1988 5.0 running rich, rough idle

[alexkol]

I bought a 5.0 Sport about a month ago and it runs rough at idle and is running rich. Ran the OBD reader and it came back with the codes 14, 22, 23, 29, 31, 41, and 81. No idea where to start, this is my first project car. Wanted to ask if you guys have any ideas of where to start or what to do right now. Thank you!!

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[74 Harley]

Write down the definitions of the codes and start with the farthest upstream. If for example the temp sensor is out it can cause rich/lean O2 sensor readings.

 

[jimntempe]

The 88's used a MAP sensor system, 89 and up used the MAF type sensor that everyone uses today. The MAP system isn't as good at adjusting itself as parts wear because it doesn't measure as much stuff in real time and adjust for deviations. I used to have an 88 5.0 mustang and one of the things I did that made it run better at 140K miles was to replace all the fuel injectors.

 

[alexkol]

The 88's used a MAP sensor system, 89 and up used the MAF type sensor that everyone uses today. The MAP system isn't as good at adjusting itself as parts wear because it doesn't measure as much stuff in real time and adjust for deviations. I used to have an 88 5.0 mustang and one of the things I did that made it run better at 140K miles was to replace all the fuel injectors.

I have been working on it with a couple buddies of mine the last couple days, and I think that's what we're gonna end up doing next. The car only stays idle for about two minutes before it surges hard and dies out. It seems like the car is being drowned out by a crazy amount of fuel, so I think we're gonna replace the injectors because a couple might be stuck open. It smokes a LOT, but isn't burning oil or coolant, it seems to be just from the sheer amount of fuel being burned

 

[alexkol]

Write down the definitions of the codes and start with the farthest upstream. If for example the temp sensor is out it can cause rich/lean O2 sensor readings.

I ended up finding all the codes, and the ones that caught my eye the most were MAF/MAP sensor (22), "Rich Fuel" (41), Air Injection Solenoids (81) and EUP/EUR/PFE (31).
I don't know what the last two are, but I think the last one has something to do with EGR right?

 

[74 Harley]

The code 31 can be caused by a carboned up egr valve (or leaking). If it were my car I would start with the map sensor and and clean or replace the egr valve. Clear the codes and give it a go.

 

[alexkol]

The code 31 can be caused by a carboned up egr valve (or leaking). If it were my car I would start with the map sensor and and clean or replace the egr valve. Clear the codes and give it a go.

The past couple weeks we've checked a variety of things, but it looks like someone before us was trying to chase this problem down and couldn't seem to figure it out. When I was checking the IAC and EGR, I discovered that they were definitely not from 88. They look pretty much brand new. The EGR works perfectly fine along with the IAC. I replaced the MAP sensor a couple of days ago with a new Motorcraft one, but it did not make a difference in how the car idles, or the amount of smoke it produces at all. The car wreaks of fuel anytime it runs. Haven't checked the codes again though.
Also, the previous owner replaced the computer module trying to fix the problem. Didn't know what it was when I bought it, but the old one was in the trunk.
A buddy of mine thinks its a wiring issue. Maybe a bad ground wire to the ECM. Don't even know where to start with that.

 

[74 Harley]

If it's a wiring issue you would probably be better off going to an electrical specialty shop. The couple hundred dollars spent can be well worth it. I did this with one of my trucks.