Following an unfortunate chain of events, I’m now in the process of changing out the ICM, coils, wires, and plugs. I have found that the previous owner (or mechanic) cross threaded every single spark plug. To make matters worse, I will just assume since they’d wrecked the car several times that these spark plugs would never need to be changed again. They’re also held in place by some sort of glue(?). I’ve only successfully been able to remove 2 plugs after soaking them in PBlaster and other products. Fast forward: I ordered a “kit” off of the big website that sells everything because it was inexpensive, came with ACDelco wires and such. Upon removing the #1 plug, I wanted to go ahead and replace it with the new plug from the kit. After having the kit for over a month, I finally opened it to find the new spark plugs are aftermarket Bosch 4504. The website said “This fits your 2002 Chevy Impala.” Okay, but these are totally different from the Autolite 606 I just pulled out. I emailed the company only to receive an email from them to send photos of both plugs side by side. I was dumbfounded at their lackluster ability to do a simple search themselves, but I sent the pictures. No response. Now... The ONLY places I can find online that say these plugs are compatible with my Impala are EBay and Amazon. Bosch doesn’t even sell these anymore. If they do, I couldn’t find any information from Bosch. So, maybe you guys could help me out? The nodes are totally different, the lengths are different, but the threads are the same. Maybe that’s why it says they’re compatible? I’m going to try to attach the pics so ya’ll can see what I’m dealing with. My main question is... CAN I actually use these plugs safely without damaging the engine more than it already is? Thank you for ANY tips and tricks you have up your sleeves! 🤓✌🏼

 

The only issue I see is you waisted a lot of money on plugs. Autolight copper are what's recommended. As far as the threads being messed up I would pull the heads and Chase the threads with a thread chaser. The reason I say that is you don't want any metal falling into the combustion chamber and wrecking the motor.

Could the plugs just be seized I to the head? Another common problem. Could they have applied anti-seize to the plugs to help them come out?

 

That what I do with plugs.Neverseise on the threads and dielectric grease on the wires. Might be right about the plug rusting or something.

 

I wish I would've kept the first plug I pulled out of the back. It was black in the middle of the ceramic part. Looked like it had been put over a flame, but just in the middle. the ends of the ceramic were pure white. The threads inside were cross threaded so badly and covered in a gunk I initially thought was oil or oil mixed with coolant, but upon cleaning out the threads and putting a new cheap plug inside there, the threads were too wide for the plug to latch on. I was turning it to screw it in and realized it just sort of slipped right down into the hole and finally caught a bit of thread at the bottom. I initially had a P0302 that kept showing so I wanted to just CHECK the plug because it was firing just fine according to my light. Turns out the ICM is bad after using the multimeter to check everything. AND there's a vacuum leak SOMEWHERE... I'll find that after this is solved, though. So, I heard from the company and they want to exchange the plugs, but the only thing they said is "We have the correct Bosch spark plugs for your car. Would you like to proceed with an exchange?" You are right about Autolite being recommended, but they also went years recommending the Dex which has been a disaster. I don't know how I'd go about chasing the threads on the #2 being as it's so widened. A mechanic friend told me I could use the BLUE thread lock, so I purchased some after I couldn't find ANYTHING other than pulling the heads. I blew out as much as I could before I finally got it loose and used my shop-vac to suck up anything left around it and as I pulled it out. Among other little things I did to keep it as clean as possible. The gunk around it very well could be anti-seize, but isn't it recommended NOT to put it on those types of plugs? I plan on using the dielectric grease for the wires as @oilcanhenry stated. I'm not sure about the anti-seize yet. I've seen and read so many conflicting answers. I appreciate both of your responses. I probably did spend too much on the plugs, but they came with an all-in-one kit that was supposed to fit my car... And it was less expensive than purchasing each individual piece (brand new) rather than ripping everything off other Impalas at my local scrap yards. Wowee! I really word salad'ed ya'll. My bad! Thank you so much!

 

Anti-seize is ok to use just don't glop it on there. I wouldn't use any thread locker on the plugs but at the same time the blue is rated for 1/4"-3/4" bolts so it should come free when you want it to. They do make a fix-a thread for spark plugs but requires using a tap and would really suggest pulling the head at that point.

​All in all I don't know what the thread locker will do. Worst case scenario is the plug blows out and you have to tap the head anyway.