Okie5.3

iTrader: (1)

Hopefully you guys can help me figure this one out. When the outside temps get down cold enough for my IATs to run 40* F and lower, the truck runs like ***. It feels down on power and has increased instances of intermittent KR. But when outside temps are up above 50 the truck runs strong.

Normally performance increases as temperatures drop from the colder more dense air allowing more O2 to be packed in the cylinders, correct? In my case power seems to increase until outside temps get down to the freezing mark, then it goes to ****.

Could a marginally lean/rich tune in warmer temps cause an even leaner/richer condition as temps drop, affecting power? I do run a one range colder plug with a .060" projected tip gapped at .040", a 160* thermostat, CAI, FTs "normally" at +/- 3-4 area, PT timing +1* from stock, WOT 26-29* with O2s in the 890-920mv range.

Any thoughts would be greatly appreciated.

SCANGBird

You're not alone. I'm trying to figure out a similar problem as well. I have a 2002 Trans Am WS6 and when the temp falls down to just above freezing, she gives me hell. All the car has done to it is an SLP airlid, Dynatech LT Headers, Hi-Flo Cats, and Magnaflow catback. An EFI car should not have a hard to start condition in cold weather, but that's exactly what I've got. As things warm up, she's fine. At first I looked at the battery and sarter. The battery tested low and I replaced it with an AC Delco Professional 75-6YR, but no dice. The starter tested fine and the alternator's diodes tested fine. Next, I thought fuel problem, so I replaced the fuel filter (car has 57,800 mi) and dropped in some Red Line SC-1 Fuel System Cleaner. Nothing thus far has helped. I'm going out of my mind because I know that hard starting like this will kill an engine after a while. I want to fix the problem but I don't know what it is, just that I've got one!

Okie5.3

iTrader: (1)

sounds like you might not be getting enough cranking enrichment during a cold start. your mods are making it breathe alot better and if you haven't tuned for those changes it could be lean on cold starts making harder to start as the temps drop.

mine starts easily cold or hot. my problem is when the temps get down to freezing the the truck becomes a dog at part throttle driving, like it is either extremely lean or really pig rich.

chrisj6

have you tried adjusting the IAT adder table? This is usually pretty conservative from the factory, maybe add some timing down on freezing temps, I had to add some back up on the hot side, b/c it was pulling wayy too much.

Chris