****** http-equiv="Content-Type" content="text/html; charset=utf-8">****** name="ProgId" content="Word.Document">****** name="Generator" content="Microsoft Word 11">****** name="Originator" content="Microsoft Word 11"><link rel="File-List" href="file:///C:%5CDOCUME%7E1%5Ctoffutt%5CLOCALS%7E1%5CTemp%5Cms ohtml1%5C01%5Cclip_filelist.xml"><!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:PunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <wontGrowAutofit/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--><!--[if gte mso 9]><xml> <w:LatentStyles DefLockedState="false" LatentStyleCount="156"> </w:LatentStyles> </xml><![endif]--><style> <!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0in; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} @page Section1 {size:8.5in 11.0in; margin:1.0in 1.25in 1.0in 1.25in; mso-header-margin:.5in; mso-footer-margin:.5in; mso-paper-source:0;} div.Section1 {page:Section1;} --> </style><!--[if gte mso 10]> <style> /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-ansi-language:#0400; mso-fareast-language:#0400; mso-bidi-language:#0400;} </style> <![endif]--> I need some help on my Excursion. It is a 2000 V10 4x4 with 125k miles. In the last three months I have replaced the MAF, the IAC valve, PCV valve, fuel filter and air filter. The plugs have about 35k miles on them. I just ran a bottle of Gumout super concentrate thru the tank, and with about 10 gallons left in the tank, the truck started missing. It seems to be intermittent in the sense that the truck starts fine, idles in park, but in gear starts to miss. Under load, it runs but may buck and miss like crazy, or runs fine till 50 mph then start missing again. At idle in gear after driving, it is definitely missing.
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There is no service engine light.

I figure it is the plugs, an injector, a blocked filter or the pressure regulator. Any other ideas or what I should check first?

 

Best guess would be a COP or two, if it's a miss the CEL will soon come on then read code or have them read at an auto part store to determine which cylinder is missing. Sometimes when in OD slowly depress the gas peddle with out down shifting will make the miss more noticeable to bring on the CEL.

 

Thanks, I wondered about the coils, but figured that the Service Engine Light would have come on pretty quick. Can a diagnostic reader tell if a coil is bad before the Code signal is sent to the light?

 

That is what mine did and had a bad coil. They could tell me what cylinder was missing, so that is the one i replaced and runs like a champ now!!

 

Well maybe and I say maybe because I'm not sure, but someone else may chime in who knows. But I had a 97 Expy (now sold) that had a weak miss that I got sick of so I took it out and beat on it until the CEL came on.

 

Is there a way to test the coils?

 

No, but they were able to tell me that i had a misfire on that cylinder, so i was hoping that is what it was, bought the part, and was good to go!

 

Great info, thanks!

 

Glad i was able to help someone out on here!! Its usually me asking questions!!

 

There is a way to test your COPs. The procedure is down in the V10 forum a search should find it for you.

Another thing to do is to simply go buy one and play round robin with it till the miss is gone.

'Course if you have a the correct diagnostic scan tool then it should find it quickly. The CEL won't light until it is really bad enough to create an emissions concern.

 

I guess I will have to go the scan tool route, as time is not my friend, and I KNOW it would take me trying all 10 before I found the bad one!

 

True! I always suggest to start in the back. The heat gets to those first.

 

You can spray a little water on the exhaust manifold and the cylinder that is not firing will not burn off the water as fast.

 

I love old school ideas, but I just need to be sure and move on. Besides it is too cold to be playing outside right now. Took it to a mechanic, it was TWO coil packs. The labor was the worst part, most likely cause he had to stand on a ladder!

 

COP's can be checked with an OHM meter but you can only check resistance of primary winding(low voltage side) and secondary winding(high voltage side) with a standard DVM or DMM, to check for insulation break down a special meter is required( high pot tester ) one that can simulate the high voltage generated by the COP. What I have found ( now sold 97 expy) is that the carbon resistor ( in the spring ) increased in value which reduces the amount of voltage to the plug.

BTW for you people that think funny things about a ( high pot tester ) this is not a joke