So I have this, uh, friend who accidentally went from 2nd to 1st instead of 3rd under heavy acceleration. He tells me that he heard a loud 'pop' and got a check engine light. He shut it down quickly and limped off the course. After a visual inspection and a restart, no engine lights, nothing leaking, no visible damage or issues. The car is running as normal under regular commuter-type use.
Anything to be concerned about? It's a pretty modern car, a lot like a Fiesta ST, 4 cylinder turbo.
If it runs fine and doesn't make any funny noises, I'd monitor it for a bit, but it's probably fine. Maybe do a compression test to confirm he didn't ding a valve.
Can your friend give more details? Shifter went into first? Shifter went into first and foot came partially off clutch? Shifter went into first and foot came all the way off clutch pedal while simultaneously continuing to floor the gas because "no lift shift"?
When did the pop happen?
But if its running regularly that's a really good sign. Maybe the pop was a speed limiter induced non-combustion event that then caused a small and harmless backfire pre-turbo.
I remember the RSX-S would do this rather easily. Shifting at WOT at 7500rpm in 2nd to first would typically result in a rod through the block and an over rev code stored on the ECU.
In this case, it is possible that the CEL is the ECU telling you (I mean "your friend") "Hey dummy! I'm not supposed to rev this high!) and storing the over-rev. I know of a few warranties on the RSX that were denied because the ECU recorded 10k+ rpm's for a brief instant (I think the record high was 10,200 but it's been a few years, ok more than a few).
I had a kid come in to the dealership I was working at and had a rod through the block on his 8th gen si. the over rev said 14,000 rpms......
There's an infamous Youtube video of just that, apparently some kids either racing or leaving the scene of street racing in a hurry. Pretty sure he did the exact same thing but he definitely blew up the engine (and went off the road).
Here it is (bad language warning)
HonestSpeedShop said:I had a kid come in to the dealership I was working at and had a rod through the block on his 8th gen si. the over rev said 14,000 rpms......
Honda motorcycles can do that, why can't the cars?
A guy I know missed a shift in his Prelude with a built H22... Rev limiter was at 9500 IIRC. He said he saw 11k by the time he got the clutch back in... Motor was perfectly fine.
In reply to rslifkin :
"Built". Key word. These were bone stock engines still under warranty.
Last time I did that I broke the journal shaft in the turbo. God that made a mess.
Sounded just like you described but there were no CEL's other indications besides no boost and a lot of smoke. Maybe pull the intake hose off and see if the turbo has any play, or at least check to see if the compressor side hit the housing. Having metal confetti go into the motor is a terrible thing.
Speaking of over-revving an engine, while this isn't car related it's pretty incredible to hear. Definitely needs sound, and turn it up. From a Reno NV air race.
The loud pop could be many things.
The damage is done whatever it is so just keep an extra eye out, do a very long oil change next time to check everything out while under the car. Check the oil too.
When I play around on a gravel road, if I get all four loose the stability control lets out a "grunt" , as it temporarily cuts power. Only had it happen twice.
As for over revving, the first thing is the valves float. Depending on how the engine is designed this may or not cause damage.
I once...My friend once performed a 2-1 money shift in my...his twincam IT Neon with a 7400 rpm chip. He was confused by the sudden braking effect, pulled it to neutral, then BACK INTO FIRST, and quite honestly thought he had broken the tach, because it seemed to take forever to come back down off the back side of the pin.
No particular immediate harm, although the center broke out of his Spec clutch disc later that season.
I had a friend do a 3rd to 4th on track and went to 2nd instead. Okay, it was me. Buried the tach past the 9,000 rpm reading (redline is 7,500). Car (FX16) ran fine for the rest of the event.
A month later had a weeping head gasket. After a new head gasket, I went on to put over 100,000 more miles on that engine.
Keep monitoring it. Hopefully, is will continue to operate normally for many more miles.
If the check engine light came on it set a code and it would be interesting to know what the code is. The pop could have been from the ECU slamming the throttle shut under high RPM and boost.
Duh, check the codes. (head slap) I will do that to see if they say anything enlightening. But I think it was just a backfire because the clutch did not come all the way out and the high-rpm event was very minimal.
Hope all is good (with your "friend").
My missed shift scare was a few years back I was briskly accelerating my '85 300ZX (auto) and tried to bump the shifter up a gear.....and sent it right into reverse(!)......Spinning the tires backwards for 50' or so was not my proudest moment.
KyAllroad said:Hope all is good (with your "friend").
My missed shift scare was a few years back I was briskly accelerating my '85 300ZX (auto) and tried to bump the shifter up a gear.....and sent it right into reverse(!)......Spinning the tires backwards for 50' or so was not my proudest moment.
Surprised it didn't lockout. I did that once in an SBC+powerglide swapped fb and as a result I was replacing ring and pinion gears.
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