Once I hit 4500 the car misses and spikes lean, what could that be?

[BlueOvalStangGT]

Im starting to beat on my car again(first time in like 7 months) and I have a problem once i get higher into the rpms. Every time at 4500 rpms, and its exactly 4500 everytime it seems, the car misses and my air/fuel ratio will spike to like 18.1 real quick. Its never done that before but now it does it everytime. I tried to save a datalog but I must have messed something up and it didnt save. Heres my hypothesis:

A: Pegging the meter. Its a Pro-M 75mm, but am I making enough power to peg a meter??(especially at 4500 rpms??)

B: Blowing out the spark or my plugs are fouled. When I first started the new motor, I drove the first XXX miles with a 10.4-1 A/f CRUISING. That cant be too good for the plugs(and the cylinder walls actually). I have a Ford Racing coil, MSD 6btm, new accel wires and motorcraft plugs gapped to .035(I think thats what it was).

What else could it be?

 

[4Jenna]

blowing spark out i say..ck the plugs, and then make sure your ign box didnt break a wire or something

 

[WhiteDevil]

HOws the A/F up to that point?

 

[BlueOvalStangGT]

Low 12's I believe.

 

[final5-0]

Keven

As the others have said, check the obvious stuff for sure.

As for the datalog ...............................

On the WOT stuff until you can do the following:

1) get familiar enough with datalogging so you can build a payload that contains the columns of data you wish to see

2) start and stop the log at the time or rpms of your choice

After you got items 1 & 2 down pat, I'd dial the spark way back and make a wot run datalogging with the rpms not exceeding 4200 rpm. If your maf volts climb close to 5.00 volts you gotta go to a maf or cal that will allow more air flow.

btw, what cal is your bullet setup for?

Grady

 

[4Jenna]

Do you have the BTM with the built in ignition box, or is it just the retard?

 

[BlueOvalStangGT]

Keven

As the others have said, check the obvious stuff for sure.

As for the datalog ...............................

On the WOT stuff until you can do the following:

1) get familiar enough with datalogging so you can build a payload that contains the columns of data you wish to see

2) start and stop the log at the time or rpms of your choice

After you got items 1 & 2 down pat, I'd dial the spark way back and make a wot run datalogging with the rpms not exceeding 4200 rpm. If your maf volts climb close to 5.00 volts you gotta go to a maf or cal that will allow more air flow.

btw, what cal is your bullet setup for?

Grady

1.) Are you talking about just datalogging rpms pulse width etc etc? If so I know how to do that,I just probably forgot to hit write to file on that run.

2.) How do I do that?

3.) How far back is way back? If by bullet you mean my maf, im not sure if it is the pro-m bullet. Mine is black plastic and I always thought it was the 75 mm, (whichever is the one that had all the problems) maybe its the 77, I dunnno.

 

[BlueOvalStangGT]

Do you have the BTM with the built in ignition box, or is it just the retard?

Pretty sure its the one with the ignition box, how do I tell for sure?

 

[BlueOvalStangGT]

Thats the other thing, if I was blowing out spark, wouldnt the car spike really rich, not lean?

 

[William741]

If it's spiking lean, it's also worth a check to see what your fuel pressure is. We've had some cougars with a pump going out and they would only miss at wot at about 4k rpm's. It might not be the problem, but check it to make sure. Good luck, Will

 

[final5-0]

1.) Are you talking about just datalogging rpms pulse width etc etc? If so I know how to do that,I just probably forgot to hit write to file on that run.

Great!

Besure to include the maf (air flow in kg/hr) and maf volts in your pay load. As the pcm can only take 5.00 volts maximum from the maf ... that will let you know if your running out of room on the maf cal.

2.) How do I do that?

Just be sure your dlog is running and the data stream is being captured to the hard drive before you start your wot run. Lift and clutch a little before 4500 rpm and tap the space bar to stop the dlog.

3.) How far back is way back?

Since your forced induction, even all the more reason to be better safe than sorry, lol.

I'd reduce the total amount by say ... 25%.

When hosing around with wot spark and fuel adjustments always think ......

BIG Fuel ... little spark!

If by bullet you mean my maf, im not sure if it is the pro-m bullet. Mine is black plastic and I always thought it was the 75 mm, (whichever is the one that had all the problems) maybe its the 77, I dunnno.

Maybe I don't know what I talking about here but I thought all 75mm ProM mafs were the bullet model. I always thought they were the chrome looking units as well.

Doesn't matter anyway if it is too small ... its too small

Grady

 

[final5-0]

Thats the other thing, if I was blowing out spark, wouldnt the car spike really rich, not lean?

The wb can't deal with a liquid, only a gas.

If you got raw gas around the sensor, it doesn't know it.

Grady

 

[95cobradude]

i would get rid of that msd btm, your tweecer should handle all your timing needs. just get a regular msd 6al and some autolite plugs.

 

[S351R"Animal"]

I had the same issue and it turned out a fuel pump went out.