Finally Got My Car Running Properly (lessons Learned)

blackstangt

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May 31, 2004
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After about a year since putting it back together from an intake swap and port job, and almost 2 years in storage (but running) before that, I figured out what I did wrong and what went wrong. My mustang runs better than ever. I had very limited free time to work on it, which caused it to take much longer than it should.

After putting the car back together, it ran like crap, I had cleaned the MAF, cleaned the plugs, replaced the coil, installed an adjustable FPR, and swapped the lower intake to one without stripped threads.

I have a fuel pressure gauge and saw that I wasn't getting adequate fuel pressure, regardless of adjustment. The new BBK FPR failed. I swapped the FPR back and got most of my fuel pressure back. The fuel pressure eventually diminished.

Since the car had been sitting for so long with 10% ethanol gas, it was possible that the tank was rusty and filled the fuel filter. I swapped the fuel filter, siphoned as much gas as I could and put in 5 gallons of fresh gas. The fuel pressure returned and I was able to get it running enough to drive it out of the garage, but making all sorts of bad noises and smells.

Next, I bought a new battery. I was running a lithium starkpower starting battery, and thought the voltage might be too high without the resistance from a lead acid battery. Switching back and forth, I killed the lithium battery permanently anyway through excessive discharge ($200 down the drain). The new battery wasn't the right size for the car, but the largest one I could buy with the most capacity from Walmart. It has performed well, but this didn't really change anything other than my ability to test things extensively without recharging.

Having to move across the country, I pushed the car onto a trailer and towed it with the moving truck.

Once settled, I got a friend to help me install a new gas tank, pump, and fuel filter, filling it with new gas. This definitely improved my fuel pressure, but it seemed lower than usual still. While running on 3 cylinders, the pressure fluctuated wildly, so I ordered a Ford FPR to see if that would help. It made no noticeable difference, but wasn't rusty at least.

I ordered a new Ignition Control Module (TFI module), since they fail pretty regularly. It seemed to make a difference, but it turned out cleaning the plugs at the same time is what caused the change.

I ordered a new distributor that came with a TFI module. The cap and rotor needed to be changed anyway and the distributor was somewhat wobbly with 240k miles on it. It seemed to make a difference, but I was back to 3 cylinders after a short time.

I was getting fuel, I was getting spark, and I was getting air and compression. Fuel was in the cylinders when checked. Using the spark plugs connected to a ground, I could see spark. There were no obstructions and good compression on each cylinder. They would run for a short time after cleaning the plugs.

I decided to open up my remaining pepper shaker (10 pin connector) and pry the pins out slightly to ensure connection. This made no change.

I could only think of one thing. The MAF. I had cleaned it gently, but there was a possibility that using rubbing alcohol damaged it, or that it became physically damaged. I noticed that one of the resistors glowed red at night with the key forward. This is how it operates, but that seemed kind of hot. I ordered a BBK 76MM MAF calibrated for 24 lb injectors. I adjusted the Throttle Position Sensor to .95 volts and left it there awaiting the MAF.

The MAF arrived and I installed it immediately. I fired up the car and it ran. It ran well. There was a little sputter upon revving the engine, but it ran better than ever before. A perfect idle that didn't require input from me at all.

I always had an intermittent fluctuating idle, since the day in 2004 that I swapped to a GT-40X crate engine, 24 lb injectors and a Vortech MAF w/calibrated tube. It was gone. I realized that one of the clips on the distributor cap was off and that solved the miss when revving the engine.

Everything was great. I went to move my car the next day and nothing. No spark. I swapped the coil and swapped it back to no avail. I was getting no spark, so the obvious part was the ignition control module. I also changed out my plugs since I had platinum coated plugs and cleaned them so many times.

I still had the Motorcraft ignition control module, so I cleaned everything, put some non-conductive thermal paste on it and dielectric grease on the connections. Problem solved. Car runs great, and I can start putting new parts on it that have been sitting in boxes for up to 2 years.

I know this is a long read, but there are a lot of lessons learned that could save people time and money:

-Store your car with a full tank of gas and fuel storage additives. buy ethanol free gas if you can get it.

-Motorcraft parts are generally better than any aftermarket parts. My ignition control module and Fuel Pressure regulator that weren't motorcraft failed instantly.

-Don't clean your MAF with anything other than MAF cleaner.

-A calibrated tube type of MAF is inferior. The newer designs have a much better track record.

-All but the most expensive lithium batteries are not up for the challenge yet. Most can't handle charging at even the amps of a stock alternator, and a constant discharge can kill them easier than a lead battery. Fortunately LiFePO4 batteries are extremely safe, safer than lead, so there were no major issues.

-Copper plugs are better for diagnosing problems, you can clean them all day and not worry about the coating.

-DO ONE THING AT A TIME. If I had run the car between each modification, I would have known it was the MAF. While this may take a little longer, do it wherever it's reasonable to do so.

-Throwing money at something does work, but it can be more expensive if done improperly. If you can, go to the parts store and try a bunch of things, one at a time, returning the parts that made no difference.

I saw no way to test the MAF, so if someone has a way to do so, please add it.
 
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jrichker

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Dumping the codes may have gotten you this...

Code 66 or 157 MAF below minimum test voltage.

Revised 10-Feb-2014 to add 95-95 Mustang code 157 and 94-95 ECC diagram

Insufficient or no voltage from MAF. Dirty MAF element, bad MAF, bad MAF wiring, missing power to MAF. Check for missing +12 volts on this circuit. Check the two links for a wiring diagram to help you find the red wire for computer power relay switched +12 volts. Check for 12 volts between the red and black wires on the MAF heater (usually pins A & B). while the connector is plugged into the MAF. This may require the use of a couple of safety pins to probe the MAF connector from the back side of it.

Computer connector for 88-93 5.0 Mustangs

Diagrams courtesy of Tmoss and Stang&2Birds

ECC Diagram for 88-90 5.0 Mustangs


ECC Diagram for 91-93 5.0 Mustangs


94-95 Diagram for 94-95 5.0 Mustangs



There are three parts in a MAF: the heater, the sensor element and the amplifier. The heater heats the MAF sensor element causing the resistance to increase. The amplifier buffers the MAF output signal and has a resistor that is laser trimmed to provide an output range compatible with the computer's load tables. Changes in RPM causes the airflow to increase or decrease, changing the voltage output.. The increase of air across the MAF sensor element causes it to cool, allowing more voltage to pass and telling the computer to increase the fuel flow. A decrease in airflow causes the MAF sensor element to get warmer, decreasing the voltage and reducing the fuel flow.

The MAF element is secured by 2 screws & has 1 wiring connector. To clean the element, remove it from the MAF housing and spray it down with electronic parts cleaner or non-inflammable brake parts cleaner (same stuff in a bigger can and cheaper too).

89-90 Model cars: Measure the MAF output at pins C & D on the MAF connector (dark blue/orange and tan/light blue) or at pins 50 & 9 on the computer. Be sure to measure the sensor output by measuring across the pins and not between the pins and ground.

91-95 Model cars: Measure the MAF output at pins C & D on the MAF connector light blue/red and tan/light blue) or at pins 50 & 9 on the computer. Be sure to measure the sensor output by measuring across the pins and not between the pins and ground.


At idle = approximately .6 volt
20 MPH = approximately 1.10 volt
40 MPH = approximately 1.70 volt
60 MPH = approximately 2.10 volt

Check the resistance of the MAF signal wiring. Pin D on the MAF and pin 50 on the computer (dark blue/orange wire) should be less than 2 ohms. Pin C on the MAF and pin 9 on the computer (tan/light blue wire) should be less than 2 ohms.

There should be a minimum of 10K ohms between either pin C or D on the MAF wiring connector and pins A or B. Make your measurement with the MAF disconnected from the wiring harness.

Actually MAF pins C & D float with reference to ground. The signal output of the MAF is a differential amplifier setup. Pins C & D both carry the output signal, but one pin's output is inverted from the other. The difference in signal between C & D is what the computer's input circuit is looking for. The difference in the two outputs helps cancel out electrical noise generated by the ignition system and other components. Since the noise will be of the same polarity, wave shape and magnitude, the differential input of the computer electronically subtracts it from the signal. Then it passes the signal on to an Analog to Digital converter section inside the computer's CPU chip.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel pump, alternator, ignition & A/C wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Computer,. actuator & sensor wiring
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Fuse panel layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif

Vacuum routing
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg