Cold idle surge Gen 1 Cobra Jet 65mm TB and Intake, LT headers

Hi everyone,

Struggling with a cold start idle surge on a 2012 GT with a FPP twin 65mm throttle body, Cobra Jet intake, and long tube headers. Once it warms up, it idles fine. This is only for the first few minutes of start up. The engine approaches stalling after throttle is applied (blipped in my attached log). Everything seems reasonable in the data log to my eyes. I suspect that the O2 sensors may be "falsely" reading rich, and thus the PCM cuts fuel, but not sure. I don't have an external WB, so it's hard to tell. Attached is my tune file and data log. Note how the idle surges after throttle blips.

Any insight is greatly appreciated.

Attachment 101175

Attachment 101176

Looks like you need to get it warm and calibrate that MAF. That reading is extremely low for a cold start.

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Originally Posted by smokeshow

Looks like you need to get it warm and calibrate that MAF. That reading is extremely low for a cold start.

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No, the MAF transfer is already dialed in...within +/- 0.03% from idle to WOT.

Here's a log of that if you're interested:

Attachment 101198

Ah, well there it is. That looks pretty good. In any case, I still think it needs more air. You should add a healthy amount to the idle airflow tables. Not sure which table Ford uses for a manual trans, Drive or P/N, so you can add to both. I would add at least 25% to start. The spark is extremely high due to the lack of air, so you have no torque reserve, which causes idle instability. The throttle also snaps closed extremely quickly, also not a great thing...but start with the idle airflow itself and see how it responds.

what are your parasitic torque losses in cold temps? have you looked for tables that deal with the portion of the logic driving torque requests when cold. what is spark doing? I dont have any experience with anything as old as a 2012.

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Originally Posted by superman07

what are your parasitic torque losses in cold temps? have you looked for tables that deal with the portion of the logic driving torque requests when cold. what is spark doing? I dont have any experience with anything as old as a 2012.

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The log file I attached should answer all those questions.

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Originally Posted by smokeshow

You should add a healthy amount to the idle airflow tables. Not sure which table Ford uses for a manual trans, Drive or P/N, so you can add to both. I would add at least 25% to start. The spark is extremely high due to the lack of air, so you have no torque reserve, which causes idle instability. The throttle also snaps closed extremely quickly, also not a great thing...but start with the idle airflow itself and see how it responds.

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I think I solved the issue.

This didn't work: I started by increasing the idle air 25% in the idle range, with no improvement. Increased it to 50% over stock...still not any improvement.

What worked: I reverted Idle Airflow (both P/N and Drive for the reason you mentioned) to 25% over stock but also adjusted the ETC Idle Throttle Angle Expected vs. Airmass function to more closely reflect the needed throttle angle to maintain idle airflow with the twin 65mm throttle body based upon a hot idle data log. As you can see from the following screen shots, my ETC Idle Throttle Angle Expected vs. Airmass values are 2.5% (1/40th) of the factory values.

Factory Settings:
Attachment 101337

New Settings that resulted in stable cold start idle:
Attachment 101336

I haven't driven the car yet, but these are the first adjustments that have impacted my cold start issue. Throttle response off of cold idle is vastly improved as well. Before it was pretty "lazy." Now it's crisp.

Here's an updated log: Attachment 101338

Sweet

Crud. The issue returned on the next cold start. Warm idle is perfect.

This is only on a cold start, which leads me to believe it's related to the O2 sensors and my LT headers.

As an experiment, tried to delay the time going to closed loop via "12462 - Closed Loop Enable Delay" but increasing those settings (200 seconds) didn't seem to have any effect. Cold idle still went closed loop after 18 seconds. Am I missing another setting I'd need to increase the delay to closed loop after startup?

Performed another experiment. I reverted "11535 - Spark Emissions Reduction Base (Drive)" and "11539 - Spark Emissions Reduction Base (Neutral)" to stock, and the issue is solved. I assume the cold start retard is warming up the O2 sensors. However, I don't have cats, and it's waaaaaay too loud on cold starts. Thus, I think there are two solutions:

1) Delay closed loop operation on cold start. "12462 - Closed Loop Enable Delay" doesn't seem to have an effect on delaying closed loop on starts. What am I missing?

2) Find some other method to warm up the O2 sensors faster. Are there some adjustments to the heaters I can make?

Thanks in advance for any advice.

In your file i still see Catalyst Protection enabled

Try disabling under fuel- Temperature control

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Originally Posted by Danielerevia

In your file i still see Catalyst Protection enabled

Try disabling under fuel- Temperature control

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You think that has an effect on cold start idle stability?

it sounds like you need more startup enrichment which is common with the cobra jet intakes.

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Originally Posted by decipha

it sounds like you need more startup enrichment which is common with the cobra jet intakes.

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False, tuned literally 30 CJ manis never needed that.

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Originally Posted by veeefour

False, tuned literally 30 CJ manis never needed that.

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Attachment 101883

Here is cobra jet tune..hope it helps

Have you tried putting your transport delay and transport constant back to stock?

also you can limit idle adder for start up ect.

Also bump that idle up alittlle bit.Attachment 101884Attachment 101884

attached a cobra jet file from a old setup. Dont use the Map points or Maf curve.