redline when throttle stuck, engine damage?
 

well i had a throttle sticking problem which i think i have solved. however, im concerned now about damage

the car pulls great and when out driving around doesnt sound any different. However, when sitting still at idle, if i rev the engine a bit, it just doesnt sound the same. its hard to describe. i guess the best way i can describe it is that its a little more throaty...like the muffler suddenly got a little louder and there is a very slight vibration that wasnt there. its not a rattle or a grinding or anything loose sounding.

i was going about 55 in 4th when i was in the process of quickly downshifting to 3rd at which time, the throttle stuck and the engine revved to redline. i was too busy trying to avoid an accident to see just exactly where on the tach the needle was, but it was definately in the red..for a few seconds with the clutch pedal depressed

should i be worried?

EDIT: i did not hit the rev limiter...the engine did not cut off momentarily. what concerns me is not so much the redline, but the fact that the clutch was in...the car was in neutral on its way to 3rd when this happened. somehow, even with my zero knowledge of engines, i tend to think this is very bad ????

Is the engine blowing any oil smoke? Does it still rev to the redline? I can't remember where I heard it, but it seems to me the stock valvetrain on virtually all flat sixes is good for 7,500 RPM. So if you caught your engine before that, you're probably fine. These motors are tough to break.

As for the throatiness, eh, maybe you blew out some muffler baffling. No biggee.

NO smoke. runs perfectly otherwise. it revs just fine. i just happened to notice when i started the car for the first time after this happened. as i was pulling out of the garage, i revved a little and it just didnt sound right and there is a very slight vibration...which unfortunately i cant describe better. went for 10 mile drive..came home and sat in driveway to listen...just aint the same

hmm. these cars are so much fun, until you think you broke something inside the motor:eek:

Probably time for a valve adjustment and a look at the oil....

i agree. i had a tapping before this happened anyway and its been at least 12K miles since the last one

I don't know how the rev limiter works on the stock SC but if it was functioning correctly it should protect the engine from this kind of damage. The danger is that the valves may have hit the pistons and bent the valves. I'd do a compression test at least and a leak down if you have the means. If the valves are bent you will have a loss of compression on the affected cylinders. Loss of compression can result in a rough idle as a symptom. Unfortunately if you have bent exhaust valves you will need a rebuild because the valves will leak and then burn until the compression is so bad the engine misses at idle.

-Andy

I ran my SC at max rev for about 30 or 60 seconds. I was in 4th and I thought I was in 5th at 120mph and I was wondering why the car wouldn't go any faster. Sterio on too loud and too much to drink (I was younger at the time). The engine was fine.

I don't think SCs have rev limiters - I think they came in with the Motronic cars, although I could be wrong. I think the SCs saftey net for over revs was provided by using a certain type of rotor arm that allows a maximum rev limit - I don't how it works, but if you could find out if your car is equipped with such a rotor arm and what it's rev limit is, then you could ascertain what the max revs you were doing during your over rev was, which might give you a little peace of mind.

I'd put my money on your engine being fine. If you'd misshifted into too low a gear then I would expect valve damage, but since it was just a sticking throttle I'd think you'd be okay - these motors are very strong. As suggested above, a change in sound may be nothing more than some crap blown out of your exhaust. I reckon if you can check the rotor arm rev calibration (if I was right about such a thing) then that might shed some light on the situation, but otherwise if your idle is smooth and revs fine without smoke I wouldn't worry too much.

ok. thanks guys. if it wasnt for the exhaust note being slightly different and what i perceive as a slight virbtation...i wouldn't know the difference. i took the car to some expressway on-ramps and hammered it good in 2nd and 3rd and it pulls as hard as ever with no strange noises or smoke or hiccups and idles exactly as it always has

i dunno why i was so worried. probably the expense of a rebuild when your not prepaired for such a thing.

NOTE:

To anyone who reads this....make sure you do some preventative maintenance and checking to make sure you do not have a throttle sticking situation. besides hurting the motor, this is very dangerous and there are at least 6 ways I can tell that a throttle can get stuck. even though ive gone through most of the throttle parts and found a few things..im going to forever be paranoid that this will happen again, though next time i will shut off engine with key and coast

The SC should have a relay that shuts off the fuel pump around 6800 RPM.

http://forums.pelicanparts.com/porsche-911-technical-forum/374948-82sc-rev-limiter.html?highlight=rev+limiter

Your risk is bent valves. Throatiness CAN be a symptom of this.

I would spring for a compression and leakdown tester and check the engine. This will easily confirm or alleviate your fears.

If you have a rev-limited you're most likely fine, but why not do this simple check so you can stop worrying you know?

Redline is not going to damage anything, you would most likely have to go 200-300 RPM over redline to really damage anything. If it's a little more raspy I'd guess a baffle in the muffler came loose.

The range is there on the redline for a reason.