New Here Nee D Some Help 89 Fox Body


New Member
Jan 20, 2014
Hey everyone. I'm new to the site so bear with me. I need some help with diagnosing my car. I'm getting a really strong exhaust smell inside the car lately. When you get on the gas it's worse and has a strong carbon smell. Here's the history. Bought the car and rebuilt the motor. Clevite 77 kit bored .30 over with a b cam, cobra upper and lower intake. Flow master delta 40 mufflers with tips factory h pipe hollowed out.
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Do you have a turn down exhaust or does it go to straight pipes out the back of the car?

The quick and dirty solution is to put catalytic converters back on the car. A more indirect solution would be to modify the exhaust and/or digitally tune for being catless.
What about blow by from the crankcase. If thats leaking into the engine compartment it could be getting into the interior through any small holes in the firewall/floorboard etc...

Are you running full PVC setup or crankcase breathers?
Could the tps sensor har anything to do with this..? I ran the car for years with turn downs and have had the tips on for a couple years . It's just started smelling so strong in the past six months..
If its a hatchback and the hatch weatherstripping is bad or not sealing right, the exhaust (and any engine compartment fumes) can get sucked into the interior due to the low pressure that gets created by aerodynamics behind the car as you're moving down the road.
Yeah all these are factors I've been trying to consider.. I rebuilt the car 7 years ago almost 8. Have about 90,000 miles on the rebuilt engine.. Was reading about the blow by you were talking about.. Could it be time for a rebuild? Cause it is rediculously strong smelling in the mornings when I let the car warm up there is a lot of visual exhaust coming out of the tailpipes specifically on the right side..
By blow by I meant compression leaking past the piston rings and into the crankcase. If the case is not sealed good or there is a problem with your PCV system, the blow by can leak exhaust and gas fumes into the engine bay which can then get into the interior.
i recently replaced the filter at the back of the intake for the pc. it was clogged up and blowing oil. how would i go about ensuring the crank case is sealed or what could be wrong with the pcv?
Dump the codes: Codes may be present even if the Check Engine Light (CEL) isn't on.

Dumping the computer diagnostic codes on 86-95 Mustangs

Revised 26-July-2011. Added need to make sure the clutch is pressed when dumping codes.

Codes may be present even if the check engine light hasn’t come on, so be sure to check for them.

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.

Post the codes you get and I will post 86-93 model 5.0 Mustang specific code definitions and fixes. I do not have a complete listing for 94-95 model 5.0 Mustangs at this time.

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



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 driveablity 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, and clutch (if present) is pressed 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 Equus - Digital Ford Code Reader (3145It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $22-$36.
Most common fault is the crossover tube at the back of the heads gets carboned up.

Care of @jrichker

Codes 44 & 94 - AIR system inoperative - Air Injection. Check vacuum lines for leaks, & cracks.

Revised 28-Oct-2009 to correct code definitions and operation.

Code 44 RH side air not functioning.
Code 94 LH side air not functioning.

The computer uses the change in the O2 sensor readings to detect operation of the Thermactor control valves. When the dump valve opens, it reduces the O2 readings in the exhaust system. Then it closes the dump valve and the O2 readings increase. By toggling the dump valve (TAB), the computer tests for the 44/94 codes.

Failure mode is usually due to a clogged air crossover tube, where one or both sides of the tube clog with carbon. The air crossover tube mounts on the back of the cylinder heads and supplies air to each of the Thermactor air passages cast into the cylinder heads. When the heads do not get the proper air delivery, they set codes 44 & 94, depending on which passage is clogged. It is possible to get both 44 & 94, which would suggest that the air pump orcontrol valves are not working correctly, or the crossover tube is full of carbon or missing.

Check to make sure that some one hasn't put a plug in the rear crossover tube mount on the cylinder head. The front ports are plugged, and occasionally someone will put the heads on and not notice the head is supposed to be installed with the crossover tube plug in the front.

Testing the system:
Disconnect the big hose from smog pump: with the engine running you should feel air output. Reconnect
the smog pump hose & apply vacuum to the first vacuum controlled valve: Its purpose is to either dump
the pump's output to the atmosphere or pass it to the next valve.

The next vacuum controlled valve directs the air to either the cylinder heads when the engine is cold or
to the catalytic converter when the engine is warm. Disconnect the big hoses from the back side of the
vacuum controlled valve and start the engine. Apply vacuum to the valve and see if the airflow changes
from one hose to the next.

The two electrical controlled vacuum valves mounted on the rear of the passenger side wheel well turn the
vacuum on & off under computer control. Check to see that both valves have +12 volts on the red wire.
Then ground the white/red wire and the first solenoid should open and pass vacuum. Do the same thing to
the light green/black wire on the second solenoid and it should open and pass vacuum.

Remember that the computer does not source power for any actuator or relay, but provides the ground
necessary to complete the circuit. That means one side of the circuit will always be hot, and the other side
will go to ground or below 1 volt as the computer switches on that circuit.

The computer provides the ground to complete the circuit to power the solenoid valve that turns the
vacuum on or off. The computer is located under the passenger side kick panel. Remove the kick panel &
the cover over the computer wiring connector pins. Check Pin 38 Solenoid valve #1 that provides vacuum
to the first Thermactor control valve for a switch from 12-14 volts to 1 volt or less. Do the same with pin
32 solenoid valve #2 that provides vacuum to the second Thermactor control valve. Starting the engine
with the computer jumpered to self test mode will cause all the actuators to toggle on and off. If after
doing this and you see no switching of the voltage on and off, you can start testing the wiring for shorts to
ground and broken wiring. An Ohm check to ground with the computer connector disconnected & the
solenoid valves disconnected should show open circuit between the pin 32 and ground and again on pin 38
and ground. In like manner, there should be less than 1 ohm between pin 32 andsolenoid valve #2 and pin
38 & Solenoid valve #1.

If after checking the resistance of the wiring & you are sure that there are no wiring faults, start looking at the
solenoid valves. If you disconnect them, you can jumper power & ground to them to verify operation. Power &
ground supplied should turn on the vacuum flow, remove either one and the vacuum should stop flowing.

Typical resistance of the solenoid valvesis in the range of 20-70 Ohms.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host)

See a very nice drawing of the Thermactor Air System (smog pump) plumbing

If you have a catalytic converter H pipe, you need to fix these codes. If you don't, then don't worry about them
i dont have a smog pump. it was removed, but the rail that runs to both of the heads is still in place hooked to both heads. there is a fitting at the end that runs to the smog pump hose that has been mashed and welded shut since the hose and smog pump were removed
i dont have a smog pump. it was removed, but the rail that runs to both of the heads is still in place hooked to both heads. there is a fitting at the end that runs to the smog pump hose that has been mashed and welded shut since the hose and smog pump were removed
No smog pump or working cat converters, ignore the 44/94 codes.
nope neither... so is that why im getting such bad exhaust smell?
More than likely, yes.

The other source of stinky gas smell is a missing or damaged carbon canister.
Charcoal canister plumbing - one 3/8" tube from the bottom of the upper manifold to the rubber hose. Rubber hose connects to one side of the canister solenoid valve. Other side of the solenoid valve connects to one side of the canister. The other side of the canister connects to a rubber hose that connects to a line that goes all the way back to the gas tank. There is an electrical connector coming from the passenger side injector harness near #1 injector that plugs into the canister solenoid valve. It's purpose is to vent the gas tank. The solenoid valve opens at cruse to provide some extra fuel. The canister is normally mounted on the passenger side frame rail near the smog pump pulley.


It does not weigh but a pound or so and helps richen up the cruse mixture. It draws no HP & keeps the car from smelling like gasoline in a closed garage. So with all these good things and no bad ones, why not hook it up & use it?

The purge valve solenoid connector is a dangling wire that is near the ECT sensor and oil filler on the passenger side rocker cover. The actual solenoid valve is down next to the carbon canister. There is about 12"-16" of wire that runs parallel to the canister vent hose that comes off the bottom side of the upper intake manifold. That hose connects one port of the solenoid valve; the other port connects to the carbon canister.

The purge valve solenoid should be available at your local auto parts store.

Purge valve solenoid:

The carbon canister is normally mounted on the passenger side frame rail near the smog pump pulley.
Carbon Canister: