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Terrible idle and then dead, tought to keep running "FAST EFI"

K85 Octane

K85 Octane

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Thank GOODNESS I didn't have this problem while in Moab. It's not fun loosing steering and brakes. :(


Just had the truck out today at the local mud hole. Everything was great. Drive about a mile on rocky dirt to the exit. Then drove another ~6 miles out of the mountain through a twisty road. Come up to the first stop light and it dies. :eek1: I get it fired back up but it wont idle, so I do the whole brake pedal and gas pedal at once thing all the way home ~14 miles :doah:

I get home and notice while parking (and trying to keep it running) that I'm blowing major black smoke. I pop the hood and have my brother take a look at the fuel pump pressure gauge. It should be ~44 psi. It will run 44psi while it's choking at idle. To keep it from dying, I bring it up to ~1200rpm and which point it's controllable, but the fuel pressure is ~34psi. That's weird.

I had an idling problem before and found it was the Walbro pump taking a dump. But it never blew black smoke and would run at 10-20psi and fluctuate wildly, no mater the rpm. :dunno:

I parked the truck for tonight. I'll deal with it another day. This is a FAST EZ EFI system and I'll be calling them later, see what they think. I noticed my computer light isn't on while the ignition is "KEYED ON". It is only on while running. I don't think it should be like that, so I'm lost there. It's not blinking, so there's no codes. :dunno:

Once off idle, truck does fine. Performed great today too, climbed all I wanted and managed to RIP OFF TWO DIFFERENT JEEPS' BUMPERS :haha: and break my yacht braid rope 3 times :(

EDIT from later post:

 
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Is there a fuel pressure regulator in the system? Sounds like it may be stuck open some and flooding the engine.
 
The gauge and regulator are one unit.

I'll thread the adjuster in and out just to make sure it's not stuck.
 
Still laughing about the Jeeps. Just wasn't going their way today.

Two Jeeps are trying to yank a stuck Jeep. I pull up to the last Jeep and hook up. I've got about 7 feet of yacht braid slack and they tell me GO! I jumped all over the skinny pedal :haha:and pulled that guys offroad bumper clear off. I don't know if the bolts snapped or if they pulled though the frame. I just looked back expecting my rope to be broken and I'm dragging his bumper :haha:


Second guy was stuck good. I yanked several times and broke my strap 3 times near my bumper. Then one guy said his bumper is coming off. I look and sure enough the bumper is bent upwards and out. Plus, his frame crossmember that goes across under the tailgate is coming out with it. I pulled that shiot a good 4" from straight (or more, gezz) :haha::haha: Then we tried the slow method with a couple trucks. Didn't work. Someone went off to find a truck with a winch and I GTFO.

My winch worked for Moab, but for some reason it didn't today. I would have had that damn Jeep out in no time flat. :doah: His winch wasn't strong enough and same for his buddies. :doah::doah:


:haha: Love it
 
Hook it up to a trickle charger and make sure the battery is fully charged.

I remember reading an article about EFI, and the engineer from FAST doing the interview said one of the most common causes for "odd" behavior is low voltage.

Maybe you fried the alternator in the mud? Its a simple and cheap thing to test anyway...

-G
 
I'll look over both of those things.
For now I can say there was some large splashing through the shallow water crossings. I'd be shocked how things can get wet 30-40minutes before it started acting up and end up being the problem. I have dual batteries and the gauges for each read 14v+ on the funky drive home.

And yeah Greg, I remember FAST emphasizing proper voltage. That will be another question for them. All the wires look good for the system, but I swear that blue ECM "power on" light should be on with the key. :/
 
My blue light does not turn on unless the engine is running in the buggy. It flashes rapidly if there is an active code set.

Verify your ECM is connected directly to the battery. Take some pictures of the readings the handheld is giving when the engine is bogging and blowing black smoke. Does the engine see the rich condition or does it see a lean condition? Any exhaust leaks?

Has your sensor been exposed to silicone recently?
 
K85 Octane said:
It should be ~44 psi. It will run 44psi while it's choking at idle. To keep it from dying, I bring it up to ~1200rpm and which point it's controllable, but the fuel pressure is ~34psi. That's weird.
Click to expand...
The fuel pressure should increase as vacuum drops. The idea behind the vacuum referenced regulator is to keep the pressure drop across the injectors closer to constant as engine load changes. (Also, it gives the injectors more dynamic range).

It's possible you have a clogged filter or bad pump so it can't deliver the flow you need, so pressure drops as demand goes up. But blowing black smoke indicates a rich condition. Do you have 2 injectors or 8? If you drop an injector, the O2 can see this as lean and richen everything until the other cylinders are way rich. I've experienced this with my MPFI and it stumbled and idled bad like you're describing, but I don't know what was happening to fuel pressure. It can also happen if you lose spark to 1 or more cylinders. The O2 is just looking at total oxygen and doesn't know there is raw gas coming through.

Will it run if you unplug the O2 sensor? Do you have a sensor on each bank? If you unplug injectors 1 at a time (engine running), is there any one that doesn't change how it runs?
 
You might want to check timing as well. I believe there are versions of FAST that don't control timing (it appears there is no discount for this handicap!). If spark timing moves it can cause all of your running symptoms, although it shouldn't affect the fuel pressure like you describe. Isn't normal pressure for that system more like 60psi?

The ECM should vary the injector pulsewidth to account for variation in battery voltage. If it doesn't run normally down to 11V or so, it shouldn't be for sale. Obviously the uP runs down at low voltages or you could never start the truck, but their software might not compensate injection properly based on voltage which would make the A/F ratio change with battery state.
 
The FAST "EZ" system is like a throttle body, but with 4 injectors under the blades.


I haven't done anything with the truck since posting this. I love the ideas but I've been busy at work playing catch up after Blazer Bash. I've also managed to really really mess up my back, which started the day after I got home from BB. It's just gotten worse. I saw a Chiropractor Tuesday, fought through it Wednesday at work, but have had to take the last couple days off. My lower back is a mess.

So bummed that I can't address this and with all your guys' help too. :(
To make things even more funky, my "silent" landlord of 30 years passed away recently and now my property is for sale. Never a good thing, especially around here.

Thanks guys
 
Ok, here's a video of what my FAST handheld is telling me. Turn the speakers up so you can hear the engine running.

I can bring it to a steady 1150 rpm and the exhaust is clear. When I let off the gas it wants to die. While it stumbles, it smokes up a storm. I am the one listening to the engine and keeping it alive. The return to a steady idle is my doing, otherwise it will die.

Some of the numbers are weird. My IAC should be around 15 at idle, yet it's WAY past that. The "engine load" percentage should mimic throttle position to a point, yet it's almost the complete opposite, spiking during idle and waning during acceleration.

This is just a start. I haven't been able to work on the truck as my back has been ef-ed up. So soon I'll climb under the hood and look for anything out of place. The truck only has 3 vacuum lines. (1) to the dizzy, which is plugged (2) to the fuel pressure regulator (3) to brake booster. The first two look good (quick visual inspection) but I haven't checked the booster...though brakes feel good.

It's too weird. Worked great all day. Get about 15 miles of my 30 mile return home and it starts acting up. Dunno. Anyway......video:


 
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Fuel pressure regulator diaphram isn't ruptured ,is it?...(if it uses the vacuum operated type)..
 
First thing first, check out the connections at the battery for the FAST. I had intermittent stumbling and stalling problems with mine that turned out to be a bad ring terminal.

Based on the video and assuming your connections are solid, it seems to work fine when reving. Which leads to me to your IAC. It seems off, when you rev it, it should go high as it tries to follow the throttle. When you return to idle it should come down to your setpoint count (around 15-20ish). What is your idle set at? Try using the manual idle set screw to get it to idle. If it works then make sure you recalibrating your tps.
 
Can you choose which parameters to display at the same time or can you only just flip through those preset screens? I'm just wondering how MAP and engine load compare. Typically the load is calculated primarily by vacuum. The IAC changing means it's probably doing closed-loop idle speed control. As the RPM drops below the preset idle speed it opens up to compensate, which it obviously can't do. In addition to other stuff that's already been suggested for troubleshooting, you could unplug the IAC to see if it does anything. If the IAC is stuck/broken, the throttle stop may not keep it open enough to maintain a good idle speed. Possibly below your normal idle the tuning isn't really set, causing the super rich stuff. You don't always use closed loop A/F control at idle speed.
 
oh, don't let my problem stop you.

I pulled the air filter and housing off. That's as far as I've gotten. Work will be crazy for the next two weeks so I've been kinda quiet about this. The C10 needs some attention too :(
 
if anything stops me it would be the price tag :laugh: other then this how does it perform? Easy to tune?
 
If you don't have a fresh engine, or one you've hopped up with tons of cash, it doesn't make sense spending that kind of money for fuel injection. You could get a decent LS motor and be ahead of the game. Both options require higher PSI fuel pumps and fuel lines.

I put this system on a slightly modified 400sb with zero miles. If I could go back and stop myself from building the engine, I would. I could have SAVED a lot of money if I had just gone LS in the first place. Having said that, the system works great overall and is idiot proof.
 
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