Surging downhill :(

RainMaker · 09-15-2006, 10:31 AM

Jeez Louis... I *cannot* get it to quit doing this.

at very low throttle downhills, the A:F oscillates between 12 and 18 and the car surges over a 2 second or so frequency.

I have heard of others having this issue, but I've never heard what tuners do about it.

I have:
Perrin Mod'd STI injectors (soon to be swapped with my 720 JECS)
Blow-through MAF (I dont think has much to do with it)

Any helpful hints?

Thanks,
Chris

R4ND0M_AX3 · 09-15-2006, 12:28 PM

Quote:

Originally Posted by RainMaker

Jeez Louis... I *cannot* get it to quit doing this.

at very low throttle downhills, the A:F oscillates between 12 and 18 and the car surges over a 2 second or so frequency.

I have heard of others having this issue, but I've never heard what tuners do about it.

I have:
Perrin Mod'd STI injectors (soon to be swapped with my 720 JECS)
Blow-through MAF (I dont think has much to do with it)

Any helpful hints?

Thanks,
Chris

yes. I get this too. It did it while stock just not as noticable. It's going from injectors completely off to barely on. I just choose a different gear to keep the car on one side or the other.

sti752 · 09-15-2006, 03:39 PM

I get a slight surging sensation at very low speeds but have never looked at my afrs while it was happening. I will have to check.

RainMaker · 09-15-2006, 04:22 PM

well, the IDCs oscillate down to 3.X. They idle at 1.15 or so... so Im suspicious of the idea that they turn "off" at 3.something.

Help?

RainMaker · 09-16-2006, 08:19 PM

Well, either way. it appears that switching form the Perrin Mod'd stock injectors to the JECS/Nismo 720cc fixed (for now) the issue totally.

-chris

**WESTI** · 09-16-2006, 08:22 PM

ya it surges a little for me too

WolfPlayer · 09-17-2006, 04:48 AM

Quote:

Originally Posted by RainMaker

Well, either way. it appears that switching form the Perrin Mod'd stock injectors to the JECS/Nismo 720cc fixed (for now) the issue totally.

-chris

t

knucklesplitter · 06-12-2007, 01:44 PM

Bump...

My car is doing this too... pretty badly after installing larger injectors. Idle, part throttle, and full thottle are fine, but decelerating in gear surges badly. I am aware of unfavorable issues with the Helix injectors, but is this really just the type of injector? What else could it be? Bad injector o-ring allowing fuel to be sucked in during the high manifold vacuum of decelleration maybe? Weird vacuum leak?

Thanks...

Matt

singlefin · 08-22-2007, 10:50 AM

Been searching for answers or fixes on this too, I experience it mostly from crusing on the freeway. With the foot pressure on the gas pedal held constant, the throttle would surge and recede, like someone is modulating the gas pedal ever so slightly. I have Deatschwerks 740cc injectors.

fullerton · 08-22-2007, 10:58 AM

that's why we don't have hills in IL.

fwiw- i was experiencing this while turning tightly... i never thought of it is an engine related event, more so something caused by a diff. i think i'll do some logging now.

09-15-2006, 10:31 AM	#1
RainMaker The Next Petter Solberg Car: 08 Z06 Corvette Fav Mod: Jack Jack Location: Portland, OR Posts: 883 Join Date: Oct 2005 Trader Rating: (3)	Surging downhill :( Jeez Louis... I cannot get it to quit doing this. at very low throttle downhills, the A:F oscillates between 12 and 18 and the car surges over a 2 second or so frequency. I have heard of others having this issue, but I've never heard what tuners do about it. I have: Perrin Mod'd STI injectors (soon to be swapped with my 720 JECS) Blow-through MAF (I dont think has much to do with it) Any helpful hints? Thanks, Chris This ad is not endorsed by this member. Please register or login to hide this ad.

06-12-2007, 01:44 PM	#8
knucklesplitter Junior STI Driver Car: '04 STI wingless sco Location: Reno, NV Posts: 133 Join Date: May 2006 Trader Rating: (0)	Re: Surging downhill :( Bump... My car is doing this too... pretty badly after installing larger injectors. Idle, part throttle, and full thottle are fine, but decelerating in gear surges badly. I am aware of unfavorable issues with the Helix injectors, but is this really just the type of injector? What else could it be? Bad injector o-ring allowing fuel to be sucked in during the high manifold vacuum of decelleration maybe? Weird vacuum leak? Thanks... Matt

08-22-2007, 10:50 AM	#9
singlefin Amateur STI Driver Posts: 13 Join Date: Apr 2006 Trader Rating: (0)	Re: Surging downhill :( Been searching for answers or fixes on this too, I experience it mostly from crusing on the freeway. With the foot pressure on the gas pedal held constant, the throttle would surge and recede, like someone is modulating the gas pedal ever so slightly. I have Deatschwerks 740cc injectors.

08-22-2007, 10:58 AM	#10
fullerton abracious Car: AW GDF-D Fav Mod: Track time Location: Near a 100oct pump Posts: 16,329 Join Date: Oct 2005 Trader Rating: (10)	Re: Surging downhill :( that's why we don't have hills in IL. fwiw- i was experiencing this while turning tightly... i never thought of it is an engine related event, more so something caused by a diff. i think i'll do some logging now. This ad is not endorsed by this member. Please register or login to hide this ad.

09-15-2006, 03:39 PM	#3
sti752 Senior STI Driver Car: 05 Subaru WRX STi Fav Mod: Exige Location: Starkvegas, MS Posts: 379 Join Date: Jul 2005 Trader Rating: (6)	I get a slight surging sensation at very low speeds but have never looked at my afrs while it was happening. I will have to check.

09-15-2006, 04:22 PM	#4
RainMaker The Next Petter Solberg Car: 08 Z06 Corvette Fav Mod: Jack Jack Location: Portland, OR Posts: 883 Join Date: Oct 2005 Trader Rating: (3)	well, the IDCs oscillate down to 3.X. They idle at 1.15 or so... so Im suspicious of the idea that they turn "off" at 3.something. Help?

09-16-2006, 08:19 PM	#5
RainMaker The Next Petter Solberg Car: 08 Z06 Corvette Fav Mod: Jack Jack Location: Portland, OR Posts: 883 Join Date: Oct 2005 Trader Rating: (3)	Well, either way. it appears that switching form the Perrin Mod'd stock injectors to the JECS/Nismo 720cc fixed (for now) the issue totally. -chris

09-16-2006, 08:22 PM	#6
WESTI Mod Pro Tempore for Premium Members Car: 06 WRB STI Fav Mod: Tial 44mm EWG Location: Irvine, Ca Posts: 5,850 Join Date: Apr 2006 Trader Rating: (9)	ya it surges a little for me too