Engine bogs down at high RPMs! Help!!

[FLSVTCobra]

The other day I took my freshly built (pistons, rods, etc.) 96' cobra to the track for the first time. Every time I accelerated the car would bog down during the higher rpms and it would feel like it wasn't going anywhere.

Could this be the clutch slipping or maybe having insufficient amount of fuel? I know that my transmission needs a rebuilt because my synchros are starting to go bad. Anyways, any advice will be greatly appreciated.
:shrug:

 

[Red98CobraStang]

when was the fuel filter changed last?

Plugs?
Wires?

Do you smell anything when the car bogs? if the clutch is slipping you would know. It would smell terrible.

 

[FLSVTCobra]

The plugs were changed only about a month ago after I build the bottom end. I don't know about the wires and the fuel filter.

 

[John4cam]

You didn't happen to put msd coil packs on it did you? I had a problem similar with em on.

Could be a fuel problem like said above, what kind of maf setup is on the car??

 

[FLSVTCobra]

Coilpacks are stock and the maf is a C&L, not sure what size, it was already on the car when I bought it. I guess I'll start by replacing the fuel filter and inspecting the injectors.

 

[Red98CobraStang]

is the compression ratio stock?

was the car tuned after the motor was rebuilt?

 

[mustangsf4life]

Fuel filter maybe. $10 part and its worth a shot.

 

[FLSVTCobra]

The compression ratio is slightly higher but not much. No, I haven't had it tuned.

 

[Blown4v]

do you still have the imrcs? did it feel like the car hit a wall, or did the engine rev but the car not accelerate?

 

[John4cam]

My c&l also gave me probs, try the stocker and see how it runs.

Just trying to eliminate everything..

 

[JasonSnake]

do you still have the imrcs? Did it feel like the car hit a wall, or did the engine rev but the car not accelerate?

+1

 

[FLSVTCobra]

Yes I still have the IMRCs. When I took off the line, the car accelerated from 1st gear, shifted into 2nd, pedal on the floor, the rpm started climbing, then all of a sudden between around 4-6k rpm the car as you mentioned hit the wall (the pull of the car drastically decreased and I believe the rpm stopped climbing, it was like hitting the rev limiter). So I shifted into third and the same happened again. Other than that it pulls hard as hell.

 

[JasonSnake]

Yes I still have the IMRCs. When I took off the line, the car accelerated from 1st gear, shifted into 2nd, pedal on the floor, the rpm started climbing, then all of a sudden between around 4-6k rpm the car as you mentioned hit the wall (the pull of the car drastically decreased and I believe the rpm stopped climbing, it was like hitting the rev limiter). So I shifted into third and the same happened again. Other than that it pulls hard as hell.

sounds like a classic case of imrc syndrome

 

[brucesvt]

sounds like a classic case of imrc syndrome

+2 yep sounds like the IMRC's need cleaning. g/l and keep us posted

 

[Tx_Diablous]

IMRC's open between 3200 to 3400 and I would think it would bog in any gear over these RPM's. Try bringing it up to these RPM's and then steadly push it up to 6,000 and see if the bog changes and you feel a drop off in the pull. There are a lot of things that can cause a bog. Fuel pump, bad coil pack, plug wires, and even a bad MAF not seeing the correct air flow can cause it. If you can data log you might be able to track it down without using the buy, replace, remove and clean and still not knowing what it is. Now having said all of that, if it seems to pull ok with steady peddle pressure I would look at the fuel system. If it bogs no matter how fast you push through 3200 then I would lean toward the MAF or the coil packs-plug wires. If it only bogs when you stomp it to the floor I would go for IMRC's.
BTW good luck this symptom sucks and could be almost anything.

 

[b dub]

Yeah I highly doubt it's your imrc's...

 

[Red98CobraStang]

The more and more I think about this, It leads me to belive the MAF function may be to blame.

Do you still have the 24lb injectors in the car?

As said before, throw on the stock MAF and see what happens.

 

[crazycarlo]

same thing happened to me at the track a month ago. Do you happen to have an aftermarket high flow fuel pump in it or an aviator pump. Mine would hit a wall at 5-5500 rpms and come to find out it was sucking the basket dry causing a lean condition and activating the knock sensors which pulled timing. I had to drill holes in my fuel basket.... now she pulles cleanly all the way to 7.

 

[FLSVTCobra]

Yeah I still have the stock 24lb fuel injectors. When I bought the car it already had a C&L maf therefore I don't have the stock one.

I also have an aftermarket fuel pump which flows at 190lph.

 

[FLSVTCobra]

same thing happened to me at the track a month ago. Do you happen to have an aftermarket high flow fuel pump in it or an aviator pump. Mine would hit a wall at 5-5500 rpms and come to find out it was sucking the basket dry causing a lean condition and activating the knock sensors which pulled timing. I had to drill holes in my fuel basket.... now she pulles cleanly all the way to 7.

What do you mean by "sucking the basket dry"? And "drilling holes in the basket"? What you have described is almost identical to what happened to me at the track. Could you be more specific? Thanks.