Cold start issues s550

[Cajuncoyote]

Hi everyone, on cold starts my car take 5-8 seconds and sometimes backfires. It recently started doing this, no new modifications. I have changed the battery along with MAF sensor. Not sure how to pressure check the fuel system on the coyotes, to see if it is a bad fuel check valve. Any help would be appreciated. I currently have a NA car with long tubes, Steeda CAI, Corsa Cat back, and Lund custom tune.

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[Deleted member 35786]

Hi everyone, on cold starts my car take 5-8 seconds and sometimes backfires. It recently started doing this, no new modifications. I have changed the battery along with MAF sensor. Not sure how to pressure check the fuel system on the coyotes, to see if it is a bad fuel check valve. Any help would be appreciated. I currently have a NA car with long tubes, Steeda CAI, Corsa Cat back, and Lund custom tune.

Car is running lean. When you first start an engine when its cold the idle is usually high for about 5-15sec or more depending on outside air temp to warm up the engine. And after that time has passed the idle comes back down. If your car is not doing that then the most likely cause is the tune. This is all computer controlled. Sounds like not enough fuel is being injected into the engine to warm it up.

 

[Cajuncoyote]

Car is running lean. When you first start an engine when its cold the idle is usually high for about 5-15sec or more depending on outside air temp to warm up the engine. And after that time has passed the idle comes back down. If your car is not doing that then the most likely cause is the tune. This is all computer controlled. Sounds like not enough fuel is being injected into the engine to warm it up.

Thanks, I had it retuned but it still is doing it, not sure what next to try. On hot starts it starts up perfect. The car drives great once it finally starts as well.

 

[Deleted member 35786]

Thanks, I had it retuned but it still is doing it, not sure what next to try. On hot starts it starts up perfect. The car drives great once it finally starts as well.

You have a sensor somewhere that does not recognize a cold engine. Might need to have the computer (ECM) reset by the dealer. Just do not say anything about a tune if your still on warranty. Backfire is a lean fuel mixture plain and simple. Good luck.

 

[ugstang17]

OP - If you have an ngage you can datalog the car under cold start conditions. Notate the Outdoor air temp when this happens. Your O2 sensors are inactive until until the heaters get them to temp and then they come into effect putting the car into what is known as closed loop. ECT and IAT may both be monitored for purposes of air temps along with engine temps to control fuel and Throttle position until the car reaches the predetermined temp to drop to normal idle and begin targeting Lamda1 (14.0). If you have an SCT X4 you can create CF4 config files to monitor a ton of things. Down load Live link II on your laptop and start playing with it. You can log fuel rail pressure, short and long term trims on bank 1 and 2, AFR bank 1,2 etc. Don't lose sight of voltage issues as well. If your alternator is beginning to go south (nothing personal folks) you can find out by checking DC output with the car running as well as AC ripple with a voltmeter. Extreme Low DC voltage (and/or high AC ripple voltage) can effect the fuel delivery with respect to pump and FI's. Not going to go into specifics trying to apply KISS method here.

I assume you have already verified the fuel filter is not in need of replacement.

If this is the first cold spell you have had with the Lund tune you may be able to get them to revisit that for you. Cold start, and Idle are the two most difficult parts of the tuning process, though the average novice seems to think they are the simplest. You are splitting hairs and controlling the FI's at or near the shortest absolute pulse they are capable of running while keeping everything happy. It is truly a balancing act.

I suggest anyone read Greg banish's book Engine Management: Advanced Tuning. Afterward you will have a new found respect for tuning and be able to better appreciate the talent it takes to create a professional tune.

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