s4 na stutters when cold

IH8DSM · 02-16-2012, 12:38 AM

Just like the title says I got a na s4 all stock that's has a random stutter issue. It really only does it when the weathers cold you'll go to hit the gas and nothing rpms don't even go up pump the gas a few times and it will start to drive normal again. does it both at idle as well as when driving when I left off the gas for a second then try to get back on it.

It idles high (1500rpms) and adjusting the top screw doesn't do anything so im swapping it with a stripped down throttle body and a different tps and hoping this will fix my issue. Just curious if there's anything else I should check or change if the new throttle body and tps doesnt fix my problem.

Its got a new fuel filter on it, fresh plugs and wires, ran chemtool throguht it twice now. The motor starts when its hot or cold no problems and was supposedly rebuilt about 30,000 miles ago.

WankelsRevenge · 02-16-2012, 12:55 AM

Im sure this might be an obvious question, but do you let it get up to temp before starting off? I had an old S4 NA and it wouldnt even idle before it got warmed up.
Ryan

IH8DSM · 02-16-2012, 01:08 AM

It takes a second to idle when its cold outside but will idle no problems after that, I've tried letting it warm up to operating temp and it usually doesn't do it as bad, instead of hitting the gas and nothing happening its like a hiccup then realizes what's going on and goes.

FC Zach · 02-16-2012, 02:00 AM

Sounds like your on the right track as far as things to pin-point the problem (TPS and TB). Sounds like the standard operating procedure.

FerociousP · 02-16-2012, 09:30 AM

If you have the BAC hooked up then turning the idle screw will do nothing unless you ground the initial set coupler as the BAC is still working to keep the idle. TPS maybe, but as you say it is idling ok, wihch is a good sign for the tps. The rest of its function can be checked with a multimeter.

sounds to me like you are running a little lean.

IH8DSM · 02-16-2012, 03:07 PM

So what are you thinking maf maybe

My5ABaby · 02-17-2012, 09:05 AM

I have pretty much anything S4 N/A for parts if you want to try swapping some stuff out.

02-16-2012, 12:38 AM	#1
IH8DSM RCC Contributor Join Date: Mar 2008 Posts: 610 Rep Power: 18	s4 na stutters when cold Just like the title says I got a na s4 all stock that's has a random stutter issue. It really only does it when the weathers cold you'll go to hit the gas and nothing rpms don't even go up pump the gas a few times and it will start to drive normal again. does it both at idle as well as when driving when I left off the gas for a second then try to get back on it. It idles high (1500rpms) and adjusting the top screw doesn't do anything so im swapping it with a stripped down throttle body and a different tps and hoping this will fix my issue. Just curious if there's anything else I should check or change if the new throttle body and tps doesnt fix my problem. Its got a new fuel filter on it, fresh plugs and wires, ran chemtool throguht it twice now. The motor starts when its hot or cold no problems and was supposedly rebuilt about 30,000 miles ago. __________________ 85 rx7 gsl-se - AA tags/ never ending project will never run

02-16-2012, 01:08 AM	#3
IH8DSM RCC Contributor Join Date: Mar 2008 Posts: 610 Rep Power: 18	It takes a second to idle when its cold outside but will idle no problems after that, I've tried letting it warm up to operating temp and it usually doesn't do it as bad, instead of hitting the gas and nothing happening its like a hiccup then realizes what's going on and goes. __________________ 85 rx7 gsl-se - AA tags/ never ending project will never run

02-16-2012, 02:00 AM	#4
FC Zach RCC Loves Me Not You Join Date: Mar 2008 Location: Eagleville, TN Posts: 2,267 Rep Power: 20	Sounds like your on the right track as far as things to pin-point the problem (TPS and TB). Sounds like the standard operating procedure. __________________ 1993 Yamaha GTS1000 1992 Celica Turbo AllTrac 1987 RX7 Sport 1979 Yamaha G1, KM24 powered 1975 Dolmar KMS4

02-16-2012, 09:30 AM	#5
FerociousP I-had-a-bad-experience... Join Date: Feb 2008 Location: M'boro Posts: 1,046 Rep Power: 19	If you have the BAC hooked up then turning the idle screw will do nothing unless you ground the initial set coupler as the BAC is still working to keep the idle. TPS maybe, but as you say it is idling ok, wihch is a good sign for the tps. The rest of its function can be checked with a multimeter. sounds to me like you are running a little lean. __________________ '15 Juke Nismo '06 MX-5 GT SOLD '04 S Silver RX-8 GT Track Day Use SOLD '90 Black TII vert w/ Sprint RE stock port/turbo DD dyno (242.6whp@5500rpm @12psi 8psi@redline) and (250ftlbtq@4800rpm @13psi) SOLD '89 GTUs 6p TII SOLD, '87 sport SOLD, '79 SA stock SOLD '91 B2600i 4x4 w/ Rx-8 LSD SOLD

02-16-2012, 03:07 PM	#6
IH8DSM RCC Contributor Join Date: Mar 2008 Posts: 610 Rep Power: 18	So what are you thinking maf maybe __________________ 85 rx7 gsl-se - AA tags/ never ending project will never run

02-17-2012, 09:05 AM	#7
My5ABaby Sigh..... Join Date: Feb 2008 Location: Murfreesboro, TN Posts: 2,377 Rep Power: 20	I have pretty much anything S4 N/A for parts if you want to try swapping some stuff out. __________________ 1986 Sport: 132k miles, 5A (Sapphire Blue Metallic), Tokico Blues, Racing Beat Springs, Custom LED tailights (only S4 LED tails in the world), SSR Mark II, Racing Beat exhaust, S5 black interior, Rotary Resurrection rebuild at 120k miles Community Service Manual RotorWiki "Imagination costs nothing; we could build square locomotives or fly to Mars" - Felix Wankel Yesterday is history, tomorrow is a mystery, but today is a gift. That is why it is called the "present."

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