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Discussion Starter #1
Alright guys, having a little detonation issue. I had been running some NGK iridium plugs (waste of money, bought em when I was a newbie) in my car for about a year (10k miles). Since I put them in I had some detonation in the lower RPMS (below 1500, 2nd gear takeoffs mostly in the winter), higher RPMs (4k+), and at WOT. Today I finally got around to just swapping them out for some Autolite coppers. When I pulled the old NGKs out I noticed they're scorched on the white part below the electrodes and the electrodes are worn down to almost nothing (I'll get pics tomorrow). Considering the package claimed 40k miles and these plugs were ****ed within 10k miles, something has to be wrong.

So the new plugs are in and I'm still getting detonation in the same areas. I'm running an 87oct tune and filling up with 89oct fuel so it's not the octane of the fuel. My buddy suggested the MAF due to my idle being a bit crazy at times (cleaned the IAC several times, helped originally but the issue has come back). I had the battery disconnected since I had to unplug the MAF and IAT to get at the passenger side plugs. When I plugged it back in I was running fairly rich and didn't have any detonation. Once the computer got all its **** figured out, the detonation was back.

So I'm thinking either my buddy is right about the MAF or possibly an issue with the tune (from Bama through AM, but my 93oct tune seems fine -just pricey right now). What do you guys think?
 

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I wouldn't think a bad MAF would cause detonation, and I am pretty sure it would throw a code right?

It could be the tune, but I don't have a tuner myself so I wouldn't personally know. For some reason I am thinking maybe coil pack throwing out too much spark? Thats all I can think of. Since you were running rich sounds like the spark couldn't keep up if my hunch is right then when the computer fixed everything to make it run right by taking a little fuel out of the equation caused detonation again... Hmmm ever look at your injectors too?

And stop cleaning your IAC :p Just buy a new one, what are they like $40? If cleaning it a bunch helped your issue initially then why not just replace it?
 

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You probably already did this but the first thing I think of is fuel treatment. BG44K or Seafoam (Quality products of some kind). Second thing I think of is engine compression loss.
Lastly- Did you reload the 87 tune file after the battery was disconnected? Do you loose it when the battery is removed for some time?
Good luck with it all.
 

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You could always try and experiment. I mean yea your speedo will be off but its just a test.

Return your car to stock and see if it goes away. That would eliminate the possibility of it being the tune. Just drive with the flow of traffic while you conduct the test. :p
 

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Discussion Starter #5 (Edited)
I wouldn't think a bad MAF would cause detonation, and I am pretty sure it would throw a code right?

It could be the tune, but I don't have a tuner myself so I wouldn't personally know. For some reason I am thinking maybe coil pack throwing out too much spark? Thats all I can think of. Since you were running rich sounds like the spark couldn't keep up if my hunch is right then when the computer fixed everything to make it run right by taking a little fuel out of the equation caused detonation again... Hmmm ever look at your injectors too?

And stop cleaning your IAC :p Just buy a new one, what are they like $40? If cleaning it a bunch helped your issue initially then why not just replace it?
You could always try and experiment. I mean yea your speedo will be off but its just a test.

Return your car to stock and see if it goes away. That would eliminate the possibility of it being the tune. Just drive with the flow of traffic while you conduct the test. :p
My thought with the MAF was that it was possibly making the engine run lean. I'll get pics of the spark plugs tomorrow so you can see what they look like but they're totally ****ed. Imagine the electrodes being the size of the needle end of a safety pin. As far as the injectors go, I've never looked at them. I may have to pull one or two out and see how they look. I honestly don't know about the coil pack. How would I test that? Anything dealing with electricity is jibberish to me :dunno (besides ghetto-rigging electronics inside the car :shiftyeyes)

And you shush about my IAC. I'll clean that ****er until it dies :shiftyeyes

I might have to give that stock tune idea a test. I could probably find out if it works or not without leaving my parking lot since I get detonation in the low RPMs too. But I think by "go with the flow of traffic" you really mean punch it and use the messed up speedo/tach as an excuse when I get pulled over :shiftyeyes

You probably already did this but the first thing I think of is fuel treatment. BG44K or Seafoam (Quality products of some kind). Second thing I think of is engine compression loss.
Lastly- Did you reload the 87 tune file after the battery was disconnected? Do you loose it when the battery is removed for some time?
Good luck with it all.
It's been a while since I Seafoamed my car (fuel, crankcase, PCV) but that is one thing I need to do again. As for engine compression, I don't even want to think about that. The only possibility off the top of my head would be a lifter causing compression loss as I do have at least 1 sticky lifter. I'm going to try kicking it's ass with a good Seafoaming and Lucas oil before I start physically digging into the engine to replace it :confused: And no, tunes are not lost when the battery is disconnected. I'd know in a heartbeat since I have 4.10 gears and my revs would be way off :p
 

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My thought with the MAF was that it was possibly making the engine run lean. I'll get pics of the spark plugs tomorrow so you can see what they look like but they're totally ****ed. Imagine the electrodes being the size of the needle end of a safety pin. As far as the injectors go, I've never looked at them. I may have to pull one or two out and see how they look. I honestly don't know about the coil pack. How would I test that? Anything dealing with electricity is jibberish to me :dunno (besides ghetto-rigging electronics inside the car :shiftyeyes)

And you shush about my IAC. I'll clean that ****er until it dies :shiftyeyes

I might have to give that stock tune idea a test. I could probably find out if it works or not without leaving my parking lot since I get detonation in the low RPMs too. But I think by "go with the flow of traffic" you really mean punch it and use the messed up speedo/tach as an excuse when I get pulled over :shiftyeyes
Yes that... And I would imagine if your maf was making you run lean it would make a code pop up right? I would imagine so.
 

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I'd switch back to a "Stockish" plug. Are the 3.8 MAF's able to be cleaned with MAF cleaner?

Change plugs, seafoam, and clean your maf if possible. See if problem goes away.

Then after you do that test flash it back to stock and see what happens
 

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I wouldn't think a bad MAF would cause detonation, and I am pretty sure it would throw a code right?
Not really. If the maf is lean in the higher flow areas then the ecu won't even know, and it can easily cause detonation. I'd run the stock tune and see how that goes. I don't think that the 87 octane "performance" tune is worth running, unless you have an auto.
 

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Discussion Starter #9
I'd switch back to a "Stockish" plug. Are the 3.8 MAF's able to be cleaned with MAF cleaner?

Change plugs, seafoam, and clean your maf if possible. See if problem goes away.

Then after you do that test flash it back to stock and see what happens
Stockish plugs are back in as of last night and the issue remained once the computer had all its settings figured out again. And yeah, the MAF can be cleaned and it has been over a year since I cleaned it last.

Not really. If the maf is lean in the higher flow areas then the ecu won't even know, and it can easily cause detonation. I'd run the stock tune and see how that goes. I don't think that the 87 octane "performance" tune is worth running, unless you have an auto.
I'll give the stock tune a shot and since I have that "free tunes for life" thing I might just order an 87 economy tune. I'm pretty sure that would be nice with the way gas prices are going :crazy
 

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If I were you I'd datalog the MAF with your tuner. Just watch on your handheld and make sure the values don't have crazy spikes or other abnormalities.

What did you gap the new plugs to? Also when was the last time you replaced your fuel filter?
 

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Discussion Starter #11
If I were you I'd datalog the MAF with your tuner. Just watch on your handheld and make sure the values don't have crazy spikes or other abnormalities.

What did you gap the new plugs to? Also when was the last time you replaced your fuel filter?
Spark plugs were gapped to .054" and I replaced my fuel filter about 9 months ago.

Edit: I just checked with my Haynes manual and it looks like they're gapped .002" too big (I'd read .054" multiple times online). Is that small of a difference enough to be a problem?
 

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Spark plugs were gapped to .054" and I replaced my fuel filter about 9 months ago.

Edit: I just checked with my Haynes manual and it looks like they're gapped .002" too big (I'd read .054" multiple times online). Is that small of a difference enough to be a problem?
Nah, that won't make a difference. I thought they were supposed to be gapped to .054 anyways.
 

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Discussion Starter #13
Nah, that won't make a difference. I thought they were supposed to be gapped to .054 anyways.
Me too :dunno I'm going out to pick up supper here soon so I'm going to see if I can figure out datalogging since I'll have a passenger to watch the tuner (I'm assuming it shows in real time?)
 

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Me too :dunno I'm going out to pick up supper here soon so I'm going to see if I can figure out datalogging since I'll have a passenger to watch the tuner (I'm assuming it shows in real time?)
Yeah. It's like MAF counts or voltage that you'll want to datalog.
 

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Discussion Starter #15
I tried datalogging twice while I was out. First time I didn't record it but I had my passenger watch the MAF readings. They were pretty much smooth with the RPMs. Second time I tried recording it as well as a number of other things. 2 minutes into the drive home my gauges started sweeping wildly and the tuner locked up :dunno So I don't think it's the MAF because when I wasn't recording it wasn't spiking at all (and I was recreating the same conditions that the detonation happens).

Also, here's a pic of one of the old plugs I pulled (I seem to remember the electrode being a lot bigger when I installed them)

 

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Detonation is all about timing. You have a tuner right? Bump up the timing. If not, get higher octane. If that stops the detonation. Keep doing it. If you keep hearing detonation. Then it's not detonation.
 

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McQ, did your car try to die on you when your gauges did the sweep? Also have you tried spraying carb cleaner around your intake for a possible leak that could be bringing in unmetered air?
 

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On a related note, I had what sounded like detonation on the dyno that ended up being a loose pulley that at the right RPMs would make an almost identical noise.
 
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