Hot Rod Forum : Hotrodders Bulletin Board

Hot Rod Forum : Hotrodders Bulletin Board (
-   Modern Electronic Engines (
-   -   2007 silverado misfire (no codes) (

poy41 12-24-2011 06:54 AM

2007 silverado misfire (no codes)
Hello all,

I have a 2007 (classic) siverado with a 4.3L and 57,000 km. I just finnished installing an amp for a 12inch sub and notice under heavy bass the head lights dimmed a dit, this is understandable as its a heavy load. So I reved the engine a bit (1800rpm) to help out the system with charging. then the check engine light started flashing. turned off the engine and back on, light was off. did the same thing, only the volume a little lower and no RPM and the light started flashing again, then when off in about 1 minute. took it for a 10km drive, stoped, accelerated, engine off/on, highway speeds, everything seems fine. ODB2 scaner shows no codes. Aslo, had to disconect the battery to hook up the amp and all this happen right after. (everything is tight on the batt.)

any ideas?

was thinking:
-'low voltage' problem.
-old spark plugs.
-bad grounds.
-bad battery

thanx for any help :)

sbchevfreak 12-24-2011 08:41 AM

Low voltage, or possibly spikes due to the heavy draw. If the headlamps are pulsing in this truck, you need to add a capacitor into the amp circuit to fix this.

Augusto 12-24-2011 10:13 AM

you must take the juice directly from the bat and install one of those big capacitors. they will fix your problem and will add some looks to your audio system.

Blazin72 12-24-2011 10:35 AM


Originally Posted by Augusto
... install one of those big capacitors...

I was going to say the same thing. If you don't have a capacitor then install one. If anything, your headlights won't dim whenever the bass hits.

poy41 12-24-2011 02:56 PM

So you all are thinking a low voltage/amperage might be causing this misfire/flashing CEL. Thats kinda what i was thinking too. I have a 4ga wire from the batt. Directly running to the amp, and a 4ga wire running from the frame to the amp (cleaned the paint off and all that). But the factory ground for the truck looks to be a 6ga wire running to the engine block and thats about it. So i was also thinking about doing the 'big 3 update' as well as a cap. Perhaps a new batt may be needed as well.

Anyone know why the misfire didnt toss a code ?? I find this odd.


Blazin72 12-24-2011 03:00 PM

Did you take care of installing a capacitor yet? Again, at a minimum it should take care of the dimming headlights on bass hits.

poy41 12-24-2011 03:13 PM

the dimming lights isnt what worries me, i know what thats from, its the CEL is whats gets me.

Siggy_Freud 12-24-2011 06:10 PM

Is the problem still occurring? If so, disconnect the audio/amp and see if it goes away. If it does, most likely your audio is pulling enough juice that it's robbing the ignition system.

poy41 12-24-2011 09:24 PM

just went for a 20 min. drive with the amp/deck off and everything was ok. dont know if i really wanna try and make the CEL flash again(misfire), as i hear its hard on the cat(s). think ill try the Big 3 Upgrade and see where i stand then.

also, when a misfire happens like this, should it be coming up more often if it were an other problem (aka sparkpugs, water in fuel, pluged injecter, etc...)?

poy41 12-30-2011 09:27 PM

So i did the 'big 3 upgrade' and there is a difference, got a cap and a yellow top battery. Will post more then there in.

Project89 01-01-2012 03:40 AM

a cap is bandaid for the dimming light problem, not saing they dont work, but unles su have a total of 2,500+ watt system there is no need for one.

i see u already did the big 3 upgrades which is what i was going to suggest, if the lights still dim out or u get voltage drops when the bass hits u need a alt with more output.

what ppl fail to realise is a cap needs to be recharged after every bass hit, if the alt is not up to the job to begin with the cap does nothing

on alot of gm stuff ive done the serpintine alts have 2 diff pully sizes on cars that would dim the lights at idle we would put on the smaller pully to speed the alt up to fix the issue at idle, so that could be something u can look into on ur truck as well

poy41 01-01-2012 03:53 AM

When changing pulleys wound you have to change belts too or would the auto tensioner do it?

Project89 01-01-2012 02:34 PM


Originally Posted by poy41
When changing pulleys wound you have to change belts too or would the auto tensioner do it?

75% of the time the tensioner wil take up the slack since the smaller pulley isnt to much smaller then the large one, worse case is u have to buy a belt that is a half inch shorter

poy41 01-17-2012 12:46 PM

So ive put a yellow top (750 amp) battery in and a cap with a voltage readout. The voltage seems to be a constant 14.5 - 14.7 and the lights are barely dimming now. But last night i drove into town and after coming out of the store and starting up the truck, a "service brake system" light came on. Restarted the truck and everything is fine. It is like -30c here with a wind chill of -42c, dont know if the cold weather would have something to do with it or not. Also rechecked for any codes, found none.

poy41 01-17-2012 02:09 PM

Too add to this, it happened again this morning. Its -36 without the wind. If i cycle thought the key, it will go off. And it hasn't came on while driving yet, only at start up.

All times are GMT -6. The time now is 05:23 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999 - 2012. All Rights Reserved.