xxx180 Posted July 24, 2020 Share Posted July 24, 2020 Hi guys 2004DE with 98k. Sudden bad misfire with code reader suggesting cylinder 4. Today I completed compression test. 5 cylinders were all 150psi however cylinder 4 had nothing. No reading at all. I would of expected something if worn rings ? Would a valve issue cause zero compression ? Any help much appreciated. cheers Colin Quote Link to comment Share on other sites More sharing options...
ZMANALEX Posted July 24, 2020 Share Posted July 24, 2020 Sounds like you have a burnt exhaust valve, so head off jobby, however, best to have a quick look with a bore scope. Quote Link to comment Share on other sites More sharing options...
xxx180 Posted July 24, 2020 Author Share Posted July 24, 2020 If it was that Alex how big a job is this for a diy person? I recently changed valve covers etc but cylinder heads are a different league I guess. Would I be best fitting a used head Cost wise mate ? Any idea on cost ? thanks for quick reply btw Quote Link to comment Share on other sites More sharing options...
ZMANALEX Posted July 24, 2020 Share Posted July 24, 2020 Small job to bore scope. Much bigger job to replace the head or the bad valve. Quote Link to comment Share on other sites More sharing options...
ZMANALEX Posted July 24, 2020 Share Posted July 24, 2020 Plenty preowned heads to choose from in this for sale thread: https://www.350z-uk.com/topic/125665-loadsa-parts-for-sale-picture-heavy-now-with-prices-and-detail/ Quote Link to comment Share on other sites More sharing options...
xxx180 Posted July 28, 2020 Author Share Posted July 28, 2020 On 24/07/2020 at 21:04, ZMANALEX said: Small job to bore scope. Much bigger job to replace the head or the bad valve. Hi Alex could it be a stuck open exhaust valve and if so anyway to unstick with head on car ? Would I see anything with valve cover off turning over engine that might give me an idea ? Is it worth running a decoke fluid through oil do you think? Car still runs albeit poorly due to zero compression on cylinder 4. regards Colin Quote Link to comment Share on other sites More sharing options...
ZMANALEX Posted July 28, 2020 Share Posted July 28, 2020 I doubt very much if it would be a stuck open valve which would certainly give you a zero compression reading, similar to a burnt out valve. If it was stuck open it would hit the piston crown and then you would be in big trouble. If you remove the cam cover, you will be able to inspect the cam, bucket and valve movements. Quote Link to comment Share on other sites More sharing options...
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