Engine Sputtering after 351W swap(EFI)
 

Hello, I need some serious help. I just did a 351w swap in my 87 Mustang GT. I have 30lb injectors with a 75mm MAF sensor that is calibrated for them. I also have BBK 75mm throttle body and a Aeromotive adjustable fuel regulator. Now when I take off, the engine starts sputtering but when I engage the clutch I revs up fine but soon as start disengage the clutch again to take off the engine starts sputtering again and blowing black smoke out the back. My whole ignition system is MSD. I do have a stock fuel pump which is soon to be replaced, but I don't think thats the problem. I have lots of other mods that I have done to the engine, but I don't think thats relavent to the problem. Please help! Thanks.

Well if the block had been recently rebuilt, you are supposed to put about 300-500 miles on it before driving it like a race car. if you had driven it hard without it wearing in, you could be leaking oil thru the valves, past the piston ring's ect. which would account for all the black smoke.

If you havent been driving it like a madman, I'd just take it easy on the engine for a few days, also make the rebuilders aware of whats going on, mabey they have some thought's or suggestions on it, and just see if it starts clearing up any.

Which ECM are you using?

The computer is the A9L.

yo blue, ignore what fritz said, he doesnt have a clue and listen very carefully to whatever PKRWUD has to say. HE DA MAN!!!!

Lmao... Ooook, might not be his trouble, but ask anyone who's built an engine if it need's a break in period. Then ask if hard driving on a freshly rebuilt engine might not result in black smoke .

what color does oil burn?
and what color indicates a rich condition?

And how many times have you heard someone say "Oh , theres tons of black smoke coming out of my car" Only to find its just a dark greyish blue.

but that doesnt cover the sputtering. Think of the big picture, and its quite apparent that you dont know enough to help this guy. Let the pro's like PKRWUD help him. No one likes to read ignorance.

Well honestly, it sounded to me like the sputtering might have been related to the stock fuel pump not providing enough pressure for anything more than an idle condition and I was waiting to see what he had to say once he replaced it.

But enough of this petty B.S. if you actualy have anything to add insofar as trying to help solve this guy's problem then please do so.

i gave him the best advice possible, to not to listen to you.....and listen to PKRWUD. You were making assumptions first that shouldnt of been made.

I did'nt simply say "Dude, you fried your engine from hard driving", I had said IF he had been driving it hard and the engine had been recently rebuilt Therefore, if he had'nt, there would be no need for concern or focus on my post. I was merely giving him a possibility to reflect on, and a valid one at that.

Do you have the vacuum line hooked up to the fuel pressure regulator correctly? If not, you will run richer as your vacuum increases. Fuel pressure needs to drop as vacuum increases and vice versa.

Have you run any injector cleaners, octane boost, or other harsh chemicals other than gasoline through your fuel system? Some fuel pressure regulators may be sensitive to certain alcohols and the diaphragm will deteriorate causing fuel to leak into the intake manifold.

A stock fuel pump is no where near being capable of supporting a 351 with 30# injectors. You would need at least a 155lph pump. I would not try to open it up with that small of a pump, but I don't think it's the cause of your problem, as you have already stated.

You may want to share your cam specs, too.

Ok guys, fritz does have a valid point about engine break-in period. Thanks, fritz.

But the smoke is definately black. As for the vaccum line for the fuel pressure regulator, there are two ports under the upper intake(Trickflow). I don't remember off hand which one I connected them to, but I don't it matters since they both lead into the same port, or does it?

The cam thats in there is a truck cam, 444 lift. That will change as soon as I get new heads for it. I didn't add any kind of additives to the fuel and every component on the engine is new.

I also thought maybe that the plug gap might be wrong too, I have them gapped to 045. They were gapped to 080!

Thanks guys for all the input!

The FPR just needs unregulated vacuum which it sounds like you gave it.

Maybe you should go to a dyno with a wide band O2 sensor and see what your air/fuel ratio is running at. You may also want to hook up a fuel pressure gauge to watch what it does when you're driving.

You should probably have your gap at about .060 or thereabouts, especially with a high output ignition. If you're running platinums, it should be even more.

What heads are you running and what do you plan to get?

One other thought. You have a 180 degree or greater thermostat installed, right? If not, your computer may be stuck in open loop mode if it never gets up to normal operating temperature.

Trying to find a dyno out here in Germany is kind of hard. I am running the stock heads that the long block came with, but I plan to replace them with Trickflow Tristed Wedge heads. Will plug gap that is off by 015 make that much difference?

Thanks

Yes, I am running a 195 thermostat.

just a thought, but did you check your codes.

Codes?

What is your fuel pressure set at? With your combo and 30# injectors your ideal pressure will be really low.

I bet you are running super rich.

Lets assume with your very mild 351 that you are putting out 300HP.

At 300HP your ideal fuel pressure would be 20 psi WOT.

At this point you are way over injected.

Really?!...I read that I should be running between 43-60 psi. I think that its currently at 48psi.

You should be at 39psi. My car is putting down 345 hp to the rear wheels with 30# injectors and fuel pressure set to 39.

Are you crazy?...........Your combo is way stouter than his @39 psi with 30# injectors he would be really rich.

He is not making much more than 300HP at the flywheel.

he is way over injected period.

Not to mention his fuel pump wouldnt support 30# injectors at 39 psi now would they. The answer is no.

Your response baffles me.

Actually, I should be running close to 400 hp(at least according to all the numbers)....hopefully!

With the stock pump your not even capable of sustaining 48psi under WOT.

Not with what you listed. And definitely not with the stock pump.

Not even close.

ok....so you're telling me that the 30 lb injectors that I have are too big?

I cant be sure with out being there but with what you have listed I would be very surprised to see you make much over 300 HP.

48 psi is way too much fuel pressure. 48psi with 30# injectors is enough fuel to support 470 HP.

You need a bigger pump for sure. And IMO even then your ideal pressure will be a little over 20psi which will give you a poor spray pattern.

You can get by with the 30 # injectors until you upgrade the engine but you will be stuck with a poor spray pattern because of the low pressure.

Dark_5.0,

His computer should be able to compensate by reducing injector pulse length based on feedback from the O2 sensors. If he were to lower his fuel pressure, he'd get a bad spray pattern, like you said, which would cause inconsistent and incomplete combustion. That could lead to more problems in fuel management since it could cause false O2 sensor readings. As you probably already know, air/fuel ratio is controlled by the computer and not what the fuel pressure is set at. If his MAF sensor is calibrated to match his 30# injectors, he should be okay. 48psi is too high which is why I brought up how much HP my engine puts out. If I can get 345rwhp with 39psi, he clearly should be able to support whatever he's getting at 39psi. Maybe he can even drop it to 30psi to see if things improve, but I wouldn't go any lower than that.

Bluethunder87, when you drop your fuel pressure to 39 or even 30 psi, be sure to reset your computer and then let your car idle for about 10-15 minutes so it can relearn it's idle.

You should really upgrade to a 155 or 190lph fuel pump depending on what your plans are. It seems that the 155 is good for at least 345 rwhp. :)

I will try this once the fuel pump comes in. Thank you very much guys for the knowledge!

Heres some food for thought on this subject .. read the article its very interesting, i think its logical and the theory fits with the experience i've had putting motors together. I've had a couple engines that i had no time to break in ... they got run hard right from the get go ... both were the longest lasting best sealing motors i've ever had.
http://www.mototuneusa.com/break_in_secrets.htm

The fact of the matter is the car is smoking black which means it is running rich.

Now that we know he was attempting to run 48psi we know why the motor was cutting out.

Yes the ecu controls the pulse width but when he stepped on the gas the fuel pressure was sky rocketing up to 48 psi WOT which would cause the rich condition he is having.

Just cut back the fuel and it should run great.

Sorry for calling you crazy Jimberg:p

I have to agree with Dark 5.0 on this. I think the main problem is that the injectors are too big. The bigger your injectors are, the lower the pressure needs to be for a near stock application. The lower the pressure, the crappier the spray pattern, and the crappier the spray pattern, the worse it will run. This is why it's important to get the right size injectors.

In any case, with the pressure that he's running, when he goes to WOT, it's going to dump way too much fuel in there, and the result will be black smoke, crappy performance, and eventually fouled plugs. Add to that a .045" plug gap, and you're just asking for problems.

Of course, that's just my opinion.

:)

Take care,
~Chris

Yes it does make sense, but thats only in cases where the shops are using the "latest and greatest" (Relative to the past decade) in machine tool technology and where micro-polishing can be performed effectively. Theres plenty of shops out there running with the same equipment their Grandfather's had used and doing excelent work with it, provided of course the traditional rules on engine break in were followed.

However, I think when it's time for a rebuild Im going to have to take it to one of the shops using top notch gear and modern techniques, of course Ive still got a decent amount of miles left in it. ( Sitting at 96K now)

Hey guys, thank you so much for the wealth of knowledge. For I am just learning the ropes of building engines and fine tuning them. I just replaced the fuel pump last night and when I get finished with some minor work that I have been doing I will fire her up again and try the advice that has been given. I will post the results once I'm done. Thanks!

Thank you also for supporting your military!