turbo 5.0 runs pig rich at idle, rough.

jongrantt · Sep 25, 2007

Alright, so I finally made the time get my car started after over a year of sitting .. figuring out some wire was ripped out of the fuel pump relay under the seat..as it would still click without it. It had me stumped forever. Its always gotta be something stupid..(including myself sometimes ha) Anyway, onto the topic..the fuel pressure is set at 42 psi on the regulator, stock ecu and ignition, removed smog pump..The timing is at 8 degrees to be "safe". I havent driven the car yet..I put brand new o2 sensors, plugs and wires..using a blow-thru setup with the 80mm maf calibrated for 42lb injectors..the car starts right away but wants to die at idle.. my eyes start to burn within seconds..it'll do ok it seems if i hold the throttle a bit but dies when the gas is let off . I hope that explaination is good enough for some help. I'm new to this site and a dummy when it comes to stuff like this. Haha.

VIPRETR · Sep 25, 2007

I believe there is a start up fuel table in your computor that needs to be changed.
It doesn't use the MAS on start up so with your 42lb injectors you are getting more than twice the fuel than with your stockers. Get a custom chip burnt for your car and that should take care of it

PUNISHER RACING · Sep 26, 2007

YOU MAY HAVE TO DRILL A BIGGER SAY 1/4 INCH OR SO HOLE IN YOUR THROTTLE BODY BLADE TO LET MORE AIR IN AT IDLE. THAT IS WHY IT SEEMS TO CLEAR UP WHEN THE THROTTLE IS TIPPED INTO. ALSO CHECK ALL YOU VACUUM LINES GOOD AND CHECK FOR VACUUM LEAKS B/T CARS ARE SHADY ACES. IF YOUR MAF IS CALIBRATED FOR 42'S AND YOU ARE RUNNING 42'S YOU'LL BE O.K.

ninety15.0 · Sep 26, 2007

Yea...you are going to have a hard time getting this thing to run smoothly without a chip. When you are in open loop (start up and high load) the car ignores the readings from the O2's and relies on pre-programed startup tables. They add a lot of fuel during cranking and startup that will really make it difficult to stay running. When i first put the tweecer on my car i was having similar issues. There is almost no way around this issue using a stock ECU. You need some sort of custom tuning.

rj95svt · Sep 26, 2007

There is no way around this problem without getting a tune. I am going to add one more little bit of information to what has already been said about the start up fuel enrichment. There is also a minimum pulse width scalar that is set up for 19lb injectors and now your injectors are more than twice as large as stock. With a good tuner your car will run and drive like stock.

jongrantt · Sep 26, 2007

Alright with that being said..i had a friend in mind who lives in the neighborhood with an SCT chip he used for his old setup..tuned for 42lb injectors, on a stock 302, 10 psi on an s-trim..same year car..so i said heck..why not? maybe it would do SOMETHING at least even though i dont have an s-trim..so i sanded off the film on the ecu to where the chip plugs in...before installing it..installed the chip..let it idle for a good 5-10 mins to give time for the ecu to maybe "learn" the chip..nothing changed really but it idling at 900 instead of 1500 like it was before..i am running downpipe out however.. the o2 sensors are 6 in+ before the exhaust exit..figure it might be back pressure to do something with it? The guy who lent me the chip said if it didnt work on my car..to try and rotate the mass air meter a bit? depending on where how you rotate the maf..determines how rich and lean it'll run? Never heard of that before but he says he read it in a magazine. I'm stumped.. I figured it would be somewhat driveable like others with simliar setups..until its tuning time. ahh :[

speedytang · Sep 26, 2007

I run a Twin Turbo and if I didn't have the PMS to remove 30% fuel at start up it would never idle when warm but if it is below 40 degrees outside I am OK since it needs the rich condition to idle. Your next thing is you will need to floor the throttle at warm start up to shut off the injectors or it will never restart because you will flood the car. You can rotate the meter and it does help but you will just move the problem usually to some other RPM.

rj95svt · Sep 27, 2007

jongrantt said:
Alright with that being said..i had a friend in mind who lives in the neighborhood with an SCT chip he used for his old setup..tuned for 42lb injectors, on a stock 302, 10 psi on an s-trim..same year car..so i said heck..why not? maybe it would do SOMETHING at least even though i dont have an s-trim..so i sanded off the film on the ecu to where the chip plugs in...before installing it..installed the chip..let it idle for a good 5-10 mins to give time for the ecu to maybe "learn" the chip..nothing changed really but it idling at 900 instead of 1500 like it was before..i am running downpipe out however.. the o2 sensors are 6 in+ before the exhaust exit..figure it might be back pressure to do something with it? The guy who lent me the chip said if it didnt work on my car..to try and rotate the mass air meter a bit? depending on where how you rotate the maf..determines how rich and lean it'll run? Never heard of that before but he says he read it in a magazine. I'm stumped.. I figured it would be somewhat driveable like others with simliar setups..until its tuning time. ahh :[

I am not sure this is a good idea. First things first if you are not running the exact same mass air meter the chip will not be anywhere near right for your car. The chip can be reprogramed for your car though and even be somewhat close but I would not get into boost with out a wideband at the very least. A centrifigal supercharger does not make full boost to redline where a turbo car can make full boost at 3,000 rpm. So it's a possibility there is not enough fuel added in the lower rpm for the boost that the turbo can build there.

millhouse · Sep 27, 2007

I disagree with most of you guys. Really, as long as your MAF is matching the injectors (and functioning properly) you should be able to get it to run well enough to idle without a tune. Hell, your drivability really shouldn’t be all that bad either.

When you set your timing to 8*, did you remember to plug the spout back in?

When you say you have to step on the throttle to get it to idle…is that because the idle rpm's are to low?

You can also try unplugging the MAF sensor to see if anything changes with your idle quality.

jongrantt · Sep 27, 2007

rj95svt said:
I am not sure this is a good idea. First things first if you are not running the exact same mass air meter the chip will not be anywhere near right for your car. The chip can be reprogramed for your car though and even be somewhat close but I would not get into boost with out a wideband at the very least. A centrifigal supercharger does not make full boost to redline where a turbo car can make full boost at 3,000 rpm. So it's a possibility there is not enough fuel added in the lower rpm for the boost that the turbo can build there.

Yeah I wasnt planning on getting on it or anything as much i would want to..if it did happen to run right..haha. Just an idea that it would change the something at the very least ya know?

jongrantt · Sep 27, 2007

millhouse said:
I disagree with most of you guys. Really, as long as your MAF is matching the injectors (and functioning properly) you should be able to get it to run well enough to idle without a tune. Hell, your drivability really shouldn’t be all that bad either.

When you set your timing to 8*, did you remember to plug the spout back in?

When you say you have to step on the throttle to get it to idle…is that because the idle rpm's are to low?

You can also try unplugging the MAF sensor to see if anything changes with your idle quality.

At first I would have to give it gas in order for it to stay alive..not because the idle was too low..because it was idling at 1500 actually..installed the chip and a friend messed with the timing a bit..and now its vice versa..with it idling forever..just as long as i dont give it gas..it'll choke up and die if i do so..I did plug the spout back in, yes. I'm going to go out there in a little bit and try unplugging the maf to see if that does anything..also rotating it if that helps.

millhouse · Sep 27, 2007

It sounds like you've got a massive vacuum leak my friend. Triple check all vacuum lines as well as the lower intake seal (particularly the valley area).

ninety15.0 · Sep 27, 2007

millhouse said:
I disagree with most of you guys. Really, as long as your MAF is matching the injectors (and functioning properly) you should be able to get it to run well enough to idle without a tune. Hell, your drivability really shouldn’t be all that bad either.

When you set your timing to 8*, did you remember to plug the spout back in?

When you say you have to step on the throttle to get it to idle…is that because the idle rpm's are to low?

You can also try unplugging the MAF sensor to see if anything changes with your idle quality.

I think you have a decent point if you are talking about HOT idle with warm/stable ect's. But on cold starts thats just not the case.

OP, Did this just start happening? Have you recently had the distributor out?

millhouse · Sep 27, 2007

ninety15.0 said:
I think you have a decent point if you are talking about HOT idle with warm/stable ect's. But on cold starts thats just not the case.

OP, Did this just start happening? Have you recently had the distributor out?

Yes, but this is not just cold starts. I agree, cold starts will be more of an issue…but it should only require slightly stepping on the throttle for a few seconds before being able to get thing moving.

rj95svt · Sep 27, 2007

The computer has start up enrichment tables set up for the stock size injectors and no matter what you do without computer tuning you will always have startup problems period. Sure you can get it to work but it will always start up very rich unless you floor the throttle to kill the injectors. not to mention the computer has a minimum pulse width which is setup for 19lb injectors and that alone could cause it to idle to rich.

With smaller injectors like 24's the size difference isn't big enough to make much of a difference but the larger the injector the more problems you will have. Most mild combos will run great with just a matched mass air meter. 94-95's are a little different though due to the load based pcm.

Bottom line is with a good tune you can make the car act just like stock. I emphisize good here because some tuners are better than others at fixing the driveability problems. You won't have to touch the throttle it will crank and idle steady and won't have the quirks a car without a good tune will have. A turbo car needs a tune anyways otherwise you are just asking for blown headgaskets or much worse.

enyawix · Sep 27, 2007

go to a turbo mustang site. google we find what you want

speedytang · Sep 27, 2007

rj95svt is correct on everything said. Matched meter to injectors does not give you a 100% running condition vehicle it just allows the car to function.
You must tune.

enyawix · Sep 27, 2007

speedytang said:
rj95svt is correct on everything said. Matched meter to injectors does not give you a 100% running condition vehicle it just allows the car to function.
You must tune.

sometimes it is close but you need a tune

ninety15.0 · Sep 28, 2007

Here's the deal. Without a tune...the only control you have over fuel delivery is pressure adjustments. Fuel injectors were designed to operate at certain pressures for a reason. At lower pressure, the spray pattern gets sloppy and doesnt properly atomize the fuel particles. The A9L family of processors did not offer an adjustment of the minimum injector pulsewidth, that didnt come along until T4MO processor family in 94. Either way the point is if you take out fuel pressure, you get sloppy injector performance and risk going lean up top, definately not what i would want to do.

You are also going to have to rescale all of the load tables in the computer as well. With a turbo you will see effective load above 100% while in boost. There are too many variables with forced induction that just cannot be overcome without a tune.

millhouse · Sep 28, 2007

ninety15.0 said:
Here's the deal. Without a tune...the only control you have over fuel delivery is pressure adjustments. Fuel injectors were designed to operate at certain pressures for a reason. At lower pressure, the spray pattern gets sloppy and doesnt properly atomize the fuel particles. The A9L family of processors did not offer an adjustment of the minimum injector pulsewidth, that didnt come along until T4MO processor family in 94. Either way the point is if you take out fuel pressure, you get sloppy injector performance and risk going lean up top, definately not what i would want to do.

You are also going to have to rescale all of the load tables in the computer as well. With a turbo you will see effective load above 100% while in boost. There are too many variables with forced induction that just cannot be overcome without a tune.

The real question is…how spot on does your tune have to be? While having a custom tune or some aftermarket piggyback/standalone is without a doubt the best route to take, it is not necessarily a "must have". There are ton's of guys running around without an optimized tune (stock) and either locked timing or a retarded base that have had excellent on track results. Sure, you sacrifice a small amount of road manners…but to some it's really not nearly as noticeable as you would think.

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