Idle problem, mabey???

[jnaut]

Mine idles right at 600 rpm when its warmed up, figured that was normal.

x2

 

[TigerClaws]

Most cars do ... My friend's KIA rpm drops about a 150 just by clicking the power windows LOLL.... This is battery power with lots of appliances and my Jeep is far less vulnerable do dim as my Grand Am 99 was ... Just dont bother with it or get a more powerfull alternator i guess...

 

[kb0nly]

Problem is even with a more powerful alternator there is still a load put on the engine, so the engine still slows down and then back up a bit as it takes on that load and then compensates, so you can't really totally eliminate it.

A bigger battery helps somewhat with that because it takes the surge until the alternator picks up to take the load, just basically acts like a big capacitor smoothing out the power like those boom caps you guys put on your big stereo amps, but still at the point the engine is still going to slow with that load.

Back in the old days this wasn't as noticeable because the alternator was cranking out power regardless, good old one wire alternators! So the engine was always at a constant speed because of the constant load.

 

[Powerslave]

The idle can't be too low, then the emissions are not optimized. I had a Geo tracker, and I installed a SILENT IDLE button on it, that basically closed the Idle Air Valve. It's just a little 1.6 I4, it idled at about 600. I press the button, and it dropped to 200, and made no noise, was just something I messed with. IT didn't stammer or studder, but if you let it on that low idle too long, the CES light came on for emissions codes, and the oil light flickered too.

 

[tjkj2002]

Adding a bigger alternator on a KJ will do nothing since the PCM controls the charge level,the PCM would need to be reprogrammed to take effect of the extra amps.Adding a higher capacity battery will help.I have no dimming or idle drop when I kick on my headlights,fogs,HID's,and renny lightbar but a battery with over 1300cca's can handle alot of accesories. since they all are tied to the battery,the alternator only ties into the battery.

 

[Prospect62]

Hey guys, not to hijack, but this made me want to ask a similar question.

For the past few weeks, when I slow down and stop at a traffic light or stop sign or something, my idle stays at about 950 until I am at a complete stand still for about 3 seconds...then it drops down to the normal 650 RPM. Bear in mind that I have a 5-speed KJ and I coast to stops in neutral every time. So I'm in neutral when this is occurring. This is at normal operating temp. I have been totally stumped by this until I read this thread...then it occurred to me!

My KJ battery has been feeling like it's starting to go south for a month or so (concurrent with the idle abnormality). Could my PCM be compensating for the weak battery by keeping my RPM's up a bit? I would have no other explanation for this idle speed issue. No CEL, no vacuum leaks.

Any ideas?

 

[kb0nly]

Hey guys, not to hijack, but this made me want to ask a similar question.

For the past few weeks, when I slow down and stop at a traffic light or stop sign or something, my idle stays at about 950 until I am at a complete stand still for about 3 seconds...then it drops down to the normal 650 RPM. Bear in mind that I have a 5-speed KJ and I coast to stops in neutral every time. So I'm in neutral when this is occurring. This is at normal operating temp. I have been totally stumped by this until I read this thread...then it occurred to me!

My KJ battery has been feeling like it's starting to go south for a month or so (concurrent with the idle abnormality). Could my PCM be compensating for the weak battery by keeping my RPM's up a bit? I would have no other explanation for this idle speed issue. No CEL, no vacuum leaks.

Any ideas?

Possibly, it could also just be a bit of lag from the PCM sensing that the load on the engine dropped when you shifted to neutral.

 

[KJedmonton]

Adding a bigger alternator on a KJ will do nothing since the PCM controls the charge level,the PCM would need to be reprogrammed to take effect of the extra amps.Adding a higher capacity battery will help.I have no dimming or idle drop when I kick on my headlights,fogs,HID's,and renny lightbar but a battery with over 1300cca's can handle alot of accesories. since they all are tied to the battery,the alternator only ties into the battery.

I think A bigger battery will my solution for this, I am just happy to know that there is not a serious problem. Besides I am pretty sure its stock but can't verify that, so it's probably time...

Thanks!!!!!!!!

 

[TigerClaws]

I have the same problem Prospect, and i also need a whats up on that too !!?? Mine is automatic 4 speed and even when im letting the gas go, the rpm will not drop before a couple of seconds (4-6 seconds) which i think is weird. Going downhill and putting it in neutral RPM does not drop but stays as high as if i was in gear and still giving gas going same speed. What could cause that ?

 

[lil black liberty]

These guys right here for the PCM upgrade:
http://www.bgperformancepcm.com/#jeep


Was also told they could program it in there to get one of these bad oscars, I mean I know it's overkill but still it would be sweet to have one:
http://www.mean-green.com/products/index.html

200 Amp Alt... because they do make them for the KJ you just got to request it be done. At least that's what they told me when I get the money for these two upgrades I'm going for it.

 

[kb0nly]

I have the same problem Prospect, and i also need a whats up on that too !!?? Mine is automatic 4 speed and even when im letting the gas go, the rpm will not drop before a couple of seconds (4-6 seconds) which i think is weird. Going downhill and putting it in neutral RPM does not drop but stays as high as if i was in gear and still giving gas going same speed. What could cause that ?

I think the PCM either just gets confused or they made it do that.

Mine does the same thing, take foot off gas and it starts to drop slowly then stops around 800-900 RPM as i come to a stop, then if i sit there a few seconds it idles back down.

It does make sense though, it keeps it at high idle for smoother acceleration from a quick stop.

 

[kb0nly]

These guys right here for the PCM upgrade:
http://www.bgperformancepcm.com/#jeep


Was also told they could program it in there to get one of these bad oscars, I mean I know it's overkill but still it would be sweet to have one:
http://www.mean-green.com/products/index.html

200 Amp Alt... because they do make them for the KJ you just got to request it be done. At least that's what they told me when I get the money for these two upgrades I'm going for it.

With money anything is possible!! LOL

Cool..