Help me diagnose my drag results.

[Tim2002GT]

This is a chart of some of my best's when I have gone to the track. What do you think would cause a 5 mph loss? Temperature? Bad tune? Clutch slippage? Tell me what you think. The car is in good mechanical condition with a recent tune-up, including plug change, air filter cleaning, MAF cleaning, oil change, trans. fluid change. Feels like it runs strong and just noses over past 5000 rpm.

 

[Mike97gt]

any pinging at all above 5k? when was the last time you changed your fuel filter?

How does the clutch feel, maybe it is slipping slightly at high rpm's?

it sure does seem like you are down some power. Since you corrected your times it makes it much easier to compare

 

[Tim2002GT]

Yeah, I changed the fuel filter when I changed the oil. About a month ago. I am pretty sure it isn't pinging either. What about a fuel pump going out? What other symptoms would that show? When I bought the car in October, they said the clutch was new, but you know how that goes

 

[GettinThere]

This is a chart of some of my best's when I have gone to the track. What do you think would cause a 5 mph loss? Temperature? Bad tune? Clutch slippage? Tell me what you think. The car is in good mechanical condition with a recent tune-up, including plug change, air filter cleaning, MAF cleaning, oil change, trans. fluid change. Feels like it runs strong and just noses over past 5000 rpm.

Hopefully it's just warmer weather, but it seems like a significant drop. Were you shifting at different rpms? Good luck with your search for a cause.

 

[COramprat]

I had a 2 mph drop in hotter weather (upper 50's compared to lower 70's). Don't even want to try in this 95 degree heat now.

 

[TonyG]

My MPH trend charts zig-zag up and down like that because of the weather. Probably when it gets cold again, your MPH will go back up.

But 5 mph seems a little extreme at your power level. I get 5 mph variation between cold and hot weather, but I'm making 440 rwhp. Percentage-wise, 5 mph for me is a much smaller variation than what it is for you.

 

[Tim2002GT]

Tonight, I was pulling out of my driveway and my car threw a P0190 code. Something about the Fuel Rail Pressure Sensor. Anyway, I cleared the code with my XCal II and it hasn't came back yet.(I drove around for about an hour after the code was thrown.) What could be causing the problems. I just cleaned and oiled my K&N last week. Could the oil have gotten on the MAF and caused this? Gonna clean my MAF tomorrow just to be safe.

 

[Tim2002GT]

So I replaced the fuel rail sensor, didn't fix it. Today, I replaced the stock fuel pump with a Focus SVT pump and it appears that was the problem. The mesh filter at the bottom of the stock pump was caked with "???". The pump itself may still be good, but I installed the focus pump anyway. The car was basically falling on its face above 4500 rpm. After the pump install, it seemed to pull all the way up to 6000 rpm.

Thanks SaleenGT2001 for the focus pump!

 

[hotmustang331]

Glad you figured out the problem! And yep that P0190 was probably due to the pump drapping rail pressure.

My car does it on occasion, but for different reasons.

 

[Tim2002GT]

Thanks for the reply! It was starting to get frustrating because it would run fine one day and the next it would spit and sputter with anything over 1/2 throttle.