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I have my mom's SSEi for the week because the CTS is in the shop. She had wanted me to do a tune-up on the car so I was scanning it with my autotap and watching the performance. It doesn't look like it needs a tune up. it didn't have any misfires and its performance was o.k. The only thing that stuck out is that under WOT it has 3.9* knock retard which seems too high to me? The knock retard starts at about 90% throttle and above. The ignition advance was over 30* until the knock retard kicked in, then it jumped way down. Is 3.9* dangerous? I can't remember what values seem acceptable. Her 00 SSEi is completely stock and has 89,000 miles on it. She wanted me to check it because her gas mileage is only 23 MPG average with mostly 55MPH backroad driving. It seems too low, but I can't find anything obvious causing the bad fuel economy. The air filter is in good condition. The Oxygen sensor seems to be o.k. too. It's rich/lean transitions peaked at 192 every 100 seconds which seems completely acceptable. Ideas?

Seems like a good average MPG.

Did you check the age/miles on the ignition wires?
How about the gap on the plugs?

My only other suggestion is running seafoam through the fuel system to clean out the injectors...possible its getting slightly starved for a good fuel spray at high throttle. Mix of 10 gal fuel, one pint of seafoam should do it.
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Spark plugs and wires are original. I don't want to waste her money and change her plugs if it's not needed. I know it's approaching 100k miles (11k more to go.) They seem to be in good shape though. I haven't checked the gap on the plugs though. I don't have the gap tester. I think I'll try the seafoam route. That stuff seems to work very well.

I can tell you that the plugs on my SSEi were completely toast at 61,000 miles and I don't drive my car all that hard. You might want to pull one of the easy ones and see what they look like.

I say just do a complete tune-up; plugs, wires, PCV, fuel filter, throttle body/IAC clean, check/clean O2 sensor(anything else?). MOST cars on avg need a tune up around 60,000-80,000 to keep like-factory running conditions/mpgs. Then you know what you got and can start diag-ing further if conditions dont improve. You'll be good for another 80,000.

Also, maybe test some components with a multi-meter to make sure there arent ify readings. Spend a Sat on the Bonne.

Anything higher than 0 is non-acceptable KR.

At 100k, its begging for a tune-up. You could do the essentials for around $100

And here I change my spark plugs every time I change the oil and the wires get changed twice a year. I had no idea that I could go so long to change the plugs. I think I will just keep up changing the plugs and wires as I always have. I do the same for the air filter. So what is this seafoam and where can I get it? I have no complaints about my MPG just since my car sat up for 3 years I think I should do it after I change out the fuel filter. Just to make sure everything is cleaned out good. One of the fuel injectors looked a little dirty when we changed the Intake so better safe than sorry I am going to say.

As it turns out, she is not running premium in it. That would probably account for the KR at 80%+ throttle.

Custom88 wrote:As it turns out, she is not running premium in it. That would probably account for the KR at 80%+ throttle.

Most certainly, and a good tune would still help with economy and performance.

So basically, if you don't run premium, it has to KR to keep from blowing the motor? Is it ok to run regular if you have to?

EVERYONE with an SSEi should be using premium. The price of premium is only a few dollars more than what you would pay for the same amount(gal) of regular. These cars run (mpgs/performance) better on premium. They were made to be run on premium.

00Beast wrote:So basically, if you don't run premium, it has to KR to keep from blowing the motor? Is it ok to run regular if you have to?

Yes, low octane fuel in a high compression or force inducted engine causes knock. The knock sensors then pull timing as they detect it. Its REALLY not good for it to have knock, regardless of it knowing how to combat it. You absolutely need to put only Premium in it.

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Listening to: Breaking Benjamin - Breath
via FoxyTunes