Light blue smoke

[06StangGT]

I did however just start the car to move it to do some yard work.

This is the only time I experience this issue. If I start the car cold, and only run it for a minute or two, I will see the puff of smoke upon next start up. I also believe like Juice said, it is in the calibration. I've seen this on two different engines.

 

[Juice]

The "fix" from Ford says: warm up engine fully. mmmmmkay

 

[tbear853]

Our '08 does it sometimes as do our Mercury GMarq and a '95 T-bird .... just some hot oil seeped past the guides last shut down.

 

[Dino Dino Bambino]

When I start my engine cold, the idle speed immediately jumps to ~1500rpm and then slowly settles down to ~1000rpm. After about a minute, I'm ready to drive off.
The trick is not to attempt to drive off too soon while the engine's still finding its steady idle speed. Otherwise it's possible to flood the engine with too much fuel and soak the plugs, causing it to bog down and stall. The tendency to do that will depend on the cold start fuel calibration in the ECU.

 

[Juice]

What is confusing me is Ford richens startup to "light off the cats" quickly as possible. But the COT protection richens the fuel mixture to "cool off the cats". Seems contradictory.

 

[eighty6gt]

smoke is black, is fuel, ignore it.

engines get a ton of extra fuel on cold start because it condenses all over the cold intake/head port/cylinder/valves/etc.

 

[LarryJM]

Old Gas will also do that. Although, I am not sure how old it has to be.

 

[Dino Dino Bambino]

What is confusing me is Ford richens startup to "light off the cats" quickly as possible.

For cold starts, the air/fuel mixture is enriched and the ignition timing is advanced in order to aid smooth operation and prevent the engine from stalling. It's akin to starting a carb engine with the choke valve closed. The cold start fuel tables are predetermined in the ECU program, and it operates in open loop mode until the upstream O2 sensors have warmed up sufficiently to read the O2 content in the exhaust gases. Then the ECU goes into closed loop maintaining a 14.7:1 air/fuel ratio.
Car manufacturers position the cats as close as possible to the exhaust valves in order to bring them up quickly to the optimum temperature where they can reduce CO, HC, and NOx emissions with maximum efficiency.
Installing long tube headers thus creates two potential problems that are made worse on cold winter days:

1. The header collectors where the upstream O2 sensors are positioned are further away from the exhaust valves. The upstream O2 sensors thus take longer to warm up, and a longer cold start open loop operation time needs to be written in the ECU program to prevent a lean condition (hesitation upon acceleration) during the transition from open to closed loop.

2. The cats are also positioned further away from the exhaust valves, and this could trigger downstream O2 sensor fault codes as the cats take longer to warm up. This also needs to be compensated in the ECU program.

 

[Juice]

FYI, on my coyote, startup timing sits @2* ATDC for the first 15 seconds or so.

 

[Dino Dino Bambino]

FYI, on my coyote, startup timing sits @ 2* ATDC for the first 15 seconds or so.

The ignition timing of my 4.6 is 19* BTDC at idle on cold start up, and 10* BTDC at idle when warm. Maximum advance is 50* BTDC at part throttle and 30* BTDC at WOT. This on 91 octane fuel. Perhaps yours is more retarded because of the 11.0:1 CR and 87 octane fuel.

 

[Juice]

No, I am on a bone stock factory gt tune currently with only the gear ratios changed. I did minor change to desired WOT afr as Ford has power enrichment coming in a little late, and way to rich after 5500 rpms. Im targeting 12.1 from 3500 on up. That has no impact on startup.