View Full Version : Odd flutter at 1.5-2k rpms.

11-18-2016, 09:12 PM
Have 91 gt with 5sfe. Engine rebuilt 10k ago with head sent out to machine shop for outsourced rebuild. Car is running great, getting near spec on mpg, no hesitations etc. sooo

Some 6 weeks ago started getting an odd flutter from the engine compartment. Occurs at 1500-2000 rpms, when accelerating, can be heard for about 200 rpm range and then disappears at higher rpms. Nut heard when idling or cruising without much load (level ground) as soon as I reach an incline, flutter can be heard as the 'load' increases. Sounds like plastic hitting metal but could easily be a wet metal sound.

I've been all over the engine compartment with a mechanics stethoscope and can't find it. I'm guessing at loose butterfly or a flapping valve shim. I was about the pull the valve cover etc but figure I'd throw this one out to the forum first


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12-29-2016, 09:51 PM
Well, now this happens. . .

Had been chasing the flutter fit some time now. Pulled the valve cover and check valve train sites , everything was good. Dig around the front of the engine - idlers, belts pumps etc - nothing. Had come to the conclusion that the noise was deep in the engine - crank or ring related.

Took off yesterday for one of my odd 150 mile RT and noticed the flutter had picked up a bit , noticeable enough to confirm it was coming down low , and then a pop/ping and the engine shuts down. I though I had blown a fuse or a wire popped out. Stopped , looked, found nothing unusual. Started right up. Half mile down the road and bang. . .

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12-29-2016, 10:15 PM

12-29-2016, 10:21 PM
So, I haven't pulled it yet, but here's what I'm guessing that happened

1 spun a bearing
2 bearing failed (the first pop)
3 partial bearing allowed startup, but bearing came out, allowing piston movement. Connecting bolts sheared and crankshaft dropped, came around and slammed the bottom of the piston against the sidewall of the engine.

Will be pulling block from dead 93. Will start a new thread with associated questions

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12-29-2016, 11:32 PM

Sorry dude. That sucks.

Normally, a rod bearing makes a much more distinctive noise than a flutter. That would have been a hard one to catch.

12-31-2016, 12:31 AM
Thanks for the sympathy. When I restarted the car, the changed noise matched a main bearing problem. I had hoped to finish the last 6 miles on the outgoing trip and park it in a safe area for a flat bed pickup the next day - only made it .5mi down the road.

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01-06-2017, 07:13 AM
Ouch! Did it punch right through the block? When my 3SGE spun a bearing it just died, with no warning or sound. One minute I was coasting in traffic, the next I'm wondering why the fun pedal isn't doing anything and my cluster says 0rpm.

01-06-2017, 08:48 AM
I suspect one if the piston cap bolts failed, the cap came off, crack rotated down leaving the piston in place, the crack came around and slammed the bottom part of three piston into the side wall.

Temps are freezing around here so I haven't had a chance to pull the motor yet.

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