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2003 STS
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78 Posts
Discussion Starter #1 (Edited by Moderator)
Hey All...
My 2003 STS is giving misfire code/SES light flashing... I took her to my mechanic friend at his shop, with good equipment/he's professional, don't worry. He said it was #2 spark plug, he took it out and it was all gross/black, number 4 was clean. He cleaned them both, cleared the codes and I drove her around town yesterday, without misfire / SES light... But of course, this morning, on my way to work, at 75 mph, the SES came back. I haven't run her codes yet, but I'm assuming it's the same P0300 misfire. Friend said if the code/light came back, I need to replace the fuel injector... (the cause of #2 / he says ) ...

Now, I'm pricing injectors, (cuz he'll let me buy the parts and provide them to him) and I read I should replace all 8.
What about the coils???

Advice please guys...
:(
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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68,404 Posts
I moved your post from another member's thread to your own thread on your own problem(s).

If the plug was totally black and fluffy fouled, that's a rich (excessively) fuel mixture. (Fouled and oily wet is - oil consumption) Rich mixtures can be either failed injector solenoid coil or stuck open. A mechanic can do electrical resistance checks on all 8 injectors to see how they compare to one another. If only one is bad, no need to replace all of them. Look at either new or remanufactured in Rock Auto. You can run a Top Tier gasoline (recommended by Cadillac) and/or try a 20 oz. bottle of Chevron TECHRON - a powerful fuel system cleaner. It might help.
 

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Registered
2003 STS
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78 Posts
Discussion Starter #4
Alright.... ordered NEW injector from Rock Auto, giving props to Cadillac Forums for the referral. :)
Should be better by Monday !! :) (God willing).

While I wait for the part, I'll get some of that TECHRON cleaner too. I need to drive her to work till then though... :(
(stupid job/roof over my head/caddy repairs)... :(
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
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19,250 Posts
Hey All...
My 2003 STS is giving misfire code/SES light flashing... I took her to my mechanic friend at his shop, with good equipment/he's professional, don't worry. He said it was #2 spark plug, he took it out and it was all gross/black, number 4 was clean. He cleaned them both, cleared the codes and I drove her around town yesterday, without misfire / SES light... But of course, this morning, on my way to work, at 75 mph, the SES came back. I haven't run her codes yet, but I'm assuming it's the same P0300 misfire. Friend said if the code/light came back, I need to replace the fuel injector... (the cause of #2 / he says ) ...

Now, I'm pricing injectors, (cuz he'll let me buy the parts and provide them to him) and I read I should replace all 8.
What about the coils???

Advice please guys...
:(
-------------------------------
in my opinion -
your problem is more likely ignition related than fuel related -
 
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