What would cause no compression in one cylinder
Thread Starter
TECH Regular
Joined: Nov 2001
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From: Madison Heights, MI
What would cause no compression in one cylinder I know a valve stuck open and I guess bad rings but what specificaly would hold a valve open or make rings go bad. I only threw a multiple misfire code and I don't hear any ticking or anything, but the dealer says no compression.
Re: What would cause no compression in one cylinder Burnt valve,broken valve, valve not seating,hole in piston generally anthing that lets air escape combustion chamber. They need to do a leak down & see what the problem is.
Staging Lane
Joined: Dec 2001
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From: Bay Area, CA
Re: What would cause no compression in one cylinder Don't forget bent valve... Most common reason a valve won't seal, especially on these engines. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
Please don't ask how I know this! <img border="0" title="" alt="[Mad]" src="gr_images/icons/mad.gif" />
Please don't ask how I know this! <img border="0" title="" alt="[Mad]" src="gr_images/icons/mad.gif" />
Thread Starter
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Joined: Nov 2001
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From: Madison Heights, MI
Re: What would cause no compression in one cylinder Well I was just driving normal and the car started to run real rough but no backfires and no noise. Then the ses light started flashing. I pulled over and hooked up the autotap and one code was there, p0300 multiple missfires. I drove it the rest of the way home about 2 miles and I let it sit overnight. The next morning I turned it on and it was still running bad but no codes. I even had all 8 misfire windows up and not a cingle one. I checked all the sensors,wires and couldn't find anything wrong. I did find a plug for the wideband tuning was halfway out but it still ran the same after I screwed it in all the way. So off to the dealer. On the way there the ses light was flashing again but still no backfires or funny noises, dealer looked at it all day and says I have no compression in one cylinder. Today they are going to tear it apart to see whats broken.
Re: What would cause no compression in one cylinder Sounds like a broken valve spring to me. It's not pulling the valve closed and allowing the air to escape into the intake or header.
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On The Tree
Joined: Jan 2002
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From: Aloha, Oregon
Re: What would cause no compression in one cylinder i had similar symptooms when my compression ring on #7 broke. Eventually the piston came apart and destroyed the motor, hence the new 389. The quick diagnosis would be to pop the valve cover, back off the rockers so the valves can seat, pull plug, pump cylinder with air. have your dipstick out, TB uncovered. then while pumping air put your ear (use a piece of vac hose as a stethescope) at each the dipstick tube, T-body then at rear exhaust tips. you will hear a steady stream of air very easily. When i did this, the air pressure actually blew the dip stick out of the tube! i had a BIG hole in the piston!!
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Re: What would cause no compression in one cylinder Probably a broken spring.
Black Magic, I edited your sig... You are not a paid advertiser, cannot advertise unless you contact me.
Black Magic, I edited your sig... You are not a paid advertiser, cannot advertise unless you contact me.
Thread Starter
TECH Regular
Joined: Nov 2001
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From: Madison Heights, MI
Re: What would cause no compression in one cylinder Cylinder number 3 valve spring is broke. If I give them a new spring the total cost will be $265. I guess i have a cool dealer.
You should really make a new thread...this one you dug up has been dead for about 9 years!
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Teching In
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From: Largo, Fl
You must have taken the wrong friend's test. I ran into a similar one in wall works when I drove the car for a check. Even with the compression rings open, you will still get SOME compressions. In addition, your car would hardly move if it was only running on 3 cylinders.
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From: Central Cal.
You must have taken the wrong friend's test. I ran into a similar one in wall works when I drove the car for a check. Even with the compression rings open, you will still get SOME compressions. In addition, your car would hardly move if it was only running on 3 cylinders.
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