misfires after new spark plugs. Need help !!!

Jacko84 said:
Yup, that’s what the Toyota tech and service advisor said until they drove it and felt the misfire. Drove and ruled out transmission. Specially since there have been no symptoms whatsoever until the new plugs.
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More likely a fuel cut or something. Your only option is just to trial and error at this point with no codes... Try different plugs and go from there, but I would be willing to bet a few bucks it is unrelated to spark. I would start with another set of plugs just to rule the only things you changed out.
 
wfo9 said:
More likely a fuel cut or something. Your only option is just to trial and error at this point with no codes... Try different plugs and go from there, but I would be willing to bet a few bucks it is unrelated to spark. I would start with another set of plugs just to rule the only things you changed out.
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I’ve considered fuel as well but I’m running on the same tank as before I replaced them and never had these symp before. I’ve driven around 70 miles at this point and still no CEL/codes. After dinner I’m just going to put back my old plugs and see if the dealership will exchange them.
 
Since you believe it's a plug and you are going to change them out anyway. Why not change back to the old plugs one at a time and check after each change if the misfire goes away. May take a while if there is a heat issue.
 
I would replace the plug wires. After 150k miles it is time, and you may have damaged one when you swapped plugs the first time.
 
yardsale said:
I would replace the plug wires. After 150k miles it is time, and you may have damaged one when you swapped plugs the first time.
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Can’t wait to see the part number for plug wires, lol.

(No plug wires)


Maybe you have a bad coil or a coil not seated properly on the plug.
 
yardsale said:
I would replace the plug wires. After 150k miles it is time, and you may have damaged one when you swapped plugs the first time.
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The wires seem to be part of a harness And I don’t even wanna think about having to replace the entire harness. I will be starting what’s easiest first.
 
Antman said:
Can’t wait to see the part number for plug wires, lol.

(No plug wires)


Maybe you have a bad coil or a coil not seated properly on the plug.
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Will be triple check in on that since this will be the third time I repeat the operation. They all went in like butter so it’s hard to believe that one may not have been seated properly after doing it twice
 
Fount The culprit. After replacing the first three spark plugs back to my old ones found that the one farthest from the firewall on the passenger side had a crack on the ceramic. Replaced it with one of my old ones and left the new ones in the other five cylinders. Took it for a test drive and it’s back to running like a champ. The question is, was it like this and I didn’t notice it before? Or did I crack it myself during installation?

 
Jacko84 said:
Fount The culprit. After replacing the first three spark plugs back to my old ones found that the one farthest from the firewall on the passenger side had a crack on the ceramic. Replaced it with one of my old ones and left the new ones in the other five cylinders. Took it for a test drive and it’s back to running like a champ. The question is, was it like this and I didn’t notice it before? Or did I crack it myself during installation?

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Most likely happened during installation.
 
And to all of this I will add that I drove close to 70 miles and about 15 key cycles without a CEL/throwing any codes and getting 13 mpg....:wacko:
 
Jacko84 said:
And to all of this I will add that I drove close to 70 miles and about 15 key cycles without a CEL/throwing any codes and getting 13 mpg....:wacko:
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It seems to take a high percentage of misfires on a cylinder to get a CEL. I had a couple of my spark plug tube sealing gaskets fail, allowing oil to enter into the spark plug tube, filling it with oil. This would cause misfires at low RPMs that affected low RPM torque very noticeably, however no CELs, ever. Vacuum out the oil and the engine runs great again for a while until it refills.

Techstream's data list has a per cylinder misfire counter, but I never watched the real time data list when the problem was occuring.
 
Last edited:
Jacko84 said:
And to all of this I will add that I drove close to 70 miles and about 15 key cycles without a CEL/throwing any codes and getting 13 mpg....:wacko:
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want something else to be paranoid about? you might have bits of ceramic in your combustion chamber EEK!!!!!!!!!
 
Hi !!...you most likely cracked it during installation...did you use a plain deep socket or a "spark plug socket" that has the rubber inside of the socket ??
 
rwrobs777 said:
Hi !!...you most likely cracked it during installation...did you use a plain deep socket or a "spark plug socket" that has the rubber inside of the socket ??
Click to expand...

Most likely. I used a spark plug socket, doesn’t have the rubber inside, this one holds on to the plug with a magnet.
 
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