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30 days ago Driving interstate speed for 3 hours, engine started to miss. Check engine light came on, pulled over care idle was very rough, turned ingnition off, restarted, car ran smooth check engine light off. Checked codes and nothing in memory. It has repeated this 2 more times after 2 or more hours of driving. Car runs fine around town but 10 days ago engine started having a single miss that causes a jolt/thud feel in the drivers compartment. Miss/jolt seems to happen when cruising and engine starts to lug before a down shift. Never feel the jolt on acceleration. Jolt is not noted with any consistant changes, will sometimes jolt once, sometimes serveal times in a 10 second period. Tach does not show change and no check engine light comes on. No work has been done recently. This car is a dream to drive but getting a little nervous. Any ideas to check/fix so can get back to enjoying the drive. This has my mechanic and me scrathcing our heads, I have done all the wrenching excpet timeing chain guide replacement 25000 miles ago. Thanks for the help.
First, you need to find out which cylinder is missfiring. For this, plug in a code reader. A missfire will trigger a DTC, even if the CEL does not come on. Once you find out which cylinder is missfiring you should swap the Coil Pack from the missfiring cylinder with one from a good cylinder. This will tell you if the Coil Pack has gone bad. If the missfire continues, check your spark plug. It may need replacement. I would recomend replacing all 6 if this is the case. If the spark plug is good and you can confirm you have a spark to the cylinder then check your injector. A clogged or worn injector is a possibility.
Thanks Lord Vader
I will check with a code reader.
I read in one of the threads about oil causing the boot around the spark plug to rot.
I checked and saw oil on one side pooled at rear cylinder. Pulled the coil pack and the boot was cracked.
Cleaned up the oil and sealed the crack,
Will drive and see if it miss fires again, as I go to get the check with a code reader.
Thanks for the reply,
will keep you posted.
If you have oil in your spark plug wells, your Valve Cover Gasket (VCG) has probably gone bad. Its rubber, and eventually gets hard and brittle and leaks. I noticed when i replaced mine their was a big leak on the exhaust manifold side, that I would have never noticed without replacing the VCG (which was caused by the VCG)
In the meantime, if swapping the coil packs did not solve the problem, then i think it may be a Camshaft Position Sensor. In the past, sometimes when they fail they can cause missfire codes.
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