Electrical Car running like crap, HELP!

1mustyLSC said:

ven with it running like poop, fuel pressure is 35-36 with vac line on. 45-46 with vac line off. Has a new 255 walbro in the tank, new fuel filter and pump sock.

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Typical newbie mistake - you put a 255 LPH fuel pump on and have overwhelmed the fuel pressure return system. Now you can't get the fuel pressure regulated to the 37-41 PSI it should be with the vacuum line disconnected.. A 155 LPH fuel pump is all you'll ever need for a Naturally Aspirated 302.
An adjustable fuel pressure regulator may not produce the desired results if the return line acts like a restriction.

How the fuel pressure regulator works
The fuel pressure regulator in 5.0 pushrod Mustangs is a shunt regulator that works in parallel with the fuel injection system. The regulator bypasses fuel back to the tank to maintain a constant 39 PSI to the injector tips. A constant pressure insures that the computer will always have the same flow rate to base its calculations on.


Cylinder balance test: use this to find dead or weak cylinders:

Revised 09-Sep-2017 Added reminder to write down the stored codes and engine running codes.

The computer has a cylinder balance test that helps locate cylinders with low power output. You’ll need to dump the codes out of the computer and make sure that you have the A/C off, clutch depressed to the floor and the transmission in neutral. Fail to do this and you can’t do the engine running dump codes test that allows you to do the cylinder balance test.

Here's the way to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

Be sure to turn off the A/C, have the clutch depressed to the floor, and put the transmission in neutral when dumping the codes. Fail to do this and you will generate a code 67 and not be able to dump the Engine Running codes.


Here's how to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.





If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.



The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.



The STI has a gray connector shell and a white/red wire. It comes from the same bundle of wires as the self test connector.


WARNING!!! There is a single dark brown connector with a black/orange wire. It is the 12 volt power to the under the hood light. Do not jumper it to the computer test connector. If you do, you will damage the computer.

What to expect:
You should get a code 11 (two single flashes in succession). This says that the computer's internal workings are OK, and that the wiring to put the computer into diagnostic mode is good. No code 11 and you have some wiring problems.
This is crucial: the same wire that provides the ground to dump the codes provides signal ground for the TPS, EGR, ACT and Map/Baro sensors. If it fails, you will have poor performance, economy and drivability problems

Some codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Dumping the Engine Running codes: The procedure is the same, you dump the codes and then you start the engine with the test jumper in place. Be sure the A/C is off, clutch depressed to the floor and the transmission is in neutral. You'll get an 11, then a 4 and the engine will speed up to do the EGR test. After the engine speed decreases back to idle, it will dump the engine running codes.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

Your 86-88 5.0 won't have a working Check Engine Light, so you'll need a test light.
See AutoZone Part Number: 25886 , $10




Alternate methods:
For those who are intimidated by all the wires & connections, see Actron® for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see www.midwayautosupply.com/Equus-Digital-Ford-Code-Reader/dp/B000EW0KHW Equus - Digital Ford Code Reader 3145.
It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $22-$36.
Order it at Walmart for a better price and free shipping


Write down the codes that the computer outputs since they will give you information on problems that are stored in the computer's memory


Cylinder balance test

If you have idle or IAC/IAB problems and the engine will not idle on its own without mechanically adjusting the base idle speed above 625-750 RPM, this test will fail with random cylinders pointed out every time it runs. The IAC/IAB must be capable of controlling the engine speed to run in the 1300-1500 RPM range. Playing with the base idle speed by adjusting it upwards will not work, the computer has to be able to control the engine speed using the IAC/IAB.

Warm the car's engine up to normal operating temperature. With the test jumper in test position, start the engine and let it stabilize. It should flash a 10 and then a 4 and maybe an 11. If no 11, then there are other codes that will be dumped.

Write down the codes that the computer outputs since they will give you information that the computer found when it is running. These are often different from the stored codes.

One of the first tests it does is to open the EGR all the way, this will cause the engine to stumble and almost die. If the engine dies here then you have EGR problems.
To start the cylinder balance test, briefly floor the accelerator past 2500 RPM and let off the accelerator. The engine will stabilize at about 1300-1450 RPM and the cut off the fuel injectors one at a time. The engine speed will drop briefly and the computer will turn the fuel injector for the cylinder under test back on. Then it starts the process for the next cylinder. When it has sequenced through all 8 injectors, it will flash 9 for everything OK, or the number of the failing cylinder such as 2 for cylinder #2. Quickly pressing the throttle again up to 2500 RPM’s will cause the test to re-run with smaller qualifying figures.
Do it a third time, and if the same cylinder shows up, the cylinder is weak and isn’t putting out power like it should. See the Chilton’s Shop manual for the complete test procedure

See View: https://www.youtube.com/watch?v=HDXrkKS4jTE
for a visual tour through the process. There is no voice narration so you have to listen carefully for the engine sounds. I posted the link for the benefit of Stangnet members who had questions about how to do a cylinder balance test. I do not own that video and I am not the creator.

Do a compression test on all the cylinders.
Take special note of any cylinder that shows up as weak in the cylinder balance test. Low compression on one of these cylinders rules out the injectors as being the most likely cause of the problem. Look at cylinders that fail the cylinder balance test but have good compression. These cylinders either have a bad injector, bad spark plug or spark plug wire. Move the wire and then the spark plug to another cylinder and run the cylinder balance test again. If it follows the moved wire or spark plug, you have found the problem. If the same cylinder fails the test again, the injector is bad. If different cylinders fail the cylinder balance test, you have ignition problems or wiring problems in the 10 pin black & white electrical connectors located by the EGR.

How to do a compression test:
Only use a compression tester with a screw in adapter for the spark plug hole. The other type leaks too much to get an accurate reading. Your local auto parts store may have a compression tester to rent/loan. If you do mechanic work on your own car on a regular basis, it would be a good tool to add to your collection.

With the engine warmed up, remove all spark plugs and prop the throttle wide open with a plastic screwdriver handle between the throttle butterfly and the throttle housing. Crank the engine until it the gage reading stops increasing. On a cold engine, it will be hard to tell what's good & what's not. Some of the recent posts have numbers ranging from 140-170 PSI. If the compression is low, squirt some oil in the cylinder and do it again – if it comes up, the rings are worn. There should be no more than 10% difference between cylinders. Use a blow down leak test (puts compressed air inside cylinders) on cylinders that have more than 10% difference.

I generally use a big screwdriver handle stuck in the TB between the butterfly and the TB to prop the throttle open. The plastic is soft enough that it won't damage anything and won't get sucked down the intake either.

A battery charger (not the trickle type) is a good thing to have if you haven't driven the car lately or if you have any doubts about the battery's health. Connect it up while you are cranking the engine and it will help keep the starter cranking at a consistent speed from the first cylinder tested to the last cylinder.




Copied from the FORD RACING PERFORMANCE PARTS catalog:

PROPERLY SIZING FUEL SYSTEM COMPONENTS

Fuel Pumps
The following information is presented assuming the above information has been taken into consideration regarding BSFC, fuel pressure and specific gravity of the fuel being used. Most fuel pumps for electronic fuel injection are rated for flow at 12 volts @ 40 PSI. Most vehicle charging systems operate anywhere from 13.2v to 14.4v. The more voltage you feed a pump, the faster it spins which, obviously, will put out more fuel. Rating a fuel pump at 12 volts then, should offer a fairly conservative fuel flow rating allowing you to safely determine the pump’s ability to supply an adequate amount of fuel for a particular application.

As previously mentioned, engines actually require a certain WEIGHT of fuel, NOT a certain VOLUME of fuel per horsepower. This can offer a bit of confusion since most fuel pumps are rated by volume, and not by weight. To determine the proper fuel pump required, a few mathematical conversions will need to be performed using the following information. There are 3.785 liters in 1 US Gallon. 1 gallon of gasoline (.72 specific gravity @ 65° F) weighs 6.009 LBS.

To be certain that the fuel pump is not run to its very limit, which could potentially be dangerous to the engine, multiply the final output of the fuel pump by 0.9 to determine the capacity of the fuel pump at 90% output. This should offer plenty of ‘cushion’ as to the overall “horsepower capacity” of the fuel pump.

To determine the overall capacity of a fuel pump rated in liters, use the additional following conversions:
(Liters per Hour) / 3.785 = Gallons
Multiply by 6.009 = LBS/HR
Multiply by 0.9 = Capacity at 90%
Divide by BSFC = Horsepower Capacity
So for a 110 LPH fuel pump:
110 / 3.785 = 29.06 Gallons
29.06 x 6.009 = 174.62 LBS/HR
174.62 x 0.9 = 157 LBS/HR @ 90% Capacity
157 / 0.5 = 314 HP safe naturally aspirated “Horsepower Capacity”

Safe “Horsepower Capacity” @ 40 PSI with 12 Volts
60 Liter Pump = 95 LB/HR X .9 = 86 LB/HR, Safe for 170 naturally aspirated Horsepower
88 Liter Pump = 140 LB/HR X .9 = 126 LB/HR, Safe for 250 naturally aspirated Horsepower
110 Liter Pump = 175 LB/HR X .9 = 157 LB/HR, Safe for 315 naturally aspirated Horsepower
155 Liter Pump = 246 LB/HR X .9 = 221 LB/HR, Safe for 440 naturally aspirated Horsepower
190 Liter Pump = 302 LB/HR X .9 = 271 LB/HR, Safe for 540 naturally aspirated Horsepower
255 Liter Pump = 405 LB/HR X .9 = 364 LB/HR, Safe for 700 naturally aspirated Horsepower

Note: For forced induction engines, the above power levels will be reduced because as the pressure required by the pump increases, the flow decreases. In order to do proper fuel pump sizing, a fuel pump map is required, which shows flow rate versus delivery pressure.

That is, a 255 liter per hour pump at 40 PSI may only supply 200 liters per hour at 58 PSI (40 PSI plus 18 lbs of boost). Additionally, if you use a fuel line that is not large enough, this can result in decreased fuel volume due to the pressure drop across the fuel feed line: 255 LPH at the pump may only result in 225 LPH at the fuel rail.


My Comments:

A lot of people oversize the fuel pump by buying a 255LPH pump thinking that the fuel pump regulator will just pass the excess gas back to the tank. It does, but… Did you ever consider that circulating the fuel around as a 255 LPH pump does will cause the gas to pickup engine heat? What happens to hot gasoline? It boils off or pressurizes the fuel tank! With most of the 5.0 Mustangs having the carbon canister removed or disabled, the car stinks like gas, and the gas mileage drops since the hot fuel evaporates away into the air.

CODE: 31 (KOEO) - EVP circuit below minimum voltage. Vref (5 volt reference voltage supplied by the computer) missing or broken wire or bad connection in circuit.

Revised 06-Aug-2016 to add clarification of the 10 pin connector possible problems

Use a DVM to check for 5 volts on the orange/white wire. If it is missing, look for +5 volts at the orange/white wire on the TPS or MAP sensor located on the firewall near the center of the car. Use the black/white wire for the ground for the DVM.
With the sensor removed from the EGR and still connected, press the plunger and watch the voltage change on the brown/lt green wire. Pull the passenger side kick panel and measure the voltage at the computer. You will need to remove the plastic cover over the wires and probe them from the backside. A safety pin may prove very useful for this task. Use pin 27, EVR input (brown/lt green wire) and pin 46, signal ground (black/white wire) to measure the voltage. The orange/white wire is Vref and should always be 5 volts -/+ .25 volt. Be sure to measure Vref at the EGR sensor to rule out any broken wires or bad connections.

Measuring the voltage at the computer helps you spot broken wiring and intermittent connections. The 10 pin connectors are especially prone to connection problems, If the voltage checks at the EGR sensor are good but not at the computer, the 10 pin connector is suspect.

See the graphic for the 10 pin connector circuit layout.



Computer wiring harness connector, wire side


Computer wiring harness connector, computer side

@1mustyLSC

The code 18 can also point to the PIP sensor inside the distributor. Check the PIP pulse at the injector with a noid light and look for spark at the spark plug.

Code 18 - SPOUT out or wiring fault - look for short to ground in SPOUT wiring going
back to the computer. Possible bad TFI or defective 22 K resistor in the IDM wiring

Revised 24 June 2019 to add comment about the need of thermal paste on TFI mounting surface.

Use a timing light to check the timing: remove the SPOUT and observe that the timing retards at least 4 degrees. Put the SPOUT back in place and observe that the spark advances at least 4 degrees.
This code can disable spark advance and reduce power and fuel economy.

Remove the passenger side kick panel and disconnect the computer connector.
It takes is a 10 MM socket to remove the bolt that holds the connector in place..
Disconnect the TFI module connector from the TFI and the measure the resistance between the yellow/lt green wire and ground.
You should see greater than 100 K (100000) ohms.
Check the resistance from Pin 4 on the computer connector (dark green/yellow) and the dark green/yellow wire on the TFI connector. You should see 20-24 K Ohms (20,000-24,0000 ohms).


Resistor location: A big thanks to liljoe07 for this information:

liljoe07 said:

Check over by the brake booster. Its not in the harness on the TFI, its on the main part of the harness over by the plugs that connect to the dash harness. About 6" or so from that, going back toward the EEC.

If I remember right, the resistor is covered in a shrink tubing that is sealed to the wires. So, you won’t be able see any markings. The shrink tubing is labeled though. It's a 22kohm 1/2 watt resistor.

Here is the location.

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Next measure the resistance between the yellow/lt green wire on the TFI module connector and Pin 36 on the computer connector. With the SPOUT plug in place, you should see less than 2 ohms.

The following is a view from the computer side of the computer connector.


This diagram is the wire side of the computer connector.


Diagram courtesy of Tmoss & Stang&2birds



If you replace the or remove the TFI, clean the mounting surface off with alcohol and apply a fresh coat of Thermal paste to the TFI mounting surface. Fail to do this and the TFI will quit working once the engine warms up.

High speed miss on a warm engine

Revised 24 June 2019 to add new source & part number for TFI removal tool .

The TFI module mounted on the distributor is one of the culprits for a high speed miss on a warm engine. The other suspect is the PIP sensor inside the distributor. If the problem does not occur when the engine is cold, the TFI module or PIP is definitely suspect. Dumping the codes may help determine which one it is. You may need a special socket to remove the TFI module, but most auto parts stores will have one for $5-$7.

It is not uncommon that the replacement parts may be defective; TFI modules made by non Ford manufactures seem to have a high failure rate.

Be sure to use plenty of the heat sink grease on the new TFI and clean the old grease off the distributor.



See you local Advance Auto parts store or AutoZone; ask for Lisle P/N 64650.

See https://shop.advanceautoparts.com/p...0kH8DTh2LmTcgnmc_E4aAuCIEALw_wcB&gclsrc=aw.ds

diagram courtesy of Tmoss & Stang&2Birds



At least EFI has a diagnostic mode to tell you what isn't working. Carburetor cars with don't have this feature and difficult problems are much harder to isolate and diagnose.

The code 31 by itself will not prevent the engine from starting or cause poor performance. The exhaust gas recirculation system does not start to work until the engine is actually up and running. You can unplug the EGR sensor plug and the problem you are now having will not go away. The code 31 will shut off the EGR system and the computer will disable and bypass any EGR functions and run without the EGR functioning.


My other comments not necessarily related to you problem, but possibly helpful.

Here's a book that will get you started with how the Ford electronic engine control or "computer" works.

Ford Fuel Injection & Electronic Engine Control 1988-1993 by Charles Probst :ISBN 0-8376-0301-3.

It's about $25-$50 from Borders.com see http://www.amazon.com/ . Select books and then select search. Use the ISBN number (without dashes or spaces) to do a search. Try searching using M-1832-Z1 instead of the ISBN number if you don’t get any positive results. You may only be able to find a used one, since the book is as old as the cars it covers. Or you order it from your Ford dealer as SVO part no. M-1832-Z1.

Use the ISBN number and your local library can get you a loaner copy for free. Only thing is you are limited to keeping the book for two weeks. It is very good, and I found it to be very helpful.

1mustyLSC said:

I tested everything (again), was all within spec as it was before. Dumped codes again, idled like complete crap as it has been.

Since you said it will throw those codes if the PIP or TFI is bad/going bad I bit the bullet and dropped a new autozone distributor in (steel gear of course) and....

ITS RUNS LIKE A TOP!!! Idles smooth, no jerking, hesitation, backfiring or anything!

I really can't thank you enough, you're really the mechanical wizard everyone says you are! Thanks for your time, very descriptive instructions, and all your solutions to what it could be. I'm gonna lay a nice burnout for you! (In Mexico of course haha)

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I am sure glad that you got it fixed and it is running good now. Lets hope that it stays that way for a long time...
Summer is here, enjoy your Mustang!