Broken inner valve spring

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Aug 30, 2011 | 04:54 AM

smokeshow

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Broken inner valve spring

I've been hunting down a misfire ever since I spent time on the dyno last Thursday. After much troubleshooting, I found a broken inner valve spring on my PRC 675 duals. Could this be the cause of the misfire? Its #7 exhaust.

Aug 30, 2011 | 12:59 PM

litle88

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Yup! I broke a TFS upgrade valve spring that came on my 220's, you should check your compression after you change the spring. Because if the piston kissed the valve then chances are you have a bent valve and it will still act like a misfire.

My buddy had a set of prc's for 10k plus miles! It's the first I hear of them breaking to tell you the truth.

Goodluck in getting it running! Mines been sidelined since mine broke and I have been upgrading ever since lol just check my sig! Lol

Last edited by litle88; Aug 30, 2011 at 01:14 PM.

Aug 30, 2011 | 01:22 PM

Sales2@Texas-speed

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I'd be curious as to WHY the inner spring broke. The handful of .675's that have broken from lofting and other control issues have all been outer springs, by and far.

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Aug 30, 2011 | 09:29 PM

smokeshow

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Turns out the spring isn't contributing to my misfire problem, at least not according to the scanner.

Edit: new plugs suggest otherwise...

Bank 2 O2 sensor is showing bursts of oxygen. Something is going on on the other side of the engine.

Last edited by smokeshow; Aug 31, 2011 at 07:20 AM.

Aug 31, 2011 | 07:19 AM

smokeshow

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So I decided to pull a few plugs to see how they look after a few days in the engine. They might have 40 miles on them. Only pulled bank 1 because the turbo and log manifold makes the other side a pain to get to. Might pull them later when I've got more time.

#7 rich...safe to assume the broken valve spring is causing that.

Old plugs:

Same pattern, rich #7. #2 also looks a little darker than the rest.

Aug 31, 2011 | 05:57 PM

Sales2@Texas-speed

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Let us know how she does with the new spring, and of course if we can help with anything else just say the word!

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Sep 1, 2011 | 04:47 AM

smokeshow

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Update...tested the secondary coils of the coil packs with the meter and found that they had over 3 mega ohms of resistance, which is way out of spec from the 5.5k they are supposed to be. So it looks to have been a weak spark. It still has a mild misfire up in the RPMs, and I noticed it was happening when the lights dimmed. SO, the alternator is getting checked out tomorrow. If its bad, that is likely the reason why the coil packs died. New valve spring also comes in tomorrow.

Quote:

Originally Posted by Matt@Texas-Speed

Let us know how she does with the new spring, and of course if we can help with anything else just say the word!

Thanks Matt. Will do. Put down 623/738 on the dyno last week with a misfire...hopefully it'll get strapped back down soon and we'll see what a strong spark will do for it

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Sep 3, 2011 | 02:02 PM

litle88

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Make sure your compression is good on #7 of it's not then your valve might be bent.

Goodluck and keep us posted.

Sep 13, 2011 | 10:04 PM

#10

smokeshow

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Got the HPT cylinder balance test to work and all cylinders are within 1%, so no valve problems. I also introduced a misfire problem with the shorter gap on the colder plugs. Went from TR6 @ .040 to TR7 @ .030 and it had that idle/low load chug. Re-gapped to .035 and its barely noticeable. Now I'm just fighting with the new SD tune trying to get it to idle. Never ends!