This isn’t rev hang. Can my throttle be sticking?

[BoratThongOwner]

I have a 2018 sport hatch 6MT with a K&N CAI; no other mods. This really only happens when the weather starts to get cold here in NJ (below 50ish), but this year it’s making my car incredibly annoying to drive.

I’m in 2nd, up at 3,500rpm, I clutch in and get off the throttle, shift to 3rd, wait for the rpm’s to start dropping before I start letting the clutch back out, still wait, still waiting, they’re still at 3,500rpm, I shift to neutral, my foot’s been off the throttle this whole time, I let the clutch out, I’m rolling at like 20mph in neutral with the clutch out and my foot off the throttle and it’s pinned at 3,500rpm.

This goes on for, I’m not kidding, 15-20 seconds. Just rolling along in neutral, no throttle input, and my car’s just humming at 3,500rpm. I even brake and come to a complete stop at a light, and it’s STILL hanging onto 3,500. Or 4,000. Or 2,500. Or whatever it was when I shifted out of whatever gear.

There are other times where I’ll shift to neutral while coasting and the revs will drop to idle like normal, but then start climbing on their own as if I was pressing on the throttle slowly (even though I’m not). Then once at a complete stop they’ll drop back to idle.

As soon as it gets cold enough, my car starts to do these things insanely frequently. Doesn’t matter what gear or what rpm, it’ll just hold onto the revs until I slip the clutch back out to force it into another gear. Is it the CAI? Is something broken/on its way out? I’ve seen a couple of posts here about this issue but 0 solutions and not much guidance.

I’m gunna take her to a shop/dealer if no one has any suggestions on what direction to go in by myself. I would really appreciate any help with this.

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[Ducota]

Does this happen when the motor is cold or randomly?

 

[BoratThongOwner]

Does this happen when the motor is cold or randomly?

Both when it’s warm and cold. Doesn’t seem to matter how long I’ve been driving. I can drive for 30 mins to the next town over and once I start going through stop signs and lights, every other time I clutch in it’ll happen.

 

[Ducota]

It’s drive by wire so nothing mechanical to stick. What happens if you let the clutch out while it's doing this?

 

[arpypat]

Did you recently install that intake? Maybe something going on with the MAF? This is quite an odd issue and not one I've read about in here... Maybe one of those rare instances where you actually have to go to a dealer lol

 

[BoratThongOwner]

Did you recently install that intake? Maybe something going on with the MAF? This is quite an odd issue and not one I've read about in here... Maybe one of those rare instances where you actually have to go to a dealer lol

Nah I’ve had the intake on for over 2 years. I run 93oct 99% of the time if that makes a difference. Tbh I don’t know that much about engines/fuel but could it be running too lean/rich or something?Maybe way too much air?

Kinda good to hear I’m not crazy and it’s not a common issue…

 

[casper]

Just to rule out the simplest possibility first - Maybe there is something jenky with your throttle pedal. It may not be mechanical, but it still has moving parts in it and a sensor to convert pedal travel to throttle opening. It’s pretty easy to remove the whole pedal (just three bolts and unplug the wire connectors - Acuity has some instructions on it for their pedal spacer product), to see if maybe it’s getting stuck or something is preventing it from coming back up all the way.

 

[Boosted_01_R]

I have a 2018 sport hatch 6MT with a K&N CAI; no other mods. This really only happens when the weather starts to get cold here in NJ (below 50ish), but this year it’s making my car incredibly annoying to drive.

I’m in 2nd, up at 3,500rpm, I clutch in and get off the throttle, shift to 3rd, wait for the rpm’s to start dropping before I start letting the clutch back out, still wait, still waiting, they’re still at 3,500rpm, I shift to neutral, my foot’s been off the throttle this whole time, I let the clutch out, I’m rolling at like 20mph in neutral with the clutch out and my foot off the throttle and it’s pinned at 3,500rpm.

This goes on for, I’m not kidding, 15-20 seconds. Just rolling along in neutral, no throttle input, and my car’s just humming at 3,500rpm. I even brake and come to a complete stop at a light, and it’s STILL hanging onto 3,500. Or 4,000. Or 2,500. Or whatever it was when I shifted out of whatever gear.

There are other times where I’ll shift to neutral while coasting and the revs will drop to idle like normal, but then start climbing on their own as if I was pressing on the throttle slowly (even though I’m not). Then once at a complete stop they’ll drop back to idle.

As soon as it gets cold enough, my car starts to do these things insanely frequently. Doesn’t matter what gear or what rpm, it’ll just hold onto the revs until I slip the clutch back out to force it into another gear. Is it the CAI? Is something broken/on its way out? I’ve seen a couple of posts here about this issue but 0 solutions and not much guidance.

I’m gunna take her to a shop/dealer if no one has any suggestions on what direction to go in by myself. I would really appreciate any help with this.

Start with the ole, disconnect battery let it sit for an hr. Could be an issue with the butterfly / motor / gearbox in the DBW throttle body. Start with a battery disconnect, cost nothing.

 

[TheCanadian]

It’s drive by wire so nothing mechanical to stick. What happens if you let the clutch out while it's doing this?

The throttle body is still physically opened - it can go bad. Generally speaking if that does happen a DTC will trigger

 

[BoratThongOwner]

The throttle body is still physically opened - it can go bad. Generally speaking if that does happen a DTC will trigger

Would that cause the CEL to come on or would I only see it through a OBD scanner?

 

[TheCanadian]

Would that cause the CEL to come on or would I only see it through a OBD scanner?

It *should* cause a CEL. The ECU would command the throttle to X % open but wouldn't get it, and then throw the CEL

 

[BoratThongOwner]

It *should* cause a CEL. The ECU would command the throttle to X % open but wouldn't get it, and then throw the CEL

Yeah never gotten one unfortunately. I’d love if it did throw one tbh since then I’d know the ECU detects a problem, but as of now it’s almost as if the car thinks it should be doing what it’s doing.

This will be the 3rd winter I’ve had the car and it did it during the first 2 as well. But when the temps dropped the other day for the first time it was almost un-drivable. Way worse than last year. Which makes it even more confusing imo; like is it something wearing out over time? You’d think if it was an air flow issue it’d remain the same season to season with the same CAI.

 

[CMarks]

Are you tuned? Does this happen when in sport mode? I would do some test drives in different maps, and sport mode and with the VSA fully disabled which will enable you to open your throttle more. Could be a bad throttle body coupler? But if thats the case i would assume your rpms would be running lower but maybe the ecu is trying to over correct causing the rpms to spike?

 

[gtman]

OP, this likely doesn't directly have anything to do with your issue, but K&N doesn't make a CAI for your car. Only an SRI. And that particular intake is known to produce inconsistent fuel trims.

 

[BoratThongOwner]

Are you tuned? Does this happen when in sport mode? I would do some test drives in different maps, and sport mode and with the VSA fully disabled which will enable you to open your throttle more. Could be a bad throttle body coupler? But if thats the case i would assume your rpms would be running lower but maybe the ecu is trying to over correct causing the rpms to spike?

Not tuned and it’s just a sport hatch (not Si) so it’s either like “normal” mode or “eco” mode. I only ever run it in normal.

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