Tune-up questions, spark plugs
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HT4100 4.1, 4.5, 4.9 Discussion, Tune-up questions, spark plugs in Cadillac Engine Technical Discussion; Hi, I am planning to get a tune-up soon. A guy at Advanced Auto Parts recommends AC-Delco Iranium plugs for ...
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    93DevilleUSMC's Avatar
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    Tune-up questions, spark plugs

    Hi,

    I am planning to get a tune-up soon. A guy at Advanced Auto Parts recommends AC-Delco Iranium plugs for my 4.9L, but the mechanic I might go to says AC-Delco Platinum plugs are better. Also, the shop suggests cleaning my fuel injection system, even though I normally run Premium octane and put injector cleaner in every so often. My last two tanks of gas have been mid-grade, however. Is that likely to foul my injectors? And what about a K&N air filter?

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    awadecki is offline Cadillac Owners Enthusiast
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    Re: Tune-up questions, spark plugs

    Any AC Delco plugs are fine. I'd go with the platinum because they're reasonably priced. I believe the iridiums are more expensive, and you really won't see much of a difference.

    Even the AC Delco regular plugs are great for under $2 a piece, but your car came with platinums, so I'd put those in there.

    Running mid-grade won't clog the injectors, but it could harm your motor if you hear pinging. The 4.9L engines have no knock sensors (unlike many other modern motors), so you're best to fill it with premium.

    An injector service is fine, but I wouldn't say that you absolutely need it.

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    Re: Tune-up questions, spark plugs

    Okay, so it's a maybe on the injector cleaners. Now, what does this pinging sound like? I haven't heard any unusual sounds out of my motor of late, but I'm not exactly sure what to listen for.

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    Re: Tune-up questions, spark plugs

    By the way, thanks for the fast response. Also, what about the K&N filter?

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    HUF
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    Re: Tune-up questions, spark plugs

    If your car runs good do not mess with engine unless you want to make your mechanics happy.
    Iranium plugs... still better than Uranium ones. LOL

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    behind-bars is offline Cadillac Owners Connoisseur
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    Re: Tune-up questions, spark plugs

    Quote Originally Posted by 93DevilleUSMC View Post
    Okay, so it's a maybe on the injector cleaners. Now, what does this pinging sound like? I haven't heard any unusual sounds out of my motor of late, but I'm not exactly sure what to listen for.

    Pinging is just an annoying "pop pop pop" noise ususlly on acceleration. If you run a tank of 87 octane you will probably hear it.

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    awadecki is offline Cadillac Owners Enthusiast
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    Re: Tune-up questions, spark plugs

    Pining usually occurs on these engines under load at around 45-50 mph (in 4th gear), and on the freeway. It's hard to describe what it sounds like. It doesn't sound good.

    You're best to fill that car up with premium...then you'll have no problems. I definitely would NOT put regular in a 4.9 engine despite what anyone says without retarding the stock timing.

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    Re: Tune-up questions, spark plugs

    LOL no way is any low grade going in my car: I don't care if gas hits $20 a gallon. So, either type of AC-Delco plug will be fine?

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    behind-bars is offline Cadillac Owners Connoisseur
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    Re: Tune-up questions, spark plugs

    Quote Originally Posted by 93DevilleUSMC View Post
    LOL no way is any low grade going in my car: I don't care if gas hits $20 a gallon. So, either type of AC-Delco plug will be fine?
    Yeah, If you dont retard timing keep 87 out, I ran it once, and once i burned a few gallons I added 93 to balance it out, sounded terrible.

    AC delco platinums are probaby a better choice, they should last close to 100k miles whereas the regular ac delco may only last about 30k. I got some delco "rapid fires" but havnet installed them.

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    Re: Tune-up questions, spark plugs

    Thanks for the advice, everyone. I'm having the tune-up done today, so I'll post again when it's done and let you guys know if any thing's improved.

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    Re: Tune-up questions, spark plugs

    Well, it`s finished! The plugs, wires, distributor, and rotor were all replaced, and the air filter was cleaned. The fuel injectors and throttle body didn't need service, which saved some money. Some Lucas oil stabilizer was put in. Now, my oil was due for a change in about 250 more miles. Should I go ahead and change it or wait a few hundred more miles? I will also have to replace my catalytic converter soon; more on this later.

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    Re: Tune-up questions, spark plugs

    Pinging sounds like somebody throwing a handfull of pebbles at a big iron pipe. The actual sound is important parts in the engine springing out of shape from the extreme stresses.
    Don't mess with Binky Bear!


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    Re: Tune-up questions, spark plugs

    Well, I don't hear that sound, and haven't heard it once in the year I've had the car. so, that is obviously some good news.

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