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Discussion Starter · #1 ·
I just picked up an 05 SEL 3.0 with 48K. The battery that is installed is a "valuecraft" 26R-VL (autozone.com) 540 CCA and 675 [email protected]. I noticed that the idle will skip and the tach drops between 600-900. My lights dim when rolling up or down the power windows.

I have had the car for 1100 miles and cycled approx 5 tanks of gas though it. Last night I was low on fuel, I filled up and parked the car across the street. after about one hour I started the car and CEL light came on. It gave 2 codes. P0300, and p0316. Besides at park or stop, the car seems to run great. The tach jumps slightly as I mentioned above. Could this be because of the "under powered" battery? I haven't checked the sparkplugs yet, but that would be my only other guess.

Where should I start. I could do plugs, wires, and ignition coil, but hate to spend $150 if the battery is a better place to start. Any reccomendations or possible places to start further diagnosing?

Thanks!
 

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code p0300

weather the battery is the direct problem or not it is the wrong battery so i recommend the Interstate heavy duty i hve them in my 92sho and my 06 vulcan which were both acting weirdly with the old batterys.
I would start the car at night and look under the hood to see if there are any plug wires arcing.
 

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That flickering light indicates a bad connection in the circuit.
First check the voltage on the battery (on posts and on clamps) with engine running at idle. Should be 14.2-14.4V... if it is less you have a bad alternator.
If there are differences between the two readings, you have bad connection to the battery posts.
 

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Elect Connections

I just picked up an 05 SEL 3.0 with 48K. The battery that is installed is a "valuecraft" 26R-VL (autozone.com) 540 CCA and 675 [email protected] I noticed that the idle will skip and the tach drops between 600-900. My lights dim when rolling up or down the power windows.

I have had the car for 1100 miles and cycled approx 5 tanks of gas though it. Last night I was low on fuel, I filled up and parked the car across the street. after about one hour I started the car and CEL light came on. It gave 2 codes. P0300, and p0316. Besides at park or stop, the car seems to run great. The tach jumps slightly as I mentioned above. Could this be because of the "under powered" battery? I haven't checked the sparkplugs yet, but that would be my only other guess.

Where should I start. I could do plugs, wires, and ignition coil, but hate to spend $150 if the battery is a better place to start. Any reccomendations or possible places to start further diagnosing?

Thanks!
Small bat will not explain what you have.

Here is a test of major connections.

You need a digital Voltmeter with pointed probes. Use a MV range 200 to 500, you do not need a high-end meter, cheap one is OK. Turn key on, but not start, headlights on high, blower on high. This loads the battery cables up to a high load. Measure voltage from pos battery post to other end of cable, which will likely be the bolt in the fuse box. This bridges from post to screw to see if anywhere along the line there is a weakness. Do the same for ground post to engine block, and also to the body. Should be 100 millivolts or less and steady. Now, you might logically think that there would be little loss to the engine block as it is not under any serious load and the big ground cable. But, there is a secondary ground strap from the body to the engine near the firewall so the load is split between the two ground cables from the battery. Key is, 100mv or less and steady.
Now, turn the lights and blower off. Start the engine. Alternator should be charging hard as you have used up some of the battery topoff voltage. Measure from the ground post of the battery to the alternator housing. You are checking the ground from that to the engine block and more. Again 100 MV or less. If your alternator is accessible, measure from the big screw, output of the alternator to the positive battery post. This checks the integrity of the large wire from the alternator to the battery. In this case 200mv or less.

Any unsteady reading, or high reading means you need to isolate the issue. Thus, from battery post to same end of the cable, one end of the cable to the other and so on.

If all is well, then time to check P300 or random miss.

-chart-
 

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Small battery will not cause run problems but start problems. Alternator generates more power than needed to run the engine.
 

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Discussion Starter · #6 ·
Thanks for the help and detailed diagnostic steps. I have several meters that I can use to complete the diagnostic steps. I pulled the front 2 spark plugs this morning,a nd they look very worn. Im going to try to find a guide on removal of the rear spark plugs since they seem to be a bit of a PIA. I haven't searched for a guide on the forum yet, but I will do so later tonight. I am sure theres one around here somewhere . Did about 150 miles yesterday and no CEL light came back on.
Here are the 2 plugs I pulled. Id say I need new ones.
Spark Plug Photos

 

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Discussion Starter · #7 ·
Changed my plugs to Autolite Double platinum this weekend (wasn't as hard as I thought), no need to remove anything from engine to change rear plugs. Gapped to .45 and my idle is really smooth now. I haven't had a chance to check voltage output as chartmaker explained, but I will check it out soon.
 
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