Orange/red spark
 

I've been troubleshooting a decrease in fuel economy from 44mpg at 50,000 to 32mpg at 100,000, all highway. City driving has been effected as well, though not as clearly. Presently I'm looking at the ignition system and noticed the voltage to the coil packs is 1 volt under battery voltage which is 12.4v, and the sparks produced by them are orange-red, vs. "bright blue". Is this normal?

2004 Corolla LE. My wife's 2006 Corolla LE had the same color spark, with a 0.1 decrease in voltage. She only has 15,000 mileage and that battery is giving 12v even.

FYI - it'd take awhile to summarize what's been done to date re: fuel economy. Long and the short of it, the car's "fine" so this is just age. An engine flush (Amsoil) and putting a few ounces of Techron in the gas tank before each fill up has bought me 2-4mpg though. I have about 100,000 miles of logs. The things are finally coming in handy.

I'd look at your engine grounds and see what kinda corrosion you have going on. That could explain the voltage drop. When you put your connections back together make sure to use some dielectric grease (aka bulb grease) so they won't corrode again.

Also, welcome to the site. :)

Drat! Hard to blend in with that "Posts: 1" up there. :-)

I'll give the grounds a go this weekend. Thanks for that. What do they look like? Screw like or something more?

BTW - I got the graph of my mileage up here: 2004 Toyota Corolla LE Fuel Economy.

Yeah, pretty much just a bolt with a wire going to it. Just look for wires that go from the engine to the chassis. If you want, you can measure the resistance between the negative post of the battery and the engine block/head. That should give you a good idea of how bad things are.

What kind of car are you driving? Not that it makes much difference, just curious as to the 44mpg statistic. :)

- LostCause

It's actually a stock 2004 Toyota Corolla LE. On very long highway drives, babying the pedal, I could get 44mpg. Absolutely stunned me. More like 37mpg for regular driving (80% highway). I'm trying to get back to that now and then lay on some of the mods (air dam, gurney flaps, wiper shield, antenna elimination, side skirts, and then the boat tail). Learning about engines in the process so it's been a lot of fun actually.

It was in there, ya just missed it :D

If it's got 100k, whens the last time you changed the wires and plugs?

The orange / red spark is evidence of reduced voltage. The bright blue / white is where it should be.
As already suggested the culprit is most likely a poor earth or old wires / plugs not longer being up to the mark.

More importantly:
One warning:
Modern energy systems can produce LETHAL voltages so don't go poking around with the engine running. It may be the last thing you ever do.

By the way Welcome from me as well.

Cheers , Pete.

Hello. The plugs were replaced at 80,000 and nothing changed. The car doesn't have spark plug wires. Its "coil on plug" and the plugs are $100/each (4 total), so I'm hoping it isn't those. I've got a book coming from Amazon on auto electronics so I'll be sure to read that before I start working with live voltage. Thanks for the warnings.

Hopefully it's just the grounds, or the battery connections. Easier than troubleshooting a circuit and all that. I'll keep the thread updated as I move along. I'm planning on cleaning the grounds on Saturday, if the weather holds.

We cleaned six grounds today. Voltage drop improved from 1.0 to 0.5, but it still has a red spark. I didn't think to measure resistance from the coil to the battery and from the ignition wire and the battery to see if there is a difference. I'll try that next weekend and see if the local autoparts store will loan me a coil for 5 minutes to see if that does the trick.