this is from a 2000 Honda Accord LX F23A1 VTEC

my mechanic recently told me my knock sensor was bad, i have no money right but definitely got to save up for it. anyways, my question is could a bad knock sensor cause VTEC to fail?
problem is when i floor my car and hit 5-6K RPM and throw it in N to roll to a stop, the engine shuts off.
so i am wondering if the failed knock sensor could cause this.
happens all the time when i floor it and hit 5-6K then drop it in N and let it roll.

 

Why would you shift to N under those conditions? Stalling when you do that could be a number of things mis-adjusted in the idle-control system.

Anyway, do you get a check-engine light? What error code?

 

i guess i don't know how to drive. i figure to slow down from 5-6K 3rd gear, i should throw it in N and hit the brakes. i guess i should throw it in second and brake instead?
the last code was the knock sensor, could be another there too.
the idle IS fucked up, i know that for a fact.
so you think it could be an idle problem?

 

Manual or auto? Auto, I'd just let it do it's thing. Manual, I'd shift up. Either way, I guess I don't understand why you're up to 5-6k when you just have to stop anyway. Well, never mind about that.

I don't think the knock sensor causes the stalling when you drop from 6k to idle. I think that's caused by mis-adjusted idle-control system.
Vacuum leaks?
Throttle body dirty & sticking?
Misguided 'mechanic' tightened the throttle cable to raise idle RPM?

Fix that stuff, adjust your BASE idle (that's different from the operating idle), & then reset your ECU. Start the engine & allow it to warm up to operating temperature WITHOUT TOUCHING THE GAS PEDAL the entire time. This allows the ECU to re-learn the behavior of the idle control system.

 

will do, thanks.
i know for a fact my idle is a bit funky but did not know it could cause operation stalls.

 

Actually, rpm dropping from a high value is a tough thing for the idle control system. It needs to have all it's stuff adjusted right. The ECU has to know how & when to open up the IACV in anticipation of the RPM dropping to idle. If it waits for the RPM to reach 750 it's too late because it takes many milliseconds for the IACV to open & by that time the RPM is low enough to stall.

IACV cleanliness, IACV response speed, TPS adjustment, & idle-air bleed screw adjustment all influence that. If you have used one thing to compensate for mis-adjustment in another thing, it gets all messed up.

 

you are are a pure genius and very helpful man.
this car has had the AT swapped for an MT.
when that happened the idle was funky because we were running with the AT ECU at the time.
so my mechanic did something to the idle.
i've since did the MT ECU in the car and never touched the idle but now i know that is what is causing the problem and how.

and also that my understanding of MT is a bit messed up. I always thought it was safer and better to throw the car in N to slow down to stop. but now i think that is not even the correct way to do slow down to stop.

 

With manual u can use the engine compression to slow you down. This is the ideal way to drive a MT car. Instead of using your brakes constantly (like freakin AT drivers ) you use the engine to slow down.

However, when downshifting it is also beneficial to the life of the engine and drivetrain if you match the rpms with the gear you are shifting into. Its also called heel-toe. In other words it is not good to let the rpms decrease to the point where the engine will have to be "pulled" up to the rpm the gear requires. This usually happens violently and is the reason it should be avoided.

I could prob drive all the way to work without using my brakes

 

I'm not sure but I think an auto-trans ECU simply has more signals that go to the tranny. Those wires will just have nowhere to connect to. The sensors & signals for the engine may not be any different.

That leaves cleaning and proper adjustment of the idle-control stuff. If he's not real familiar with Hondas, he could have done the same thing with a car that has had a 5-spd from the factory.

Using one thing to compensate for another, is a shortcut technique with a long history. It takes time (& your $$$) to do it right. Many times it works OK, but you've discovered one situation where it DOES make a difference.

 

well my mechanic is also a friend so all of this fixing is done free of charge unless a part is needed.

he had told me something about the idle being funky and leveling right with the AT ECU so he had to put a gasket or something to simulate enough air getting into the idle sensor. so, now we need to remove it and set it back to normal.

also like i said the knock sensor is busted too.