Just installed new injectors an now car idols rough

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Just installed new injectors an now car idols rough

February 12, 2013, 09:48:14 PM

Just installed a new set of 21 lb injectors in a stock 5.0 in my 86 bird it has a rough idle at times an what's to die when I stop an put it in park any ideas on what I need to do to fix it or add to it oh an it don't drink the has it guzzles it an I need it for my daily driver so I need the fuel consumption to go down ALOT LOL

Just installed new injectors an now car idols rough

Reply #1 – February 12, 2013, 09:53:53 PM

Is it a mass air car ? It needs a matching maf and if its not a mass air car bigger injectors will not work

Just installed new injectors an now car idols rough

Reply #2 – February 12, 2013, 10:12:09 PM

Stock tells me that it's speed density which I'm guessing it still is. Go back and install 14lb injectors. You can't change them out (without chips and a tune). There's no reason to use larger on a stock motor.

Just installed new injectors an now car idols rough

Reply #3 – February 12, 2013, 10:29:07 PM

injectors are way to big for the stock efi system

Just installed new injectors an now car idols rough

Reply #4 – February 12, 2013, 10:39:12 PM

@stang8u
The car runs fine while driving its just when it's at a stop it may want to idle rough they work in the car
@seek
I was tring to get as close to stock as possible I tried looking up stock injector size online an all I could find was 20 lb injectors so I ordered 21 I still have the stock ones they only have 121000 miles on them but I have them I guess that will be next to clean an reinstall old injectors or have it tuned or find a chip for it

Just installed new injectors an now car idols rough

Reply #5 – February 12, 2013, 11:40:45 PM

I really don't want to get into that upper intake again any ideas on were to look for a chip or who
makes one

Just installed new injectors an now car idols rough

Reply #6 – February 13, 2013, 12:36:55 AM

Just a chip still won't work. A chip won't do diddly to a stock engine anyway, but that's not the point here.

The EEC is set to run on 14 lb./hour injectors. Also, changing injectors and/or a cam in a speed density engine is also a big no-no.

There's no magical fix for your problem, save going back to 14# injectors. That's a fact. I'm not trying to be a know it all, but a lot of us have been playing with these cars for a long time, and we know in our sleep what can be done and what can't.

It's true, it amy run rather well at speed, but, as you state, it idles like shiznit because the injectors flow more fuel than what the EEC's parameters are thinking are there. Hence, it runs pig rich.
With the car running, can you smell unburnt or raw fuel from the exhaust?

Don't believe us? Take it to a sniffer and see the amount of hydrocarbons from the tailpipe.

Want to make some power? Get some GT40 heads, an HO cam, and some good headers and exhaust. Throw that on, combined with an EEC (either speed density, or mass air, your choice) and then let the fun begin.

But....even on a newer 5.0, even with mass air, you can't just slap injectors in without also stepping up the Mass air meter. Everything has to work in conjunction with each other.

Good luck.

Just installed new injectors an now car idols rough

Reply #7 – February 13, 2013, 12:51:54 AM

Quote from: ThunderbirdSport302;409240

Just a chip still won't work. A chip won't do diddly to a stock engine anyway, but that's not the point here.

If it has the settings for the new injectors, it should be fine. Any settings can be overridden in the EECIV. It's pointless though.

Quote from: 86TBIRD;409228

I really don't want to get into that upper intake again any ideas on were to look for a chip or who
makes one

IF something like that worked, it would be cost-prohibitive. There is nothing you could "buy" off the shelf. All you can do is find a tuner who will charge you by the hour to guess at the tune until it's right enough. They'd need a wideband sensor installed on your car, software that has a base tune to build from, and likely a dyno. I can't see anyone putting effort into such a feat since these are NOT mustang EECs without you spending thousands of dollars for no reason. Just stick the 14lb injectors back in. Why did you pull them in the first place?

Just installed new injectors an now car idols rough

Reply #8 – February 13, 2013, 02:14:38 AM

Or; OP, find a wrecked Mustang with a good engine. Acquire said engine, and EEC. Install both into your car. Change fuel pump, and add necessary wire for mass air, if engine is not speed density.
There's a writeup on CoolCats.net about this, and so much more. Your car I take it is an '86, so it would be pretty much drop in and run, since your car is a 5.0, no wiring would need changed, unless the engine and eec are mass air.

Seek, I feel that with smaller throttlebody and E6 heads, even 19# injectors would be overkill for his engine...assuming a chip could fool the EEC into it. There's still a lot of fuel to account for. I don't think there's a workable way to do that, or else we would've known about it long ago....or else it's just so much easier to throw on E7 (at least) heads and toss in an HO cam. I don't know, but I have a feeling that with his injectors, unless he puts on better heads, an aftermarket cam, and at least an HO intake, he'll have problems with idling, fuel economy, and eventually plugged cats due to carbon buildup.

It's about akin to putting a 750 double pumper Holley on an old stock 5.0, and expecting it to run perfectly without putting smaller jets in...of course, what I know about carbs can be written on a flea's back.

Just installed new injectors an now car idols rough

Reply #9 – February 13, 2013, 02:17:50 AM

I can see where the EEC would ground the higher-rate injectors for a shorter time, but as you state, it's not at all cost effective to tune the EEC for that. OP, there are literally tons of cars to get 14# injectors from. No rocket science to getting them, cleaning them, and reinstalling them. New pintle caps and o rings are available at any decent parts store, too.

keep us updated :)

Just installed new injectors an now car idols rough

Reply #10 – February 13, 2013, 02:42:43 AM

@tbirdsport
Thanks for the advise I'm learning as I go on this ole car but now if I converted the car to mass air would that be enough just wondering thanks
@seek
I pulled them because the car has been setting for over 6 year it was my first car an I thought if I was going
To make I my daily drive I didn't need to go running after parts every weekend trying to keep it running
So I made one BIG order to summit racing I got new tires drums shoes shocks struts plugs wires "fuel pump an sending unit" (turned it that was my problem all along) INJECTORS new rotors pads an fuel filter some what starting at the ground an going up but u got to have good footing on the road or you'll just slide off the edges

I do have a HO intake upper an lower just no throttle body would that also help thanks

Just installed new injectors an now car idols rough

Reply #11 – February 13, 2013, 06:17:12 AM

Simply put never just throw injectors in a car that are to big. 21 LB injectors are a bit to big. @200Hp and 80% DC with fuel pressure @40 LBS you should have a 16 LB injector. With that a 21 Lb injector at the same parameters can sustain 275 Hp.

Even a 19 LB injector is a bit big but workable to an extent. A 24 is a bit to big. Guys are getting in to the 325HP range with 24 injectors. Just saying!

Are your original injectors GREY?? If so they are in fact 14 LBS!!

The 1986-95 HO 302 Mustangs use a 19-pound injector.
The 1996-2003 4.6 SOHC Mustangs use a 19-pound injector.
The 1993-95 Cobra Mustangs use a 24-pound injector.
The 1996-2001 Cobra Mustangs use a 24-pound injector.
The 2003 Cobra Mustangs use a 39-pound injector.
The 1987 - 1988 TC uses a 35 LB injector

Just installed new injectors an now car idols rough

Reply #12 – February 13, 2013, 12:08:41 PM

Quote from: ThunderbirdSport302;409245

Seek, I feel that with smaller throttlebody and E6 heads, even 19# injectors would be overkill for his engine...assuming a chip could fool the EEC into it.

It's simple to change the injector settings if there is a base tune to go from. I know the things are way too big for the stock motor. He'd need a completely different engine to make use of 19+ lb injectors, but the functions in the EEC COULD be modified to work fine with the larger injectors. There is no way that it has any purpose though - even the stock injectors are fine for mild part swaps, and they don't require changing the EEC in any way.

From this entire thread, and confirmed a few posts down, he is fairly young and may not have the means to do a HO swap. I recommend installing HO parts (other than an intake) since we don't know his current mechanical level. He's looking to get the car running. 14lb injectors are the thing to use.

Also op, when my car was stock and had minor mods like the HO intake, I would average 22mpg taking suburban roads to college without either a heavy or light right foot. On the highway I'd get 30mpg, 34 after some mods. Since increasing my power, I'm down to like 18mpg on the same suburb route and my highway is right around 30-31. You should be able to get pretty good fuel economy if you just get the car running right, with stock parts.

Just installed new injectors an now car idols rough

Reply #13 – February 13, 2013, 12:33:30 PM

Also, OP, if you're looking for some HO stuff, I have an intake, complete with 19# injectors, throttlebody, fuel rail, injector harness, etc.
I also have an EEC from a lincoln mark 7 (same as Mustang HO) that will work with the intake. All you'd need is an HO cam, and some heads, I think I have a set of decent E7s as well, but shipping them wouldn't be cost effective.

It's an option, if you're inclined.

If you were closer, I could help you put it on, and show you some stuff along the way.

Just installed new injectors an now car idols rough

Reply #14 – February 13, 2013, 05:34:39 PM

I appreciate all the advice I'm just going to swap out the injectors an be done with it the ho swap would be nice but after just buy a house an with my boy turning one this next month I think I have things that come first
@ seek
What mods u run to get the 30+ mpg