Efi To Carb Plz Help

Lscam580

Active Member
Aug 27, 2014
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Grand Rapids Mi
Ok I did Hci change out over a week ago and I have been through all the checks and still can not get it to idle. What is the bare min I have to do to change to a carb setup. I have a brand new intake and carb sitting on the shelf never used.
 
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Ok I did Hci change out over a week ago and I have been through all the checks and still can not get it to idle. What is the bare min I have to do to change to a carb setup. I have a brand new intake and carb sitting on the shelf never used.
hello;

exactly what head, cam and intake did you install?

how does it run other than at idle?

what is your ignition timing?

did you do an air leak test?

how much preload is on the lifters?


if you want to dump the efi, in addition to the carb and intake, i would get a different distributor.
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I have tfs heads tfs intake and tfs stage 1 cam, total timing is 38 degrees had a great engine builder help me out and everything is where it should be. I pulled codes and I get nothing. There is not one code reading. Just gives me the initial code. And I've done koeo and koer and still nothing.. I have a msd dist. sitting there on the shelf. Was going to build a 408 and have all parts sitting there. Distrib, intake, carb, cell, 5/8 aluminum cell, blue pump, all an fittings. Every thing to convert so I'd be spending no cash out of pocket. The efi just revs high. Even went as far as getting the supid speedo cable and sensor off 89 when I did maf swap. Not one darn code
 
Other then the idle problem it runs great and pulls extreamly hard through out the powerband. I've had everything checked out and no leaks I've spent a ton of money on new maf throttle body injectors everything and still no codes.. I am ready for a carb to rid the issues, and throw the other crap in the trash. Y should I not go with a carb?
 
I'm starting to believe some combo's are just too out of range for even a MAF car to compensate for.....mine included. I've run codes, replaced parts and it still runs rich down low and randomly surges. I think I'm going to have to break down and buy the Moates chip and a wide band set up and play with the fuel tables a little.
 
I'd like to see my idle less then 1000 Rpm's I'm at 1350-1500rpms now

Have you messed with the idle screw on your throttle body? If not, I'm gonna say you've got a good sized vacuum leak somewhere. Time to go over all of the vacuum lines again and get out a bottle of brake clean and start spraying around vacuum lines, intake gaskets, PCV, intake tube, etc. Something is definitely a miss.
 
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I've honestly done just about everything. Carb it goes.. How do I use stock fuel pump and still run a carb
You don't, you will need a carb fuel pump. EFI pumps are alot of pressure damn near 6 x's the amount of pressure you want on a carb setup. I have a carb setup. Although I agree with others, if I had factory EFI. I would never convert it to carb, unless it was strictly drag and I had absolutely no one to help tune.
 
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I replaced all rubber hoses,shot small amounts of break cleaner to each rubber connection, intake gaskets, upper and lower. Changed out new pcv, sprayed every where. I do have a Mallory adjustable fuel pressure regulator from 60psi to 2psi that will work for a carb won't it that's y I bought it. I'm half temped to sell the stupid car and start over
 
I replaced all rubber hoses,shot small amounts of break cleaner to each rubber connection, intake gaskets, upper and lower. Changed out new pcv, sprayed every where. I do have a Mallory adjustable fuel pressure regulator from 60psi to 2psi that will work for a carb won't it that's y I bought it. I'm half temped to sell the stupid car and start over
You can regulate down into carb pressure range with that regulator. Not completely positive, but regulating an EFI pump that isn't meant to put out that little pressure will kill the longevity of its life. From what I recall though, if you had a fuel pump controller that would work safely. Someone will correct me if I'm confused.
 
I replaced all rubber hoses,shot small amounts of break cleaner to each rubber connection, intake gaskets, upper and lower. Changed out new pcv, sprayed every where. I do have a Mallory adjustable fuel pressure regulator from 60psi to 2psi that will work for a carb won't it that's y I bought it. I'm half temped to sell the stupid car and start over

I am a carb advocate, (one of the few) and you run this gauntlet everytime you make a post like yours here.
The fact of the matter here is that whatever is wrong w/ your current system, it will go away as soon as you swap over to the carb.The biggest reason for that will be that whatever is currently wrong w/ the EFI system, you are applying a shotgun blast solution to a bullet hole problem.
The one thing you will have to do if you do convert over however, is change out the FI pump, and use that Holley blue to deliver the fuel. Using that mallory reg that you have is asking it to restrict too much FP, (kinda like you pinching off a garden hose that has the water turned on full blast) and sooner or later either the pump will give up based on the constant restriction, or you'll spring a leak, and I don't have to tell you that could be a bad thing real quick.

What you'll get when you convert is a car that'll require a technique to get it started, and will more than likely require some time spent changing out things like jets/metering blocks, power valves, and squirters. The fact that the carb doesn't meter fuel as efficiently as a properly working FI
system does, you will probably have a more notably rougher idle, and all of those changes you make to the carb will have to be changed when, and if you ever drive into a significant elevation change. All stuff a good working FI system will compensate for automatically.

I'd keep trying to save the EFI if it were me. It's there, it's working, and if and when you find what's wrong w/ it, your current self will thank your future self for not changing it over.
 
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You guys with idle/stall problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix your idle problems without spending a lot of time and money. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix. :D

It's free, I don't get anything for the use of it except knowing I helped a fellow Mustang enthusiast with his car. At last check, it had more than 159,000 hits, which indicates it does help fix idle problems quickly and inexpensively.

If you have worked your way though the checklist, let me know. I will ask you some oblivious questions and maybe even some irritating ones. It is for the purpose of understanding what you have for mods and then what you have or haven't done on the checklist
 
Well I found the problem., not so happy right now. The lower intake is good but the upper intake has a 2" crack on the under side by the throttle body housing. I just bought this setup brand spanking new and have been extra cautious putting it together. Called summit and they want me to send it back. I think now would be a good time to convert. I am not pleased with the product if it contains a crack straight from the box. It seems to get bigger as the motor gets warmer.