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EFI running lean

BrianS

Member
Joined
Oct 11, 2005
Messages
12
I have a 68 mustang gtcs witch I just finish installing my EFI for a 86-93 mustang. Im using my 68 302 long block with an EFI intake with all new senors and a new main harnes from motorspot SVO and new ecu from motorspot.

The car fires right up but wont hold a idle. I can put my hand infront of the intake to restrick the air flow and it will hold an idle and run right, as soon as I remove my hand it will run like shit and will stall out. there is no check engine light on. I disconect any senor and the light comes on so I know it is working.

I am lost and need help with my problem and no I cant take the car to a shop.
 

rvrtrash

Well-known member
Joined
Apr 25, 2003
Messages
3,649
To bad you can't take it to a shop, 'cause that's what I'd recommend. Since you can't, start by taking a vacumn reading and looking for a vac. leak. Check your fuel pressure to make sure it's correct. EFI runs a lot higher fuel pressure than carb's. Are the injectors firing in the correct order for the older firing order? After that, you'll need an analyzer so you can see what the sensors are reporting. Just because the check engine light doesn't come on doesn't mean all the sensors are accurate. Hope this gets you started in the right direction.
Steve
 
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BrianS

Member
Joined
Oct 11, 2005
Messages
12
yes I know my firing is right and i have plenty of fuel and it shows no vac leak... you see Steve, I need someone that know pasted those steps. but thanks for your input. if you have anything else to and please let me know.
 

Mosesatm

Well-known member
Joined
Jan 18, 2005
Messages
9,009
Probably not going to find too many people like that here. Steve is one of our best, if not THE best.
 

joedls

Well-known member
Joined
Mar 12, 2005
Messages
1,980
Location
Lake Forest, CA
Mosesatm said:
Probably not going to find too many people like that here. Steve is one of our best, if not THE best.

Probably doesn't need anyone anyway. According to his signature line, he's done it all.
 
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BrianS

Member
Joined
Oct 11, 2005
Messages
12
all Im asking if someone mybe knows what to do in the problem that im having, to help me narrow the diagnoising time. If anyone has any suggestion please let
me know, and lets not get off the subject im not putting anyone down.
I have taken Steve's advice before.
 

joedls

Well-known member
Joined
Mar 12, 2005
Messages
1,980
Location
Lake Forest, CA
BrianS said:
all Im asking if someone mybe knows what to do in the problem that im having, to help me narrow the diagnoising time. If anyone has any suggestion please let
me know, and lets not get off the subject im not putting anyone down.
I have taken Steve's advice before.

I apologize if I misunderstood your prior post. It did seem to me that you were insulting Steve's advice. I'm glad that's not the case. I hope someone can help you figure out your problem. I know I can't.
 

jk89cat

Well-known member
Joined
Mar 10, 2005
Messages
213
Location
vernon hills, IL
well heres a good question, are you using the 5.0 ho firing order with the stock 68 cam? with using the 86-93 mustang, requires the ho and 351 cam. the so tbird /cougar /crown /grandmarquis, would be sutible to use for the stock cam if thats what your doing otherwise, you may not have the intake sealed enough for the intake to pull a proper seal , you could also have a bad iac . i will be doing a ho style swap when i get my galaxie done, i want to make a efi/overdrive 67 / 68 gtcs clone / restomod
 
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BrianS

Member
Joined
Oct 11, 2005
Messages
12
Thanks for understanding.
My best bet is to just step back for a week or too and not think about this EFI
problem and go back with a clear mine.
 
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BrianS

Member
Joined
Oct 11, 2005
Messages
12
my firing order on the EFI is the same as the 302 becuase of the main harness
you can get the one that fires the 351 order...... the part # at the end are difernt.
 

rvrtrash

Well-known member
Joined
Apr 25, 2003
Messages
3,649
I just logged back in. Thanks for the compliments guys.:embarass: I don't know what else to say.
Steve
 

jk89cat

Well-known member
Joined
Mar 10, 2005
Messages
213
Location
vernon hills, IL
hmm, i think thats your problem, if the pcm you have is out of a mustang , or tuned for one, and your usign the std 302 firing order, that is , its not the same firing order. i really think this is what going on, you have a ho computer and have the engine set up for a std output 302 , in which the cam , pcm, firing order and upper intake are diiferent
 
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BrianS

Member
Joined
Oct 11, 2005
Messages
12
when I was working today, my coworker/buddy told me to pinch the return line to the gas tank to see if my fuelregulator is working. He told me I may need a ajustable fuelregulator to increase the fuel in the line.

So I thought 45-60 on my fuel is in spec, but 60-80 is the right presser to run the EFI. So I pinched the return line and started the car
IT RUNS, IT HOLDS AN IDLE, IT RUNS GREAT!!!!!!
So I now know what to do install an ajustable fuel regulator..
 

jk89cat

Well-known member
Joined
Mar 10, 2005
Messages
213
Location
vernon hills, IL
ok, thats a different way of diagnosing it, what kind of fuel pump you running? should be around 190 lph you could just have a bad fuel pressure regulator too
 

rvrtrash

Well-known member
Joined
Apr 25, 2003
Messages
3,649
BrianS said:
He told me I may need a ajustable fuelregulator to increase the fuel in the line.
QUOTE]

Gee- a fuel pressure problem. I wish I'd thought of that.:wink: I'm glad your buddy at work could help you out.

Steve
 
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