87 Mustang running rich

87 foxbody · Jun 8, 2010

Hey guys I'm new to this site. I've been having some trouble with my mustang and I've been trying to figure it out for the last couple weeks and havnt had any luck, so I thought it was about time to find some people who knew a thing or two about these cars.

Its a 87 gt convertible mustang that I got about 2 months ago. When I got it, it ran great and was a good car. When i got it it had the stock 302 in it. Well a couple weeks ago the oil pump went bad on the car and I thought it would be a good idea to switch the motor out for one with a little more power. I had a 82 gt mustang with a fuel injected 302 bored over to a 306 with some torquey heads and a mild mild cam.

So I took the upper and lower intake off the stock 302 and put it on the 306 and dropped it in the car and wired everything up and got it running. I put some headers on it and for now I'm runnin about 3 foot of 3in pipe off each header.

I got the timing decent and I've got new spark plugs, wires, cap, rotor, and gaskets everywhere. But the car is running pretty rich and I cant figure out why. I've played with the timing alot and still cant get it to run right. It has a rough idle and when I'm trying to maintain speed it misses out pretty bad.

When I hammer it it runs pretty good, but thats the only time I can get it to run right.

Any help would be really awesome guys.

By the way my name is Jayden and I'm from wichita ks

PLEASE HELP ME

BYRDPE · Jun 8, 2010

any codes? what do the plugs look like? are you using the stock maf? if so, do you have another you could try?

Mustang5L5 · Jun 8, 2010

Where are your o2 sensors located on the exhaust?

Run the codes. I have a feeling you may get some o2 codes.

87 foxbody · Jun 8, 2010

I pulled the plugs today and they were black as hell. So I went ahead and replaced them because I thought they were black from running open headers because my o2 sensors are right at the end of the headers. I put some exhaust on it so the o2 sensors wouldnt read to much oxygen and its still runnin the same.

How do I check for codes on a fox? It doesnt have a maf. Its speed density I'm pretty sure.

I was thinkin maybe the map sensor??

Mustang5L5 · Jun 8, 2010

Run the codes first before throwing parts at it

http://www.stangnet.com/mustang-forums/735179-code-reader.html#post7306096

That thread shows how to do it. A good investment is to pick up a code reader. I have the one below. It was cheap but very easy to use. It's a good investment to have with these cars.

Digital Ford Code Reader (3145)

87 foxbody · Jun 8, 2010

OK, so I'm gonna have to count flashes or do they make a scanner that will plug in and tell me the codes?

I tried autozone but they dont have any scanners that will work on my car. They only have obd2

HISSIN50 · Jun 9, 2010

Jayden, hit the links that Mike posted (they're underscored in his post). You might find that Checker/Shucks/Kragen/O'Reilly has the one Mike uses in stock.

I like the O2 thoughts above. Also just check real quick to make sure there is vacuum going to the MAP sensor. Do this after pulling codes so you don't log an artificial MAP code.

Good luck.

Cornell82 · Jun 9, 2010

Another thing you stated it is still a speed density car, fords speed density was not that great and throwing a motor in with a mild cam, headers, opening up the exhaust and other things can throw off the computer. This will make it run like crap and 'load' up as the older cars with too large of a carb would do. This helps explain why it runs better when keeping your foot in the gas than when idleing. I have had 2 88's (currently have one) that people have rebuilt and put in cam's ported the heads and put aftermarket intakes on with exhaust mods and they do not run worth a crap due to the EEC does not know what to do with mixing Air/Fuel ratios correctly.

Try changing it over to MAF if you are going to keep it an EFI motor, or switch it to a carb setup to take advantage of the build. Both are about the same amount depending on what parts you use.

87 foxbody · Jun 10, 2010

Cornell82 said:
Another thing you stated it is still a speed density car, fords speed density was not that great and throwing a motor in with a mild cam, headers, opening up the exhaust and other things can throw off the computer. This will make it run like crap and 'load' up as the older cars with too large of a carb would do. This helps explain why it runs better when keeping your foot in the gas than when idleing. I have had 2 88's (currently have one) that people have rebuilt and put in cam's ported the heads and put aftermarket intakes on with exhaust mods and they do not run worth a crap due to the EEC does not know what to do with mixing Air/Fuel ratios correctly.

Try changing it over to MAF if you are going to keep it an EFI motor, or switch it to a carb setup to take advantage of the build. Both are about the same amount depending on what parts you use.

ya thats what I've been thinking about doing. I think I will end up switching it over to carb setup.

For now to get it on the road which would be cheaper/easier to do, switch it to a carb setup or switchin it over to maf??

seedeezy · Jun 11, 2010

I vote for mass air conversion

87 foxbody · Jun 11, 2010

I had speed density computer on it in my last mustang. I had a 82 mustang with a efi setup on this exact motor and it ran great. The only thing different between then and now is I have headers on it and its a different upper and lower intake from the 87 mustang, but the intakes were both stock.

So I dont understand why it wont run the way it did before. I have been workin on it for a while and just want it to be on the road

rbrackin15 · Jun 11, 2010

Grow some balls and make that thing a mass air car. There are alot more possibilites with a mass air car than speed density. That is your problem. I ran my car for about a week with heads, cam, and intake on speed density and it ran like **** and could barely breath while I was driving it. Coverted it to mass air... no problems. still smells like gas but thats from from the 225 pump and fuel pressure turned up for the giggle gas!!!http://www.stangnet.com/images/smilies/Smilie_Canada_Flag.gif

Mustang5L5 · Jun 11, 2010

How bout checking the codes before throwing money at the car?

Nothing wrong with efi and nothing wrong with speed density. Plenty of people make them work just fine with decent mods....myself included.

KamiKaziDK · Jun 12, 2010

rbrackin15 said:
Grow some balls and make that thing a mass air car. There are alot more possibilites with a mass air car than speed density. That is your problem. I ran my car for about a week with heads, cam, and intake on speed density and it ran like **** and could barely breath while I was driving it. Coverted it to mass air... no problems. still smells like gas but thats from from the 225 pump and fuel pressure turned up for the giggle gas!!!http://www.stangnet.com/images/smilies/Smilie_Canada_Flag.gif

WTF does balls have to do with this?? And there are a few more possibilities with mass air, but not a ton. Upgrading to a new computer system because a car is running a little rich is horrible advice.

3" exhaust for one is way too big, that along with just dumping it after the headers is not a good idea really, that's part of the reason your low end torque is missing. You said the engine ran fine in your other car....pull the computer out of that car and try that out if it's just laying around. What "torquey" heads and "mild mild" cam did you put on this 306? can you be more specific than that?

rbrackin15 · Jun 12, 2010

well.. if you guys weren't stupid ****s... you would know that a maf sensor has a whole lot to do with a the air fuel ratio. and that may be why it is running rich. A mass a air conversion is one of the best things you can do to a speed density car it takes a whole lot of guess work out of it because the computer does it for you. and yes. you can make power on a speed density car but unless you burn custom tunes for people like myself its really not worth the time.http://www.stangnet.com/images/smilies/Smilie_Canada_Flag.gif rep. canada even though i dont live there anymore.

KamiKaziDK · Jun 12, 2010

rbrackin15 said:
well.. if you guys weren't stupid ****s... you would know that a maf sensor has a whole lot to do with a the air fuel ratio. and that may be why it is running rich. A mass a air conversion is one of the best things you can do to a speed density car it takes a whole lot of guess work out of it because the computer does it for you. and yes. you can make power on a speed density car but unless you burn custom tunes for people like myself its really not worth the time.http://www.stangnet.com/images/smilies/Smilie_Canada_Flag.gif rep. canada even though i dont live there anymore.

So the mass air...that's not on his car....has a lot to do with air/fuel ratio???? at your god like knowledge!! lol. You quite obviously have no idea what speed density is cause you really have no idea what he's done to his car and you're telling him to spend a bunch of money to change over to something he probably doesn't need.

v8only · Jun 12, 2010

I've dealt with speed density and run-rich for a long time.

If you've got an aftermarket cam in, then it's reducing it's vacuum signal to the computer. The computer relies on full amount of vacuum 17+ pounds at idle to know where the throttle is at. If it has less vacuum than that, then the engine assumes you've got your foot buried into the throttle, and gives it more gas. THis is why it runs well at heavy throttle. However, less vacuum at idle, and it puts too much gas in at idle. I had a situation with a blocked vacuum port, and was putting 0 vacuum at idle to the MAP, and it was dumping the same amount of fuel into the motor that it would have at full throttle. HOLY CRAP, talk about billowing clouds of black smoke out the pipe, and raw fuel coming out the tailpipes! Even through full catalytic converters (4) it smoked out the entire garage, then went into the house and set off the carbon monoxide detectors on the second story. LOL, my wife was NOT happy. They had to vacate the house for a few hours.

Usually I too tell people to pull codes first, but in this case, the first thing you need to do is to take a vacuum reading. Under 17 pounds, and it's not enough, period. Do you have less vacuum because of the cam, or a vacuum leak?? If it's the stock cam, then find your vacuum leak, if it's an aftermarket cam, then convert to mass air. It's a 4 wire harness conversion and plug, and is a HELL of a lot easier than converting to carb, TRUST ME. It's an extremely simple conversion.

CDQICKGT · Jun 12, 2010

rbrackin15 said:
well.. if you guys weren't stupid ****s... you would know that a maf sensor has a whole lot to do with a the air fuel ratio. and that may be why it is running rich. A mass a air conversion is one of the best things you can do to a speed density car it takes a whole lot of guess work out of it because the computer does it for you. and yes. you can make power on a speed density car but unless you burn custom tunes for people like myself its really not worth the time.http://www.stangnet.com/images/smilies/Smilie_Canada_Flag.gif rep. canada even though i dont live there anymore.

Dude who are you to be calling anyone stupid?!?!? you have 7 post in 3 years....not that my stats are any better, but i spent 39 months in iraq with scarse net access. Whats your excuse? to busy giving people bad advice offline.

87 foxbody · Jun 13, 2010

ok, I will work on converting the car to maf, and i will get a vac reading and throw it on here for you guys to see. I havnt checked codes yet, and I unplugged the map like you told me not to so I know it will throw a map code, but it runs a lil better with the map unplugged. I can cruise on the highway and not miss out to much. But its on the streets that it runs the worse.

Thank you guys for the help. I'm really glad I joined this site

87 foxbody · Jun 13, 2010

As far as what heads and what cam are in the car I cant be for sure. I was told when I bought the car that it had a cam and heads.

Its definitly got alot more power then the stock 302 had so I know there is some truth to it

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