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Please help with this Miss issue under boost in cold temps

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JimP

Active Member
Joined
Nov 28, 2007
Messages
764
It's getting cold here almost zero over night and early in the morning. I've been working nights and taking the car to work. It's fine on the way to work when it's about 10 degrees out, on the way home in the morning it's close to freezing.

When under boost, around 20psi. The car will pop and miss. It pulls very hard up to about 15-18 psi. I have a new ignition module, NOS AC coil, new wires, newish plugs. Car idles and drives fine, no knock what so ever. I'm seeing O2's in the 780-800 range with Alky. This issue is worse the colder it is out. Any help would be appreciated. As mentioned above, I recently replaced the coil and ignition due to a misfire earlier this year. I was good until it started getting cold out. I have also seen 25+lbs of boost on the gauge briefly while it's gotten colder.

Any advice is appreciated. other mods in SIG if that helps.

Jim
 
I had same issue with mine as it got colder out. I had to remove fuel in 1st gear to solve problem. That's all I can tell you. Don't know why, but that's what I did to cure my problem.

Do you have a scanmaster? Who's chip?
Post up some numbers
 
I should have mentioned it's worse is second and third gears. No issue in first at all. I have an Extender chip, LS1 MAF and translator. All scan master numbers are good at idle.
 
Does a turbo car need alky when it's zero deg's? Just curious.
Have you retuned for the cold air?
 
Spark plugs, try first tighter gap you may have to go with a colder plug
Sometimes when making a lot of boost you can blow out the plug that happened to me
 
Thanks for the suggestions. I'll try those tomorrow. I'll start by changing out the plugs and gapping a bit tighter. I wasn't sure if I needed Alky when it's that cool out, I'll turn up the trigger point and slow down the pump and see what happens.

As for tuning for the cooler weather, I haven't changed anything. My timing sits at 25 degrees idle, set at 23 for first and 21 for second and third. My O2's numbers always fall in the 780-800 zone with the occasional 810-820. I do see lots of black exhaust while under boost lately. Engine temp is usually around 165
 
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