Hello,

I've been slowly sorting out minor performance issues with my engine. I recently replaced the fuel rail pressure regulator and that resolved several issues. The pressure tested good at idle, but I noticed some fuel at the vacuum port connection. New regulator has meant better starting, idle quality, acceleration and fuel economy. It doesn't get better than that....

Pursuing further fuel economy, I noticed on my trip computer that I rarely show better than 23 mpg during a coast down to a stop. Most cars will cut fuel completely during motoring until you get close to idle. Looked at several manuals and troubleshooting guides and sure enough they say the throttle position sensor has a signal for full throttle and idle. Full throttle gives enrichment and idle will cut fuel until you drop below 13-1400 rpm.

One manual (ALLDATA) gives the test values at the ECM connector in the trunk. Should have closed circuit between pins x and y at idle. I get ~30 ohms. So then I go pull the connector off the sensor. There's three pins on the sensor, center and left close at idle, center and right close at full throttle. All open otherwise. The I look at the connector and there are only pins for the full throttle - the third pin slot is empty - and everything looks untouched from the factory.

So, my assumption is that for my US version they didn't use the idle fuel cut functionality but they must have in other markets. My only assumption is that to meet US emissions they had to keep fueling to keep the catalyst warm. This sound familiar to anyone? Anyone hooked up the idle circuit and found it to work?

Thanks for any comments. Ben.....

 

I can confirm that USA cars (and Canadian, perhaps?) were indeed different than ROW models with respect to the throttle switch. Other details foggy at the moment. Will do some mulling


Cheers
DD