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2004 Deville base
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19 Posts
Discussion Starter #1
I’ve been trying to find out what is causing my misfires and having a heck of a time. Last year I replaced the plugs, injectors, maf, radiator, surge tank and my car was fine until a month or so and it’s been sitting up with me trying to figure out why it’s running rough, the ses blinking, loss of power and the fuel level says half a tank and says “lo” at the same time. Tomorrow I hope to check the Egr and fpr, and other ideas on these issues?
 

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2004 Deville
2004 Deville, Silver, Gone, but not forgotten, 1972 Eldorado, 1974 eldorado, 1975 CDV
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687 Posts
Before anything else do a block test, If you haven't already, to rule out head gaskets.
 

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2004 Deville base
Joined
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19 Posts
Discussion Starter #4
There is another issue that I’m wondering about, a couple of the bolts on the valve cover won’t tighten. What can be done for that
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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87,099 Posts
Start by pulling the DTC's. Post them AND their definitions.


There is another issue that I’m wondering about, a couple of the bolts on the valve cover won’t tighten. What can be done for that
Sounds like stripped threads. About all you can do is retap and Helicoil if it is the threads in the head. If you are lucky and it only the bolt threads, then just replace them.
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
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19,688 Posts
STEP #1 - ALWAYS - check for DTC's - Diagnostic Trouble Codes - using the on-board scanner -
if you don't know how - go here -

post any codes you have -
ALONG WITH THEIR DEFINITIONS -

include whether they are C-Current or H-History -

for code definitions - go here -


here is a how-to video -

=============================

IF you get code P0300 - which I expect -
P0300 is a generic misfire code -
our on-board scanners will not display WHICH cylinder is misfiring -
although that information IS stored in the computer -

take the car to any big auto parts store and ask them to check the codes -
P0301 is a misfire in cylinder #1 - P0302 is cylinder #2 - P0303 is for cylinder #3 - etc-

once you discover WHICH cylinder is misfiring -
diagnosis is MUCH easier -
 
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