From Mustang EFI back to carb

[Chief Master Sergeant]

I’m about ready to give up on this EFI journey. The engine is a 96 Explorer. If I do this, what intake should I use. Used an Edelbrock Performer on my stock motor in the past. Will this match up with the GT40 heads? Or is there something else I should look at?


Sent from my iPhone using Tapatalk

 

[nvrstuk]

Edelbrock will be fine.

Can I ask what went wrong on the journey? What type of EFI did you try using?

 

[Chief Master Sergeant]

Edelbrock will be fine.

Can I ask what went wrong on the journey? What type of EFI did you try using?

Mustang EFI from a 90 Mustang. Been fighting a high idle and nothing seems to remedy it. New computer, almost all sensors have been replaced, and no indication of vacuum leak. Just when I think I’ve got a solution, a test drive has me at stop lights with the engine screaming. Never had these issues with a carb.


Sent from my iPhone using Tapatalk

 

[EPB72]

CMS,,, just curious have you checked your tps signal wire output at closed throttle and closed to wot sweep ,,,and do you know if the throttle stop screw has been messed with?

 

[ransil]

IAC upside down
bad IAC
pin 30 not grounded
shitty ground -EECIV-Block-Battery

 

[Chief Master Sergeant]

CMS,,, just curious have you checked your tps signal wire output at closed throttle and closed to wot sweep ,,,and do you know if the throttle stop screw has been messed with?

I checked the voltage at KOEO at under 1v. I did set base idle, per guidance I saw on Youtube. Haven't checked it as you mentioned though.


Sent from my iPhone using Tapatalk

 

[EPB72]

for the tps ..off the top of my head the 3 wire colors are orange,green and black,,,referece voltage ,,signal return and sensor ground,,With a multimeter set to volts Back probe the signal return wire and the meter ground lead to a good ground ,with key on engine off expect to see below 1v ,, .8v being ideal,,,now slowly open the throttle till fully open now expect to see near reference voltage,,but while moving throttle watch meter for a constint climb in voltage readings no drop outs,,and as ransil suggested recheck grouds

 

[Eoth]

I took a explorer back to carb just because I didnt have the time to get it sorted out before a roundup... Then when I had the time, I just got lazy and installed a Fitech system. No regrets but in hindsight it would have been less work just to get the OEM EFI working.

 

[Chief Master Sergeant]

for the tps ..off the top of my head the 3 wire colors are orange,green and black,,,referece voltage ,,signal return and sensor ground,,With a multimeter set to volts Back probe the signal return wire and the meter ground lead to a good ground ,with key on engine off expect to see below 1v ,, .8v being ideal,,,now slowly open the throttle till fully open now expect to see near reference voltage,,but while moving throttle watch meter for a constint climb in voltage readings no drop outs,,and as ransil suggested recheck grouds

Yeah, I watched a Youtube video on setting the voltage for the TPS. Couldn't get the voltage right with the stock one I had, so I bought a new one and it worked. Set to below 1v. Maybe I'll try what you suggested today. Grounds will be checked for sure

 

[nvrstuk]

Chief- I sure hope the responses you're getting help you figure it out!!

Worth trying all these suggestions from some extremely knowledgeable EFI- way past my level... I was just hoping my asking the question what was wrong would get the help coming strong!

Good luck!

 

[Jdgephar]

I hope you get it fixed too! I'm cheering for you. I also have the 1990 mustang fuel injection in mine. I love it, I don't want to go back to a carb. I'm curious to see if you get it fixed and what the issue is!

Any chance the throttle cable is just getting hung up, and not closing the throttle plate all the way? More fuel without the air also I would think just floods out the engine instead of revving higher and higher.

Also, did you check the codes on the EEC?

I added an extra spring to the throttle. The one that came in my kit was too light, and my foot would hurt after driving a little while from holding back (yeah, there's a whole science for how much spring pressure on the skinny pedal). It's much better for me now.

 

[Timmy390]

I added an additional spring to my EFI as well.

Tim

 

[Chief Master Sergeant]

I hope you get it fixed too! I'm cheering for you. I also have the 1990 mustang fuel injection in mine. I love it, I don't want to go back to a carb. I'm curious to see if you get it fixed and what the issue is!

Any chance the throttle cable is just getting hung up, and not closing the throttle plate all the way? More fuel without the air also I would think just floods out the engine instead of revving higher and higher.

Also, did you check the codes on the EEC?

I added an extra spring to the throttle. The one that came in my kit was too light, and my foot would hurt after driving a little while from holding back (yeah, there's a whole science for how much spring pressure on the skinny pedal). It's much better for me now.

I’ll try an extra spring. And yes, I ran the codes. Talked through them with a few brothers and nothing seemed to work. I’ll try some of these tips and get back on here. Thanks to everyone for the tips.


Sent from my iPhone using Tapatalk

 

[73azbronco]

Another opportunity to take it to a ford dealer let them scan it. I know they have a multitude of mustang guys screwing their stuff up so they know how to fix an oops.

 

[WheelHorse]

If you let it start and warm up does it idle fine in the driveway?

If its after you go down the road the high idle occurs, do you have the speedo sensor hooked up? I fought this one time and found out it was not hooked up. Once I hooked it up , it could sense when I came to a stop and then it would idle as it should.

 

[jw0747]

Here are four suggestions on how to correct idle in Mustang EFI:

https://www.muscularmustangs.com/iac.php

 

[Chief Master Sergeant]

If you let it start and warm up does it idle fine in the driveway?

If its after you go down the road the high idle occurs, do you have the speedo sensor hooked up? I fought this one time and found out it was not hooked up. Once I hooked it up , it could sense when I came to a stop and then it would idle as it should.

Pretty sure it is, but I’ll check. That’s exactly what’s happening. Haven’t found a tighter spring yet. Hoping it can be something that simple.


Sent from my iPhone using Tapatalk

 

[Chief Master Sergeant]

Here are four suggestions on how to correct idle in Mustang EFI:

https://www.muscularmustangs.com/iac.php

I tried this before, but will do it again. Thanks


Sent from my iPhone using Tapatalk

 

[noslo5o]

You should try the Base Idle Reset Procedure.

1. Clean TB with carb cleaner and nylon brush (toothbrush size). Engine off, fully open TB blade and spray/brush TB until all gunk and oil residue is cleaned.

2. Allow to dry, or close TB blade and start engine until it clears all carb cleaner fumes/liquid.

3. Let engine idle...if it doesn't, increase idle speed via TB stop screw until engine stays idling on its own.

4. Disconnect IAC valve, if engine dies repeat 3 with IAC disconnected.

5. Set idle speed to the lowest setting possible between 650-850 rpms with IAC disconnected. It is key to use the lowest possible to prevent idle surge, rolling, etc once the IAC is connected as follows.

6. Turn engine off, and reconnect IAC

7. With Ign On Eng Off, check TPS voltage output....if it's between .8vdc - 1.0vdc, it's OK. This voltage check should be done between the Green and Black wires at the TPS side connector as shown in the pic below (FYI: Green = TPS Signal, Black = SIGRTN, and Orange = VREF)....(-) terminal of the DVOM on the Black wire and (+) terminal on the Green wire.



8. Disconnect battery (-) for 3-4 minutes.

9. Reconnect battery, start engine, allow it to idle for 2-4 minutes to confirm setup,

10. If idle speed falls too low or stalls, increase idle speed via the TB set screw a little at a time.

11. Turn engine off for 20 seconds, re-start engine and repeat 9 - 11 if required.

12. Reconfirm TPS output is within the .8vdc - 1.0vdc range optimum range.

NOTES:

1. No need to reset ECM KAM (reset computer), the TPS minimum value used for idle control, is reset automatically by the EEC-IV every time the ign is cycled on-off for 20 seconds-on.

2. If the TPS output is within 6vdc - 1.1vdc, it's still acceptable, since no TPS failure codes will be generated, and it falls within the EEC-IV .5vdc - 1.19vdc working range.

13. Allow a 10-20 minute "relearning" period under normal driving conditions (drive cycle).....you're done!

 

[Timmy390]

My understanding of the issue is the idle is fine till you drive it and come to a stop. Once stopped the idle is high and never settles down. After it cools off its back to idling correctly.

Couple of things. What is the cold idle? What is the high idle once warmed up?

While the issues I had were big cam and SN95 EFI not liking it I did find some interesting things when troubleshooting.

When cold the engine runs off a set table in the ECM then once warm it starts adjusting for the conditions it sees with all the sensors. A bad coolant sensor can cause a high idle after the engine is warm. Not sure the 90 Stang had a air intake temp sensor but the 95 did. It also can cause issues.

Vaccum leak is most likely the issue IMO if it truly is only idling high after warm. I found my brake booster was leaking internally and causing 200 or so higher idle after warm.

Remove and replace all rubber plugs and he the vinyl vacuum caps. The will not crack. All my rubber ones cracked in less than a year.

Tim