I need a little advice on something. I recently did an engine swap from the stock 302 i had to a HO motor out of a 91 mustang. everything had been running fine during break in, but while driving it to the parts store, the truck cut out on me and acted like it was being drowned out with fuel. i have changed the pressure regulator and put new spark plugs on it. the problem i have now is the truck is smoking, bad. The truck has started running rich and the smoke is thick and black. i was wondering if this could possibly be an egr valve? the engine is brand new and my dada and i rebuilt it from the groung up. any opinions would be greatly apppreciated.

 

Need a little more info. Carb or EFI?

 

its fuel injected.

 

I can't see an EGR valve causing a rich condition. The first thing I would do is pull the codes. See these sites for more info on pulling codes and what they mean.

http://www.mustangworks.com/articles...-iv codes.html

www.fordfuelinjection.com

It could be a number of things causing it, from a bad sensor to something that may have been left unconnected. Let us know how it goes.

 

Sounds like bad O2s but check your connections first.

 

Check computer codes, check fuel pressure.

It's the first two things that you do whenever there is a problem with EFI.

 

If you're trying to run a Stang H.O. motor with the pickup's Speed Density EFI system, that's your problem. Too much cam for the program. Different firing order too.

 

Thats true, but I doubt that's his deal because he said it was running fine during break-in.

 

Running it in the driveway and out on the road are two different things. I've seen lots of motors that ran fine in the driveway, but couldn't pull their own weight once out in the street.

 

it also did good on the road for a while. it just started actin up after about 10 minutes. right before i was about to get on the interstate. it also drove good the day before, but i didnt drive it that far.the engine has also been gas fouling plugs. all of them. i tried to get the codes, but the computer didnt send any info. any suggestions? me and my dad cant figue out what the problem is, but whatever it is, it aint good.

 

are you running the truck ecu or the stang ecu? what injectors are on that motor? are you running the ho firing order? whats fuel pressure at the rail?

 

im running the truck ecu, the mustangs injectors are on it, and im not sure about the pressure at the rail, but it does have plenty of pressure. i am running the HO firing order. I have also removed all tha smog junk. We plugged the holes in the back of the heads also. I also have all my top end on it. (intake, throttle body, etc.) . i am using the mustangs heads.

 

Interesting. The truck ECU is speed density which means it doesn't react well to drastic changes to the engine because it just can't adapt like a MAF computer can. If the engine is breathing better with the better heads that could cause the engine to lean out a bit. If the cam is more aggressive than your vaccum at light idle would be lower which could increase your fuel rail pressure which could cause the engine to run a bit rich. Removing the SMOG equipement shouldn't cause the kind of problems you are experiencing. You should try replacing the O2 sensor and see if that has any effect. Perhaps it during the engine install some chemicals got into the exhust system which destroyed the O2 sensor. Not being able to get codes of the computer doesn't help things either.

Another thing, if the engine runs fine fine when you first start it up and then badly soon after, that definately sounds like an O2 sensor issue. When you first start engine the ECU manages the engine in what is called "open loop". That means it doesn't care what the O2 sensor says, it just follows a set of default values stored in it's memory. Once it warms up, it switches to a "closed loop" situation where it uses the O2 sensor to try and fine tune the air fuel ratio. If it's getting bad readings from the O2 sensor, then you definately could end up running either too rich or too lean.

 

Bad o2 sensor readings would throw a code.

You brought up open/closed loop - within 2-3 minutes the computer switches to closed loop. He said it started after about 10 minutes...the computer was in closed loop for a period of time with it running ok.

So you did a KOER and KOEO test and didn't see any codes? Nothing in continuous memory? Did you get the code for system pass? I want to make sure this was done correctly...it sounds to me like you should have codes. You should definitely have codes if you removed smog equipment and didn't make computer related changes to refect those missing parts.

Have you checked for vacuum leaks?

The mustang engine has the same heads - so there's no problem there.

Again, very true but he said in the first post that he had it out on the road.

Take your battery cable off and reset the computer - see what it does.

I'm guessing that means you're using the truck's intake, tb, etc?

The clearer you are and the more detail you can give - the better we can help you.

It doesn't react well to changes in vacuum...it can be fine with changes to the engine. The lobe separation on the camshaft will alter the vacuum - which will alter the load the computer sees. There are many misconceptions about SD.

The mustang injectors are 19s like the stock truck's. You have to run the HO firing order because it has a mustang cam in it. I also have a feeling that your problems relate to the fact that you have a mustang MAF cam in that engine - and are using a truck SD computer.

Do you have the truck cam you can swap in it?

 

My mistake, I wasn't very clear when I said SD computers doen't react well to drastic changes in the engine. If you change the heads, cam or intake manifold such that the engine breaths much differently, you will in effect be changing the vaccum curve which would effect how the engine runs.