Bogging Issue

fastford87

New Member
May 17, 2009
18
0
0
Ringgold, GA
Ive got a 87 LX coupe 5.0 5 spd and I am having this problem with the car stumbling or bogging down when it reaches 4000 rpm in any gear. It has a 70mm throttle body 24lb. injectors and mass air on an HO intake and stock fuel pump . The car dies then comes back when you let off the gas. I have a trick flow street burner intake (not on yet) but do you think if this was on, it would stop stumbling? Any help would be grateful. Thanks :nice:
 
  • Sponsors (?)


Did you build this combo yourself or buy it off someone else? Is this a real Mass Air conversion or did someone just hang a MAF in the intake plumbling? The 87 model 5.0 Mustangs did not come with Mass Air from the factory. What model computer is in the car?

A stock engine does not need 24 lb injectors. The MAF will need to be an aftermarket item designed to work with 24 lb injectors or you will need a custom dyno tune and chip to make the 24 lb injectors work properly. A mismatch between the stock tune and the 24 lb injectors will cause all kinds of strange problems.
 
Did you build this combo yourself or buy it off someone else? Is this a real Mass Air conversion or did someone just hang a MAF in the intake plumbling? The 87 model 5.0 Mustangs did not come with Mass Air from the factory. What model computer is in the car?

A stock engine does not need 24 lb injectors. The MAF will need to be an aftermarket item designed to work with 24 lb injectors or you will need a custom dyno tune and chip to make the 24 lb injectors work properly. A mismatch between the stock tune and the 24 lb injectors will cause all kinds of strange problems.

+1

That sampling tube inside the MAF has to be a 24lb injector sampling tube. C&L makes these for about $40. Make sure to call and ask if it's to fit a stock MAF I'm not sure if it's different than their aftermarket fit.

If your MAF is correct, I've seen this stumbling happen for a couple of reasons...

1) Distributor is bad (or at least the little sensor deal in it). I've also seen an MSD dizzy do this for an unkown reason.
2) Vacuum is wrong, but that is usually at lower RPM
3) Adjustable fuel pressure regulator is set wrong
4) And as stated above, a reoiled K&N will sometimes slosh it's oil on the wire inside the MAF. I actually had that problem on a GMC truck once.


Also check the dizzy cap and make sure the contacts are clean. When's the last time you had a tune up?
 
I bought it this way and I do believe he or someone else put the MAF sensor on. It has the plug for the sensor , when I unplug it it still runs the same. I did find the metering sticks at summit. I dont think it has an adj. pressure regulator Ill have to look tomorrow. Do you think that that might be part of it if its losing pressure along with the metering stick being stock? Let me know if I should take the MAF off or keep it on or something. I dont know much about Mustangs, my first one, I'm actually a Chevy man Thanks for the help
 
Check with a voltmeter with your key on not running and see what your throttle positon sensor voltage is through out the throttle range. Use the black for ground I believe it is the wire next to the black one. One wire will be a constant 5 volts the other will increase with the throttle. It should also be set around 0.95-98 at idle I believe.
Your 24lbers are a little much for a stock motor. And do you have an aftermarket mass air meter calabrated for them. The stock meter you cannot change out tubes or anything. Only on an aftermarket C&L you can do that.

I have an HCI 306 w/ 24lb injectors and the only way I could get it to run right even with a calabrated mass air meter was with a tune. It kept loading up my #5 cylinder and I dont know why and neither does my tuner. But the tune fixed it.
 
I would go with a Pro-M calbrated for 24lb injectors. I had a C&L 73mm and it ran like s****. Put a 75mm Pro-m and it ran stronger but with my setup I still needed a tune to get the full potential out of it.
Did you check the throttle postiion sensor?
 
The MAF body and sensor are designed to match each other. Type A sensor works with Type A bodies. Therefore you can't swap sensors between different part number MAF bodies and maintain proper calibration. However, the bodies and sensors are not necessarily calibrated together to create a precision matched pair.

The output voltage of the MAF is a function of the air flowing through it. The MAF itself does not know about injector sizes, nor does it care. All it sees is that an increase in airflow means a corresponding increase of MAF output voltage. Altering the design of the MAF body can alter the flow past the sensor.

The OEM ford system was designed to use internal computer tables to match the voltage output of the MAF to a calculated injector turn on time. The injector table uses only one size injector in its calculations. This is a much more accurate means of determining the engine’s fuel requirements. Using a different MAF than the one the computer was designed for can upset the computer's calculations and the air/fuel ratio.

What aftermarket MAF’s do is try to fool the computer by either changing the amount of airflow over the stock electronics (C&L method) or by altering the sensor itself (Mass Air Systems method). The goal for both methods is to change the output voltage of the MAF so the computer calculates new data that is used to vary the pulse width sent to the injectors.

Unless I am mistaken, C&L tells you to use the MAF sensor that came with the original car. On a 89-93 5.0 Mustang, that was a E9ZF-12B579-xxx
 
The MAF body and sensor are designed to match each other. Type A sensor works with Type A bodies. Therefore you can't swap sensors between different part number MAF bodies and maintain proper calibration. However, the bodies and sensors are not necessarily calibrated together to create a precision matched pair.

The output voltage of the MAF is a function of the air flowing through it. The MAF itself does not know about injector sizes, nor does it care. All it sees is that an increase in airflow means a corresponding increase of MAF output voltage. Altering the design of the MAF body can alter the flow past the sensor.

The OEM ford system was designed to use internal computer tables to match the voltage output of the MAF to a calculated injector turn on time. The injector table uses only one size injector in its calculations. This is a much more accurate means of determining the engine’s fuel requirements. Using a different MAF than the one the computer was designed for can upset the computer's calculations and the air/fuel ratio.

What aftermarket MAF’s do is try to fool the computer by either changing the amount of airflow over the stock electronics (C&L method) or by altering the sensor itself (Mass Air Systems method). The goal for both methods is to change the output voltage of the MAF so the computer calculates new data that is used to vary the pulse width sent to the injectors.

Unless I am mistaken, C&L tells you to use the MAF sensor that came with the original car. On a 89-93 5.0 Mustang, that was a E9ZF-12B579-xxx

Thanks that was helpful.