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paulrice
User
Apr 2, 2010, 4:42 PM
Post #1 of 2
(1312 views)
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2004 cadillac seville sls 8cyl po300 code random misfire changed spark plugs still code brought to local garage and told me i needed crank sensors put upper and lower crank sensors in but still have code and sputters sprayed intake with ether looking for vacume leak nothing seams to run without a skip at over 10,000 rpm shakes at idle and sputters
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Sidom
Veteran
/ Moderator
Apr 2, 2010, 8:54 PM
Post #2 of 2
(1305 views)
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Man I sure hope you aren't tachin that poor caddy out to 10 grand.....
I'm just messin with you,,,, I know what you meant........ considering all the typos I make,,,, I have no room to talk......
After you've taken care of the basic stuff, if the miss is still there it gets a little harder to diagnose and does require proper tools...
The 1st thing that really needs to be done it to find out which cylinders are missing. A scanner that can access the misfire monitor makes things a lot easier. From what you posted it sounds like possibly a vacuum leak or valvetrain problem...
After you've pinpointed the cyls, that area needs to be checked for vacuum leaks around all possible sources. Run a compression check & running compression check to see if there is any help there. An inspection of the valves with a boroscope for any telltale little brown lines on the valve faces that would indicate they aren't sealing fully could be very helpful & timesaving. Once the mechanical end of it has been checked out and if everything is good then checking out the comp systems begins. There are systems that can fail and give you drivability problems without setting codes. If they go bad but stay with in their parameters, they won't set a code.
A fuel pressure reading should be taken. Normally fuel problems are noticed more at high rpm (like say....10 grand.....ok, ok..I'll stop) & under load, so more than likely is not going to be your problem but it's still a good idea to make sure that system is good & within specs
Like I mentioned once the maintenance stuff has been done if the problem is still there, without the proper equipment, it's really tough to nail down and you're almost limited to guessing.....
Hopefully this will help you some... Good luck
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