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Discussion Starter #1
Well I remember seeing something similar to this but I cant find it on the search. I was having some problems with lean codes on my 99 cobra. It was giving codes p0171 and p0174 which is lean on banks 1 and 2. So I took it to a shop to a chip dyno tuned for it. They said they thought the maf was causing the lean code and said they fixed it but on the print out of the dyno I get spikes in the fuel curve and they could not figure out why. Anybody have any suggestions. This is the baseline dyno run after they made the adjustment for the maf.

this is the run with the least spikes in the fuel curve. this was all done on a mustang dyno.
 

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Discussion Starter #2
well I cant seem to get the pic to show. anyway maybe you can imagine what I am talking about. it is just a sharp spike where the air fuel jumps from 14 to 14.45 and then back down. the tuner said it was pulling timing but he did not know why. sometimes there would be 1 or more of these spikes in the dyno run. any help please.
 
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