1990 5.0 Swapped Into 68 Mustang Problems!!!

Texasag10 · Nov 30, 2014

Hello,
I recently pulled a 1990 5.0 for a donor motor to put into my 1968. Engine was completely rebuilt. I went back with typhoon upper and lower intake, anderson n41 cam, and twisted wedge 170cc heads. Also went with 27lb Bosch injectors. I used a painless performance 60510 harness to get this set up in the old stang. It also has a tremec 5 speed. Car has a brand new walbro 255lph inline fuel pump. I blocked off the egr, it is unplugged. The MAP sensors, intake air temp, water temp, IAC, TPS, and MAF are all in use. bama has burned a chip for the A9L computer in the car. MAF, TPS, and TFI module are all brand new. I am not running o2 sensors as I have long tube headers and the bungs are welded on just down streem of the collector. I will run o2 sensors if I can get the car to run good enough to make it to the muffler shop.

Here is my issue:
With the MAF plugged in the car idles a little on the rough side and hangs at a high idle for too long after you get engine rpm up. When you punch the throttle engine completely cuts off. As soon as you let off the throttle it runs again.

With MAf unplugged, The car runs 100% better. throttle has instant response and it idles flawlessly

The only codes I can get are:
15
85-CANP failure
96- fuel relay

Has anyone ever had these symptoms?? Am I missing any sensors that should have been transferred from the fox body? Any help would be greatly appreciated!
Thanks

jrichker · Nov 30, 2014

Do you have an aftermarket MAF that is designed to work with 27 LB injectors?

Texasag10 · Nov 30, 2014

No i have factory MAF. Bama performance knew this when they burned my chip. I forgot to mention, I also have a professional products 70mm tb.

Texasag10 · Nov 30, 2014

Is it necessary to have a calibrated MAF, or can they accomplish the same results through tuning?

jrichker · Nov 30, 2014

Start with a calibrated MAF to at least get the engine running reasonably well. Then if you feel the need for additional tuning, get a custom chip burned from the dyno run results.

Micheal Nadeau · Nov 30, 2014

There is no such thing as a calibrated MAF. The transfer function is done via the computer. The amount of air flowing across the sensor just determines a voltage, which is sent to the pcm and transferred into value "x" That value is then used, with information from the TPS, VSS and (don't quote me) but the Baro sensor as well to determine the amount of fuel and spark to deliver. You can go grab any MAF that fits an 89 and up Mustangs and swap it out.

madspeed · Nov 30, 2014

Not true, but true to an extent. But, where in the world would you find any maf calibrated for 27# injectors? Get a custom tune to pull it all together, or grab some factory 19# injectors that the factory maf was designed to work with and make it all happy

jrichker · Nov 30, 2014

Micheal Nadeau said:
There is no such thing as a calibrated MAF. The transfer function is done via the computer. The amount of air flowing across the sensor just determines a voltage, which is sent to the pcm and transferred into value "x" That value is then used, with information from the TPS, VSS and (don't quote me) but the Baro sensor as well to determine the amount of fuel and spark to deliver. You can go grab any MAF that fits an 89 and up Mustangs and swap it out.

Granted that Ford OEM MAFs were not designed for a specific injector size, and the injector flow characteristics were part of the computer's internal program.

BUT for aftermarket parts, MAFs are calibrated for injector size, since it is easier to "lie" to the engine about the amount of airflow that it is to custom burn a chip to modify the fuel/air ratio to match airflow and injector on timing. You can sell a modified MAF with lot better results than sell a custom chip based on guesswork. Pro-M (www.promracing.com/‎) and other aftermarket MAF suppliers have been doing it for years. It works reasonably well, but is less than optimal.

Diagrams courtesy of Tmoss & Stang&2birds

Visual comparison of the Ford Fuel Injectors, picture by TMoss:

Micheal Nadeau · Nov 30, 2014

Everything I have ever read and understood about MAF systems, would say that a MAF sensor is a just a voltage based sensor. It adjusts voltage based on the amount of air applied to it. It doesn't know how big the injectors are. It knows that X amount of air equals Y voltage. The PCM determines the voltage, and based on the written program for said injector size, the injector pulse width is increased or decreased. You can manipulate a mass air by putting it in a sample tube, which will adjust the velocity of the air. You are tricking the MAF into sending a different voltage in order to treat larger injectors as if they are the stock size.

Micheal Nadeau · Nov 30, 2014

Pro M has there sample tubes essentially built into the MAF unit and C&L has interchangeable tubes that are bolted to the MAF housing.

mikestang63 · Nov 30, 2014

Never heard of a MAF for 27# injectors. You sure you don't have 24#? Also, if Bama did a tune, I have to assume they took into effect the injector size to adjust the MAF voltage accordingly. Did they also put in the tune that you have no EGR or O2 sensors?

madspeed · Nov 30, 2014

Doubt it, as they are pretty much a canned tune

Texasag10 · Nov 30, 2014

yes they are for sure 27# bosch part number 0280156048. Bama knew that we used 27# injectors but i dont think they took into account the egr or 02 sensors. If i trailer this thing to the muffler shop just to get the o2 sensors functioning, do you think the computer will be able to adjust for the lean condition or whatever is causing the engine cut out?

Texasag10 · Nov 30, 2014

I still have the original 19# injectors on the shelf, but anderson ford told me they would not keep up.

madspeed · Nov 30, 2014

I'd get Bama to fix your tune

madspeed · Nov 30, 2014

The o2 sensors and egr can be tuned out. If i paid for a tune that my car wouldnt run on, I get my tuner to fix it

Texasag10 · Nov 30, 2014

I totally agree. Im not very well versed in the EFI world, as I am a diesel mechanic. I have called them and they are giving me the run around telling me the tune was written correctly. They said it was more than likely a bad MAF or nicked wiring. I replaced the MAF with no better results, and the entire harness is brand new. Im not sure what my next step is. Maybe get the o2 sensors in and then head to a local tuner to re burn my chip correctly?

Micheal Nadeau · Nov 30, 2014

Well considering you don't have codes for o2 sensors, I would say Bama wrote the O2 sensors out in the tune........
I wrote a dissertation before realizing that a code 15 is the EEC Relay. Which makes sense with the fact that you also have the fuel relay as well.........

Micheal Nadeau · Nov 30, 2014

Code 15 diagnosis, vio ProDemand

Texasag10 · Dec 2, 2014

**update**
After talking with Bama Tunes, they have determined that they cannot make tables for the 27lb injectors without the injector high slope, low slope, breaking point, and the battery voltage compensation. Of corse bosch refused to release any of that information to me. I called the guy who sold me the injectors and he is going to trade me for some 24lb ford racing injectors to make my life easier... I hope bama can write a tune to pull all this crap together!!

1990 5.0 Swapped Into 68 Mustang Problems!!!

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