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Discussion Starter · #1 ·
This is my first post, and would like some help from the forum. I have 105k on my 06 LR3 so I decided to change the spark plugs (something I have done on other vehicles with no problem). The truck was rough idling slightly upon startup and when stopped, so I hoped this might help.

I purchased the oem plugs from auto zone and torqued them in to the 18lbs recommended by the Rave guide. It said to torque the coil screws to 4lbs but my wrench didn't go that low, so I tightened them with a normal wrench.

After install the truck now idles way rougher than before! It jumps from 500-1000 rpms back and forth and now I have the "Reduced Engine Perfomance" notification. Ironically, when I drive it for a few it idles perfectly (even though the reduced engine performance still is present).

I have double checked all connections and everything is correct. Could it be a bad plug? I didn't check gap settings as I was told the plugs come with factory gap already set. Can the error message be read by an OBD tool from the local parts store? or does it require a specialized tool?

Thanks in advance!
 

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You really won't know what wrong until you get the codes read, but I would try your best to determine if it is simply a bad idle, or if the engine is actually misfiring. If you think it's just a bad idle (dipping down and almost dying but all cylinders are firing and the engine runs fine under load), then I would go out and look at your vacuum lines and see if you may have bumped any or knocked them off... maybe a brittle vacuum hose cracked somewhere?

It is unlikely that there's anything wrong with the plugs and even if there was, you would be getting a misfire and reduced performance while driving. However, even if that IS the case, my money would be on a bad coil pack rather than a spark plug. They can be a lot more finicky than plugs (at least that's the case with my Audi).
 

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Discussion Starter · #6 ·
Thanks for the feedback. It was late and I must have read the obd response wrong! I took the MAF off and cleaned it as well as the throttle body. It now starts perfect with perfect idle! Here's a pic of the throttle body. I'm assuming this was the culprit. Maybe the new spark plugs just intensified the issue? Nonetheless, it's fixed. Thanks!
 

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disco biscuit
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I was gonna say MAF but it throws a MAF code which is usually easier than a guess. It has a computer system which usually can tell close to what is wrong. Glad it worked out and the follow up is appreciated. We don't get enough of that here.
 
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