91 306 Issues

Check the vacuum hoses at the back of the upper intake ..also take a look on passenger side of motor at the plastic vacuum lines that goes to the egr/intake and smog stuff.

KPatterson said:

Just traded this 91 for a jeep that I had a few days ago. Bored 30 over, roller rockers b cam and a bunch of other stuff. Very clean car just doesn't run right or have the power it should. It`s definitely running rich. Brakes are very stiff with not much power. When I mash the brakes in park, it wants to die. Second Fox Body for me. I did pull the codes of 81 82 84 and 85 which indicates a vacuum leak. To the naked eye/ear I cant locate it. Any suggestions where to start?

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Those are emissions related codes. They do not necessarily point to a vacuum leak.

Code 81 – Secondary Air Injection Diverter Solenoid failure AM2. The solenoid valve located on the back side of the passenger side wheel well is not functional. Possible bad wiring, bad connections, missing or defective solenoid valve. Check the solenoid valve for +12 volts at the Red wire and look for the Lt Green/Black wire to switch from +12 volts to 1 volt or less. The computer controls the valve by providing a ground path on the LT Green/Black wire for the solenoid valve.

With the with the ignition on, look for 12 volts on the red wire on the solenoid connector. No 12 volts and you have wiring problems.

With the engine running, stick a safety pin in the LT Green/Black wire for the solenoid valve & ground it. That should turn the solenoid on and cause air to flow out the port that goes to the pipe connected to the cats. If it doesn't, the valve is bad. If it does cause the airflow to switch, the computer or wiring going to the computer is not signaling the solenoid valve to open.

Putting the computer into self test mode will cause the solenoid valve to toggle. If you listen carefully, you may hear it change states.

Code 82 – Secondary Air Injection Diverter Solenoid failure AM1. Possible bad wiring, bad connections, missing or defective solenoid valve. Check the solenoid valve for +12 volts at the Red wire and look for the Red/White wire to switch from +12 volts to 1 volt or less. The computer controls the valve by providing a ground path on the Red/White wire for the solenoid valve

With the engine running, stick a safety pin in the Red/White wire for the solenoid valve & ground it. That should turn the solenoid on and cause air to flow out the port that goes to the pipe connected to the heads. If it doesn't, the valve is bad. If it does cause the airflow to switch, the computer or wiring going to the computer is not signaling the solenoid valve to open.

Both 81 & 82 codes usually mean that some uneducated person removed the solenoid control valves for the Thermactor Air system in an attempt to make the car faster. It doesn't work that way: no working control valves can cause the cat converters to choke and clog. If you do not have cat converters on the car, you can ignore the 81 & 82 codes.

Code 84 EGR Vacuum Regulator failure – Broken vacuum lines, no +12 volts, regulator coil open circuit, missing EGR vacuum regulator. The EVR regulates vacuum to the EGR valve to maintain the correct amount of vacuum. The solenoid coil should measure 20-70 Ohms resistance. The regulator has a vacuum feed on the bottom which draws from the intake manifold. The other vacuum line is regulated vacuum going to the EGR valve. One side of the EVR electrical circuit is +12 volts anytime the ignition switch is in the run position. The other side of the electrical circuit is the ground path and is controlled by the computer. The computer switches the ground on and off to control the regulator solenoid.


Code 85 - CANP solenoid - The Carbon Canister solenoid is inoperative or missing. Check vacuum lines for leaks and cracks. Check electrical wiring for loose connections, damaged wiring and insulation. Check solenoid valve operation by grounding the gray/yellow wire to the solenoid and blowing through it.
The computer provides the ground for the solenoid. The red wire to the solenoid is always energized any time the ignition switch is in the run position.

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:




Finding vacuum leaks

Revised 04-Aug-2011 to add pintle cap, PCV grommet & power brake check valve grommet to checklist.

There is no easy way to find vacuum leaks. It is a time consuming job that requires close inspection of each and every hose and connection.

Small vacuum leaks may not show much change using a vacuum gauge. The range of "good readings" varies so much from engine to engine that it may be difficult to detect small leaks. The engine in my first Mustang pulled about 16.5" of vacuum at 650-725 RPM, which I consider rather low. It was a mass market remanufactured rebuild, so no telling what kind of camshaft it had. Average readings seem to run 16"-18" inches at idle and 18"-21" at 1000 RPM. The only sure comparison is a reading taken when your car was performing at its best through all the RPM ranges and what it is doing now. Use one of the spare ports on the vacuum tree that is mounted on the firewall near the windshield wiper motor.

Use a squirt can of motor oil to squirt around the mating surfaces of the manifold & TB. The oil will be sucked into the leaking area and the engine will change speed. Avoid using flammable substitutes for the oil such as propane or throttle body cleaner. Fire is an excellent hair removal agent, and no eyebrows is not cool...

The vacuum line plumbing is old and brittle on many of these cars, so replacing the lines with new hose is a good plan. The common 1/8” and ¼” vacuum hose works well and isn’t expensive.

The PCV grommet and the power brake booster check valve grommet are two places that often get overlooked when checking for vacuum leaks. The rubber grommets get hard and lose their ability to seal properly. The PVC grommet is difficult to see if it is correctly seated and fitting snugly.

Fuel injector O rings can get old and hard. When they do, they are prone to leaking once the engine warms up. This can be difficult to troubleshoot, since it is almost impossible to get to the injectors to squirt oil into the fuel injector mounting bosses. If the plastic caps on the fuel injectors (pintle caps) are missing, the O rings will slide off the injectors and fall into the intake manifold.

Fuel injector seal kits with 2 O rings and a pintle cap (Borg-Warner P/N 274081) are available at Pep Boys auto parts. Cost is about $3-$4 per kit. The following are listed at the Borg-Warner site ( http://www.borg-warner.com ) as being resellers of Borg-Warner parts:
http://www.partsplus.com/ or http://www.autovalue.com/ or http://www.pepboys.com/ or http://www.federatedautoparts.com/

Most of the links above have store locators for find a store in your area.

Use motor oil on the O rings when you re-assemble them & everything will slide into place. The gasoline will wash away any excess oil that gets in the wrong places and it will burn up in the combustion chamber. Heat the pintle caps in boiling water to soften them to make them easier to install.



Diagram courtesy of Tmoss & Stang&2birds



Vacuum leak due to slipped lower intake manifold gasket...

Ask Nicoleb3x3 about the intake gasket that slipped out of place and caused idle and vacuum leak problems that could not be seen or found by external examination. I don't care what you spray with, you won't find the leak when it is sucking air from the lifter valley. It simply isn't possible to spray anything in there with the lower manifold bolted in place.





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/ Everyone should bookmark this site.

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

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

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

TFI module differences & pinout
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

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

Can you give us a picture of the engine bay? Close ups around the vacuum tree, brake booster and upper intake and one overall would be good for a start.

You may want to figure out what parts are on the rear disc upgrade. If the wrong MC was used, that will cause the pedal to feel wrong.

Also list the mods to engine, including the meter and injectors.

2000xp8 said:

You may want to figure out what parts are on the rear disc upgrade. If the wrong MC was used, that will cause the pedal to feel wrong.

Also list the mods to engine, including the meter and injectors.

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Would the wrong MC also cause the engine to almost die when you push the brake pedal hard? He has that problem too, stiff pedal and near stalling motor when pedal is pushed hard when in Park.

Are you still using the Egr?

FoxMustangLvr said:

Would the wrong MC also cause the engine to almost die when you push the brake pedal hard? He has that problem too, stiff pedal and near stalling motor when pedal is pushed hard when in Park.

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Sounds more like a booster or vacuum issue if it's almost stalling. But in other cases if the master cylinder bore isn't correct for the sizing of the brakes the pedal could be hard to push.

No serial # or calibration info on that ProM, sucky. What color are your injectors? Orange is stock 19# and blue is 24# injectors (24# being ideal if you have aftermarket alum heads). I don't see a brake proportion valve, shouldn't there be one?

You said the car isn't running right and is running rich. Can you describe what it's doing that is indicative of it not running right? How do you know it's not performing up to par? Checked fuel pressure yet? I see you have a BBK adjustable fuel pressure regulator under the EGR unless i'm mistaken.

Have you done basic (new owner) maintenance to the vehicle since you got it? I do this as soon as I get a new used vehicle...
Change oil & filter regardless how new it looks
drain cooling system, inspect hoses and refill
pull and check all spark plugs and wires
pull distributor cap and inspect
replace fuel filter
pull all tires off and inspect rotors, calipers and brake pads
inspect ball joints and suspension related items

Some people drop the ball on keeping their car in good shape and running right.

Pull the plugs to be sure if you're running rich. Smelling gas upon start up is common because 1) Car bypasses all smog equipment and sensors and dumps fuel during cold start, 2) No catalytic converters will cause a fuel odor on our 5.0 because the Cats job is to burn any excess fuel and other particles leaving the engine. No Cats means excess fuel is not being burnt now creating an odor out of your tail pipe and people think they're running rich when it's not the case.

If your brakes are not working well then it's either a bad booster or most likely when somebody upgraded the brakes on that car they either didn't upgrade the MC or they didn't use the right size when they did upgrade. Also I believe there should be a proportion valve for your brakes which is typically mounted on the firewall and I didn't see one in the pictures but I'm not positive about that. @Mustang5L5 is the brake swap guru as far as i'm concerned but you need to know what parts where used (what size rotors & calipers for front and rear) in order to get the most accurate info.

KPatterson said:

EGR is bypassed. I cant even power brake to boil the tires. Not much low end power. Pull really hard when it gets past 4k. I can tell its running rich at start by the smell. 24lb injectors.

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Sorry for the multiple responses. The slow to start and then kick up in power sounds like you may have a different cam that is more top end oriented. Is your car geared? Problem is if the previous owner didn't know much about the car (which is common w/ 5.0's) then he may be guessing at which cam is in it. If you were to put a TFS2 cam in your engine with stock 2.73/3.08 gears the car (allegedly) would fall on it's face on the low end and then come alive at the higher RPM's. That why there is a recommendation for gears when you buy some cams. For example, a TFS2 cam requires 3.73 gears for a T5 trans minimum which is the combo I have. (I know you said you think you have a B cam, i'm only using the TFS2 cam as an example to make a point).

To find your rear end gearing jack up both tires, put a piece of tape on the tire and one on the drive shaft. Count how many times the drive shaft rotates to ONE rotation of the tire.

Unless you can see it with your own eyes you should believe NOTHING that the previous owner told you about the car. Assume he's wrong about everything especially when things aren't performing like they should. All to often on Stangnet people are hammering others on making a combo work right instead of slapping a bunch of crap together and hoping it performs well.

You got that clean Fox just to sell it? I'm jealous

KPatterson said:

He said it has 4:10s. Can anyone recommend a good Fox Body shop around Atlanta? I`d like to drop it off somewhere and have them write a list of every mod it has. I took it in as a trade hoping it would be an easier sale then the jeep I had. It`s a very clean car with near perfect interior.

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Pics and we got you covered. Will work for @DoritosLocosTacos

Not that and it matters but your EGR is bypassed so you have a CEL and codes for that. You can buy a EGR simulator and block off plate on EBAY and just remove the EGR valve.