Scooby2.5 Posted August 19, 2012 Share Posted August 19, 2012 Switched back to E85 and mine stumble is clearly gone after the weather cooled off. Wonder what could be being affected by the heat? As I stated earlier mine only does it really with the A/C on. Link to comment Share on other sites More sharing options...
prodrifterx Posted August 20, 2012 Share Posted August 20, 2012 TYPE OF STUTTER/STUMBLE Steady throttle/Increasing throttle/Both: steady/increasing 1/2+ throttle only between 2k-3k rpm, mostly noticable at tip-in and around 2200-2800 MODS Intake: stock with k&n drop in Exhaust: cnt catless dp, invidia catless up, stock header/crossover/cbe Fuel: stock Turbo: stock Engine Management: stock Tuner and revision of tune(if you don't mind): cobb ap base stg 2 93 oct map MAINTENANCE Sensors changed: none Plugs changed: less than 1000 miles and less than 2 wks ago Coil Packs changed: no OTHER SYMPTOMS Check Engine Light: no Etc: knock count seems high at 25-40 in 1.5hrs in 45-50mile commute from dc to central md, but unsure if of concern after browsing cobbs site in technical/faq sections. RESULTS What has and hasn't worked for you: nothing atm If something worked, how long has it been working for: n/asuggestions? new thread? section to be searching? was wondering if there was a base tune that cobb or vendor had to possibly remedy issue. isnt acting like a plug/coil issue. didnt make a difference between 91/93 stg 2 maps. stumble/hesitate/flat spot less severe with the oem tune/map in it, yet it did it throughout entire powerband. on a 06 lgt mt with 90k. no issues prior to any of these mods. all mods done at once within the last month while it was down for 4-5wks for mods/maintenance and clutch. Link to comment Share on other sites More sharing options...
Mega Users seabass07 Posted August 20, 2012 Mega Users Share Posted August 20, 2012 Sounds like yours could just be knock. Have you logged at all? Knock count is only useful when you are logging it alongside rpm, load, etc. Link to comment Share on other sites More sharing options...
cfaber Posted August 20, 2012 Share Posted August 20, 2012 TYPE OF STUTTER/STUMBLE Steady throttle/Increasing throttle/Both: steady, at idle, sometimes while falling back to idle. MODS Intake: K&N stock. Exhaust: stock Fuel: 93oct Turbo: stock Engine Management: cobb ap, fuel saver map, but noticed with performance as well Tuner and revision of tune(if you don't mind): MAINTENANCE Sensors changed: gutted STI uppipe /w bung welded closed and resistor. Plugs changed: all Coil Packs changed: switched around, no problems found. OTHER SYMPTOMS Check Engine Light: CEL with misfire on CYL4 Etc: Studder only when AC is on and at idle. RESULTS What has and hasn't worked for you: plugs, oil, filter, MAF cleaning If something worked, how long has it been working for: reflash (temporary or permanent) Noticed this much more after installing new clutch and slighly lighter FW. Winning the internet Link to comment Share on other sites More sharing options...
prodrifterx Posted August 20, 2012 Share Posted August 20, 2012 (edited) Sounds like yours could just be knock. Have you logged at all? Knock count is only useful when you are logging it alongside rpm, load, etc. yea have 4 datalog files. need to adj which parameters are crucial to log/watch and which i can ignore to lessen the file size. im thinking its something tune/timing related. **do base maps exist or have they been made for an LGT equipped with catless up/dp? jw. still datalogging. thinking maybe a boost creep/spike issue but not due to boost levels but in the concept of the undivorced bellmouth of the cnt dp on a stock turbo/engine. pending map availabilty im tempted to reinstall oem two piece dp and retest/re-datalog. Edited August 21, 2012 by prodrifterx Link to comment Share on other sites More sharing options...
BlackWagon GT Posted September 7, 2012 Share Posted September 7, 2012 (edited) TYPE OF STUTTER/STUMBLE Steady throttle/Increasing throttle/Both: Steady, light throttle; around 2000-2500 RPM MODS Intake: None Exhaust: None Fuel: 93 Turbo: Stock Engine Management: Cobb AP Stage 1 Tuner and revision of tune(if you don't mind): MAINTENANCE Sensors changed: None Plugs changed: ~36k miles ago, according to what I was told Coil Packs changed: No OTHER SYMPTOMS Check Engine Light: No Etc: Intermittent slight hesitation when transitioning from deceleration or light throttle to part-throttle. RESULTS What has and hasn't worked for you: I haven't tried anything yet as I don't wan to just throw darts to try to fix the problem. I've been logging and analyzing different sensor data sets trying to find something anomalous but I haven't found anything obvious. I loaded the Stage 1 as soon as I got the car but, I don't remember or didn't notice the surging on the test drive(s). If something worked, how long has it been working for: n/a Edited September 7, 2012 by BlackWagon GT Link to comment Share on other sites More sharing options...
cfaber Posted September 7, 2012 Share Posted September 7, 2012 don't know if this has anything to do with the studder but I recently replaced the gas cap and haven't had a studder since. Winning the internet Link to comment Share on other sites More sharing options...
cfaber Posted September 19, 2012 Share Posted September 19, 2012 So interestingly the stumble is back, Watched tonight with AC on while idling it would bounce down to about 500 RPM's then jump back up to 1500-1700 then dump back down into the low RPM range. This was totally out of the blue. Winning the internet Link to comment Share on other sites More sharing options...
m sprank Posted September 20, 2012 Share Posted September 20, 2012 No CEL for the TPS? TPS acting up can make idle go hay wire and cause stalls, etc. Link to comment Share on other sites More sharing options...
cfaber Posted September 20, 2012 Share Posted September 20, 2012 No CEL, and it was only for a second, if TPS was out of adjustment / reading bad I would think I would see this much more frequently. Winning the internet Link to comment Share on other sites More sharing options...
m sprank Posted September 20, 2012 Share Posted September 20, 2012 1 TPS at throttle and 1 at pedal. Usually they throw a code when acting up. Link to comment Share on other sites More sharing options...
cfaber Posted September 20, 2012 Share Posted September 20, 2012 yeah no code at all. What I did was start the car (it was already warmed up), back out of a space, quick bit of power then shift to neutral and brake (waiting for the wife). at that point no pedal input just stand on the brake and watched it bounce wildly for a second or two then it went right back to normal. Winning the internet Link to comment Share on other sites More sharing options...
cfaber Posted September 20, 2012 Share Posted September 20, 2012 I think the "bouncing" was just an effect of the ECM trying to keep the car from stalling out as the RPM's dropped to critical levels. So really it was bounce up, then fall back down to stall, the back up again. Winning the internet Link to comment Share on other sites More sharing options...
NSFW Posted September 21, 2012 Share Posted September 21, 2012 I've seen vacuum leaks cause idle to bounce around. If you have an AFR gauge, or if you can log it, that might be interesting. Link to comment Share on other sites More sharing options...
m sprank Posted September 21, 2012 Share Posted September 21, 2012 Yes. Leaks can cause this too. Heck, there are a few sensors that could make it happen. Link to comment Share on other sites More sharing options...
cfaber Posted September 21, 2012 Share Posted September 21, 2012 yeah I had the ap in the car at the time but it wasn't hooked up. If I can catch it in time I'll stick it on there. Like I said, it was quick then over and not experienced since. Winning the internet Link to comment Share on other sites More sharing options...
m sprank Posted September 21, 2012 Share Posted September 21, 2012 Vacuum leak should be constant. Link to comment Share on other sites More sharing options...
BlackWagon GT Posted October 10, 2012 Share Posted October 10, 2012 Update: I added timing into my low-RPM/low-load ignition table based on NSFW's data and it made no difference for me. It still has that rough misfire-like feel through the same RPM range as I noted previously. Link to comment Share on other sites More sharing options...
NSFW Posted October 10, 2012 Share Posted October 10, 2012 Bummer. Link to comment Share on other sites More sharing options...
stuck686 Posted October 11, 2012 Share Posted October 11, 2012 when i had a nitro rc car any stutter would be from not enough fuel Link to comment Share on other sites More sharing options...
m sprank Posted October 11, 2012 Share Posted October 11, 2012 Stutter on a r/c car and stutter on a computer controlled efi engine is far different. Link to comment Share on other sites More sharing options...
ericem Posted October 15, 2012 Share Posted October 15, 2012 when i had a nitro rc car any stutter would be from not enough fuel soo ill just richen up the low speed needle a bit. Link to comment Share on other sites More sharing options...
NSFW Posted October 15, 2012 Share Posted October 15, 2012 soo ill just richen up the low speed cells in the fuel table a bit. Edited for accuracy. I tried that, honestly, and it didn't help. Link to comment Share on other sites More sharing options...
Skidude Posted October 15, 2012 Share Posted October 15, 2012 I cleaned my MAF sensor this weekend and my stumble went away completely. We'll see how long it lasts, but it was dirty because the previous owner installed a K&N and I haven't changed back to a paper filter yet. Link to comment Share on other sites More sharing options...
lee07 Posted October 15, 2012 Share Posted October 15, 2012 Mine went away about 95% after I put in a smfw Link to comment Share on other sites More sharing options...
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