Fox dumping fuel at idle afr 10:1

Mattjhop23 · Aug 5, 2024

so I'm kinda just running down the line cause some things are probably old. got tuned few months ago stock bottom end 302 made 540 wheel v2 14 lbs of boost. went to start it after a little cruise over the weekend hard start started drove 3 miles home. next morning rough start idle surge, running rich 10:1. I've replaced intake sensor, engine coolant temp, just got a new ecu a9l my next steps are stu ck injector or maf is bad its a pro m maf. cylinder 5 and 8 was dripping fuel when i pulled them after a few start and idles. just some extra knowledge.

Noobz347 · Aug 5, 2024

Sounds like you have at least two injectors that are stuck open. Pull them and send them off to get flow tested.

What tune? Is it a chip tune? Have you reseated both, the ECU and the chip?

What does your fuel system consist of?

Injector size
Fuel pump
regulator
rails

Mattjhop23 · Aug 5, 2024

Noobz347 said:
Sounds like you have at least two injectors that are stuck open. Pull them and send them off to get flow tested.

What tune? Is it a chip tune? Have you reseated both, the ECU and the chip?

What does your fuel system consist of?

Injector size
Fuel pump
regulator
rails

fuel system is stock, stock pump 42 lb ford motorsport injectors aeromotive regulator on stock rails been like that since i got it but fuel is going to be upgraded this winter i have a sct chip on a a9l i had a very reputable shop look at the tune on a dyno april and they said that they wouldn't change a thing its good.. Buddy's friend owns a racing company said $20 a injector to have tested a cleaned

AeroCoupe · Aug 6, 2024

Have you checked for codes? CEL will only illuminate for emissions related codes but others can be present and it will never flash.

I am just going to say it...there is no way in hell the stock 88 lph in tank pump is moving enough fuel for the motor to generate 540 rwhp. It will take north of 250 lph to do this so at a minimum there is a 255 lph pump in the tank and possibly an external inline booster pump.

Mattjhop23 · Aug 6, 2024

AeroCoupe said:
Have you checked for codes? CEL will only illuminate for emissions related codes but others can be present and it will never flash.

I am just going to say it...there is no way in hell the stock 88 lph in tank pump is moving enough fuel for the motor to generate 540 rwhp. It will take north of 250 lph to do this so at a minimum there is a 255 lph pump in the tank and possibly an external inline booster pump.

I just got a build sheet when I got the car and said nothing about a pump I assumed it was stock and injectors were just at max duty cycle. I’ve personally never pulled the tank, I have ran codes only codes that come up are engine temp code cause I ran the test before operating temps cause it dumps fuel and floods out. Engine temp sensor brand new and plug connector checks good. The only other codes that show up are 42/92 which are both bank systems rich.

Cheapskate207 · Aug 6, 2024

I think a 255lph will support 570hp? Anyway..

Is the car throwing any codes? That’s probably the first place to start. Having the injectors tested and cleaned it’s probably not a bad idea anyway if you bought the car with them installed.

Also, 540 hp on a stock bottom end. I see you live life on the edge lol

AeroCoupe · Aug 6, 2024

If you are showing both banks rich then I would look for where the O2 harness plugs into the main engine harness. That came unplugged on me going home one time and the car ran rich and like crap. Took some looking around and out of frustration just happened to see it. Its that or both your O2's took a dump at the exact same time.

Mattjhop23 · Aug 6, 2024

I was wondering if one went bad if both banks would run rich. I literally put couple hundred miles on the car parked it for few hours and then trouble starting. I’ll do that tomorrow and check the harness make sure plug connectors are good. Appreciate all the advice.

Mattjhop23 · Aug 6, 2024

Cheapskate207 said:
I think a 255lph will support 570hp? Anyway..

Is the car throwing any codes? That’s probably the first place to start. Having the injectors tested and cleaned it’s probably not a bad idea anyway if you bought the car with them installed.

Also, 540 hp on a stock bottom end. I see you live life on the edge lol

Yea tell me about it when I got it needed some things addressed pcv vented terribly kept blowing lower intake seals made 428 when I got it but I figured let’s send it lol only engine temp sensor (ran the test before operating temp was up cause it’ll flood the car out and dry if it idles to long. But other than that just both banks super rich 42/92 were codes

Mattjhop23 · Aug 11, 2024

AeroCoupe said:
If you are showing both banks rich then I would look for where the O2 harness plugs into the main engine harness. That came unplugged on me going home one time and the car ran rich and like crap. Took some looking around and out of frustration just happened to see it. Its that or both your O2's took a dump at the exact same time.

Anyway I can test the plugs when I first got it it had rear lower intake leak and rear main the o2 plugs from the o2 sensors were filled with oil. Anyway to test plugs themselves o2 side and engine harness side

AeroCoupe · Aug 11, 2024

Clean them out with a mass air meter cleaner and an old tooth brush. Let them dry / evaporate then use some anti-ox like this stuff and put them back together.

https://www.lowes.com/pd/Gardner-Bender-1-oz-Ox-Gard-Anti-Oxidant-Compound/4514334

That should clean them up and keep the water and other crap out of them.

Mattjhop23 · Aug 11, 2024

Is their any way to check the plug that the relay for the MAF. I meters the relay and it’s good but I was wondering if I could meter the plug on the harness to see if that’s good while I’m at it. Since both banks being rich could be a MAF issue… appreciate it. I was just giving a update been kinda burnt out on the car for the last week

AeroCoupe · Aug 11, 2024

What MAF is on the car? I am not sure a stock MAF would be able to move enough air for the blower but I am not super knowledgeable on forced induction.

I googled up an injector calculator and plugged in 8 cylinders, 540 rwhp, and supercharged. To get enough fuel for that combo through the 42 lb/hr injectors you have to at a minimum use 90% duty and 60 psi to get it down to 40 lb/hr injectors. At 100% duty and 45 psi they are just adequate. Are you sure they are 42? They will have a green top if they are stock Ford units.

Mattjhop23 · Aug 13, 2024

AeroCoupe said:
What MAF is on the car? I am not sure a stock MAF would be able to move enough air for the blower but I am not super knowledgeable on forced induction.

I googled up an injector calculator and plugged in 8 cylinders, 540 rwhp, and supercharged. To get enough fuel for that combo through the 42 lb/hr injectors you have to at a minimum use 90% duty and 60 psi to get it down to 40 lb/hr injectors. At 100% duty and 45 psi they are just adequate. Are you sure they are 42? They will have a green top if they are stock Ford units.

I’m 100% sure they are ford Motorsport I was figuring they are running over duty cycle. It has a pro-m MAF that is calibrated to the injectors. I contacted pro-m racing to see if they can test and if needed recalibrate the MAF. I’m putting new plug wires on for s and giggles. But if injectors are running over max it would explain if they are acting up. After handful of starts and idles I pulled plugs. These are brand new plugs through them in when it started idling rich. The 2 plugs that are clean are cylinder 1 and 5 the rest were black fouled. Appreciate the repeat reply’s

Noobz347 · Aug 13, 2024

Is that oil or fuel on those plugs?

AeroCoupe · Aug 13, 2024

The injectors cannot be driven past 100% duty. The issue is at 100% duty the ability to control the fuel flow is pretty miserable. IMO tou really should move up in injector size (like 60’s) and go to a Lightning 90mm MAF and get it retuned. Tuner should have a mass transfer function for the Lightning 90mm MAF. Only thing after this would be the fuel pump being too small but an inline booster pump will help that if needed.

Mattjhop23 · Aug 14, 2024

Noobz347 said:
Is that oil or fuel on those plugs?

Fuel

Noobz347 said:
Is that oil or fuel on those plugs?

fuel.

TOOLOW91 · Aug 14, 2024

Start checking vaccum lines and make sure nothing is off. Causing the car to suck unmetered air will make it do odd things

General karthief · Aug 14, 2024

Pull the FPR vacuum line off to check for fuel smell.
Oh NO SMOKING!!

2000xp8 · Aug 14, 2024

I don't think i'd waste time building out the fuel system for this engine.
IMO, just dial it back. 540rwhp is on borrowed time anyway not to mention the difference between 540rwhp and 500rwhp on the street is negligible.
I think people underestimate how long and how much money replacing an engine that split the block costs.
Blowing it up in epic fashion could be a 20k mistake that takes years to correct (if ever).

Fox dumping fuel at idle afr 10:1

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