Fuel Cutoff question
 

Can you check with a Scan-gauge II if your vehicle has fuel cutoff?

If yes, what is the procedure?

Paul

k8crd -

Here is one way that may work :

1 - Go to instant gauge section and set one of the gauges to be MPG.

2 - Drive around in gear.

3 - Take foot off accelerator pedal. If the instant MPG is 9999, then you probably have fuel cutoff.

CarloSW2

The way I figured it out was going down hill when the engine was cold and I noticed that the engine didn't get warmer = no fuel injected.

Shadetree method... ziptie a plastic tube near your injectors.... feed the other end (gotta be 6ft long or so) through the firewall with the speedo or throttle cable, bring it inside the car.... and listen to the end of it while you're driving.

downhill=no load with high airflow thus no warming up. unless it's a 5 miles downhill, no dice. plus, engine temp change over the length of an average hill is negligeable anyway.

CarloSW2:

Thank you for replying!

I did what you suggested with instaneous mpg gage, rpm gage, and tps gage set on the scan gauge and car in gear.

When the foot is removed and the tps drops to 19 at approximately 1600 rpm the instaneous mpg goes to 150 MPG instead of 9999.

My scan gauge was purchased in 12/06 so maybe only the lastest version of it reads 9999 ????


Paul

k8crd -

That sounds similar to what I see. The "9999" is most likely a compromise MPG. When there is fuel cutoff, there is essentially infinite MPG. This is a divide my zero condition ( "N" MPH / 0 GPH), so the Scangauge compensates by reporting maximum MPG that can be displayed on your screen, aka 9999.

In terms of which version reads 9999, I think this would be the same across firmware versions. I have an SGI, so I don't have the better version that you have. If you go to the ScanGauge website, you can download these manuals to see what version of the firmware you have :

Product Support Center
https://www.scangauge.com/support/
If I had an SGII with the firmware version that supports XGauge, I would try to create an XGauge for the short term fuel trim. This would require you to get the specs on the "request id" (not the right name) for the short term fuel trim for your car. I think this is likely to be unique for different car ECU/PCMs.

Feel free to contact the Scangauge folks with your question :

Contact us by e-mail
https://www.scangauge.com/contactus.shtml
CarloSW2

No, most engines do not cut off fuel to the engine, ever.
That's 99.999% of them, do NOT.
Thank you.

I guess I'm one of the lucky few to drive some of the 0.001% of cars that have deceleration fuel cut-off? My old '87 Cavalier and my current '07 Aveo both do it. Older Scangauges (including IIs with older firmware) don't show fuel cut-off in the MPG and GPH gauges with many vehicles, so look at the LP gauge to see if it goes into open-loop while decelerating. My Aveo won't enter DFCO below 40 mph, regardless of the gear it's in, and it stays in DFCO until around 1200 rpms.

Ford implemented it in some EEC-III and all EEC-IV and up, so most Fords from about 1990 up should do it. I've heard it's down to 1800RPM but don't know if that's universal or application specific, I believe the EEC-IV reference I got that from was on a Mustang tuner site. Some Mazda's, Jaguars and anything else with Ford engine management should do it. Chrysler's SMEC and SBEC in V6 engine applications is believed to do it from about '87 but don't know RPM or other conditions, may have been more aggressive from '92 up when they changed some stuff. Not sure about chrysler 4 cyl and turbo applications. Don't know about DSM and mitsubishi sourced chryslers. (avenger, stealth, colt etc)

Anyway, since that covers a lot of cars topping the best seller lists since the early 90's, dodge minivans, ford escorts, tauruses, F-150s.... I'd figure that's rather more than 0.001%