Engine Car at mechanic, need second opinion info to help get it home

7991LXnSHO

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Long story short as possible. I have a 91 5.0 that I had to send to Ford to get re assembled and running when I moved to another town and lost the parking space.
The fuel is probably 3+ years old, and may not have had StaBil in it. (Life and health happened.)
So now the Mustang specialist at Ford has it back together, (YEAH!) But it runs rough, can pop or back fire out the intake, and the headers hit 410 degrees in less than 5 minutes of running. (BOO!)
1. Does this sound about right for a 3 year old, 1/4 tank of gas? I know what old gas runs like in carbs and bet the fuel needs changed.

2. Although it is appearing to run rich, the mechanic reports the fuel rail pressure gauge (I left it on for tuning) read in the 20’s. I will guess he did not remove the vacuum line for this reading. About what would the pressure be at idle with the line on?
What should fuel pressure read/be set to with the line off and blocked?

3. Please confirm that a B or E cam, headers, ported heads and intake, and high flow cats and exhaust will run fine with a stock 9AL computer, and will even idle fine (with some cam lope) when setting idle like @jrichker ‘s instructions. (Although a tune would be nice.)

More info -
It ran great before I took it apart for a harmonic balancer, a new air/smog pump, a few other minor things, and let it set too long.
I can not give you key on engine off or running codes. Supposedly their OBD 1 code reader is old and does not work half the time, and if the dash light did not go on, he did not think there were codes he could pull with the paperclip method. I have had many codes without the CEL light ever coming on before.
Thanks for confirming my memory about these items.
 
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General karthief

wonder how much it would cost to ship you a pair
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I know the a9l computer will work with those mods, sounds like your 'ford mustang' specialist ain't so special if he doesn't know what to do if he can't pull codes, print a copy of jrichker's surging idle checklist and give it to him, that and fresh gas will help him out.
(I can't believe he didn't put fresh gas in it and don't know how to check fuel pressure) popping in the intake suggests a lean condition. Low fuel pressure or timing likely off.
 

7991LXnSHO

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I am thinking the fuel is first. He wants to drop the tank
and flush it to insure all the junk is out. The car looks almost good enough for large shows, no rust, so I do not mind the tank being done right, even though I asked them to use a siphon pump or remove the pressure gauge and get the fur (i typed fuel) out from the rail and powering the built in pump. It's only money.

Can anyone chip in on what the fuel pressure should be at idle with the vacuum line hooked to the regulator? What a about when the line I'd off and capped,, when it is adjusted?

I do not think timing was changed while the car was apart, but the timing marks are not with the balancer mark. We had a long discussion on the old board when I saw the new balancer was the same way and the timing.light (without the Spout in) and a piston stop say TDC is at the hole in the tab, not by the marks.

Funny fact. The Carfax says the odometer has gone around three times, twice, or reads actual mileage. It is in that chronological order. Maybe it is like the red Belvedere named Christine.

When I got it, the computer kept changing the codes it spit out, most of which were absolutely goofy. The same dealership checked the constant ones out while getting me a salvage computer from down the road. Then I had a place suggested on here replace the age fried caps and something else so I have a spare.
 
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jrichker

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Check fuel pressure:

The local auto parts store may rent or loan a fuel pressure test gauge if you don't have one.

Disconnect the vacuum line from the fuel pressure regulator. Check it for evidence of fuel present in the line by removing it and blowing air through it. If you find fuel, the fuel pressure regulator has failed. Reinstall the line; leave the fuel pressure regulator end of the vacuum line disconnected. Then cap or plug the open end of the vacuum line and stow it out of the way.

Connect the fuel pressure test gauge to the Schrader port located just behind the alternator.

Turn the ignition switch on & start the engine. Observe the pressure: you should see 38-41 PSI at idle.

Turn the ignition off; reconnect the vacuum line to the fuel pressure regulator. Then disconnect the fuel pressure test gauge. Watch out for squirting gas when you do this.

Fuel pressure with the vacuum line connected (very bad idea to test it this way) will run 28-32 PSI. Variations in engine vacuum will cause variations in fuel pressure if testing is done with the vacuum line connected and the engine is running.

Fuel pump pressure test

Disconnect the larger of the two fuel lines up by the Schrader valve. It is the return line and does not have the Schrader valve on it. Find a piece of rubber fuel hose and clamp it on the return line coming from the regulator. Stick a bolt in the other end of the hose and make sure that all your connections are tight and leak proof as possible. When this powers up, you don't want fuel squirting everywhere. Hook up the fuel pressure test gauge. Turn the ignition switch on and watch for leaks. You may want to use a helper inside the car to cut the switch off quickly if you have a leak. To trick the fuel pump into running, find the ECC test connector and jump the connector in the Upper RH corner to ground.





Putting the distributor back in and setting the timing.

Revised 28-Apr-2018 to add photo & description of the SPOUT connector and SPOUT jumper .

You can forget about anything beyond this point if you don't have access to a timing light. You will never get the timing set right without one.

Note: If you don't have access to a timing light, most of the larger auto parts stores will rent or loan one if you have a credit card or leave a cash deposit.



Putting the distributor back in is fairly simple. Pull #1 sparkplug, put your finger in the sparkplug hole, crank the engine until you feel compression. Then line up the TDC mark on the balancer with the pointer on the engine block.

The distributor starts out with the #1 plug wire lined up at about 12:00 with you facing it. Align the rotor to about 11:00, since it will turn clockwise as it slides into place.

Align the distributor rotor up with the #1 position marked on the cap, slide the distributor down into the block, (you may have to wiggle the rotor slightly to get the gear to engage) and then note where the rotor is pointing.
If it still lines up with #1 position on the cap, install the clamp and bolt. If not, pull it out and turn 1 tooth forwards or backwards and try again. Put the #1 spark plug back in and tighten it down, put the clamp on the distributor, but don't tighten it too much, as you will have to move the distributor to set the timing. Note that there is no such thing as one tooth off on a 5.0 Mustang if you follow the spark plug wire order on the distributor cap. If it doesn't align perfectly with #1 position, you can turn the distributor until it does. The only problem is that if you are too far one way or the other, you can't turn the distributor enough to get the 10-14 degree optimum timing range. If the TFI prevents the distributor from being turned enough to get 14°, there is a simple fix. Pull the distributor out and turn the rotor 1 tooth counterclockwise Don't move the wires from the positions shown on the cap on fuel injected engines!!!! The #1 position cast into the cap MUST have the spark plug wire for #1 cylinder in it. Do it differently and the timing for the fuel injectors will be off. The computer uses the PIP sensor to time injector operation by sensing the wide slot in the PIP sensor shutter wheel. If the injector timing of #1 and the firing of #1 do not occur at the right time, the injector timing for all other cylinders will be affected.

Setting the timing:
Paint the mark on the harmonic balancer with paint -choose 10 degrees BTC or 14 degrees BTC or something else if you have NO2 or other power adder. I try to paint TDC red, 10 degrees BTC white and 14 degrees BTC blue.

10 degrees BTC is towards the drivers side marks.

Note: setting the timing beyond the 10 degree mark will give you a little more low speed acceleration. BUT you will need to run 93 octane to avoid pinging and engine damage. Pinging is very hard to hear at full throttle, so it could be present and you would not hear it.

Simplified diagram of what it looks like. Not all the marks are shown for ease of viewing.

ATC ' ' ' ' ' ' ' ' ' '!' ' ' ' ' ' ' ' ' ' BTC
---------------- > Direction of Rotation as viewed standing in front of the engine.

The ' is 2 degrees.
The ! is TDC
The ' is 10 degrees BTC
Set the timing 5 marks BTC. Or if you prefer, 5 marks towards the driver's side to get 10 degrees.

To get 14 degrees, set it 7 marks BTC. Or if you prefer, 7 marks towards the driver's side to get 14 degrees.

The paint marks you make are your friends if you do it correctly. They are much easier to see than the marks machined into the harmonic balancer hub.

At this point hook up all the wires, get out the timing light. Connect timing light up to battery & #1 spark plug. Then start the engine.

Remove the SPOUT jumper
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It is the 2 pin rectangular plug on the distributor wiring harness. Only the EFI Mustang engines have a SPOUT. If yours is not EFI, check for a SPOUT: if you don’t find one, skip any instructions regarding the SPOUT. The SPOUT (Spark Out) enables the computer to control the spark advance. When the SPOUT is removed, the ignition timing reverts to the base ignition timing set by either the spark rod inside the distributor or the physical position of the distributor.

Warning: there are only two places the SPOUT should be when you time the engine. The first place is in your pocket while you are setting the timing and the second is back in the harness when you finish. The little bugger is too easy to lose and too hard to find a replacement.
Start engine, loosen distributor hold down with a 1/2" universal socket. Shine the timing light on the marks and turn the distributor until the mark lines up with the edge of the timing pointer. Tighten down the distributor hold down bolt, Replace the SPOUT connector and you are done.

The HO firing order is 1-3-7-2-6-5-4-8.
Non HO firing order is 1-5-4-2-6-3-7-8

 

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Mustang5L5

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With the vac line on, pressure should still be around 35psi give or take. A quick blip of the throttle and it should snap up to 39 psi.

I have a cowl mounted gauge and I've never seen the pressure under 35psi at all...well maybe when the engine is off.

My guess is you have a fuel supply issue. Either pump, blockage or bad regulator.
 

7991LXnSHO

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I have sent a link of this discussion to the service manager and a link to @jrichker ’s surging idle checklist. I will let you know what happens after the fuel is flushed. If it still does not run well with new gas, I have been told they will go into diagnostic mode (including codes), and will find out for sure what went wrong while it sat too long. Thanks for confirming my memory on these items!
 

Noobz347

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If he drops the tank, change the pump.

If there's nothing wrong with the pump, disconnect the fuel supply line at the rail and pump the fuel tank dry. Re-connect and fill with new gas.


Jr's image above shows you how to run the pump continuously until the fuel tank is empty.


Once again, if he drops the tank (assuming you're paying for these man hours) then replace the pump! They're cheap!
 
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7991LXnSHO

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I got my Mustang home today by a borrowed tow dolly. Ford replaced the fuel and filter, deciding the pump was fine. They cleaned the BBK MAF (which has few miles on it). They reset the timing by hand so it ran a little better, but now surges and still runs like crud, (the timing mark is very suspect). They left the new BBK cat H pipe slid back (so open headers) so I can confirm the new cats are not an exhaust blockage after it is running right and I do not melt them in the mean time. They set the fuel pressure according to instructions by @jrichker . And they or the tow place chipped a big piece of paint off the driver’s door strip! :-(

I did get the KOEO and CM test run and failed to get a KOER test result - probably because of how bad it surged and misfired (with some intake popping), and the check engine light was cycling with the surging.
I will check the vacuum and timing mark next, along with looking for a loose MAF connector, hoses, and visual inspection.. (The surging idle checklist is in my mind, but code 66 may be the issue.)
So here are the codes tonight.

11
10
66 - MAF fault, below minimum voltage?
95 - Fuel pump secondary circuit fault?
 

jrichker

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Code 66 or 157 MAF below minimum test voltage.

Revised 15 mar 2018 to clarify how to do resistance checks on the MAF wiring

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 wiring harness connector, wire side
71316.gif


Computer wiring harness connector, computer side side
88243.gif




Diagrams courtesy of Tmoss and Stang&2Birds

ECC Diagram for 88-90 5.0 Mustangs
88-91_5.0_EEC_Wiring_Diagram.gif


ECC Diagram for 91-93 5.0 Mustangs
91-93_5.0_EEC_Wiring_Diagram.gif


94-95 Diagram for 94-95 5.0 Mustangs[/b]
94-95_5.0_EEC_Wiring_Diagram.gif



How the MAF works

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

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.


Check the resistance of the MAF signal wiring
For the next 2 checks make your measurement with the MAF disconnected from the wiring harness.

Pin D on the MAF wiring harness and pin 50 on the computer (dark blue/orange wire) should be less than 2 ohms. Pin C on the MAF wiring harness 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.

Reconnect the MAF to the wiring harness and proceed to the next section.

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

Code 96 causes & tests 91-93 models. – KOEO- Fuel pump monitor circuit shows no power - Fuel pump relay or battery power feed was open - Power / Fuel Pump Circuits. The fuel pump circuit lost power at one time or another.

Revised 24-Mar-2017 to add text about the A/C Wide Open Throttle relay and using the wire colors to identify which relay is the fuel pump relay

Clear the codes by disconnecting the battery and turning on the headlights for about 5 minutes before reconnecting the battery. This will clear any remaining codes. Drive the car for several days and dump the codes again. In many cases, this clears the 96 code.

Look for a failing fuel pump relay, bad connections or broken wiring. On 91 model cars, the fuel pump relay is under the driver’s seat. The fuel pump relay is located under the Mass Air Meter on Fox bodied stangs built after 91. It can be confused with the A/C Wide Open Throttle relay which is in the same area. Use the wire colors as shown in the diagram below to identify which relay is the fuel pump relay.

Diagram of the fuel pump wiring for 91-93 cars.


Look for power at the fuel pump - the fuel pump has a connector at the rear of the car with a pink/black wire and a black wire that goes to the fuel pump. The pink/black wire should be hot when the test connector is jumpered to the test position. To trick the fuel pump into running, find the ECC test connector and jump the connector in the lower RH corner to ground. No voltage when jumpered, check the fuel pump relay and fuse links.




Power feed: Look for 12 volts at the pink/black wire (power source for fuel pump relay). No voltage or low voltage, bad fuse link, bad wiring, or connections. Remember that on 92 or later models the fuel pump relay is located under the Mass Air meter. Watch out for the WOT A/C control relay on these cars, as it is located in the same place and can easily be mistaken for the fuel pump relay.

Relay: Turn on the key and jumper the ECC test connector as previously described. Look for 12 volts at the dark green\yellow wire (relay controlled power for the fuel pump). No voltage there means that the relay has failed, or there is a broken wire in the relay control circuit. Be sure to closely check the condition of the relay, wiring & socket for corrosion and damage.



91-93 Models:
Using the diagram, check the dark green/yellow wire from the fuel pump relay: you should see 12 volts or so. If not the relay has failed or is intermittent. Check the inertia switch: on a hatch it is on the driver’s side by the taillight. Look for a black rubber plug that pops out: if you don't find it, then loosen up the plastic trim. Check for voltage on both sides of the switch. If there is voltage on both sides, then check the Pink/black wire on the fuel pump relay: it is the power feed to the fuel pump. Good voltage there, then the fuel pump is the likely culprit since it is getting power. No voltage there, check the Pink/black wire, it is the power feed to the fuel pump relay & has a fuse link in it. Good voltage there & at the dark green/yellow wire, swap the relay.

All testing is done with the ignition switch in the Run position. Do not forget this crucial step.

The pink/black wire should have the same voltage as the battery positive terminal +/- 0.25 volt. If not, then the fuse link for the fuel pump has opened up.

With the test jumper in place the green/yellow wire should be the same voltage as the pink/black wire +/- 0.25 volt.

If not, look at the red wire: should have the same voltage as the battery positive terminal +/- 0.25 volt.
If not, then check the yellow wire on the EEC relay located on top of the computer. This one is hard to get to. It should have the same voltage as the battery positive terminal +/- 0.25 volt. If not, then the fuse link for the computer has opened up.

If the red wire does not have the same voltage as the battery positive terminal +/- 0.25 volt and the yellow wire on the EEC relay does, then check the red/green wire on the EEC relay. It should have the same voltage as the battery positive terminal +/- 0.25 volt. If not, then the ignition switch is defective or the fuse link in the ignition wiring harness has opened up, or the EEC relay is defective.

All testing is done with the ignition switch in the Run position. Do not forget this crucial step.

The pink/black wire s should have the same voltage as the battery positive terminal +/- 0.25 volt. If not, then the fuse link for the fuel pump has opened up.

With the test jumper in place the green/yellow wire should be the same voltage as the pink/black wire +/- 0.25 volt.

If not, look at the red wire: should have the same voltage as the battery positive terminal +/- 0.25 volt.
If not, then check the yellow wire on the EEC relay located on top of the computer. This one is hard to get to. It should have the same voltage as the battery positive terminal +/- 0.25 volt. If not, then the fuse link for the computer has opened up.

If the red wire does not have the same voltage as the battery positive terminal +/- 0.25 volt and the yellow wire on the EEC relay does, then check the red/green wire on the EEC relay. It should have the same voltage as the battery positive terminal +/- 0.25 volt. If not, then the ignition switch is defective or the fuse link in the ignition wiring harness has opened up, or the EEC relay is defective.

Diagram courtesy of Tmoss & Stang&2birds
IgnitionSwitchWiring.gif
 

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7991LXnSHO

Now I want a 10 year badge
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Thanks, guys for the fast responses!
The fuel pressure was supposed to be fine with the vac line unhooked. And the vacuum is not consistent enough to get any reading hooked up. This was a red herring from Ford.
J - thanks for reposting the MAF worksheet, I have one printed out, but this will make sure I have the newest version.

Right now, it runs like a third round demo derby car’s motor. Ford should have checked the MAF code out as long as they kept it, so I am not taking anything for granted as I check it out.
 

7991LXnSHO

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I found a nice day and not too bad of back for a little detective work.

1. The MAF connector was not even close to being plugged in well! Red to black reads close to the battery voltage. Wires C-D are now 1.14 v at a bit over 1000 RPM, but will drop to zero periodically. I am replacing the BBK meter with a C&L housing (76 mm, for the 24 Lb injectors) and a new Delphi sensor to avoid using the 27 year old factory sensor. I also am weary that this is the second BBK sensor i bought that went after too few miles. Ford had removed it to clean it, but who knows how well. ( @jrichker )

2. The timing was set at After, not Before, top dead center, but supposedly "where it ran best". I was not sure of my piston stop and the timing marking after it was parked, but the tape is correct. Now it is running much better at 12 Btdc, and the headers are not glowing or stinking to high heaven. ( @General karthief ) I also spins up right. And even with Ford leaving the H pipe slid back, open for diagnostics, it almost sounds like it did with the old flowmasters instead of a demo derby car.

3. The P trap shape part of the smog pump hose was installed resting against the passenger header! I rotated that as far as I could to avoid that smoke.

4. The brass L fitting for the fuel pressure meter was dripping under pre-start pressure, which was new. That needs to go after I get it tuned. Can someone tell me where to get the right Schrader valve and cap that is fuel resistant? Mine dissapeared and I hope it is something the FLAPS carries.

Now it runs, I need to get out with my Surging Idle Checklist just to make sure everything is OK and I can idle it back down a little more.