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Thread: Engine has a miss, need ideas
02-08-2012, 07:24 PM #1
Engine has a miss, need ideas
It's a 98 Suburban with the 350. Code reader at O'Reiley says its a "misfire on cylinder 5." I put new plugs, wires, cap, and rotor on it. Been running Chevron fuel injector cleaner also. It's got better, but still has a miss. Can't feel it at idle, but it's bad between 1200 to 2500 rpm. Can't feel it after that. I'm trying to check out everything I can before I go through the expense of getting new fuel injectors. She's got 162,000 miles on the od. I put some Engine Restore in after an oil change, sounded like a spring popped loose around the num 5 cyl when I poured it in on a hot engine. I'm thinking if the valve was stuck, it might have been stuck open because the old plug was black which tells me it was still firing. You guys think a bent pushrod or broken valve spring would cause the misfire and trouble code?1998 K1500 Suburban
1977 Chevelle Malibu
"I'm proud to defend your right to be an idiot!" From a friend in the military.
02-09-2012, 02:35 PM #2
It definitely is possible. Put a stethoscope on it and you will know if something is bent or broken.2010 Chevy Silverado Z71 ext cab.4x4
72 Monte Carlo 350-415 hp- sold (June 2011) to pay medical bills
79 Impala 350 4bbl 375 hp- sold (June 2011)to pay medical bills
"If He asks you to go a mile go two"
02-09-2012, 09:31 PM #3
I did, but my ears aren't trained enough with those to hear if something is wrong. I've listened around the other valves and can't really hear a difference. I don't really think I've got a broken spring, but I'm not ruling out the bent pushrod.
By the way, thanks for the reply
Last edited by BoneHead; 02-09-2012 at 09:32 PM. Reason: forgot something
02-09-2012, 10:36 PM #4
02-09-2012, 11:31 PM #5
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If it was a bent pushrod or broken valve spring it would miss at all RPM's not just between 1200 and 2500 RPM.
Also the fact that the code reader is saying "misfire on cylinder 5" is a pretty good indication it's electrical, you wouldnt get a specific cylinder code for a cylinder missing due to a bad valve.
The code reader is catching and reading ignition pulses.
It could be an injector but before I replaced an injector I'd do a little testing on #5 cylinder to see if it was firing correctly. You could use a timeing light or an inline plug testor to watch for strobes and make sure its firing.
Look at your ignition system, you put on new wires, cap, and rotor, how does you distributer look, any possibility it's got worn bushings and excessive play in the shaft that could be causing a misfire?
02-10-2012, 07:49 PM #6
Pulled the valve cover today. Springs and pushrods were as expected, just fine. Finished the day working on installing a pair of Flowmasters. Gonna finish those up in the morning and then check out the plug and make sure it's firing. Gonna do it old school. I don't have any of those fancy testers, although I do have a timing light. Gotta see if it's got spark first.
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