Open for thoughts
10-15-2011, 09:09 AM
#1
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Year: 2001
Model: Cherokee
Engine: 4.0L I6
Open for thoughts
I just want to hear some people's thoughts, and I guess share an experience.
A couple of weeks ago I left my dome lights on overnight. Yes I know, I'm a dumb *** for it. I should have learned but apparently not because a couple of nights later I did it again. It was pouring and I was in a hurry to get inside. It wasn't a smart set of moves and I was pretty angry with my self.
Anyways, after the second time of getting jumped I took off to drive around to charge up. While I was driving I came to a stop light. It started to idle rough. I popped it in neutral and gave it a little gas. The light turned green and I went on to the next light. At that light, it idled rough and then died. In the city, with a string of traffic behind me. It started back up perfectly. From there I drove straight to a Sears Auto center, as that was the closest thing around and I quite frankly didn't know what else to do at the time. I thought it was the battery so went in and explained what happened. They said they didn't think it was the battery and convinced me to pay for a $20 test. They said the battery was fine and the alternator was bad. I went home to replace the alternator and dad said it was fine, so we didn't. Instead we replaced spark plugs because I have been wanting to and never go the chance. Over the course of a few days it started hard, like it was very cold out, but it wasn't. I went to AutoZone to have them run their battery check. They said the battery was bad and the alternator was fine. The next morning, it wouldn't start so I replaced the battery. It seems to be running fine. At stop lights it seems like it is idling a little bit rough and the RPMs are a tad low. But I could still be paranoid about the way it was acting the day it died at the light on me.
What are normal idle RPMs? Mine is running just under 500 at idle, in drive, with the brakes on.
Sorry for the long post lol. Also, I would not suggest going to a Sears auto center for work. They nearly caused major damage to my Jeep. They left the battery bracket sitting on top of the engine block. I drove nearly 50 miles with out realizing it. I didn't see a need to check under the hood after they worked on it, I thought they were professionals.
A couple of weeks ago I left my dome lights on overnight. Yes I know, I'm a dumb *** for it. I should have learned but apparently not because a couple of nights later I did it again. It was pouring and I was in a hurry to get inside. It wasn't a smart set of moves and I was pretty angry with my self.
Anyways, after the second time of getting jumped I took off to drive around to charge up. While I was driving I came to a stop light. It started to idle rough. I popped it in neutral and gave it a little gas. The light turned green and I went on to the next light. At that light, it idled rough and then died. In the city, with a string of traffic behind me. It started back up perfectly. From there I drove straight to a Sears Auto center, as that was the closest thing around and I quite frankly didn't know what else to do at the time. I thought it was the battery so went in and explained what happened. They said they didn't think it was the battery and convinced me to pay for a $20 test. They said the battery was fine and the alternator was bad. I went home to replace the alternator and dad said it was fine, so we didn't. Instead we replaced spark plugs because I have been wanting to and never go the chance. Over the course of a few days it started hard, like it was very cold out, but it wasn't. I went to AutoZone to have them run their battery check. They said the battery was bad and the alternator was fine. The next morning, it wouldn't start so I replaced the battery. It seems to be running fine. At stop lights it seems like it is idling a little bit rough and the RPMs are a tad low. But I could still be paranoid about the way it was acting the day it died at the light on me.
What are normal idle RPMs? Mine is running just under 500 at idle, in drive, with the brakes on.
Sorry for the long post lol. Also, I would not suggest going to a Sears auto center for work. They nearly caused major damage to my Jeep. They left the battery bracket sitting on top of the engine block. I drove nearly 50 miles with out realizing it. I didn't see a need to check under the hood after they worked on it, I thought they were professionals.
Last edited by NateXJ01; 10-15-2011 at 09:10 AM. Reason: I don't like the title
10-15-2011, 11:11 AM
#2
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Year: 1993
Model: Grand Cherokee
Engine: V8
Neither Sears nor the Azone have the lock on stupid techs. That said a bad battery will drag the alternator down to nothing at idle. Likewise a bad alternator will be most noticible at idle. 500 rpm idle is not that unusal, I think your fine.
Ron
Ron
10-15-2011, 04:50 PM
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Year: 1997 & 1998
Model: Cherokee
Engine: 4.0
First, your idle speed is just fine. Nothing there to worry about.
You replaced the battery. One more thing not to be concerned about. The rough idle is hard to determine by what you said. All straight 6s have some inherent roughness. Both of our XJs don't idle as smooth as a V8 or even a V6. Our previous two Jeeps didn't either. They're both tuned and run great otherwise.
You can check your charging system by yourself effectively and cheaply. While idling, alternators put out less voltage by nature. The faster they spin, the more they put out up to their maximum output. If yours is failing, it will effect idle by not putting out enough voltage to fire the plugs efficiently. At idle, a 90 amp alternator can put out as little as 12 to 15 amps. Here's how to check your charging system by yourself. All you will need is a multimeter which can be purchased anywhere for as little as under $10 at Harbor Freight or a bit more at a retailer, auto parts store, Sears, etc. Make sure to go with a digital model. They are much easier to read. I spent $50 on mine at Sears because I use it frequently and for more than the vehicles.
Make sure the battery is charged completely prior to testing. This is important to insure a valid test. Set the multimeter to 20 volts DC. Attach the red lead (+) to the positive terminal of the battery, the black (-) to the negative. Start the XJ. Look at the reading. Running at idle with no accessories on, you should have at least 13.5 volts or near that. A couple tenths of a volt less is no biggie. Now, start turning things on, lights, blower, etc. Look at the reading. It shouldn't be down below 13. If it is, rev the engine while reading the meter and still having everything on. You should have readings between 13.5 and 14.5.
If the idling reading with stuff on came down to near 12 or below but came up at high revs (don't race the engine, just rev it to 1500-2000 rpms or so), the alternator is weak and on borrowed time. If it never came up much above 13 regardless of rpms, it's weak. If it was reading normal to start and never changed much, your problem is elsewhere.
If the alternator seems weak or is questionable, replace it now. Save yourself the hassle later.
You replaced the battery. One more thing not to be concerned about. The rough idle is hard to determine by what you said. All straight 6s have some inherent roughness. Both of our XJs don't idle as smooth as a V8 or even a V6. Our previous two Jeeps didn't either. They're both tuned and run great otherwise.
You can check your charging system by yourself effectively and cheaply. While idling, alternators put out less voltage by nature. The faster they spin, the more they put out up to their maximum output. If yours is failing, it will effect idle by not putting out enough voltage to fire the plugs efficiently. At idle, a 90 amp alternator can put out as little as 12 to 15 amps. Here's how to check your charging system by yourself. All you will need is a multimeter which can be purchased anywhere for as little as under $10 at Harbor Freight or a bit more at a retailer, auto parts store, Sears, etc. Make sure to go with a digital model. They are much easier to read. I spent $50 on mine at Sears because I use it frequently and for more than the vehicles.
Make sure the battery is charged completely prior to testing. This is important to insure a valid test. Set the multimeter to 20 volts DC. Attach the red lead (+) to the positive terminal of the battery, the black (-) to the negative. Start the XJ. Look at the reading. Running at idle with no accessories on, you should have at least 13.5 volts or near that. A couple tenths of a volt less is no biggie. Now, start turning things on, lights, blower, etc. Look at the reading. It shouldn't be down below 13. If it is, rev the engine while reading the meter and still having everything on. You should have readings between 13.5 and 14.5.
If the idling reading with stuff on came down to near 12 or below but came up at high revs (don't race the engine, just rev it to 1500-2000 rpms or so), the alternator is weak and on borrowed time. If it never came up much above 13 regardless of rpms, it's weak. If it was reading normal to start and never changed much, your problem is elsewhere.
If the alternator seems weak or is questionable, replace it now. Save yourself the hassle later.
10-15-2011, 05:01 PM
#7
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Year: 1996
Model: Cherokee
Engine: 4.0
Sorry to jump in on the conversation but my 96 sport is barely running over 0 rpms when at a stop but fine when I'm up to speed any idea about that
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10-15-2011, 11:38 PM
#8
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Year: 2001
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Engine: 4.0L I6
First, your idle speed is just fine. Nothing there to worry about.
You replaced the battery. One more thing not to be concerned about. The rough idle is hard to determine by what you said. All straight 6s have some inherent roughness. Both of our XJs don't idle as smooth as a V8 or even a V6. Our previous two Jeeps didn't either. They're both tuned and run great otherwise.
You can check your charging system by yourself effectively and cheaply. While idling, alternators put out less voltage by nature. The faster they spin, the more they put out up to their maximum output. If yours is failing, it will effect idle by not putting out enough voltage to fire the plugs efficiently. At idle, a 90 amp alternator can put out as little as 12 to 15 amps. Here's how to check your charging system by yourself. All you will need is a multimeter which can be purchased anywhere for as little as under $10 at Harbor Freight or a bit more at a retailer, auto parts store, Sears, etc. Make sure to go with a digital model. They are much easier to read. I spent $50 on mine at Sears because I use it frequently and for more than the vehicles.
Make sure the battery is charged completely prior to testing. This is important to insure a valid test. Set the multimeter to 20 volts DC. Attach the red lead (+) to the positive terminal of the battery, the black (-) to the negative. Start the XJ. Look at the reading. Running at idle with no accessories on, you should have at least 13.5 volts or near that. A couple tenths of a volt less is no biggie. Now, start turning things on, lights, blower, etc. Look at the reading. It shouldn't be down below 13. If it is, rev the engine while reading the meter and still having everything on. You should have readings between 13.5 and 14.5.
If the idling reading with stuff on came down to near 12 or below but came up at high revs (don't race the engine, just rev it to 1500-2000 rpms or so), the alternator is weak and on borrowed time. If it never came up much above 13 regardless of rpms, it's weak. If it was reading normal to start and never changed much, your problem is elsewhere.
If the alternator seems weak or is questionable, replace it now. Save yourself the hassle later.
You replaced the battery. One more thing not to be concerned about. The rough idle is hard to determine by what you said. All straight 6s have some inherent roughness. Both of our XJs don't idle as smooth as a V8 or even a V6. Our previous two Jeeps didn't either. They're both tuned and run great otherwise.
You can check your charging system by yourself effectively and cheaply. While idling, alternators put out less voltage by nature. The faster they spin, the more they put out up to their maximum output. If yours is failing, it will effect idle by not putting out enough voltage to fire the plugs efficiently. At idle, a 90 amp alternator can put out as little as 12 to 15 amps. Here's how to check your charging system by yourself. All you will need is a multimeter which can be purchased anywhere for as little as under $10 at Harbor Freight or a bit more at a retailer, auto parts store, Sears, etc. Make sure to go with a digital model. They are much easier to read. I spent $50 on mine at Sears because I use it frequently and for more than the vehicles.
Make sure the battery is charged completely prior to testing. This is important to insure a valid test. Set the multimeter to 20 volts DC. Attach the red lead (+) to the positive terminal of the battery, the black (-) to the negative. Start the XJ. Look at the reading. Running at idle with no accessories on, you should have at least 13.5 volts or near that. A couple tenths of a volt less is no biggie. Now, start turning things on, lights, blower, etc. Look at the reading. It shouldn't be down below 13. If it is, rev the engine while reading the meter and still having everything on. You should have readings between 13.5 and 14.5.
If the idling reading with stuff on came down to near 12 or below but came up at high revs (don't race the engine, just rev it to 1500-2000 rpms or so), the alternator is weak and on borrowed time. If it never came up much above 13 regardless of rpms, it's weak. If it was reading normal to start and never changed much, your problem is elsewhere.
If the alternator seems weak or is questionable, replace it now. Save yourself the hassle later.
Thanks for that insight. I am pretty sure my Dad did that and said it was ok. Like I said, I think that the rough idle is just something in my head. I think that I think about it more now than I did before.
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