North American Turbocoupe Organization



Broken Cam???Valve Stuck open???kinda long, lots of questions
Kev Offline
Posting Freak
#1
I posted a week or so ago saying that my car had suddenly began to have some kind of catching or popping sound in the engine and there was an extreme loss of power. I first thought maybe it was a broken rod, but the loud knock isn't there. The timing was checked and it was dead on. I took the car to my mechanic, which I trust and he knows my car, he tested it out and said there was a dead spot in the engine. Maybe floated a valve or punched a hole in a piston. The car is blowing absolutely no smoke, so the hole in the piston is ruled out, right? I'm not losing oil, and the oil looks fine. (Had to drive the car about 7 miles to get it home after this happened). How exactly does a floated valve work? Does that mean that it's stuck open or closed? What is the possibility that one of the lobes broke off the camshaft? Or that the camshaft broke in half or something? The car will still sit and idle, just every few seconds it has a catching sound and dies down a little, but only for a second. When trying to accelerate, it makes the same sound as a front wheel drive car makes when the boots are bad on the cv joints, kind of a popping. Has anyone ever experienced anything like this, or heard of it? Any suggestions? Thanks

Kev
Kev
1988 TC 5spd
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Hybridbird Offline
Posting Freak
#2
A burnt valve or valve seat yeah.A burnt piston should smoke ...but then so should a valve.A broken lobe or cam?????Man I sure hope not or something......I don't see it.IThat would take an AWFUL lot of stress,and your cam belt would break long before that.Speaking of which how old is your belt?Maybe it stretched and skipped a tooth?One tooth doesn't sound like much,but can be as much as 7 or 8 degrees I think.That's enough to atleast give you problems or worse depending on which way it goes,advance or retard.How old are your wires?

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Too much fun, what's that mean?That's like too much boost,there's no such thing.
"Finch....get the f*ck away from that Ficus......that's a jizz-free Ficus!"
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Pete D Offline
Administrator
#3
I think you can rule out the camshaft breaking in half. Valve float refers to the valves not closing completely because the springs are not strong enough to close them. This most often is a sign of weak valve springs and higher rpms where the time available to close the valve is shorter.

What you might have is a broken/cracked valve spring. When you last posted I recommended that you or your mechanic put a vacuum gauge on it and see what the needle does. That's still my recommendation

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NATO Member. it's not a vice, it's an obsession
"The nice thing about each new day is nobody ever used it before" Barnaby Jones
88 TC X 2, 86 SVO, mods list at
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Pete Dunham


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Chuck W Offline
Posting Freak
#4
A couple years ago while driving back to Indy from SC, the XR7 developed an engine vibration...closer inspection revealed a dead #2 cylinder..but why? It made no noises and seeing as I was in Asheville, NC and wanted to get home...I just drove it. Aside from a vibration it ran fine.
When I finally pulled the head I found an 1/8"x1/8" chunk out of the exhaust valve. There had been a major amount of carbon build-up from when the FRP was bad at it was running 90psi fuel pressure at idle! A chuck of carbon had obviously gotten lodged between the valve and head and thus the broken valve.
Anyway...run a vacuum gauge on it like Pete said...since your actually hearing a sound it may be a bad valve spring...

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I don't know what your problem is, but I'll bet it's hard to pronounce.
83 TC Clone, 80 Cougar XR-7, 85 Volvo 244 Turbo, AND 88 Scorpio
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Dan E Offline
Posting Freak
#5
Also maybe a collapsed Hyd. Lash Adjuster (lifter) ???

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Dan Eaves
88TC 5spd, Crower 5.5" Sportsman Rods, Short Wiseco Pistons bored .030" Over, Ported Head with Polished Combustion Chambers, Gutted & Polished Upper, Ported & Polished Lower, Polished T/B, Ported E6, SVO T3 .63AR Turbo, Bosch Bypass Valve, 3" DP w/No Cat, 2 1/2" DynoMax single cat back w/DynoMax Super Turbo Muffler, RR Cam, K&N in Fenderwell, Gillis Boost Valve, Centerforce I Clutch, Removed A/C, Polished Wheels, Polished Valve Cover, Polished Crank and W/P Pulleys, Walbro 255LPH HP Pump, Kirban Adj FPR, and the DAMN Heater Core is new too !

NATO MEMBER (Vice Chairman...if it's a vice...I deal with it)
Dan Eaves
88TC 5spd Vermillion Red, Polished...everything...
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Kev Offline
Posting Freak
#6
Thanks for the replies. The timing belt is brand new, it broke about 2 weeks ago and I had a new one put on and the timing reset. My mechanic has the car now, I'll find out next week what the trouble was. He said he'd take the valve cover off and look at the head, if it's not evident, he'll take the head off. Man, I hope it's something easy. Thanks again.

Kev
Kev
1988 TC 5spd
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