Cold start dwell

[Bitsyncmaster]

I was checking the dwell on another D yesterday and the cold start duty cycle was 60%. I immediately thought the WOT switch was stuck on but once it went closed loop the duty cycle was normal and the WOT switch worked (setting 60%).

Normally you would get 50% on the cold start unless it's really cold (winter). This is suggesting the thermal throttle enrichment switch is mis-calibrated. Anyone see this happen before? Would seem like a very rare fault.

Not that it makes that much difference in the warmup.

I guess it could be an ECU fault. Think the ECU sets 50% until the O2 sensor starts working.

[Ron]

I think you are on the right track since the WOT switch is in parallel with the thermal throttle enrichment switch on the LG wire. I would guess the TTE switch or the LG wire is grounded.
ECU?...don't tempt the Devil.

[David T]

I was checking the dwell on another D yesterday and the cold start duty cycle was 60%. I immediately thought the WOT switch was stuck on but once it went closed loop the duty cycle was normal and the WOT switch worked (setting 60%).

Normally you would get 50% on the cold start unless it's really cold (winter). This is suggesting the thermal throttle enrichment switch is mis-calibrated. Anyone see this happen before? Would seem like a very rare fault.

Not that it makes that much difference in the warmup.

I guess it could be an ECU fault. Think the ECU sets 50% until the O2 sensor starts working.

There is some variation between cars and meters. You also don't get a nice, clean, solid connection, especially using the ground terminal in the diagnostic plug.

[DMCMW Dave]

I was checking the dwell on another D yesterday and the cold start duty cycle was 60%. I immediately thought the WOT switch was stuck on but once it went closed loop the duty cycle was normal and the WOT switch worked (setting 60%).

Normally you would get 50% on the cold start unless it's really cold (winter). This is suggesting the thermal throttle enrichment switch is mis-calibrated. Anyone see this happen before? Would seem like a very rare fault.

Not that it makes that much difference in the warmup.

I guess it could be an ECU fault. Think the ECU sets 50% until the O2 sensor starts working.

What was the ambient temp when started? I have seen this early in the morning here (we turn the heat WAY down at night/weekend) but the engine block temp was probably 50 degrees or less.

[Bitsyncmaster]

Air temp was 68 deg F. I tested another car after that one and it worked correctly. 50% during warm up.

[Ron]

It grounds at 59F. Unplug the WOT and see if the LG is grounded. If so, do a shake test then use a heat gun or similar to see if it goes away...otherwise, you know where you have to go...