a.lim Posted April 20, 2011 Share Posted April 20, 2011 I'm trying to diagnose a problem here. My car stutters at WOT (wide open throttle) when it hits boost. I believe this "stutter" is different from the common stutter issue that some owners have during mid RPMs when accelerating. I even got a CEL one time when I was going WOT but it turned off quickly and my AccessPort didn't read any codes. Under boost and WOT it almost sounds like my turbo spool is fluctuating up and down very fast. It's hard to explain, but I took some data logs. I would greatly appreciate it if someone can take a look at it and shed some light. Mods include: -Blouch Dominator 2.5R turbo -DW 750cc injectors -Walbro 255 LPH -Perrin FMIC -AVO intake -Tial BOV -Cobb APdatalog18.csvdatalog16.csv Link to comment Share on other sites More sharing options...
Spec B Posted April 20, 2011 Share Posted April 20, 2011 You have some knock from 4000-4400 RPM, it should be fixed but it's not terrible. Can you do a LV and log knock sum? Also, check your misfire (roughness) counts and post up your mods. Something is up. On datalog 18 your mass airflow is jumping all over the place on WOT and you made a lot less power (and less boost) than on datalog 16. Link to comment Share on other sites More sharing options...
bmx045 Posted April 20, 2011 Share Posted April 20, 2011 Hmm, interesting that the CEL came on then went off. My friend had a similar problem with his STi and a shitty tune. The CEL was wastegate malfunction with stutter but only at wot once in a while, pretty sure it ended up being fuel cut....he's getting retuned saturday and will find out how it goes at EFI Link to comment Share on other sites More sharing options...
a.lim Posted April 21, 2011 Author Share Posted April 21, 2011 You have some knock from 4000-4400 RPM, it should be fixed but it's not terrible. Can you do a LV and log knock sum? Also, check your misfire (roughness) counts and post up your mods. Something is up. On datalog 18 your mass airflow is jumping all over the place on WOT and you made a lot less power (and less boost) than on datalog 16. I'm going through my AP now. I enabled Roughness for cylinders 1-4 and knock sum, but I don't see "LV" what exactly does that stand for? Are any of these variables it? -Dynamic Advance -Feedback Knock -Fine Knock Learn Link to comment Share on other sites More sharing options...
a.lim Posted April 21, 2011 Author Share Posted April 21, 2011 Hmm, interesting that the CEL came on then went off. My friend had a similar problem with his STi and a shitty tune. The CEL was wastegate malfunction with stutter but only at wot once in a while, pretty sure it ended up being fuel cut....he's getting retuned saturday and will find out how it goes at EFI I was searching over NASIOC about the stuttering at WOT and everyone was saying it might be electrical related. But I don't see how? Was your friend's issue definitely a wastegate malfunction? Link to comment Share on other sites More sharing options...
bmx045 Posted April 21, 2011 Share Posted April 21, 2011 I was searching over NASIOC about the stuttering at WOT and everyone was saying it might be electrical related. But I don't see how? Was your friend's issue definitely a wastegate malfunction? Wastegate malfunction is the code, it's caused by overboosting- much of which can be dealt with through a tune albeit all mechanical items are proper. I think his code went away on its own, not sure. You should do some logging and post it up.... Link to comment Share on other sites More sharing options...
Spec B Posted April 21, 2011 Share Posted April 21, 2011 LV = Learning View, it's a completetly different reader and can be downloaded on the romraider forums, you will need a tactrix cable to do it tho. It basically shows your fuel correction trims and learned knock table... Do a WOT run while logging RPM Load Wastegate MAf V Maf g/sec Feedback knock correction Fine knock correction Boost Timing Roughness on each cylinder Link to comment Share on other sites More sharing options...
a.lim Posted April 21, 2011 Author Share Posted April 21, 2011 LV = Learning View, it's a completetly different reader and can be downloaded on the romraider forums, you will need a tactrix cable to do it tho. It basically shows your fuel correction trims and learned knock table... Do a WOT run while logging RPM Load Wastegate MAf V Maf g/sec Feedback knock correction Fine knock correction Boost Timing Roughness on each cylinder I did a quick log this morning before I got to read this post. I added a couple more variables. I'm getting high numbers on cylinder 3 and I'm assuming that's not good. I'll do another log with the variables you mentioned, but here's my latest log for now.datalog20.csv Link to comment Share on other sites More sharing options...
Spec B Posted April 21, 2011 Share Posted April 21, 2011 Looks like the misfires may be the cause of the problem. I suggest that you swap the injector to another cylinder and see if the misfire moves along with it. If there is no change, swap coillpacks and see iff the misfire moves. I get 0 misfires at WOT. Also, you are knocking at 4000 rpm pretty consistantly it seems...gotta get that fixed. Link to comment Share on other sites More sharing options...
a.lim Posted April 21, 2011 Author Share Posted April 21, 2011 Thanks for the help I really appreciate it. I have somewhat of a general idea now and you saved me a couple bucks! Link to comment Share on other sites More sharing options...
a.lim Posted April 22, 2011 Author Share Posted April 22, 2011 Is engine knock related to cylinder misfire? If I correct my misfire, will my knock be eliminated or are they independent issues? Link to comment Share on other sites More sharing options...
Spec B Posted April 22, 2011 Share Posted April 22, 2011 They should be independent of each other..the knock issue can likely be fixed by pulling some timing in that region. Link to comment Share on other sites More sharing options...
subi_snipe223 Posted May 3, 2011 Share Posted May 3, 2011 ....the common stutter issue that some owners have during mid RPMs when accelerating.... I have this problem. Can anyone point me to the thread where I can get some tips on resolving this issue? Or tell me what the problem is? I am still currently tuning my stage 2 tune. Thanks Link to comment Share on other sites More sharing options...
LGTDude05 Posted September 27, 2018 Share Posted September 27, 2018 I have been having this problem for a while now and cannot seem to figure it out. I replaced all coil packs, plugs and injectors and it still continues. I even get a fuel smell in my car! In desperate need of help!! . Link to comment Share on other sites More sharing options...
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