Cold loud start

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11-06-17, 11:50 AM

#16

lawrence1

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does the IS-F not have a SAS (secondary air system) to help with emissions? I know the GX460 does as it is a known problem area. Most cars nowadays have an air injection pump that runs on cold starts to warm up the cats faster.

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11-06-17, 01:42 PM

#17

isfvss

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Only a simple air flap that opens with vacuum over 3600 (controlled by the ecm) in the air box, no air pump, like all computer cars cold start is all computer.Anyone on here that remembers "give it more choke"

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11-06-17, 05:06 PM

#18

lobuxracer

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Quote:

Originally Posted by lawrence1

...Most cars nowadays have an air injection pump that runs on cold starts to warm up the cats faster.

Where do you get this information? There are no air pumps on any Toyota, Lexus, or Scion coupe or sedan. Since Camry is usually the #1 selling sedan, claiming most have air pumps is stretching it quite a bit.

Quote:

Originally Posted by Lexus Technical Training

Lexus Engine Control Systems II Course L874
On some models with a V8 engine, during cold engine start, air injection is turned ON and adds fresh air to the exhaust stream to help speed catalyst warm-up. Under specified operating conditions, the ECM signals the air injection driver to turn ON the electric pump. The pump draws ambient air in through a filter and pressurizes it.

Those "some models" are all SUVs or trucks. LX, GX, Tundra, and Tacoma all get hits on P2442, secondary air injection valve stuck. There are no sedans or coupes with this DTC.

Last edited by lobuxracer; 11-06-17 at 06:05 PM.

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11-16-17, 03:40 PM

#19

Leander311

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This has been driving me nuts too. Was guessing it's a combo of delayed and/or added DI injector output coupled with much later spark timing to heat the pre-cats.

Creative tuners can do a lot without necessarily having to use cam "trickery"...

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11-16-17, 06:33 PM

#20

lobuxracer

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I don't think this has anything to do with tuning. There is a pin in the cam drive sprocket that locks the cam drive position while oil pressure is building up. There were lots of problems with this pin in the 2GR engines and they suffered a rattling sound on hot start because the pin didn't lock consistently. Lexus went through four design changes and still had issues (one of the reasons I traded my IS350 for my IS F). It sound to me like the pin is doing its job, but the cam timing is optimized for starting, not running, and once there is sufficient oil pressure to release the pin, the engine quiets down.

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11-16-17, 08:15 PM

#21

Leander311

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Wish Rafi w/RR Racing would chime in... they know more about these mills than anyone.

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06-29-18, 06:57 PM

#22

Gs460FBO

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The main thing causing the excessive loud startup is a heavy ignition timing retard. This a simple and fast way to create some heat during initial startup and burn off excess fuel to help the cats live a little longer. Simple as that.