slight engine knock

[z4roady05]

well, last night i was turning a corner at maybe 35mph. i proceeded to downshift and when i did the tach spiked almost immediately. which would be called going into the wrong gear(lol) which has happened to many ppl im sure. i did as usual and put it in right gear and drive off. well i noticed it didnt have pickup power so i pulled in gas station and put in neutral. the idle was rough and the tach was jumping in between 800-1000rpm. very scary sight i must say. well i got back on road and car drives fine just has rough idle. i got up to 75mph to see what it would do and ran fine. but as soon as u stop it has rough idle. so i came straight home and when i go to shut down car i hear light knock. i open the hood and it sounds like my valve are having a "fight"! even more scared by this point. so at this point im thinking of me having to buy new engine lol just me panicking. tommorow i will go to dealer and tell them to check service light to see what it says and tell them about noise. my question is how much info should i tell them? i really wasnt racing or anything just freak accident. should i tell them i went into wrong gear? has anyone else had this problem or heard of it? thanks in advance.

 

[inTgr8r]

Sorry to break the news to you, but....
They can tell if there was mechanical overrev.
The data gets logged

 

[z4roady05]

Sorry to break the news to you, but....
They can tell if there was mechanical overrev.
The data gets logged

umm that sucks. i heard about that before, but didnt know how it was used. so is that saying because of over-rev they wont warranty it?

 

[Adam D]

I assume you went into first at 35mph Did you dip the clutch immediately? I'm not sure what the top speed is in 1st but would have though it was at least 30 ish so maybe it didnt overrev too high?

I'm sure someone with one of those gear ratio programs can calculate the theoretical engine speed and how much over the stock limiter it would be. I'd have thought these engines are strong enough to take some punishment and an increased rev limit as don't some remaps do just that?

Hope its an easy fix chap!

AD

 

[fire-n-ice]

Uh-oh.. :? , that would definitely concern me since your valves started rattling immediately following the over-rev..so, it's been today already, did you take it in, any news?

 

[Zeefour]

In theory you can't over rev the motor because of the "rev limiter", the reverse is when you are accelerating through the gears and hit the rev limter, although its more shock to the driveline and motor when selecting the wrong gear at high speeds

 

[inTgr8r]

In theory you can't over rev the motor because of the "rev limiter", the reverse is when you are accelerating through the gears and hit the rev limter, although its more shock to the driveline and motor when selecting the wrong gear at high speeds

(unless I misunderstand you).... Respectfully, I have to disagree.
That only applies as you accelerate in a gear.

Mechanical over rev occurs with a mis-shift to a lower gear,
which causes the rear wheels to drive the engine past safe rev limits.
Over rev limiter can't prevent this.

 

[z4roady05]

i brought the car to dealer today and they didnt have a slot til December 3rd. but after i started it up for them they said just leave it here and we'll get to it in between cars sometime this week. it really drives fine once ur moving just the dang idle. i thought my motor would b a lil stronger than that. i went into second so i know i wasnt going that fast. no way was i taking a red light corner near 45mph! like ive money shifted before but u realize when u do it. i really didnt know what happened. i noticed a lil carbon on tailpipe after driving it 30 miles to dealer. man this sounds so bad. if and when they fix it i think ill still be better off trading it in lol

 

[inTgr8r]

It's possible the previous owner pulled a money shift.
The damage doesn't always manifest itself right away.

Maybe your mild shift was the final straw.
..I hope it works out for you.

 

[z4roady05]

It's possible the previous owner pulled a money shift.
The damage doesn't always manifest itself right away.

Maybe your mild shift was the final straw.
..I hope it works out for you.

yea i bought it with 4k miles. im not sure if it was demo or previous owner. id hate to have to tell my insurance company they have to buy engine lol thanks everyone for your comments.

 

[fire-n-ice]

I don't really understand...you were downshifting in a curve and hit 2nd instead of..?? The only other gears in the south position are 4th and 6th, if you have a sixspeed, neither of which would wring your clutch at 45mph..thinking like InSTG8er and maybe there was already prior damage..hmm?? :scratchhead:

 

[Adam D]

I assumed he was doing 4th -> 3rd and found 1st?

 

[inTgr8r]

I assumed he was doing 4th -> 3rd and found 1st?

IDK... that's not easy to do, carrying any kind of speed.

 

[Zeefour]

In theory you can't over rev the motor because of the "rev limiter", the reverse is when you are accelerating through the gears and hit the rev limter, although its more shock to the driveline and motor when selecting the wrong gear at high speeds

(unless I misunderstand you).... Respectfully, I have to disagree.
That only applies as you accelerate in a gear.

Mechanical over rev occurs with a mis-shift to a lower gear,
which causes the rear wheels to drive the engine past safe rev limits.
Over rev limiter can't prevent this.

Yep thats what i meant by shock to the driveline and motor..

 

[inTgr8r]

In theory you can't over rev the motor because of the "rev limiter", the reverse is when you are accelerating through the gears and hit the rev limter, although its more shock to the driveline and motor when selecting the wrong gear at high speeds

(unless I misunderstand you).... Respectfully, I have to disagree.
That only applies as you accelerate in a gear.

Mechanical over rev occurs with a mis-shift to a lower gear,
which causes the rear wheels to drive the engine past safe rev limits.
Over rev limiter can't prevent this.

Yep thats what i meant by shock to the driveline and motor..

..