No DFCO?

[Kodak]

I've been operating under the assumption that my pickup probably has the fuel cutoff feature. I was never sure of the exact rpm at which it kicked in, but I assumed it was a little under 2k somewhere, and I thought I felt a little bump at 1800.

Now that I have the SG-e I can find out for sure. Well, I took 2nd gear out to a little over 3k rpm, started engine braking, and expected the gauge to read 9999 to indicate cutoff. The gauge read pretty high, like in the low 100's, but it did not appear to cut fuel. In fact, coasting in neutral versus coasting in gear appears to net better FE.

Did I not rev high enough to reach DFCO, or am I reading the gauge incorrectly? I used the instant mpg feature. For the record, I certainly did have my foot entirely off the throttle, and the engine speed in the low 3,000s.

Thanks for any insight.

[SentraSE-R]

1. Your truck may not have DFCO. Our '06 Hyundai Elantra didn't have it.
2. I don't know if SG-e handles DFCO. If it does, it should have a way to set TPS cutoff values, and a way to display when you go into open loop.
3. Check if your truck goes into open loop when decelerating in gear, throttle off. That will tell you if it's going into DFCO.

[Kodak]

Ah, that's right! I can check if the O2 sensors are being used. Thanks for that. I'll try it today.

[Kodak]

I forgot about this for a while, but made an interesting observation yesterday that I can't interpret.

Fuel cutoff is supposed to engage above a certain rpm, right?

Well, yesterday I was engine braking in 2nd gear. The engine speed was in the low to mid 2k's, and the SG-e was reading some reasonable number that I can't recall.

Then, I felt a very minor 'bump' after the engine fell below X rpm, after which the gauge read 9999. Odd. I suspected the exact opposite. I though the injectors would cut off at high rpm, and reengage after falling below a certain value.

Do you suspect a gauge setting issue, or is this how the Canyon's Vortec 2900 works?

[AndrzejM]

Sometimes there is a switch on the throttle that signals closed throttle to ECU. Maybe yours is just malfunctioning? Check this, maybe that is causing the trouble.

[jakobnev]

I assume your engine was fully warmed up when you tested this?

[Kodak]

Originally Posted by AndrzejM

Sometimes there is a switch on the throttle that signals closed throttle to ECU. Maybe yours is just malfunctioning? Check this, maybe that is causing the trouble.

Hmm. For what it's worth, zero throttle input usually reads a throttle position of ~18. It varies a bit from 17 to 18. I've read that this is normal, and it's been that way since I've had the gauge.

Originally Posted by jakobnev

I assume your engine was fully warmed up when you tested this?

Yes. Normal operating temperature, so I'm sure it was in closed loop.

[Mulder25]

In my car, when i first got the scanguage, it was reading 9999 when i let off the accelerator. I could feel the engine braking effect. I was getting insane values on my average though, as high as 75MPG/AVG. As it says in the manual for the gauge, the accuracy will improve over time. This refers to when you fill up, and input data in the scangauge. My theory is that it is calibrated at the factory for 'x'Gas x 'y'RPM = 'z'GPH. When you fill up, you tell it that your car actually used X* amount, and it will adjust its computing accordingly. Once mine had a 5 fill-ups, and about 3000 miles, it started reading something like 142MPG with no throttle. The average economy dropped, and is now displaying accurately. I think the scanguage is designed not to show 9999 unless you haven't calibrated. Who is to say that this is the exact number? You could, in theory, go an infinite amount, but this would throw off the average faster than you can blink.
I can feel the engine braking, and now, since my brakes are bad, regularly employ it. It is rare that i ever touch the brake pedal(exception to hold steady at a red light, or to decelerate those last 5MPH that first gear cant do.
If there is even a tiny amount of fuel being injected it would greatly decrease the resistance of the engine, and would not allow compression braking. (can be calculated mathematically, but i am running out of time to continue writing this...)
The gauge now reads a couple thousand MPG, but not 9999 if i turn off the engine, put it in neutral, and coast. This is because it defaults to 0.05GPH, even if i am sitting, parked, engine off, but key in, it will say this...
You have DFCO, trust me. The gauge will get more accurate as time goes.

I reset mine because it glitched and thinks i pay $72/gallon, and when i try to adjust, it wont go lower than 71.8... EVEN THAT DIDNT SOLVE THAT!!! but i regret that i lost the calibration...

[IsaacMTSU]

My S-10 with 4.3L VORTEC glides so bad that engine braking for more than 5 seconds is rare Haha. In my friend's 2010 VW Jetta Sportwagen, you can downshift (auto with manual shifter) and engine brake. When you do, you have to engine brake for about 10 seconds THEN it will cut off and the factory gauge will show "----". When you first start engine braking, it goes down usually to around 30MPG or so before it shows "----".

[Ford Man]

If I'm in 5th gear in my '97 Escort wagon it goes into DFCO within 1-2 seconds after releasing the throttle. If I recall correctly it stays in DFCO until the RPM's reach about 1100-1200 RPM. When I first got my Scan Gauge II it didn't show that it was going into DFCO. I calibrated something, without looking at the owners manual I don't remember what it was, but afterward it showed it was going into DFCO mode. I'd be very surprised if your truck doesn't have DFCO, I'm pretty sure even my '88 Escort has it.