Idle problem, mabey???

[KJedmonton]

Alright so I don't know if this is a new problem or I am just starting to notice it more, but when I am just idling (after the engine is all warmed up) every now and then I feel the engine kind of do a "dip" in the idle, and the headlights dim for that brief second as well. I also see a dimming of the headlights as well if I press on the brakes or roll down the window. I don't really notice a dip in the rpm gauge when it happens, the plugs are new (problem still happened with old plugs), and no codes. So I am at a loss... Any Ideas???(bowdown)

 

[lil black liberty]

You know mine does that too.. I replaced the battery with an Optima Yellowtop and I still have the problem. Could it be an Alternator issue??

 

[LibertyTC]

dip an doodle

ya it will dip when the compressor kicks in for a second (loose hill an pulling power) Compressor will run with heat on and in defrost settings, and cold etc.
Really I wonder why kj's came with about 600 CCA batteries. My lights will dim often at idle when stuff is on and compressor kicks in. It is like also that the charging circuitry cant keep up to the draw..........WEAK !!SHOCKED.gif
Wonder how much a 1000CCA battery fully charged would tune things up.

 

[KJ zGal]

Mine does the same thing but it's never caused me any real problems, knock on wood...so maybe the old, "if it's not broke, don't fix it," idea comes into play here? Unless it's stalling out on you, that is...

 

[JeepJeepster]

Lights dimming is normal. Ive got a 1000CCA red top and they will dim at idle. They will dim at hw speeds if I use the power seats, guess those things really pull the amps.

 

[Powerslave]

Mine idles at about 500rpm; I thought 600-800rpm was about right for an Automatic... I get some dimming on mine when at idle, and the fan kicks in. That's somewhat normal, but it should not dim so much that it looks like they were about to go off completely.

From what was read here, the ECM controls the voltages, so even with a more powerful alternator, the ECM only allows amps through, for the one it came with, and would need updated for the larger one, like what's in the renegade. These come with a 130some amp alternator, and the Renegade a 160some amp, so, you still would only utilize the 130some with the better alternator. The ECU would need reprogrammed for the larger amp alternator...

Again, not carved in stone, someone else may know the exact info.

 

[Boiler]

what kind of RPM are you running at idle? Mine does this only when I'm sitting below about 1100. Usually I notice when I run windows. Also, if you run multiple windows, they go slower. Simply lack of juice for the system. It is probably a combination of alternator, RPM, and reality. I've had other cars do this, some worse than others.

Pretty sure it is just an efficient electrical system. If it would keep everything running at 95%+ during your lowest electrical output, most of the time you'd be wasting energy created extra potential just to not experience dimming / slow windows.

I would have to say I wouldn't worry about it unless it is effecting driving / visibility.

 

[Boiler]

That does seem like a bit slow for RPM but what do I know...

Mine does it a little and I idle at about 900 RPM.

 

[Powerslave]

900 yours idles? Well, even if 800 was the average, yeah, mine is only 500rpms. Sometimes 550 or 600, but never above. I guess I will adjust the idle today...

 

[kb0nly]

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

 

[Atrus]

From what was read here, the ECM controls the voltages, so even with a more powerful alternator, the ECM only allows amps through, for the one it came with, and would need updated for the larger one, like what's in the renegade. These come with a 130some amp alternator, and the Renegade a 160some amp, so, you still would only utilize the 130some with the better alternator. The ECU would need reprogrammed for the larger amp alternator...

Good point, never thought of that. I always just thought if/when I needed a new alternator I'd throw the higher output version on there.

 

[KJedmonton]

So it kind of sounds like a normal thing to happen, thats good because I didn't really know were to start! I did not care to much about the lights dimming, it was more the drop/shake in the engine that was making me scared... Oh I think mine idles around 600/700 when warm. Thanks everyone!!!!!!!!! (woot)

 

[Atrus]

Every car I have owned has done that slightly. I wouldn't worry.

My Jeep dims the headlights when I roll the windows up. All of my past vehicles have done that too. It's a decent amount of current draw to complete that task.

 

[Atrus]

Also, the tach may not be that accurate. You see 500 rpm, it could be 700. You'd need a scantool to really know.

 

[kjweston]

yeah mine idles right at about 600

 

[Jeepin05]

Same here, dead on 600 rpm at idle.

 

[kb0nly]

So it kind of sounds like a normal thing to happen, thats good because I didn't really know were to start! I did not care to much about the lights dimming, it was more the drop/shake in the engine that was making me scared... Oh I think mine idles around 600/700 when warm. Thanks everyone!!!!!!!!! (woot)

That little drop shake at idle seems very normal with most modern vehicles, my wife's PT does that, our minivan kinda felt the same way, i don't know why they do it for sure. I had a mechanic tell me once its just the way the computer behaves monitoring the fuel/air ratio at slower engine speeds, a slight stumble can be felt, but the computer thinks its normal and doesn't register something like a misfire. Make sense at all??

If you speed it up to 1000 rpm that feeling goes away, so it just seems to do it down at idle.

 

[kb0nly]

Same here, dead on 600 rpm at idle.

Sounds like 600 is the norm..

Couldn't find it in the service manual what it should be set to, but i'll go with what everyone else has.. LOL

 

[Warren.fischbeck]

That little drop shake at idle seems very normal with most modern vehicles, my wife's PT does that, our minivan kinda felt the same way, i don't know why they do it for sure. I had a mechanic tell me once its just the way the computer behaves monitoring the fuel/air ratio at slower engine speeds, a slight stumble can be felt, but the computer thinks its normal and doesn't register something like a misfire. Make sense at all??

If you speed it up to 1000 rpm that feeling goes away, so it just seems to do it down at idle.

I would think that idle would be the lowest rpm prior to stall that the computer can achieve. The studder just might be the computer finding that sweet spot...

 

[kb0nly]

I would think that idle would be the lowest rpm prior to stall that the computer can achieve. The studder just might be the computer finding that sweet spot...

Exactly...

Thats what i was always told anyway.