounced if you have a lot of your accesories running.
Secondly, it sounds like you may have a "lazy" IAC. When you let off of the throttle, your IAC should respond quickly and open up to let more air flow through the idle passage in your throttle body. I would recommend removing TB, clean out the carbon buildup in the idle passage in the TB, and the IAC pintle.
When you are at home tonight do this. Let the car idle, don't pay any attention to what it is doing, turn on the AC and observe what happens.
If the three of us are correct your car will most likely die. The IAC, if working properly, should open to allow more air in to compensate for the added AC pull.
Even if this doesn't do anything take the IAC out and clean it with carb cleaner and clean out the cavity where the IAC sits and the throttle body as well. This will cost zero dollars and will give you an idea if this is it or you need to start other checks.
Sorry, actually all five of us at this point. I had to diagnose a bad IAC and fuel leak down at the same time. It took a lot of research here on the forum but I finally figured I had two issues going on. That was a booger for a rookie like me.
Last edited by RetiredSFC 97; Feb 10, 2010 at 05:13 PM.
Thread Starter
Cruising
Joined: Jun 2009
Posts: 11
Likes: 0
When you are at home tonight do this. Let the car idle, don't pay any attention to what it is doing, turn on the AC and observe what happens.
If the three of us are correct your car will most likely die. The IAC, if working properly, should open to allow more air in to compensate for the added AC pull.
Even if this doesn't do anything take the IAC out and clean it with carb cleaner and clean out the cavity where the IAC sits and the throttle body as well. This will cost zero dollars and will give you an idea if this is it or you need to start other checks.
But I will replace the battery, and clean the IAC and TB tonight.
Team Owner
Joined: Jan 2009
Posts: 73,568
Likes: 33
From: Somewhere in Mo
St. Jude Donor '09-'10, '14
I hvae a 97 Dodge ram and when the battery died on it, it would not idle at all. If I gave it a little throttle it would run like a champ. A typical IAC failure. My point is these batteries can do weird things.
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