Runin' Rich

pull some codes and check the fuel pressure with a gauge the regulators have a tendency to go bad and richen things up real bad. Is it runnin rough, idle fine, start up ok

check for vacuum leaks as well. the HEGOs see that and dump fuel in to attempt to compensate...

check your fuel pressure with a gauge it sound kind of like a vacuum issue

If you have a vac leak, the HEGO [Heated Exhuast Gas Oxygen](O2, Lambda, whatever) sensor sees unburnt air,(lean) and pours fuel in to compensate. my 5.0L was leaking through a EGR delete plate and did the same thing.

Pull your plugs, and see if it's just one cylinder, or all of them that are rich.

Or- pull the codes - you can do it with the check engine light, (if equipped) and a piece of wire. if no Check engine light is present, use a test light or a volt meter. Or by a $5 code reader for OBD1 cars. some parts stores pull them for free.

Dump the codes and see what the computer says is wrong…Codes may be present in the computer even if the Check Engine light isn’t on.

Here's the link 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.

See http://www.troublecodes.net/Ford/





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.



89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.



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.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 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 http://www.midwayautosupply.com/pc-7208-90-equus-digital-ford-code-reader-3145.aspx – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.

Go through jrichker's post and pull codes to see whats up. I would then just start checking the most obvious things. Obviously you are getting a lot of fuel. Get an adjustable fuel pressure regulator and a pressure gauge to mount on the end of the fuel rail. I would check the injector function with a noid light to make sure they are all functioning correctly and none are stuck open.

Pull the oxygen sensors and check their condition...replace if they are looking rough. The O2's are going to be the main contributor to the air fuel ratio. As oxygen sensors get old they switch slower and therefore dont respond as quickly to changes in AFR. Let us know what you find

PS. The search function on this site is excellent, there are a lot of very experienced stangers who have posted some excellent testing and diagnostic information. Test first...replace parts second.

ninety15.0 said:

Go through jrichker's post and pull codes to see whats up. I would then just start checking the most obvious things. Obviously you are getting a lot of fuel. Get an adjustable fuel pressure regulator and a pressure gauge to mount on the end of the fuel rail. I would check the injector function with a noid light to make sure they are all functioning correctly and none are stuck open.

Pull the oxygen sensors and check their condition...replace if they are looking rough. The O2's are going to be the main contributor to the air fuel ratio. As oxygen sensors get old they switch slower and therefore dont respond as quickly to changes in AFR. Let us know what you find

PS. The search function on this site is excellent, there are a lot of very experienced stangers who have posted some excellent testing and diagnostic information. Test first...replace parts second.

Click to expand...

+1. o2's is what came to my mind

SEdwards said:

Thanks guys. I bought a code scanner from Autozone for $30 and it narrowed it down to (4) possible solutions: Map Sensor, TPS Sensor, 02 Sensor and EGR Valve. All had been recently replaced except the EGR Valve so I hope that does the trick. I will post results by the weekend. Cross your fingers for me. Also, how do I put a pic of my stang on here and change my username?

Click to expand...

When you get codes, post the actual code numbers. I have a complete list of the code definitions and what to check and test to fix them on 5.0 Mustangs.

a bad egr valve is just like a vacuum leak it will cause a big chug and huck black smoke