EFI TO CARB

crookman10 · Oct 22, 2008

I have an 88 5.0 and am sick of efi problems. It has 300 rwhp on dynojet surging idle, no idle and car cant make up its mind on where to run on cold starts, So after searching and spending all sorts of money on sensors Im throwing in the towel. So now im leaning to a carb. I know I need new intake front cover fuel pump distributor, and a carb, I have never dealt with a carb before not sure which size carb fuel pump or what intake to get, this car sees mostly street with occasional road course, and very rarley drag strip action.Thanks

Foxfan88 · Oct 22, 2008

is the car speed density??

57fairlane · Oct 22, 2008

If you just run it on the motor, a 650 holley dp and a holley blue will be fine.

crookman10 · Oct 22, 2008

Foxfan88 said:
is the car speed density??

no its mass air conversion

2KsilverGT · Oct 22, 2008

You don't need a different front pump cover. You can still use your fact dist if you want too. Or buy a HEI conversion Dist and use that. i've been thinking about swaping to Carb also.

85_SS_302_Coupe · Oct 23, 2008

Just make sure you know something about tuning a carb or you'll have just as many problems with the carb as you are with EFI.

90notch_5.0 · Oct 23, 2008

i have a 600 holly dp and works fine but make sure you know how to do carb kits because they often get dirty but when they are good they are good. I have a edelbrok air-gap and it feels nice i will recomended.

85_SS_302_Coupe · Oct 23, 2008

Rebuilding a carb is such an insanely easy task to do...if you can turn a screw and read an exploded parts diagram, you shouldn't have any problem rebuilding. Most times it's as simple as new needle/seat, new power valve, new gaskets, reassemble.

Black1987Stang · Oct 23, 2008

85_SS_302_Coupe said:
Just make sure you know something about tuning a carb or you'll have just as many problems with the carb as you are with EFI.

I agree....

I know how you feel mines surging and the whole deal but Im getting it all figured out with my Tweecer. All you need is some computer work on your tune but thats entirely up to you.

I personally like being able to switch my tune at the turn of a knob and not worry about flooding, fast idle cams, chokes, wrong jet and accelerator pump sizes and so forth but theres pros and cons on both....just my 2 cents

Gearbanger 101 · Oct 23, 2008

If it were me, I'd just take it to a shop that new what they were doing and work the gremlins out of the EFI set up. It could be something as simple as a bad TPS or O2 sensor. At this point (at pretty much any point really), you'll spend more money and time converting backwards from the EFI than you would forging ahead with your current platform.

The way I’ve always seen it is that carburetors are great from a cost perspective aspect if you’re starting from scratch, or from a performance aspect if the particular class you race in requires it, but for any other purpose….EFI is the better choice. Carb lovers may argue the points all they wish, but facts are facts. And the fact is that when both systems are being run at optimum levels, the carb set up is always going to be the lesser of the two systems. A proper running EFI set up will make more horsepower/torque and display better drivability characteristics as well as increased fuel efficiency in the process.....all while requiring less maintenance.

If the thought of complete simplicity is worth more to you than all of the points above, then by all means convert to a carburetor. Just don’t make your decision to do so under false assumptions. Carbs have their share of problems too. If you think running a malfunctioning EFI system is bad, try running a carb’d set up that hasn’t been kept on top of its entire life. It’s enough to make you want to burn your car to the ground!!!

1987stangman · Oct 23, 2008

Did this problem present it's self before or after the mass air conversion? I am a huge EFI guy my self but I am not opposed to carbs at all I just think EFI is the way to go but I have made it a point to do a lot of research to understand how it works. I have some idea's that could be of assistance to you I think but you need to tell me what you have tried up to this point. Just throwing sensors and meters at the car will not fix things that need human adjustment.

crookman10 said:
no its mass air conversion

crookman10 · Oct 23, 2008

1987stangman said:
Did this problem present it's self before or after the mass air conversion? I am a huge EFI guy my self but I am not opposed to carbs at all I just think EFI is the way to go but I have made it a point to do a lot of research to understand how it works. I have some idea's that could be of assistance to you I think but you need to tell me what you have tried up to this point. Just throwing sensors and meters at the car will not fix things that need human adjustment.

ok i have had the car for a year mass air conversion was done when i bought it. As I was pulling off the highway the day i bought it i was down shifting then just puushed in the clutch doing about 10mph and it died. Never thought much of it. Then last winter came i did a trick flow kit 30lb inj. and all the goodies, was having idle surge problem then I did idle reset and it was ok but had a humming coming from t-body but it was all good otherwise it idled best around 900 to 1000 which was fine with me as long as it ran. So i took it to a dyno shop that specializes in mustangs they burned a custom sct chip turned the idle down then the surging and it dies again on deacceleration, only when the car is warm. here are the sensors ive changed used all ford sensors tps iac o2 tpi mod. and ive checked for vac leaks about a dozen times. When the car dies it fires right up and you can smell the gas. The guy at the dyno shop told me that its probabaly a bad wire somewhere, being that he charges 125 an hour and dosent know about how long it will take him said it could be 1 hour or ten hours i havent been in a huge hurry to take it back. thinking it could be the vss but my buddy is a ford mechanic and he said that would have nothing to do with it. Please help

Darkwriter77 · Oct 23, 2008

Trust me, you think you've got problems diagnosing drivability issues now with EFI, wait 'till you've disconnected the ECM and all those sensors and you have to tweak everything manually. Things don't always stay adjusted, and you're likely going to wind up with an even bigger headache because the conversion will create so many new variables for you to diagnose and tweak that you'll want to set the thing on fire and push it off a cliff.

As suggested, save yourself a lot of time, money, and frustration and just stick with the EFI - get it checked out by a pro (keep looking 'till you find someone in your area knowledgeable and willing) and once you've got the little bugs worked out, you'll be good to go.

Just a thought, aren't 30# injectors a bit much for a 300-horse setup? I would think 24# injectors would be a better match, since you don't even need those until you're up into like the 250+ range, no?

What sensors, SPECIFICALLY, have you already checked/replaced?

2KsilverGT · Oct 23, 2008

Have you tried lowering the fuel pressure or even eliminating the IAC with a manual IAC. I have a 331 with 185 AFR's and I run 30LB injectors. The injectors are probly too big. Try cutting the fuel pressure down a bit to see if it helps. I have major surging idle if i run over 35 psi of fuel. I have a manual idle air controller and that solved the majority of my problems. It's a cheap fix that usually works well..

Foxfan88 · Oct 23, 2008

a severe rich condition at idle will cause surging.
if the tuner is good and did a good tune, it shouldnt matter if the injectors are too big or not. a proper tune will run fine with oversized injectors.
i'm not a master tuner, but i have managed to get my car running good with 42lb injectors. WAY oversized for my combo since i took my blower off. but it runs fine and doesnt have any hiccups, it drives great.

and i might as well replace the VSS, its cheap and i am pretty sure it can cause issues with stalling when pressing the clutch in while rolling.

any vacuum leaks, big vac leaks will cause all sorts of problems.
whats your fuel pressure with the line pulled from the regulator?

try setting the FP to 39 psi with no vac, and set the base timing to 10* and take it back to the tuner and have him mess with it if you can.

if you have replaced all the sensors and everything and the car still acts up, i'd be guessing its in the tune or something mechanical like fuel pressure or vac leaks maybe. just some ideas.

and EFI>carb, dont swap to carb, thats taking a step backwards and will cause you headaches.

2000xp8 · Oct 24, 2008

What you are trying to do here is not logical.

First off, you had a chip done on a car that didn't run right to begin with. If it doesn't run right before the chip, all you are doing is bandaiding a real problem.

Second, you don't want to pay the mechanic to find out what's wrong, but you are willing to fork out at least $700 to convert it to a carb.
Third you are going to trash the value the of the car with a carb swap.
I find nothing wrong with a carb, on a car that came with one from the factory. Converting an EFI to one is senseless.

Fourth, your injectors are too big.

What kind of mass air meter you running?
List your mods in full.

myslo50 · Oct 24, 2008

u need to hook up a scan tool to it to see what sensors are doing

my buddy had a problem with idle when he pushed the clutch in and out, found out it had a bad ground in the tps ground wire. incorrect maf meter for injector size will cause problems. check to see if the maf conversion was done right, loosing fuel pressure when hot?????????

crookman10 · Oct 24, 2008

2000xp8 said:
What you are trying to do here is not logical.

First off, you had a chip done on a car that didn't run right to begin with. If it doesn't run right before the chip, all you are doing is bandaiding a real problem.

Second, you don't want to pay the mechanic to find out what's wrong, but you are willing to fork out at least $700 to convert it to a carb.
Third you are going to trash the value the of the car with a carb swap.
I find nothing wrong with a carb, on a car that came with one from the factory. Converting an EFI to one is senseless.

Fourth, your injectors are too big.

What kind of mass air meter you running?
List your mods in full.

trick flow h/c/i
30lb. inj
c&l mass air with correct meter tube and c&l pipe
msd 6al, msd coil and dist.
adj fuel pressure reg.
70 mm bbk t body
190 lph fuel pump bbk
sct chip with custom tune

crookman10 · Oct 24, 2008

2000xp8 said:
What you are trying to do here is not logical.

First off, you had a chip done on a car that didn't run right to begin with. If it doesn't run right before the chip, all you are doing is bandaiding a real problem.

Second, you don't want to pay the mechanic to find out what's wrong, but you are willing to fork out at least $700 to convert it to a carb.
Third you are going to trash the value the of the car with a carb swap.
I find nothing wrong with a carb, on a car that came with one from the factory. Converting an EFI to one is senseless.

Fourth, your injectors are too big.

What kind of mass air meter you running?
List your mods in full.

its not that i dont want to pay a mechanic to do the work but i dont want to take it there and have the bill end up being over a grand, because i just spent my whole "car allowance" on parts dyno and tune. plus the guy said he was going to take care of the surging idle through the computer thats why i brought it to him the way it was, but when he said that everything that he did in the computer didnt help and i should bring it back over the winter which means he would have to track down the wire at 125 an hour and i cant even guess how many wires there are to check like i said before could take an hour and it could take ten hours, by the time he finds it and fixes it. I know this guy is good he is highly recomended in the stang community here. as far as the injector size i told him what i was getting and thats what he told me to get because the car has 300 at wheels so about 340 at motor and 24's are good up to 350? horse at wheels, if you want to help read all the posts if you just want to smack bother someone else

2000xp8 · Oct 24, 2008

No smack talk, just giving you facts.
Heres what you should do:

Lose the 30's and use 24's.
19's are almost capable of 300rwhp (naturally aspirated) so 30's are wayyyy too much.
Ditch the C&L meter, you wouldn't be the first to have problems with one of those, when it came to idling and driveability. Get a PMAS 75mm.
I'd pull the chip out, any mild street car that needs a chip to idle, has another problem that needs to be addressed.

You really don't need to throw money at these problems issue i suggest to you, the 30's can be sold for 24's and the C&L can be sold for a PMAS meter.

Not to insult your mechanic, but it's common knowledge on a NA 300rwhp mustang that you use 24's. Been that way for almost 20 years.

EFI TO CARB

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