caseiffert Posted May 7, 2009 Report Share Posted May 7, 2009 Allante has 77K, dealer says something in engine causing rough idle, their best guess is a stuck valve. Oil has been Mobil 1 10-30, daily driver. No issues with electrical, fuel, computer. Any suggestion on what to do? Link to comment Share on other sites More sharing options...
Ed Hall Posted May 7, 2009 Report Share Posted May 7, 2009 First thing I would do is check your EGR valve. It may not be closing properly and either need cleaning or replacement. A partially open EGR valve will definitely cause rough idle. Next thing I would do is clean the throttle blades. You might also have a bad injector or two. Link to comment Share on other sites More sharing options...
adallak Posted May 7, 2009 Report Share Posted May 7, 2009 Allante has 77K, dealer says something in engine causing rough idle, their best guess is a stuck valve. Oil has been Mobil 1 10-30, daily driver. No issues with electrical, fuel, computer. Any suggestion on what to do? I would say it is hard to find a 4.9 or 4.5 engine nowadays which would not suffer from rough idle to some extent. The problem is mostly electrical. I do have rough idle for a few years and still cannot find the culprit. Replaced a lot of parts including all fuel injectors. I personally just got tired of all of those repairs/replacements at some point and gave up. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
KHE Posted May 10, 2009 Report Share Posted May 10, 2009 I suggest having a shop hook up an ignition analyzer - the scope will show the cylinder(s) that are misfiring. Once you know what cylinder(s) are misfiring, you can diagnose the problem without throwing a bunch of parts at it. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
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