rough idle after doing big 3 upgrade

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=123997
Printed Date: July 21, 2025 at 3:35 AM

Topic: rough idle after doing big 3 upgrade

Posted By: mrm1776
Subject: rough idle after doing big 3 upgrade
Date Posted: October 18, 2010 at 10:22 PM

I just did the Big 3 upgrade in my 2004 Toyota Camry. I ran 0 gauge from the alternator to the battery with a 100 amp fuse in between. Re-did the factory ground wiring going from the battery to chassis and from the battery to engine block with 4 gauge wiring. Ran a new 0 gauge wire from the battery to the chassis.

Now I'm getting a little bit of a rough idle. Car seems to idle at about 500 RPM. If I hit the gas to get it to about 600 it smoothes out.

Anyone else had this problem or know of a way to slightly increase idle speed? I'm fairly sure the idle speed is computer controlled, but I'm not 100% sure.

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MECP Basic Installation Tech
Certification ID: CEA195600
Pioneer AVIC-X920BT
Polk Audio DXi 6500 - front
Rockford Fosgate Power T1693 - rear
Alpine MRP-F300
Alpine MRP-M500
Alpine SWR-1242D

Replies:

Posted By: i am an idiot
Date Posted: October 18, 2010 at 10:46 PM

Recheck all areas you worked in, you may have knocked a vacuum hose off.

Posted By: mrm1776
Date Posted: October 18, 2010 at 11:42 PM

Roger that... I'll have to check that tomorrow. And it could be something else completely non-related that just evidenced itself tonight. The car has 160,000 on it.

-------------
MECP Basic Installation Tech
Certification ID: CEA195600
Pioneer AVIC-X920BT
Polk Audio DXi 6500 - front
Rockford Fosgate Power T1693 - rear
Alpine MRP-F300
Alpine MRP-M500
Alpine SWR-1242D

Posted By: awdeclipse
Date Posted: October 19, 2010 at 7:13 AM

Drive the car around a bit and see if it smooths out. The ECU lost all of its trim values when you disconnected it from battery power.

If it doesn't improve in a day or two then you may have knocked something loose or missed a connection as the other poster mentioned.

Did it always idle around 500? Or is it idling lower now after the power fail to the ECU?

Posted By: mrm1776
Date Posted: October 19, 2010 at 9:56 AM

Seems that it has always idled pretty low. I'll check today to make sure nothing got knocked loose and then I'll just drive it around to see if it fixes itself.

-------------
MECP Basic Installation Tech
Certification ID: CEA195600
Pioneer AVIC-X920BT
Polk Audio DXi 6500 - front
Rockford Fosgate Power T1693 - rear
Alpine MRP-F300
Alpine MRP-M500
Alpine SWR-1242D

Posted By: mrm1776
Date Posted: October 19, 2010 at 7:59 PM

I think it was the air flow sensor. I unclipped it and reseated it back in. No more rough idle.

-------------
MECP Basic Installation Tech
Certification ID: CEA195600
Pioneer AVIC-X920BT
Polk Audio DXi 6500 - front
Rockford Fosgate Power T1693 - rear
Alpine MRP-F300
Alpine MRP-M500
Alpine SWR-1242D

Posted By: oldspark
Date Posted: October 19, 2010 at 8:28 PM

Classic!
I was thinking awdeclipse had it with the "power reset" (as per most systems - Delco, Japanese etc).
Or ImAnIdiot on the "bumped something" theme. (And the AFM may have been bumped!)

What I like is OP mrm1776 doing the classic first cut diagnosis - disconnect & reconnect all connectors. [And fuses - but they should also be rotated to transfer fuse problems.]

So now the beast can self-tune itself.

Thanks for showing that the most complex problems may be fixed very simply. (In retrospect of course!)

Posted By: mrm1776
Date Posted: October 19, 2010 at 8:32 PM

I had actually disconnected the air flow sensor during this project to make it easier to remove the air box.

Glad it was an easy fix and didn't require me undoing ALL of my hard work from yesterday. I did pick up about 0.4V at my amp just by replacing these wires.

Posted By: oldspark
Date Posted: October 19, 2010 at 9:16 PM

Like I said - easy fix.
I said NOTHING about the cause of the problem. (I wish we had the 5th Amendment here in Oz! I have to rely on senility instead.)

And it was NOT wasted time since you proved my point - disconnect and reconnect - it fixes most problems. (Though in this case, not the cause.... LOL!!!) (Read: Dude - been there; done that. And still going there...)

Besides, the 0.4V is a nice gain. That can be at least a 6% gain in the amp's output power.

Congrats on both outcomes.