Idle problem

Posted this on another page on this forum but did not get anything. Maybe I was in the wrong place? 92 5.0 70 mm throttle, 76 mm mas air with 19# sample tube . Cold air kit with K&N . Ported upper manifold to match throttle body, under drive pullys. All else on engine is stock. Bad idle problem after engine reaches operating temp and is at a stand still in drive. (It is an AOD) Say, if im at a traffic light to long idle will suddenly drop to the point that i have to "feather" the gas with the brake. I have cleaned the K& N , clean idle solinoid, new plugs, cleaned and re lube "salt & pepper". Adjusted TPS with volt mtr. to around .99. New cap and rotor. Ford racing wires not replaced. They are still fairly new and show no sighns of any wear. My performance shop pulled out a lean code in the computer and i had a "check " light befor he cleared it. Oh, cleaned the maf sensor also. Plugs were white as a ghost when i changed them which only makes sence with the lean code. Timing set to factory. Here is what I think the next step is and were YOU chime in and tell me what ever you think. # 1 Vacume (cheap to fix / hard to find) . #2 Injectors(OUCH!!) #3 Fuel pump ( I have a 190ltr) that I never put on brand new in box. I am really not comfortable with a fuel pump upgrade or injector upgrade(I bought a 24#set on e-bay) . As factory fuel sys should be able to handle 225 rear wheel horses that I have a dyno slip for. This car has 58 thou original miles . I love my car but this is FREAKIN PISSIN me off!!!! I have been at this for a month.

If you can upgrade the fuel pump and you HAVE one, then do so and be done with it

Likely nobody knew of an exact fix and stayed quiet, but ME... Everyone knows I NEVER stay quiet even when I don't know schitt from Shineola

I do know this... You haven't imparted enough info yet...

How long is TOO LONG at idle in drive?

Does the idle pick back up after you've feathered the fuel, or must you Continue doing it from then on, or until the engine has been shut off and cooled down?

Knowing these things is good and helpful.

You may get diffrent readings to your computer from your O2 sensor combined with your Coolant temp sensor and the computer is leaning out the mixture to fix a problem that only it can see...

To long is about 3 min. Yes , I must feather pedal at every stop after that. Are you sayin its the temp sensor or O2s or both? I had a 97 Ranger that O2s went bad at about the same mileage my stang is at now. HHUUMMM!! Thanks for at least sayin somthin!! Idle does get better after engine cools off completely and is re started. Just so you know (I forgot to mention), this motor has always ran at first mark below half on temp gauge. Even in the Carolina dog days of summer the gauge never hits half way mark. WHICH IS WHY the motor should be a little rich NOT lean. With my very moderate mods , do u think the motor / injectors can handle a 190ltr. pump? Can it also handle the 24# injectors too?? I kinda wanted to get this prob fixed before moving on to any more performance upgrades. Oh, bye the way FE, I been watchin you and was counting on you NOT being quiet!! thanks again.

Originally Posted by FEandGoingBroke

If you can upgrade the fuel pump and you HAVE one, then do so and be done with it

Likely nobody knew of an exact fix and stayed quiet, but ME... Everyone knows I NEVER stay quiet even when I don't know schitt from Shineola

I do know this... You haven't imparted enough info yet...

How long is TOO LONG at idle in drive?

Does the idle pick back up after you've feathered the fuel, or must you Continue doing it from then on, or until the engine has been shut off and cooled down?

Knowing these things is good and helpful.

You may get diffrent readings to your computer from your O2 sensor combined with your Coolant temp sensor and the computer is leaning out the mixture to fix a problem that only it can see...

What about vapor lock???

Vapor lock isn't possible on EFI (you watch someone will find a way to say it happened just to make me look bad).

Check your fuel pressure and verify its not too low (I assume you have a shop manual to tell you how to do it), I'd also recommend an adjustable fuel pressure regulator when you can get around to it.

Originally Posted by ZephyrZ7

Vapor lock isn't possible on EFI (you watch someone will find a way to say it happened just to make me look bad).

Check your fuel pressure and verify its not too low (I assume you have a shop manual to tell you how to do it), I'd also recommend an adjustable fuel pressure regulator when you can get around to it.

Sorry I failed to say I have an adjustable regulator. Gauge in engine compartment is set at 43psi with engine running and vacume (static pressure) removed. Yes, I have a Ford shop manual for this car. Just an opion but if you have a car you care about and cant fork over 75 bucks for the shop manual , well then, you souldnt have the CAR!! Sorry, but no virgin here. Been around cars for 33 years . I am 43. Been under cars since i been 10 year old (says the guy who can`t fix his idle problem!!) . Your answer is however quite valid though and a raise in fuel pressure may be needed . At 43 psi though I would be afraid to raise it much more as the injector spray pattern may become irratic (for 19# injectors) or " lock up" an injector (good-buye motor)!!! Thanks for you help as I do honestly need it. I did learn that vapor lock is out of the question . So, see, smarty pants (me) learned somthing .

One of your sensor wires maybe broken or intermitant. Look inside the connectors to see if one of the terminals is pushed in, or corroded...

Only thing I can think of.

43# on a 24 # injector is fine. You can run up to 50psi on a 24# injector, I rarely see less than 40 PSI of running pressure on a stock vehicle and most times it's closer to 50.

I don't think the lean is from fuel pressure.

I'm still thinking it's a sencor like Coolant temp, (many car's built after 1990 generally have 2, one for puter one for gauge), or O2 sensor giving false readings that's why the lean and since it's still working the computer won't see it as a code to set...


FE
P.S. Thanks for the compliment. It means a lot to me, and very likely pisses off 2 people here that can't stand the sound of my fingers on the keyboard But you don't see them responding to you... Just me, the dumbass who never shut's up

Originally Posted by Mikes66

One of your sensor wires maybe broken or intermitant. Look inside the connectors to see if one of the terminals is pushed in, or corroded...

Only thing I can think of.

Litte confused!! There are about a dozen sensor wires on an efi mustang. Are we talkin temp, air , idle , voltage, ect.?? or #5 all of the above! Definatley could be a wiring problem. One of the most(if not, the most) difficult things to find on any car. Thank you very much! This is a
very low milage car but also 16 years old. Point is, if it is plastic or rubber , it will break if you touch it.

Originally Posted by FEandGoingBroke

43# on a 24 # injector is fine. You can run up to 50psi on a 24# injector, I rarely see less than 40 PSI of running pressure on a stock vehicle and most times it's closer to 50.

I don't think the lean is from fuel pressure.

I'm still thinking it's a sencor like Coolant temp, (many car's built after 1990 generally have 2, one for puter one for gauge), or O2 sensor giving false readings that's why the lean and since it's still working the computer won't see it as a code to set...


FE
P.S. Thanks for the compliment. It means a lot to me, and very likely pisses off 2 people here that can't stand the sound of my fingers on the keyboard But you don't see them responding to you... Just me, the dumbass who never shut's up

I want to be clear. I am currently running 19# @ 43psi. 24# are sitting on my desk wainting on a stable engine to put them in. Going to try water temp and air temp sensors first . Then move onto O2 sensors. You got me stumped on the one for puyter? Were is it??