Multiple Issues With 93 Mustang

[79MercCapri93]

I have a 93 Mustang GT, and I am having multiple issues with it right now. I bought the car a couple years back from an old friend of mine who let it sit for about a year or so in a barn down in South Carolina. Originally the car belonged to my brother and i ended up getting it some time later and have been trying to get it back up and running to get on the road again. Here's a list of everything on the car at this time before i get into the problems.

302 with no engine work done to it
Set of BBK shorty headers
BBK high flow H-Pipe
Flow Master cat back
Ford Racing under drive pulleys
8MM Spark Plug Wires
70MM Throttle Body and Spacer
70MM MAF from a SN95 Mustang (replaced the old one to run the bigger TB and Spacer and the old MAF was bad) MAF is set up for 19# injectors
BBK Cold air intake
Upper intake has been opened up to support the larger MAF, TB, and spacer
King Cobra Clutch
Stock 19# injectors

It used to have a Fluidyne radiator, until a couple of days ago because it was running way to hot and even with my garage door open i was sweating my ass off. I changed it to a stock radiator i bought from Autozone as well as a 160 degree thermostat.


So, as i said the car had been sitting for some time and had to replace quiet a bit of stuff already, I changed the exhaust to a set of Flowmaster cat backs i got from my father in law since the exhaust on it was rusted out, changed the flywheel because it was not the right balance and was making the car shake (have not gotten a chance to change out the balancer up front yet). and the bell housing was cracked so i had to replace that as well.

Before i left on my deployment i checked the radiator and it had brown sludge inside of it and the motor and so when i got back a couple of months ago i flushed the system in hopes that it would get it cleaned out, it did to an extent but the car still ran hot so i changed out the radiator and added the thermostat since there was not one before as well as a new temperature sensor. The car seems to run a little bit better as far as the heat goes, but im still having issues with the it seeming to run real rich or something. The oil slightly smells like gas, but with the car running the oil pressure gauge is good for a bit and then it starts floating from a normal medium down towards 0 and will constantly jump around every so often between that. I changed out the oil pressure sensor/ sending unit and thought it might do the trick but long behold, nothing happened. But letting the car run even with the garage door open, after a couple of minutes the exhaust is so bad it begins to burn your eyes. It also sounded like there was a flutter on the passenger side of the motor and that there might be a slight air leak somewhere around the intake and TB, but im almost wondering if the guy that ported out the intake might have left a slight lip on the inside thats catching the air. But when i turn off the car it sounds like its pulling air real hard and then shuts off. Theres no check engine lights on and im at a complete loss with whats going on.

Any help would be greatly appreciate.

V/R
Chris

 

[jrichker]

Step 1.) Dump the codes
Step 2.) Do a cylinder balance test.

See the tech note below for both 1 & 2...

Cylinder balance test:

Revised 25 March 2012 to add necessity allowing the KOEO tests to finish before starting the engine and the need for a properly functioning IAB/IAC to run the cylinder balance test.

The computer has a cylinder balance test that helps locate cylinder 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 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 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.

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 1400-1600 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. Use a jumper wire or paper clip to put the computer into test mode. Let it finish the Key On Engine Off (KOEO) code dump. Start the engine and let it go through the normal diagnostic tests, then quickly press the throttle to the floor. Remember to keep the clutch pedal (5 speed) depressed to the floor during the test. The engine RPM should exceed 2500 RPM's for a brief second. The engine RPM's will increase to about 1450-1600 RPM and hold steady. The engine will shut off power to each injector, one at a time. 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


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. 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, 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.

See the link to my site for details on how to build your own blow down type compression tester.

 

[79MercCapri93]

Greatly appreciate it, I am assuming that this is something that would be a lot easier done if i had another person to start the vehicle and while i use a test light? or can this be a one person job?

 

[jrichker]

Greatly appreciate it, I am assuming that this is something that would be a lot easier done if i had another person to start the vehicle and while i use a test light? or can this be a one person job?

It is a one person job if the car has a working check engine light. Install the test jumper, turn the ignition to run, but do not start the car. Take note of the flashes and remember that it takes two groups of flashes to make one code. After all the codes have dumped, start the engine and repeat the process to get the engine running codes.

 

[79MercCapri93]

i got a code 67, 10, and 11 KOEO in that order, i tried getting any codes with the vehicle running but i didnt get any codes at all

 

[79MercCapri93]

the mustang also has the stock T-5 transmission in it, just incase that needs to be known as far as the codes go

 

[79MercCapri93]

finally got codes with the car running, got a 6 off the bat and looks like its only running on 6 out of the 8 cylinders which would explain quiet a few problems

 

[79MercCapri93]

changed out the spark plugs and the wires and did the cylinder balance test and everything passed, cleared out the all the old codes in the system and nothing came back. seems to be running a little bit better, still seems to run a little rich but not as bad as it was before that i can tell right now, but still cant figure out the floating oil pressure gauge, could it possibly be just the gauges messed up or could it have something to be with the oil pump?

 

[jrichker]

Cars without catalytic converters will stink because there are no converters to remove the pollutants that cause the stink.

The following is a Quote from Charles O. Probst, Ford fuel Injection & Electronic Engine control:
"When the mixture is lean, the exhaust gas has oxygen, about the same amount as the ambient air. So the sensor will generate less than 400 Millivolts. Remember lean = less voltage.

When the mixture is rich, there's less oxygen in the exhaust than in the ambient air , so voltage is generated between the two sides of the tip. The voltage is greater than 600 millivolts. Remember rich = more voltage.

Here's a tip: the newer the sensor, the more the voltage changes, swinging from as low as 0.1 volt to as much as 0.9 volt. As an oxygen sensor ages, the voltage changes get smaller and slower - the voltage change lags behind the change in exhaust gas oxygen.

Because the oxygen sensor generates its own voltage, never apply voltage and never measure resistance of the sensor circuit. To measure voltage signals, use an analog voltmeter with a high input impedance, at least 10 megohms. Remember, a digital voltmeter will average a changing voltage." End Quote

Testing the O2 sensors 87-93 5.0 Mustangs
Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. You'll have to pull the passenger side kick panel off to gain access to the computer connector. Remove the plastic wiring cover to get to the back side of the wiring. Use a safety pin or paper clip to probe the connections from the rear.

87-90 5.0 Mustangs:
Computer pin 43 Dark blue/Lt green – LH O2 sensor
Computer pin 29 Dark Green/Pink – RH O2 sensor
The computer pins are 29 (LH O2 with a dark green/pink wire) and 43 (RH O2 with a dark blue/pink wire). Use the ground next to the computer to ground the voltmeter. The O2 sensor voltage should switch between .2-.9 volt at idle.

91-93 5.0 Mustangs:
Computer pin 43 Red/Black – LH O2 sensor
Computer pin 29 Gray/Lt blue – RH O2 sensor
The computer pins are 29 (LH O2 with a Gray/Lt blue wire) and 43 (RH O2 with a Red/Black wire). Use the ground next to the computer to ground the voltmeter. The O2 sensor voltage should switch between .2-.9 volt at idle.


Testing the O2 sensors 94-95 5.0 Mustangs
Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. You'll have to pull the passenger side kick panel off to gain access to the computer connector. Remove the plastic wiring cover to get to the back side of the wiring. Use a safety pin or paper clip to probe the connections from the rear. The computer pins are 29 (LH O2 with a red/black wire) and 27 (RH O2 with a gray/lt blue wire). Use pin 32 (gray/red wire) to ground the voltmeter. The O2 sensor voltage should switch between .2-.9 volt at idle.


Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter. Do not attempt to measure the resistance of the O2 sensors, it may damage them.

Testing the O2 sensor wiring harness
Most of the common multimeters have a resistance scale. Be sure the O2 sensors are disconnected and measure the resistance from the O2 sensor body harness to the pins on the computer. Using the Low Ohms range (usually 200 Ohms) you should see less than 1.5 Ohms.

87-90 5.0 Mustangs:
Computer pin 43 Dark blue/Lt green – LH O2 sensor
Computer pin 29 Dark Green/Pink – RH O2 sensor
Disconnect the connector from the O2 sensor and measure the resistance:
From the Dark blue/Lt green wire in the LH O2 sensor harness and the Dark blue/Lt green wire on the computer pin 43
From the Dark Green/Pink wire on the RH Os sensor harness and the Dark Green/Pink wire on the computer pin 43

91-93 5.0 Mustangs:
Computer pin 43 Red/Black – LH O2 sensor
Computer pin 29 Gray/Lt blue – RH O2 sensor
Disconnect the connector from the O2 sensor and measure the resistance:
From the Red/Black wire in the LH O2 sensor harness and the Red/Black wire on the computer pin 43
From the Dark Green/Pink Gray/Lt blue wire on the RH Os sensor harness and the Gray/Lt blue wire on the computer pin 29

94-95 5.0 Mustangs:
Computer pin 29 Red/Black – LH O2 sensor
Computer pin 27 Gray/Lt blue – RH O2 sensor
From the Red/Black wire in the LH O2 sensor harness and the Red/Black wire on the computer pin 29
From the Dark Green/Pink Gray/Lt blue wire on the RH Os sensor harness and the Gray/Lt blue wire on the computer pin 27

There is a connector between the body harness and the O2 sensor harness. Make sure the connectors are mated together, the contacts and wiring are not damaged and the contacts are clean and not coated with oil.

The O2 sensor ground (orange wire with a ring terminal on it) is in the wiring harness for the fuel injection wiring. I grounded mine to one of the intake manifold bolts

Make sure you have the proper 3 wire O2 sensors. Only the 4 cylinder cars used a 4 wire sensor, which is not compatible with the V8 wiring harness.

Replace the O2 sensors in pairs if replacement is indicated. If one is weak or bad, the other one probably isn't far behind.

If you get only code 41 and have changed the sensor, look for vacuum leaks. This is especially true if you are having idle problems. The small plastic tubing is very brittle after many years of the heating it receives. Replace the tubing and check the PVC and the hoses connected to it.
A secondary problem with only a code 41 is for cars with an intact smog pump and cats. If the tube on the back of the heads clogs up the driver’s side, all the air from the smog pump gets dumped into one side. This excess air upsets the O2 sensor calibration and can set a false code 41. The cure is to remove the crossover tube and thoroughly clean the insides so that there is no carbon blocking the free flow of air to both heads.

 

[79MercCapri93]

Just got a chance to mess with the car, ran it again for codes and got a 41 and a 91, could that still deal with the smog pump? Or is it more likely time for new 02 sensors? I'm trying to get a multimeter this weekend, thank you again for all of the help!

 

[79MercCapri93]

Just got a chance to mess with the car, ran it again for codes and got a 41 and a 91, could that still deal with the smog pump? Or is it more likely time for new 02 sensors? I'm trying to get a multimeter this weekend, thank you again for all of the help!

 

[jrichker]

Check the voltages coming out of the O2 sensors if you have any doubts. Then check the O2 sensor harness resistance between the O2 sensor socket and the computer.. Be sure to disconnect the O2 sensors from the harness when you check the resistance. The ohms function applies a test voltage that can damage O2 sensors.

Otherwise, replace the O2 sensors. At $40+ each, owners often avoid replacing them.

 

[79MercCapri93]

lookin like im going to be replacing the 02 sensors, hopefully this weekend coming up since i have off for memorial day. im also looking at changing out the harmonic balancer since the car has a shake to it when i press the gas, looked like someone had the wrong weighted flexplate and balancer before, got the flexplate changed out and now i just have to do the balancer. Do i just need a puller to change out the balancer and put the new one on?

 

[jrichker]

The harmonic balancer requires a puller to get it started moving. Usually once it breaks loose, you can pull it off by hand if things aren't rusty or full of burrs. Use a thick coating of Never Seeze on the crankshaft when you put the new balancer on. It will protect the crankshaft from corrosion and make removal easier if you have pull the balancer again.

 

[79MercCapri93]

once the balancer is off, for the install of the new one, am i good to just bolt it back down or is it recommended to use an installer for putting the new one on?

 

[jrichker]

No puller or pusher tool needed for balancer installation. Just muscle and a big breaker bar...

 

[79MercCapri93]

was able to get the balancer off, after i got the 15/16 bolt off, the balancer came off just with a slight pull using my hands, got the new one on now, but the car still has a shake to it, and im still having issues trying to isolate where that shake is coming from as well as what could be causing the oil pressure gauge to fluxate after the car idles for a couple of minutes.

 

[79MercCapri93]

i also replaced the O2 sensors as well, now i just have to figure out the oil pressure gauge fluxuation, the shake that the car has and the temperature gauge. which doesnt read above 130 right now, but i have a 160 degree thermostat in and that keeps opening up from the heat which makes no sense on why it would only read 130

 

[79MercCapri93]

i fired up the car again and found that even when its not throttled its not right. the only way i can really describe it as if its thudding? as it fires, not like a knock, but more of one of the cylinders isnt firing correctly. I ran the code scanner on it and its not popping any codes. could this possibly be a lifter thats stuck? i looked at some other threads on forums and saw that people are saying if it shakes at idle that its a possible stuck lifter, is this signs of that? thank you again for all of the help youve given me!

 

[jrichker]

A vacuum gauge will detect a sticking valve or lifter. Intake valves and lifters typically cause a 5-10 sweep in vacuum if they are sticky. Every time the engine comes up on compression, the vacuum gauge indicator will do the sweep thing.

The simplest way to find sticking valves is with a cylinder balance test that I recommended in an earlier post.