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Discussion Starter · #1 ·
My buddy just got his bullitt dynoed and now he is having sputtering problems when its cold and when he hits the throttle it sounds like its getting to much fuel and when he gets it past 2500 rpm it clears out but if you let it idel down and do it again it will do it all over again and it does it also at opperating temp but not as bad. He said it sounds like it wants to die when he takes off in first gear and really has to work the throttle and when hes driving down the hwy you can feel the car loading up with fuel cause it jerks and when you punch it ALOT of black smoke comes out. His AFR is 13.0 on 93 octane and 12.3 on 114 octane. He doesnt no if its the fuel filter and its not getting enough fuel or its getting to much fuel any help would be great thanks
 

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idle should be at about 14.0-14.7; WOT on an N/A car around 13.0. has he checked and cleaned his IAC and/or MAF sensor? did they tune the car at all while it was there? what about his 02 sensors....fouled?
 

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Discussion Starter · #3 ·
I didnt ask him about the IAC or MAF sensor and yes yhey tuned the car he got it back and went to put gas in and it ran bad rite away so he thought bad gas ran the tank out and filled up with 100 unleaded and doing the same. How often should you clean the IAC?
 

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Change the fuel filter, do you know what gap the spark plugs are set at?
 

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Discussion Starter · #5 ·
We cleaned the IAC and it still sputters. It idels great the idel is at 800 and when you give it gas it spits and sputters bad, and dark watery substaince comes out of the tail pipes
 

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is the car cold when the dark watery substance comes out....water mixed with the fact it is running rich if so. if stock cams, the idle should be about 6-650. A/F at idle: 14.0-14.7 and at cruise. clean the MAF sensor and what about the 02 sensors? throwing any codes (check engine light on?)?
 

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Discussion Starter · #7 ·
No codes and no light on he just had new cams put in thats why he had it dynoed so im thinking 02 sensor is bad. We are stumped on this but I told him to call the shop and take it back
 

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may just be in the tune. just had cams put in mine and took awhile to get it right.
 

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Discussion Starter · #9 ·
Okay now after checking the car over to find why it was sputtering and blowing black smoke and dripping water out of the pipes we came to an answer! He was running 100 unleaded octane on his 93 tune and the B didnt like that to much we ran it low filled it up with 93 and BAM problem solved!! I cant beleive that the 100 octane would do that and make it run like crap and he even called the tuner and the tuner said it would only make it run better any one else have this problem?
 

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interesting...never heard that but suppose it is possible.
 

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ProSystems said:
Now as we said in another post, with too high of an octane the engine can interpret the mixture as being lean as it has an unburnable mixture displacing a location where burnable fuel should be and there are left over available oxygen molecules looking for a companion. These unburnable molecules are what makes the mixture lean.
http://www.prosystemsracing.com/scoop040909.html

Pretty much gives you the explanation for the problem..
 

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If you car is tuned for 93 run 93 if you want to run a higher blend then go back and ask for a flip chip to be installed. Once your car is tuned the computer cannot raise or lower the ignition to compensate for the added octane.
 

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