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Cold start tuning

RobSVT-t

CEG'er
Joined
Jan 15, 2004
Messages
94
Location
Miami, Florida
On cold starts, the car will idle fine for the first minute, then it starts to bog and fluctuate, after it warms up, it fine. any ideas as to why? If i put any load on the engine, like driving, it'll have a very rough time staying running. It also does this when i blip the throttle.

Robert
 
chill buddy

chill buddy

well, i can see this forum wont be worth a d@mn!

Yeah whatever... :rolleyes:

I didn't see this post till tonight.

Anyway, It sounds like you are getting in unmetered air. Seems like it is fine in closed loop when the O2 sensor is driving the train...as in when the car is warm and throttle is not touched but when the throttle is blipped or under load the MAF has to tell the pcm what the change in airflow is.
I'd make the good guess you got a loose pcv, or loose crankcase vent line/valvecover vent line, vacuum leak, or loose hose/clamp after the maf.
 
Last edited:
I double checked everything. Nothing is loose anywhere. I'm pretty sure it's in the tuning, cuz i had changed some values for the MAF transfer function to try and get the idle a/f to a more ideal ratio, but i never touched any "cold" tuning settings from what the base tune was from the guy who sold me the package.

here is a picture of my MAF transfer function:
0001.jpg
 
Well, you didn't say you were screwing with the maf function earlier in your post either.. That kinda amounts to the same thing.

Still, I looked at your values and they aren't that far off that you can't idle or even rev the motor.

Something else then....
 
i've changed the isc_neutral_idle but when i revert it back to the base file, it gets worst and barely runs at all, so i put them back to where i had them.

Robert
 
The last time I saw the software it was rpm vs. mass tics. Push the accelerator up to 1500 rpms and check mass tics on the data logger. Let the revs fall to the next point, probably 1000. Write down the tics and so on. Then, IIRC go back to your neutral table and enter in those values.
 
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