most unusual idle problem ever

[born2tune]

alright so when the marker lights are off my car idles at around 1500-1600 rpms, but when i turn the marker lights on (with or without the headlights) my car slowly calms to 850-900 rpm which it feels perfect all day and all night but when its off it seems like i got my foot reving lightly 24/7

also to top it off my instrument panel illum.control knob is what adjusts my air/fuel ratio mixture (somehow).
i bought it like this and i didnt figure it out till time when by and i got a good feel of the car and its internals, if you know what i mean.
i have owned it for a long time now and i have done alot of mods to it but just now i figured to give it a shot to see what i can learn/findout about it.

its either removing all the jacked up wiring and doing it right, but then i might affect the way the car is running? or it will probably fix it, but i know the dsm for never wanting to be "a normal operating car" ever but i want some points of view from you guys and i will proceed from there

this is a link of the video i took so you can see it for your self!
see to believe!!

fyi, i recorded it in HD format .
YouTube - weird idle mod? dsm 2g eclipse talon 4g63t awd

 

[dsmfa9nutter]

First of all, W.T.F. Secondly, the idle is probably caused by you having a near dead battery, turning on lights increases the demand on the alternator which puts more load on the engine which causes the idle rpms to drop. I don't believe your dimmer switch changes your a/f ratio. It's more likely that whoever installed the gauge sourced power from the wrong spot and it's messing with the gauge's functionality.

 

[xhackerekx]

for me bad ground for A/F gague.

 

[ArticNemesis]

Dead battery and/or dying alternator (perhaps just a bad electrical ground.) Your AF gauge is nothing more than a light show.

 

[born2tune]

First of all, W.T.F. Secondly, the idle is probably caused by you having a near dead battery, turning on lights increases the demand on the alternator which puts more load on the engine which causes the idle rpms to drop. I don't believe your dimmer switch changes your a/f ratio. It's more likely that whoever installed the gauge sourced power from the wrong spot and it's messing with the gauge's functionality.

well im pretty sure the "ratio control" is nothing more than sending less or more voltage to the gage, im thinking because its power is attached to the cluster lighting as i dim/turn the knob i also send less voltage to the gage altering it to where it shows a false image. this is all the previous owners fault.

and its not a dead battery, 1 because its a new battery and trust me i know how slowly dying batteries act, but im thinking its also some bad wiring at a point when the engine was rebuilt by the other owner.

and theres no telling where to start once people start splicing and re-routing and doing shitty jobs and not caring about the future or theyre saftey and most important it shows no pride in your work!!!

thanks for the help tho!

 

[95talongirl]

yeah... i'd see how that gauge is actually wired up.... it does seem like it was wired into the dimmer switch.. which is weird. I bet if you find a better source for the power feed and ground, it'll fix it.

As far as the idle dropping when the lights are on, i agree with the above post... (espically if its cold..) more load on the alternator...

 

[twdorris]

Wow. That's pretty cool, actually.

It doesn't seem like a dead or dying battery to me. It seems like the ECU is actually picking a different target idle point and then slowly adjusting the ISC to achieve it. The only thing I can think of that might cause it to do that would be a funky coolant temp sensor reading. But without a datalog it's going to be really hard to know what's possessing the ECU. A datalog would probably tell you in 30 seconds what's going on.

EDIT: I suppose it could also be some strange ground offset throwing everything off.

Thomas Dorris
ECMTuning, Inc.