Need Help Getting 91 Gt Legal And Driving Asap


New Member
Feb 5, 2014
Hi everyone-

This is a long post. I'll put the essential stuff at the end.

I don't usually post on forums but googling, "how to unmolest my car" was popping up some less than desirable results...

Some background: I just bought a 91 GT. I used to drive my uncles 98 Stang when I was a kid and enjoyed it a lot. I've always been partial to more classic cars but they are mostly out of my price range, and the fox body is sexy. Essentially I wanted to get an older car to fix up and learn my way around. However, some unplanned events happened and I ended up carless and needed to get one asap so I wasn't bumming rides everywhere or walking, etc. I started looking for a newer car, almost put a down payment on a couple, almost bought a Hyundai that I didn't want just for a warranty just to be "safe."

I'm not very car savvy. I have changed oil, clutch and just general maintenance stuff on an old Ford Escort I drove, but thats about it. So I knew it would be a gamble, but even if I lose a bit of money, gaining the knowledge to be able to fix my own sh*t is worth it in the long run.

The car is in pretty good shape, interior and exterior are nice, frame isn't bent, and has a clean title. It looks better than it runs in fact, so I can tell someone at least cared for it superficially at one point.

The Car: The story I was told is that it had two owners and was purchased for a daughter as a daily driver. The ad even said it was a Cobra - all original, which I know Ford didn't make in 91. Also, it was kept in the garage and they needed to clear space as she was getting a larger car and no longer used this one as much. He said it had no leaks and that the gas was almost out, and they always got the oil changed at a certain shop. The guy was either lying or he knew less about cars than me (not sure if that's possible?).

To the point: I knew something was off as the car was unnaturally loud (a disgusting kind), also felt like I was kind of missing some power, but in general a pretty smoothish ride. After inspection I noticed a few things that I figured would be simple to fix with some help and research, that even allowed me some bargaining power.

-Exhaust chopped off w/ no muffler present. Looks like just welded and TAPED! exhaust tips to the h-pipe? (the cause of the gross sounds I'm guessing)
-Fuel gauge not working
-Car was not in fact taken to the shop he said. There was a sticker for an oil change date from a different company that even eluded to the fact the car had been sitting much longer than he lead on.

I actually talked him down quite a bit!

So at least to me, all signs point to the car previously belonging to some "butcher" who thought he was a serious racer/mechanic and defiled it a bit. Hopefully for my sake, not too much.

It has been a couple days since I bought it. Between work and school my time gets eaten up pretty fast and I really haven't had much of a chance to bust out the manual and start digging in. I have a 30 day but I assume it wont pass smog in its current state (no cat, I think).


HELP: So pretty much what all this is leading up to is that I need to get some help and opinions. Ideally I would like to put some nice stuff in my car, have already been compiling a list of to-do and to-buy. The issue is since I am limited on time and I need to get it running safely hopefully by this weekend, but I have to juggle studying/assignments and other crap.

It drives. But...

My concerns:
Sweet smell after driving (antifreeze?)
-Pretty big oil leak
-Obnoxious noise from lack of muffler (especially in the cabin) and unsafe ventilation of exhaust fumes
-Any unknown issue that I haven't found...
-I don't want a ticket

At this point, my most likely plan of action was to take it to a mechanic and have them get it in running order, then I would do upgrades and maint. from then on. It is not ideal, but I don't see a better option as I need to have my own car but at this time can't commit the time to learn how to repair it properly. I have some money that I saved by not purchasing a more expensive car, but I'm not rich.

Of course I'd like to get a sweet paint job, sick rims and haul ass. But I need it to run well first.

What do you guys think?
Where do I start?
Will I end up with crappy parts on my car if I go to a mechanic and don't have my own stuff for him to install?
Anything I did not think of?

I will check back periodically. If you guys need pictures (the "exhaust" is kind of humorous) or something, let me know.

Thanks in advance :)
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Sweet Smell after driving - If the smell is in the car, figure heater core

Where is the oil leak? front of engine or back?

Buy a cheap catback for now. You might even be able to pick up a used one off Craiglist.

Fuel gauge could be a number of issues. Could be the sender (I just replaced mine to get the gauge working again)
I would post up whatever pics you can so we can get an idea of its condition. How many miles on it? Any engine noises? Wheres the oil leak coming from? The exhaust part is the easy part, but what kind of smog testing must you go through?
Fuel Quantity gauge troubleshooting 87-93 Mustangs


The red/yellow wire (power supply to gauge & sender) should have 12 volts when the ignition is in the start or Run position.

Troubleshooting the gauge and sender circuit:
Since the sender uses a variable resistor, sum the resistor values of 22 Ohms (empty value) & 145 Ohms (full value). That gets you 167, which you divide by 2: that gets you 83.5. So in theory, 83.5 ohms is 1/2 full. A trip to Radio Shack for the closest combination of resistors to make 83.5 ohms gets you one 68 Ohm (Catalog #: 271-1106) + one 15 Ohm (Catalog #: 271-1102) for a total of 83 Ohms at the cost of $2 plus tax. Wire the resistors in series to make a resistor pack and cover it with heat shrink tubing or electrical tape. The 83 Ohms is close enough to the 83.5 Ohm figure that it shouldn't matter. Disconnect the electrical connector shown in your for the tank sender unit. Connect one end of the resistor pack to the yellow/white wire on the body side fuel sender electrical connector and the other end of the resistor pack to ground. Make sure nothing is touching that isn't supposed to and turn the ignition switch to Run. If I am correct, the fuel gauge will read 1/2 full, or very close to it. If it does not, then the odds are that the gauge or anti-slosh unit are bad.

How and why the test works…
Most of the fuel gauge failures give a stuck on full or stuck on empty as a problem symptom. Using a resistor combination that mimics 1/2 tank allows you to decide if the gauge and anti-slosh module are the problem source.

If the gauge reads about 1/2 tank with the resistor combination, that points to the sender as being the culprit.

If the gauge reads full or empty with the resistor pack in place of the sender, then the gauge or anti-slosh module is at fault.

Fuel gauge sender testing and replacement
The next steps require dropping the fuel tank and removal of the fuel level sender. Here are some useful tips...

I have done the tank removal three times, and the main issues are getting the car up on jack stands and getting the gas out of the tank. DO NOT try to do this job without jack stands. Becoming a pancake is not part of the repair process.

Pumping out the old gas:
If the old pump still works, you can use it to pump the tank out.
1.) Separate the pressure line (the one with the Schrader valve on it) using the fuel line tools.
Look in the A/C repair section for the fuel line tools. They look like little plastic top hats. You will need the 1/2" & 5/8" ones. The hat shaped section goes on facing the large part of the coupling. Then you press hard on the brim until it forces the sleeve into the coupling and releases the spring. You may need someone to pull on the line while you press on the coupling.

Use a piece of garden hose to run from the pressure line to your bucket or gas can. Make sure it is as leak proof as you can make it. Fire and explosion are not part of the repair process...

2.) Jumper the fuel pump test point to ground.


Turn the ignition switch to the Run position. the fuel pump will pump the tank almost dry unless the battery runs down first.

Some 5 gallon paint pails lined with garbage bags are good to hold the gas. The garbage bags provide a clean liner for the pails and keep the loose trash out of the gas so you can reuse it. If you decide to use a siphon, a piece of 1/2" garden hose stuck down the filler neck will siphon all but a gallon or so of the gas.

Remove the filler neck bolts and put them in a zip bag. Disconnect the supply & return lines by removing the plastic clips from the metal tubing. If you damage the clips, you can get new ones form the auto part store for just a few dollars. I have used tie-wraps, but that is not the best choice. Then you remove the two 9/16" nuts that hold the T bolts to the straps. Put the nuts in the zip bag with the filler bolts. Pull the plastic shield down and away from the tank. Once the tank drops a little bit you can disconnect the wiring for the pump & fuel quantity sender.

The fuel gauge sender assembly comes out by removing a large metal ring that unscrews from the tank. There is a separate mounting/access plate for the fuel pump and fuel gage. You are supposed to use a brass punch to tap on the ring so that you don't make sparks. Look closely at the rubber O ring gasket when you remove the fuel gauge sender.
When you install the metal ring that holds the sender in place, watch out for the gasket O ring. Some RTV may be helpful if the ring is not in excellent condition.

The tank to filler pipe seal is a large rubber grommet. Inspect it for hardening, tears and damage. At $20 from the Ford dealer, it might be a good idea to replace it.

I used a floor jack to help lift the tank back in place. You may find that it is the only time you really can make good use of a helper.

All resistance measurements should be made with the power off.

Note from bstrd86 - 86 and older fuel tank sender units are 73 ohms empty, 8-12 ohms full.

The yellow/white wire will show a voltage that varies with the movement of the float on the sender unit. To test the sender, set your Ohmmeter or DVM on low Ohms. Then disconnect the sender and connect the Ohmmeter or DVM to the yellow/white and black wires from the sender unit. Move the float arm while watching the Ohmmeter or DVM. You should see the reading change from 22 to 145 ohms +/- 10%.

If the Ohmmeter or DVM resistance readings are way off, replace the tank sender unit.

Use extreme caution if you do the next step. Fumes from the gas tank can easily ignite and cause a fire or explosion.
With the sender unit out of the tank and connected to the body wiring harness, turn the ignition switch to the Run position. Move the float arm and the fuel gauge indicator should move. If you are very careful, you can use a pair of safety pins inserted in the connector for the yellow/white and black wires to measure the voltage as you move the float arm. The voltage will change, but I have no specs for what it should be.
Do not short the safety pins together or to ground. If you do, you may damage the anti-slosh module or crate a spark. A spark with the fuel tank open could cause a fire or an explosion.

If the voltage does not change and the tanks sender passed the resistance tests, the anti-slosh module or gauge is bad.

Anti-Slosh module pictures courtesy of Saleen0679


Copied from DrBob

I worked on an 88 Mustang today that had similar symptoms. Short version, I took the “anti slosh module” off of the back of the instrument cluster and replaced the electrolytic capacitor. Fixed it for $1.39 with a part from Radio Shack.

In an attempt to help other folks, here’s the long version.
Remove the “anti slosh module” located on the back of the instrument cluster. There was a single Torx screw holding mine to the cluster.

Find the electrolytic capacitor. It will be the largest, 2 wire component on the board. The capacitor may have a red or blue plastic wrapper on it. Mine was red.

The wrapper should have printing on it. Look for printing that looks something like this:

The “100uF” tells you this is a 100 micro Farad capacitor. The “+25V” tells you the capacitor is rated for 25 Volts. Yours may be different. You may use a higher voltage part but don't use a lower rated voltage part. If you use a lower voltage part the capacitor might open later on down the road or it could be as bad as catching fire.

If you can’t find the printing you’ll need to remove the part. You have to anyway so nothing wasted. However pay close attention to the way the capacitor is oriented on the board.

One end of the capacitor will be bare metal with a wire sticking out. The other end should have some sort of insulation over it with a wire sticking out. The bare metal end is the negative end while the insulated end is the positive end. Pay attention to which end is connected to which hole on the board.

Get a replacement part. I got mine at Radio Shack, $1.39. Here’s the info:
100µF 35V 20% Axial-Lead Electrolytic Capacitor
Model: 272-1016 | Catalog #: 272-1016

Fuel tank sender unit:

Be sure to get the lock ring and a new seal if you order the tank sender unit.\

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.
Curious about you not having cats and seeing what the left side of your engine bay looks like. Whether or not you have all supporting parts, smog pump, lines etc to the heads. If you just have cats you may need to find a good ole boy or lazy shop, who doesn't do the visual inspection hardly, just the final numbers.
Sweet, thanks for the replies guys. Been at work all day. I'll take some pics hopefully today (get off at night), if not tomorrow and post. I like the tutorial!

I am in NV. Haven't been able to look under and see where the leak is, its pretty messy though. No noises that I can tell, but it is kind of hard to hear with that damn exhaust.