JAKE_MORSE Posted December 5, 2011 Share Posted December 5, 2011 Hey guys! have a head scratcher here. Aviator that has an engine miss on the left bank only. hotline had us replace head and retest. same result. then hotline sednt field engineer and hye said to replace head again. still same hotline suspeted excesive backpress. tetted with gauge. ok coils ok plugs ok relitive comp weak in 6 and 8. any ideas? Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted December 6, 2011 Share Posted December 6, 2011 Codes? Fuel trims? Mechanical comp test - maybe a leak test if warranted? Maybe a year and miles might help? Quote Link to comment Share on other sites More sharing options...
JAKE_MORSE Posted December 6, 2011 Author Share Posted December 6, 2011 dtcs for all left bank cylinders misfire. fuel injector leak test passed , but the relitive comp. test showed that cylinder #6 and #8 were 6, and 8 percent. lngtrm fuel trim was -13% on left bank and +4 on the right bank. This is a 2004 modle. with 120km. coils have been swapped back and forth with no change. Ford had us verify base engine timming.ok. Also, the head has been replaced 2 times.as per Ford. This idles like a piece of crap, but it cruises and has lots of power. only has miss at idle. Quote Link to comment Share on other sites More sharing options...
lmorris Posted December 6, 2011 Share Posted December 6, 2011 Did the new head come with a new camshaft? Obviously its base engine at this point. Plus one on the mechanical compression test. Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted December 7, 2011 Share Posted December 7, 2011 It's a bit time consuming and difficult to verify proper cam timing on a mod motor using a lab scope and what not. This sounds like a chain one tooth off. All mod motors will run rough at idle one tooth off, run rough at idle and down the road with two teeth off, and will bend shit if three teeth off. Short term fuel trims will be the easiest thing to warrant removing the timing cover and "realigning" the chains. The long term fuel trims are supporting it already. Quote Link to comment Share on other sites More sharing options...
mchan68 Posted December 7, 2011 Share Posted December 7, 2011 My "m-chan68 crystal ball" is calling either a bad cylinder head #3 (be it valve(s) sticking in the guide(s), bad folower(s) or cam lobe(s), etc.) or bottom end issue with cylinders #6 and #8. A very easy way to rule out valve timing, would be the answer to the question "does it set a HARD P0340 fault?" If the answer is NO, then valve timing is NOT the issue. Another way to rule it out, is to see if you can view the power balance graph. If I'm not mistaken, a pop-up screen will appear, indicating CMP and CKP are out of SYNC if valve timing is out. In a nutshell, my vote is on a base engine concern. Quote Link to comment Share on other sites More sharing options...
BrunoWilimek Posted December 12, 2011 Share Posted December 12, 2011 It's a bit time consuming and difficult to verify proper cam timing on a mod motor using a lab scope and what not. This sounds like a chain one tooth off. All mod motors will run rough at idle one tooth off, run rough at idle and down the road with two teeth off, and will bend shit if three teeth off. Short term fuel trims will be the easiest thing to warrant removing the timing cover and "realigning" the chains. The long term fuel trims are supporting it already.I once had a 4.6 with one timing chain out one tooth. The fuel trims were opposite. One bank high, the other low. Since only 2 cylinders show compression issues and 2 heads have failed to fix the problem, I would suspect either bottom end issues or a partially plugged cat. Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted December 12, 2011 Share Posted December 12, 2011 I thought about that only after I had hit the submit button. Quote Link to comment Share on other sites More sharing options...
JAKE_MORSE Posted December 13, 2011 Author Share Posted December 13, 2011 Thanks guys, we are pulling the front cover in the morning and checking the marks. I will keep you posted and let you know the results. Quote Link to comment Share on other sites More sharing options...
JAKE_MORSE Posted December 19, 2011 Author Share Posted December 19, 2011 Well we found out that the chain tensioner was weak causing the missfire. Hot line helped out on this one also,thanks guys Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted December 20, 2011 Share Posted December 20, 2011 Quote Link to comment Share on other sites More sharing options...
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