Electrical system surge/instability

[BDEE]

I noticed last winter that every once in a while my electrical system would have a sort of surge condition at idle. What I mean by this is that the lights including headlights, tail lights, dome lights and dash lights all would have this pulse effect going dim and bright quickly and repeatedly.

My battery ended up getting pretty weak over the winter so I replaced it and had my alternator tested by the local shop. The alternator was in pretty good shape. After replacing the battery it seemed that the issue was greatly reduced.

Fast forward to the last few weeks, and the issue has been increasingly more noticeable, to the point where it's noticeable even when it isn't dark out and while driving as well.

I've done some searching here and on google and have found instances where the lights will shut off completely and other weird gremlins but nothing for this.

Other notable information:

I do have a scan gauge II that I use to monitor a few things, one being the system voltage. It's usually running between 13-14.7 volts but will sometimes dip to 12 and sometimes even 11.x while stopped. The readings are not consistent at all.

I have noticed what sounds like a low volume high pitched whine that is throttle based as well. Throttle pressed = whine, mostly noticeable at highway speed, but off throttle the noise stops.

I also have been having an intermittent p0306 code which I haven't sorted yet, plugs, coil have been replaced. Kind of wondering if this is related, though I haven't ruled out injector or injector wiring.

I am also running an aftermarket stereo with powered sub, so it shouldn't be loading the system heavily.

Any ideas? I'm getting pretty annoyed with it.

I apologize for the novel.

 

[uss2defiant]

I think you may have something slowly draining the battery. Test your battery again.

try moving the coil to a different location and see whether the error follows.

 

[libertybob]

Hmm....

I would disconnect and clean all the grounds on the vehicle. I had a similar problem on a Honda and found it was a corroded ground. Then, I would pull the fuse on the aftermarket stereo to see if the pulsations stopped. Aftermarket equipment sometimes leads to strange things. Two ideas to consider.

 

[CactusJacked]

To make sure your sub isn't shorting out, remove it from the electrical system and monitor the Jeep some more as you've been doing.

 

[BDEE]

Thanks for the replies. I will start with the sub and grounds and go from there for the surging.

With the misfire code, one of the shops I had it at for other issues, tried swapping coils with no luck on eliminating the cause.

 

[uss2defiant]

did the problem follow or it stayed w/ cylinder #6?

 

[libertybob]

#6 misfire

I would replace the #6 plug with a new NGK to remove it as a suspect. I once had an AC plug with cracked porcelain new from the box. Didn't notice it until I fired the engine and got a miss. If it isn't the plug or coil, then get a test light to plug in the wiring harness connector for #6 to make sure the coil is getting a steady signal to fire from the PCM. You can borrow the test kit from Autozone. Intermittent electrical problems often come from corroded or bent connector pins. Is there any significance that #6 is under the coolant tank? Food for thought.

 

[BDEE]

did the problem follow or it stayed w/ cylinder #6?

The problem stayed with cylinder 6.

I would replace the #6 plug with a new NGK to remove it as a suspect. I once had an AC plug with cracked porcelain new from the box. Didn't notice it until I fired the engine and got a miss. If it isn't the plug or coil, then get a test light to plug in the wiring harness connector for #6 to make sure the coil is getting a steady signal to fire from the PCM. You can borrow the test kit from Autozone. Intermittent electrical problems often come from corroded or bent connector pins. Is there any significance that #6 is under the coolant tank? Food for thought.

When the problem first arose, I had the plugs swapped while it was in for service. The problem did not change, but I did figure out they put some fancy Bosch plug in and when I checked the gaps they weren't even right. I bought some copper Autolite plugs and gapped them and installed myself. The problem has been consistent the whole time. I have heard of wiring issues near the coolant reservoir before..

 

[uss2defiant]

got to go with the NGKs

 

[libertybob]

Yep!

Yep, go with NGK's. My '03 3.7 has a label under the hood calling for NGK plugs and even specifies the part number. I would not use any other plug as Liberty's seem sensitive to plugs.

 

[Billwill]

Could be a bad injector causing a misfire.

 

[BDEE]

So I have not yet solved the idle misfire (haven't tried yet honestly) but I did solve the pulse issue.

The other day I got home from work and 10mins later headed out to the gym. The jeep unlocked with the remote fine but when I turned the key and it acted weird then went straight to no electrical power. I had just tested the battery and alternator a few days prior so I moved along from there. Turns out the two piece positive battery connector was not tight (not horribly loose either) at the joint where the cable connects to the part that bolts to the battery post and I was able to move it around. Probably didn't help that I had connecting wires on there for my sub and light bar as well. I'm guessing the pulse came from engine vibration causing possible intermittent contact. I tightened it back down and the jeep started right up and there is no more pulsing or crazy voltage readings.

 

[LibertyTC]

I always clean the battery terminals with a wire brush or emery cloth before installing the terminals.
If you have a lead acid battery, these red & green felt battery protectors limit corrosion.
53769[/ATTACH]"]

You must be registered for see images attach

Best advised to check terminals a few times a year for bring tight.
Re the coil packs, try measuring them, should read around 7-9k ohms if I remember right.
53771[/ATTACH]"]

You must be registered for see images attach

 

[BDEE]

I always clean the battery terminals with a wire brush or emery cloth before installing the terminals.
If you have a lead acid battery, these red & green felt battery protectors limit corrosion.

Best advised to check terminals a few times a year for bring tight.
Re the coil packs, try measuring them, should read around 7-9k ohms if I remember right.

Thanks! I'll have to check out those felt battery protectors, I've never seen them before. I will definitely check the coil packs too, as I still have the one I pulled off originally.

 

[NewerJeeper]

Mine kind of pulses too when I have lights on at night and doors open the lights inside kind of pulse a little getting dimmer and brighter. I just got Jeep so im going through all the bugs on it. The battery looks new. and lasts a while while playing radio with engine off so I don't think its battery. I'll have to check that funky positive battery connection thing that was mentioned.

 

[LibertyTC]

The only correct way to know if your battery is any good, is through a load test.
Most shops have an electronic load tester, and this is a good idea in fall before winter.
As temperatures drop, less cold cranking amps are available, so you want a battery that can pass a load test.
53776[/ATTACH]"]

You must be registered for see images attach

I currently have a new AGM (Exide Edge) rated at 770 CCA. Here you can see the CCA results from a Midtronics load tester with print out.
AGM batteries (absorb glass mat) are more powerful& fully sealed, therefore wont offer corrosion to terminals.

 

[M38 Bob]

Being fully sealed doesn't in any way make them more powerful. It does make them spill proof if turned upside down. Handy in an air plane, hope to never need that in my vehicle. It does make them more susceptible to over charge and damage from such. "Absorbed glass mat". That means that all the available acid is what a fiberglass mat can hold. Means they're rather acid starved to begin with. They have great potential, just not really in automotive service. They are a great profit maker for smart marketers though.


My experience with them has been in the recreational marine industry. By far the best choice in your yacht, houseboat, etc for inverter use. You can fasten em up in an enclosed space and not have to worry about outgassing corroding the hell out of nearby sensitive assemblies. NOT a problem when the whole engine compartment has an open bottom and thousands of CFM of airflow.

Bob


Sent from my iPad using Tapatalk