Possible broken valvespring.....
Thread Starter
Melting Slicks
Joined: Nov 2003
Posts: 2,911
Likes: 2
From: Honolulu Hawaii
Possible broken valvespring.....
Man, I've been trying to get to the source of this P0300 code and read that I may have run into a broken valvespring. Having never had this happen before, and without pulling the heads....
1) Can anyone tell me what symptoms I would run into if this was the case?
2) Also, is it possible I didn't drop the valve?
3) If I did suffer from both of the aforementioned, what happens when you drop a valve? eg. loud noise, catastrophic failure, engine shutdown, etc...?
EFI-1 still seems to be running at about 90% but extra rich. Lot's of popping on deceleration. I was hoping it was a possible chafe going on with the fuel injector harness, or bad 02's, maybe a bad coil. I'm a bit worried if it is a broken spring that I may have done some big damage as I have had her out since then trying to log and troubleshoot the codes. I'm planning on doing a compression test sometime next week, but figured I'd get a head start on the issue in the meantime...Worst case scenario.
Thanks for any help guys.
Aloha, Dave
1) Can anyone tell me what symptoms I would run into if this was the case?
2) Also, is it possible I didn't drop the valve?
3) If I did suffer from both of the aforementioned, what happens when you drop a valve? eg. loud noise, catastrophic failure, engine shutdown, etc...?
EFI-1 still seems to be running at about 90% but extra rich. Lot's of popping on deceleration. I was hoping it was a possible chafe going on with the fuel injector harness, or bad 02's, maybe a bad coil. I'm a bit worried if it is a broken spring that I may have done some big damage as I have had her out since then trying to log and troubleshoot the codes. I'm planning on doing a compression test sometime next week, but figured I'd get a head start on the issue in the meantime...Worst case scenario.
Thanks for any help guys.
Aloha, Dave
Tech Contributor
Joined: May 2008
Posts: 2,843
Likes: 16
From: Howell Michigan
St. Jude Donor '09-'10-'11
You don't have to pull the heads to check for a broken valve spring. Not a big deal to pull the valve covers to inspect springs. If the engine is still running and doesn't have a miss chance is you haven't damaged anything. If you have worries about valve springs, pull the valve covers a take a close look at each one. 20 to 30 minute job at most.
Thread Starter
Melting Slicks
Joined: Nov 2003
Posts: 2,911
Likes: 2
From: Honolulu Hawaii
Dave,
You don't have to pull the heads to check for a broken valve spring. Not a big deal to pull the valve covers to inspect springs. If the engine is still running and doesn't have a miss chance is you haven't damaged anything. If you have worries about valve springs, pull the valve covers a take a close look at each one. 20 to 30 minute job at most.
You don't have to pull the heads to check for a broken valve spring. Not a big deal to pull the valve covers to inspect springs. If the engine is still running and doesn't have a miss chance is you haven't damaged anything. If you have worries about valve springs, pull the valve covers a take a close look at each one. 20 to 30 minute job at most.
Race Director
Joined: May 2005
Posts: 15,960
Likes: 21
From: West Norriton PA
St. Jude Donor '08
Check Ignition Wires (Resistance), Spark Plugs (Cracked Insulators or Burned Wires), Check Coil Packs and harness.
Try to get someone with a OBDII reader that can tell you what cylinders are missing, The code would appear as P0307 if it was cylinder (7) etc .....
Try to get someone with a OBDII reader that can tell you what cylinders are missing, The code would appear as P0307 if it was cylinder (7) etc .....
Thread Starter
Melting Slicks
Joined: Nov 2003
Posts: 2,911
Likes: 2
From: Honolulu Hawaii
Good input guys. I should give a bit more info.....
Changed plugs/wires. EFI-1 has about 7k mi on her. No burned wires, plugs indicated rich mixture in most cylinders. Checked, double checked fuel injector harness, chassis grounds, checked all electrical connections and used dielectric paste in each, cleaned MAF, disconnected, cleaned and reconnected each fuel injector plug.
Haven't pulled the valve covers yet, haven't swapped 02's but they are not throwing a code.
Changed plugs/wires. EFI-1 has about 7k mi on her. No burned wires, plugs indicated rich mixture in most cylinders. Checked, double checked fuel injector harness, chassis grounds, checked all electrical connections and used dielectric paste in each, cleaned MAF, disconnected, cleaned and reconnected each fuel injector plug.
Haven't pulled the valve covers yet, haven't swapped 02's but they are not throwing a code.
Safety Car
Joined: May 2003
Posts: 3,814
Likes: 105
From: Dearborn Heights Michigan
Broke a spring on my 2000 last year. There was a loud clicking noise and the car wouldn't go over about 40mph. Did not drop a valve, if you did there would be much, much noise.
Above posts right on, just pull the valve covers and you will find out.
Above posts right on, just pull the valve covers and you will find out.
Burning Brakes
Joined: Oct 2008
Posts: 898
Likes: 25
From: Dallas, TX
Are you still running the stock mid pipe? Mine was clogged and gave me a P0300. I ran down everything else just like you are and ended up replacing the pipe under warranty (8yr/80k miles). If you still have front HO2 sensors, pull one at a time and test the pressure. Should be around 2 psi. My driver's side was at 15psi and ran pretty bad. 
New pipe, problem went away. P0300 can be pretty frustrating.
New pipe, problem went away. P0300 can be pretty frustrating.
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Thread Starter
Melting Slicks
Joined: Nov 2003
Posts: 2,911
Likes: 2
From: Honolulu Hawaii
Great post. I have LG LT's and I'm running the hi-flow cats. I do have the bypass pipes, but I don't want to **** off everyone in the zip code when I start EFI-1 up at night.
Burning Brakes
Joined: Sep 2006
Posts: 985
Likes: 0
From: Cumming Georgia
Racer
Joined: Dec 2006
Posts: 297
Likes: 0
valve spring
I doubt it is a valve spring. With a broken valve spring for some reason LS engines don't like to run. Thank god for that, as I think that has saved many of us thousand of dollars in repairs and rebuilds!
