It's Alive ( barely )

Lightweight · May 3, 2007

I tore the engine down, life happened, and 1 1/2 years later it's back together. I rebuilt the whole thing and replaced all the stock H/C/I stuff w/ Y303 heads, a Comp cam ( .533/.544, 215/220, 114 ) and a Cobra intake. I also installed 24lb injectors and deleted the smog pump. I'm still SD

I went to fire it for the first time, and while it started, it's definately not right. It runs extremely rough, blows more black smoke than a locomotive, and has to be kept above 1200 rpm to stay running. What do I do? What could I have messed up? I need help. This is my 3rd SBF to rebuild, but the first 2 were 289's. I wouldn't have a problem if this one had a carb too, but I'm totally new to EFI and have no idea where to start or even what to look for.

Bullitt347 · May 3, 2007

You did not say what year the car was. So I will hazard a guess that when you installed the bigger fuel injectors you did not replace the MAF with one calibrated for the 24 lb/hr injectors, or have the ECU flashed for the injector change. If that is the case the ECU still thinks that the engine has the stock 19 lb/hr injectors and is overfueling the engine because of the larger injectors. If that is not the case, then I need more info to help out.

BlooDReigN · May 3, 2007

Your problem is the speed density. It doesn't have a clue what to do with that big cam and the bigger injectors. You need to do a mass air swap with a MAF calibrated for those injectors.

vristang · May 3, 2007

I don't know if the cam is causing any problems, but the injectors certainly are...

Your options are...

Put the 19's back in, as I don't think you require 24's yet
Convert to MAF, as mentioned above, using a calibrated MAF
Get the SD ecu custom tuned or get a personal tuner and make the necessary changes yourself

Again, I am not certain that the cam is causing any issues.

The injectors ARE an issue though.

EDIT: Can you measure your intake vac readings at idle?

Good Luck and Let Us Know,
jason

Lightweight · May 4, 2007

The car is an '87 LX 5.0 w/ an AOD. I had discussed my combo with some of the SD guru's on another site, and was under the assumption that the computer was able to trim 24lb injectors. Just nothing larger than that. I also made sure to pick a cam that fell just within the limits of what was said to work. I know I'm pushing the edge, but even though the cam is high lift, it still has a mild duration and LSA. Aren't those the #'s that are important to SD?

I've had a couple people suggest a new MAP. Would a bad MAP sensor cause this?

I'll try and get a vac reading. How much vaccuum should I have?

88mouse · May 4, 2007

map would cause it to jump up and down at idle. ITs not the cam and the speed density I ran my car for a year with the TFS1 cam and cobra intake with out a proablem. What your fuel pressure at?

Lightweight · May 4, 2007

Ok, unless the stock regulator went bad on me, the FP is whatever the factory setting is. I don't have an adjustable regulator or a FP gage. Do I need them?

The set the TPS voltage to .94 v

The timing is 11 degrees btdc

The vaccuum @ 1000rpm is 6 in. ( That's the lowest rpm I can keep it running )

It fires right off when I turn the key.

So you don't think it's the MAP? I was going to replace it anyway, until I found out what they cost. Those things aren't cheap!

vristang · May 5, 2007

You have a couple of issues...

The 24's are wrong, you need to get the 19's in place.
The computer cannot correct for a different size injector!

You should be getting more than 6" at idle.
Either you have a vac leak, or there is something wrong with your valve timing.
I would guess vac leak...

Start with the injectors.
While you have the upper manifold off, inspect all of the vac hoses for cracks.

jason

blown90 · May 5, 2007

There are so many factors that could be causing this. He could have even installed the distributor off a tooth!

whtpny · May 5, 2007

Just start with the injecters. One step at a time.

BlownFiveLiter · May 5, 2007

Bullitt347 said:
...or have the ECU flashed for the injector change.

It's not possible to flash the ECU in these cars. It would require a chip to be added on.

blown90 said:
There are so many factors that could be causing this. He could have even installed the distributor off a tooth!

The only problem installing the distributor off a tooth would cause is limiting the turning ability of the distributor itself, when trying to time it. If you could physically turn it enough, you could install it 180° out and still get it timed correctly.

All signs point to using the 24lb injectors with the SD computer. I agree with everything vristang has recommended in trying to get it running right, but in my opinion, your best bet is to take the plunge into the MAF conversion.

vristang · May 6, 2007

Matt,
Actually with EFI (EDIT: SEFI) you can get the dist '1 tooth off'
The car usually runs, but just doesn't feel right.

The ecu uses the dist signal to time the injector pulses.
Because of this the dist needs to be precisely synchronized with the camshaft/crankshaft.

A little off topic, but it's important to get the word out on that...

jason

blown90 · May 6, 2007

Thank you, from my own experience!!

Lightweight · May 7, 2007

I really was hoping to avoid a MA conversion, but it may be my best option. A few of the charts I saw about injector size in relation to horsepower, listed the 19's to only be good to about 280hp. I hoped to be just over 300hp NA with my combo, and have plans for nitrous, so I got the 24's. Was that 280 RWHP instead of crankshaft HP? Could I just get a FP regulator and pull the pressure back on the 24's? Since I didn't plan on reusing them, the 19's have just been sitting out on my workbench. Would they still be okay to use, or will I have to have them cleaned? I'm bound to have a vac leak somewhere, so I'll start looking.

Thanks again for helping out an EFI newbie.

vristang · May 7, 2007

Most injector calculators will use flywheel Hp, not rwhp.

If you need 24's then the options are MAF conversion, or custom tune the SD system.
MAF conversion may be cheaper in the short term.
If you are considering a tuner package, now is the time to SERIOUSLY consider if you want to take on the role of tuning your own car.

If the 19's have not been contaminated with a lot of dust and debris, then they should be ok. If not 19's are easy to find in a j/y.

Backing off the fuel pressure for the 24's will cause fuel metering issues, due to the lack of sufficient pressure in the fuel lines.

Plugging in the 19's is the best thing you can do at this point. That should clear up most of your issues.
jason

Lightweight · May 8, 2007

I know a couple of the vac hoses under the intake could use replacement, so I'll get two things at once. I'll put the 19's back in, and eliminate a possible a vaccuum leak. I'll just have to make sure my 19's are still usable. There is bound to be someone around here to clean / test them for me. Even if I do need the 24's, I'll know for sure that they are the curent problem. I'll start on that tonight and see what happens.

vristang · May 8, 2007

Sounds like a solid plan

Let us know how it goes...

jason

Lightweight · May 8, 2007

Put my 19's back in, and ( aside from losing engine response ) nothing changed. Still won't run below 1000 rpm. Still blows gobs of black gas smoke out the pipes.

If this were a stick shift race car, I'd be all set. Ignore the black cloud, keep the rev's up, and it seems to run great.

Guess I'll put my 24's back in, and look into something else.

vristang · May 8, 2007

whether you still have the problem or not...
The 24's are wrong for your stock SD ecu.
Put them in if you like, but it may make diagnosing this issue tougher.
You will be diagnosing around a known problem.
I won't harp on it, so this will be the last time I recommend against the 24's (for now anyway).

I need to read over this thread again...
jason

EDIT:
How long did you give it to adjust?
How long did you let it run?

vristang · May 8, 2007

Lightweight said:
The vaccuum @ 1000rpm is 6 in. ( That's the lowest rpm I can keep it running )

Lightweight said:
Put my 19's back in, and ( aside from losing engine response ) nothing changed. Still won't run below 1000 rpm. Still blows gobs of black gas smoke out the pipes.

These 2 things add up to valve timing or a MASSIVE vac leak.

How did you adjust the valves when you put in the cam?

Just for giggles, hook the vac gauge up to the pcv valve. This will either show pressure in the crankcase (this is the normal condition), or it will show crankcase vac (which will indicate a lower intake gasket vac leak, common to the lifter valley).

Pull the vac line from the fuel pressure regulator, and see if it is wet with fuel. When the diaphragm ruptures extra fuel dumps into the intake.

This one should have been the first thing I suggested, my apologies.
Pull the KOEO and KOER diagnostic codes.
If the problem is a sensor, this will clue you into it.

Finally, this is a little beyond my comfort level (I don't normally get involved in the diagnosis of problems, and for good reason), so I am requesting the mods to move this to the general tech thread.
This should give your thread more exposure, as most folks don't check this sub-forum too often.

Good luck,
jason

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