Trying to understand engine miss.
Have my daughters 04 sable gs dohc back at the house do to christmas break from school and it's having an engine miss problem.
I was able to pull some codes of po 301, 316 and the very common 345 gas cap code.
Some history here to get things started.
After a transmission rebuild the car came home with a slight engine miss with no codes so I went in and r&r the intake manifolds to replace the s/plugs (motocraft AGSF platinum) as a starting point. Checked all coils visually and for spark and the all appeared good. Replaced all plug boots as some appeared to have etchings from tracking and re installed the plunums. Problem solved I thought. Four months later the car is back with a engine miss and code po306. Checked out the # 6 coil, good vis and spark and swapped it out with # 5 and that gives me a 305 code. New coil in the # 6 hole and were good to go for another 4 months.
Now four months later same troubles of an engine miss. The engine starts fine with a smooth idle unlike the past but once she has a load on her and the foot on the brakes she stumbles just a little bit.
At freeway speeds with a soft accelleration she misses but under a heavey pedel she's as smooth as can be.
Now before I tear into her again maybe a little guidence from some who have had similar senerios.
Go read the misfire sticky on the top of the maint&repair forum then come back if you are still scratching your head with anything new you have learned.
It does sound like another bad coil though. If you have access to a PC and scan tool you can use OBDWiz to pull up data from $06 mode to see which cylinder is misfiring but not throwing a code.
Replace the coils with good brands not the cheap stuff! BWG or Motorcraft!
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Ok Sam, I read your article regarding engine miss prior to posting and everthing you suggested, checked out good or has been replaced except for the coils under the manifold. Guessing I just really don't want to pull the manifolds again. This time I'll replace all the coils under the manifolds with quality coils like you suggested.
My OMD tester doesn't show that the miss in # 1 hole. is by a defective coil only that that's the cyl. misfiring. Can a OMD tester actually get a signal from the pcm that a specific coil is defective?
Thanks for the help.
Today went in and replaced cyliders # 1, 2 & 3 with new dealer coils and got her back together. She now has developed a new and different poor running condition and with in a few miles threw out some codes. Coils c, d, e, f primary/secondary coil circuit malfunction. Whats with this? Friday the 13 was last week.
You may want to start chasing back wiring/connectors for a fault
Started up this morning and she runs good.
I'm pretty sure that the shop light I used was too close to the pcm or connectors somewhere and heated things up.
Something I need to be extra carefull with in the future.
Thanks for all the help.
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