Blackzenki82

alright guys, just recently, my gas pedal/throttle has been acting funny... let me give you the low down.... FYI motor is a S13 Blacktop SR

when i first crank my car in the morning and drive away, everything is smooth, and even, then it gets to operating temp and the throttle is jumpy.. ya know right when you push the pedal for a "cruising" speed? well that little sweet spot is no longer there, it's either no gas, or accel, and it bumps like that while driving, so i had just hold the pedal in the sweet spot anymore, is either coast or GO, but it's not like WOT, just as if i have the pedal down a tad past "cruise"

so ro reitterate, if it's not "coasting" it will go (with a slight bump) into accelerate... my "cruise area is gone, but only AFTER the car has warmed up..

here's my possible theorys....

A. Throttle position sensor, once the coolant warms the TB up, the TPS goes a little haywire..

B. clutch not grabbing, although it is a ACT unsprun 6 buck, with fidanza, it should grab like a mofo, and only has about 300 miles on it... but when cold, and preengagement, it will make a whine/grinding noise (throwout bearing not greased enough whine most likely)

C. a catch somewhere either in my gas pedal or throttle cable, but that REALLY wouldn't explain why it doesn't do it when cold... on at operating temp...

i'll be going outside in a few minutes to put a volt meter on the TPS, check the throttle cable, and the predal... ANY input would be greatly appreciated, as this isn't a MAJOR problem, but it kinda sucks driving around town, and only having "coast" or "accelerate" with a "dunk" sounds as it transitions...

thanks guys, and on with the suggestions!!!

Matt Vassallo

lol, my car does that when i have the afc set too low. it's almost like it fucks with the minimum injection time or something.


you're on the right thinking with tps / tip in / etc. disconnect o2 sensor also, o2 does nothing but problems.

Epstein

You may be self-learning yourself into a hole. The A/F Alpha learned value only comes into play at low throttle. Once you exceed that throttle position, you go back to the map value. If you've learned way too lean, the car will be slow and jerky, especially since the ECU will probably pull timing since not-cool things are probably happening at mega lean cruise. Self-learn is completely dictated by O2 sensor.

Blackzenki82

so what would you suggest, is layman's terms? lol, if it was your motor that is...

BTW, i just checked TPS, it's at exactly .47, and i also checked my ECU for codes, and got 55 back, all clear... i also replaced the DTS a while back to fix some earlier problems...

why would it do it only after the car warms up?

Epstein

You know what. Unplug the O2 and try it like that. If that doesn't work, do a boost leak test concentrating on the intake manifold.

During warmup, the ECU enriches the mixture. This is completely off once you hit 60*C engine temp. It might just be that you're running way lean and the enrichment during warmup is compensating for it.

Blackzenki82

i'll give that a go... like in 5 minutes...

but i'm basically all stock, no bigger injectors, i mean, i got a walboro 255, if anything, i thought that would make me run rich..

could timing be an issue?

NeedCAforS13

I was having similar issues. Unplugged the o2 sensor, no more problems. Haha.

I was running skinny redtop o2 on blacktop s13 ecu though...

Blackzenki82

okay guys, disconnected my o2 sensor (fat type), and went across town to pick up my son from school. the ride there was great, ran a bit smoother, faster accel, and the A/F gauge (narrowband, i know, but it actually reads fairly accurate, and not a fireworks show) was reading just past stoich in the bottom part of rich... under accel though, it dropped into the red of lean... but all the way there it was nice and smooth, although it was idling at around 1500rpm...

on the way back home was a different story, in 4th and 5th, as soon as it got up around 4k rpm, it was like it was missing, i checked the A/F gauge while it was skipping and was reading in the stoich/rich area while cruising, but under acceleration, it skipped more and went down into the red of lean, almost pegging...


HELP!!!!! Epstein, you're the man, i know ya got some idea up your sleeve about whats going on....

Epstein

So now you're just lean under med/heavy throttle? Is it misfiring?

Blackzenki82

yeah, it seems to be straight misfiring.... i reconnected the o2 sensor, and now it doesn't do the original problem, but now it misfires, lean under idle (w/o2 hooked up),, under heavy throttle, leans out and misfires...

i checked the ECU for codes, and it comes back as code 43 AKA TPS sensor... ARG!!!!!


what I'm considering doing is butting my buddys 550CC's/Z32 maf/ Enthalpy tuned ECU back in... but i was having problems with that, hard starts, stalling (BOV not recirculated I'm sure)

he got said ECU from his buddy, and put it on his red top, and ran/started/idled fine...

all three of us, who've used the ECU w/mods have about the exact same mods, now i know that no two engines are alike, but it ran really good and hauled serious ass...

also as a side note, i think i found out why i was idling at 1500rpm, my BOV is leaking, and blows out under vacuum.. as soon as you cover the opening, the idle drops and sits right at 800rpm, let off, and it goes back up to 1500rpm...

i know this is alot of info to take in, but i'm REALLY just trying to dial this car in...

but if all it is, is just the TPS, then i guess a good start would be replacing that, and then starting all over again.... now to fine a TPS sensor on the cheap....