Just changed spark plugs and now I got a nasty lump

ganador01

Founding Member
Jan 21, 2002
1,581
2
38
Dallas/Fort Worth, Texas
Ok I just changed my spark plugs to champion copper 407/rs14Lc on my 1997 3.8.

I was using autolite 764s gapped at .035 for the nitrous. I put in the 407s gapped at .052.

Now, when my car is not moving, it has a nasty lump that comes about every few seconds or so. I checked to make sure i put on all the wires right and from what I can see, i did. What else could suddenly cause a lump to appear in the idle.

I changed my settings on my chip back to stock and still the lump was there. I know it sounds like I put a wire on the wrong plug but im 99% certain i didnt. When i went to recheck the wire locations, everything looked right. I.e. bottom wire went to first plug, middle went to 2nd, bottom went to 3rd plug...etc.

Anyone have any clue as to what the problem could be? As soon as my engine cools off im going to check the drivers side rear plug again to make sure the gap is correct. That is the only one i didn't recheck before I put it in. I dropped 2 plugs and bent one of the tips and maybe i bent that one too and just didn't notice it. Athough, I checked every plug after that to make sure the gap was correct.

Any ideas people?
 
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ganador01:

I'm sorry to say it but I think that "lump" is normal. I've had my '98 for three years and have done two tune ups with it with the same results (ie....lump). If you do find something is wrong please let me know, maybe it's wrong with mine too. Good luck.
 
doc4444 said:
ganador01:

I'm sorry to say it but I think that "lump" is normal. I've had my '98 for three years and have done two tune ups with it with the same results (ie....lump). If you do find something is wrong please let me know, maybe it's wrong with mine too. Good luck.
I wouldn't be worried if i had the lump before the spark plug change....on my car its not normal.
 
Good news....for me at least... I fixed the problem. It ends up that the number 6 cylinder plug had a closed gap in it. It happened to be the only plug i didnt recheck before I put it in...I guess it was the 2nd plug i dropped. Oh well, car is idling normal, champion plugs work fine.
 
ganador01 said:
Ok I just changed my spark plugs to champion copper 407/rs14Lc on my 1997 3.8.

I was using autolite 764s gapped at .035 for the nitrous. I put in the 407s gapped at .052.

Now, when my car is not moving, it has a nasty lump that comes about every few seconds or so. I checked to make sure i put on all the wires right and from what I can see, i did. What else could suddenly cause a lump to appear in the idle.

I changed my settings on my chip back to stock and still the lump was there. I know it sounds like I put a wire on the wrong plug but im 99% certain i didnt. When i went to recheck the wire locations, everything looked right. I.e. bottom wire went to first plug, middle went to 2nd, bottom went to 3rd plug...etc.

Anyone have any clue as to what the problem could be? As soon as my engine cools off im going to check the drivers side rear plug again to make sure the gap is correct. That is the only one i didn't recheck before I put it in. I dropped 2 plugs and bent one of the tips and maybe i bent that one too and just didn't notice it. Athough, I checked every plug after that to make sure the gap was correct.

Any ideas people?

do not use the 407's with the nitrous they are too hot

use RS12YC (401) gapped at .035" they are the coolest plug in that line

also autolite 104's or delco R44LTS6 are also the right heat range