5.7 mid acceleration surge

[oneno]

Alrighty, I have a 05' Rumble Bee with custom exhaust w/cat delete. When I bought the truck it was, I never had the opportunity to take it to my shop as the truck was not local, didn't realize the cats were deleted til I got it home on dry ground and crawled under it. It has spark plug defoulers packed with steel wool plugged into the 20 sensors so no cel or codes. Had it about 2 mos when it started surging at mid acceleration around 27 mph and 58 mph, it lurches and then and has a raspy snarly tone to the exhaust and then stutters until I decelerate and then you can here it go back to normal. No codes, no cel. I changed the egr valve , cleaned the throttle body went through a tank of gas added seafoam to this last tank I added today. Always run 89 mid octane without any problem. Has a K&N cold air intake and checked and cleaned everything I could in regards to potential over spray of the filter charger. Took it to the dealership in my frustration and they said it wasn't throwing any codes and do to the fact that it wasn't stock exhaust and had the catalytic converters removed they wouldn't touch it. In fact the tech said it had a tune done so I asked if they could reflash the ecm to sock then to remove the tune and they said they are not allowed to touch "tuned" trucks? I just added seafoam to this tank and I'll run it through and if it continues and I'm dead yet, I'll add some high flow aftermarket cats and see if the dealer can reflash then. Can anybody offer any help or any insight? this is driving me crazy! 2005 Rumble Bee w/52K K&N cold air intake cat delete dual exhaust and mystery tune.

 

[oneno]

Had the ecm reflashed, the tech said it was behind by three updates, so now I have replaced the egr valve, the throttle body, cleaned the AIT, replaced the 2 forward 02 sensors, installed 2 new flowmaster high flow cats, checked plugs, checked for any vacuum air leaks around throttle body, performed the throttle sensor reset, and had the ECM reflashed and it still surges as if I'm giving it a quarter more throttle than I am during normal acceleration, till I let off the pedal. When it tops out during the surging if I let it, it lurches and stutters as if fuel starvation so I just ordered a new MAP Sensor and will install it when it arrives in a few day. When looking at the MAP Sensor I noticed it had the two mounting holes that showed wear from a previous installed sensor that must have been the original stock sensor. It looked like the original was the type that mounted with 2 bolts on either side but now it has the cheaper push in type? wonder why a truck that had less than 50k on the odo when I bought it in the spring would already have had the original map sensor replaced? and why wouldn't they replace it with the type that came stock? is there any difference between the 2 MAP sensors? Throughout all of this, the truck is not throwing ANY codes and no cel. no rich smelling exhaust and happens mostly while cold but still happens but with less frequency when warm.

 

[TheSatinPumpkin]

Is there a higher stall tc installed?

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[oneno]

The TC is stock.

 

[truckin151]

throttle body stock?

 

[Redtruck-VA]

Some piggy back tuning manipulates the MAP signal, the previous owner might have experimented. The surging is usually associated with the front O2s, did you use oem sensors? Without codes it is tough to nail down. Maybe check fuel pressure to see if it is stable. Good luck..

 

[oneno]

it was the MAP sensor. The previous owner had the screw in type and it required the more shallower bolt on type. So after I did everything ,it ended up being a 20 dollar MAP sensor...go figure.