Tungsten Posted December 21, 2009 Share Posted December 21, 2009 (edited) Ok first of all heres my setup: VG30E with Auto Doug Thorley Short Tube Headers with 2.25" collector 2.00" Midpipe 2.00" Magnaflow NON-CARB Catalytic Converter 2.00" Flowmaster 60 series muffler 2.00" Tailpipe Now when the truck warms up, it runs slightly rich, and its good for a few minutes until it gets warmed up. When starting to accelerate now it doesn't dump enough fuel and almost stalls out the engine! I checked the ECU, it checks out as 55. This happened right after I put on the Flowmaster 60 muffler, it was good with the stock one but sounded crappy. I think what happened is it used to rely on the extra back-pressure to keep it going but not anymore. The exhaust flow improved and so did my fuel economy and even sounds nice now but its like WTF to drive. Can anyone help me out? I can make a video if you want to see it. Edited December 21, 2009 by Tungsten Link to comment Share on other sites More sharing options...
MY1PATH Posted December 21, 2009 Share Posted December 21, 2009 when is the last time you, cleaned your MAF Changed your o2 sensor Reset your ECU so It can generate new fuel curves? the above sould be considered in that order anytime you do anything that noteably effects how much can go in an out of the engine. replacing a clogged muffler or cat with a high flow alternative fall into that category. but you did it all and more. If you go into fuel ratio mode on your ecu and drive It will tell you if your are more than 5% lean or more than 5% rich. Link to comment Share on other sites More sharing options...
Precise1 Posted December 21, 2009 Share Posted December 21, 2009 Your set up is almost identical to mine, and I do not have that issue. Right now I suspect that my intake is the restrictive point, but it doesn't stumble or hesitate or die. Did you replace the O2 sensor? Check the resistance of the two outer most pins, it should be between 1-1000 ohms IIRC. Just for kicks check the wiring connector to the MAF. Have you ever changed your fuel filter. To answer your question, no, you shouldn't need to have your ECU remapped. B Link to comment Share on other sites More sharing options...
Tungsten Posted December 21, 2009 Author Share Posted December 21, 2009 (edited) when is the last time you, cleaned your MAF Changed your o2 sensor Reset your ECU so It can generate new fuel curves? the above sould be considered in that order anytime you do anything that noteably effects how much can go in an out of the engine. replacing a clogged muffler or cat with a high flow alternative fall into that category. but you did it all and more. If you go into fuel ratio mode on your ecu and drive It will tell you if your are more than 5% lean or more than 5% rich. idk about MAF, looks clean o2? theres no code for that... i reset the ECU by turning the diagnostic screw Your set up is almost identical to mine, and I do not have that issue. Right now I suspect that my intake is the restrictive point, but it doesn't stumble or hesitate or die. Did you replace the O2 sensor? Check the resistance of the two outer most pins, it should be between 1-1000 ohms IIRC. Just for kicks check the wiring connector to the MAF. Have you ever changed your fuel filter. To answer your question, no, you shouldn't need to have your ECU remapped. B fuel filter was changed recently yes whats the interval on those? Edited December 21, 2009 by Tungsten Link to comment Share on other sites More sharing options...
Precise1 Posted December 21, 2009 Share Posted December 21, 2009 Normally quite a bit, as in years and 10s of thousands of miles but if you have crap in your tank, it could be much more frequent. I ask as that is usually step 1 if there is a fuel delivery issue, especially when it is only when high fuel flow is needed. Check your o2 sensor next. Do you have any exhaust leaks? B Link to comment Share on other sites More sharing options...
Tungsten Posted December 22, 2009 Author Share Posted December 22, 2009 no exhaust leaks at all o2 sensor checks out fine i get more than 5 green blinks in 10 seconds on the ECU ill try cleaning the MAF again... anything else? Link to comment Share on other sites More sharing options...
MY1PATH Posted December 22, 2009 Share Posted December 22, 2009 To answer your question, no, you shouldn't need to have your ECU remapped. sorry I didn't make that clear idk about MAF, looks clean o2? theres no code for that... i reset the ECU by turning the diagnostic screw if the o2 sensor has deposits on it blocking a proper reading it will not throw a code the diagnostics screw only resets stored codes, resetting the ecu itsef required disconnecting the battery long enough for it to lose any sored information on how it made your engine run. Your engine runs differant and it needs to 'learn that' I a similar probem when I did headers (hesitaed but did not stall)and full exhuast, a mechanic told me to change the o2 and unplug the battery for 4 hours. turn the key & hit the brakes before re-connecting (completes the drain) It ran rich for about an hour after I did that but no more hesitating and it felt allot better all around. Link to comment Share on other sites More sharing options...
Tungsten Posted December 22, 2009 Author Share Posted December 22, 2009 so a plugged up o2 will do that...you could be right about that one Link to comment Share on other sites More sharing options...
GrimGreg Posted December 22, 2009 Share Posted December 22, 2009 Another possibility is that the new O2 sensor bung (you said new mid-pipe) is to long and the sensor isn't sticking into the exhaust flow properly. Link to comment Share on other sites More sharing options...
Tungsten Posted December 22, 2009 Author Share Posted December 22, 2009 no it worked fine before but thanks for the tip Link to comment Share on other sites More sharing options...
Indigent Posted December 22, 2009 Share Posted December 22, 2009 Did you run the other mode checks? I would run mode II which is the mixture ratio feedback monitor test. It will tell you for sure if you are running either rich or lean. Link to comment Share on other sites More sharing options...
Tungsten Posted December 23, 2009 Author Share Posted December 23, 2009 ok well i just unplugged the battery ill see what happens when i plug it back in even if it does work good, im still planning on replacing the o2 sensor because the old one is probably covered in crud Link to comment Share on other sites More sharing options...
MY1PATH Posted December 24, 2009 Share Posted December 24, 2009 ok well i just unplugged the battery ill see what happens when i plug it back in even if it does work good, im still planning on replacing the o2 sensor because the old one is probably covered in crud that was almost 6 hours ago I think you can plug it back in now. It worked for me, did it work for you? Link to comment Share on other sites More sharing options...
Tungsten Posted December 31, 2009 Author Share Posted December 31, 2009 ok well after i unplugged the battery i came up with a flu... now that i got better i got the o2 sensor replaced with a dealer one truck runs better but i unplugged the battery again to see if i can get an even better calibration Link to comment Share on other sites More sharing options...
Tungsten Posted January 1, 2010 Author Share Posted January 1, 2010 sorry I didn't make that clear if the o2 sensor has deposits on it blocking a proper reading it will not throw a code the diagnostics screw only resets stored codes, resetting the ecu itsef required disconnecting the battery long enough for it to lose any sored information on how it made your engine run. Your engine runs differant and it needs to 'learn that' I a similar probem when I did headers (hesitaed but did not stall)and full exhuast, a mechanic told me to change the o2 and unplug the battery for 4 hours. turn the key & hit the brakes before re-connecting (completes the drain) It ran rich for about an hour after I did that but no more hesitating and it felt allot better all around. Yep! That fixed it, thanks! Feels a bit different but it pulls like a train now in the 2500-3500 range. Link to comment Share on other sites More sharing options...
MY1PATH Posted January 1, 2010 Share Posted January 1, 2010 Glad your feeling better Glad your pathy's running better Glad restting you ecu with a new sensor helped you gain full benifit of all your mods. Link to comment Share on other sites More sharing options...
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