Idling issues and hard shift

[Alpine_jake]

About a week or two after i got my L67 swap done I started coming across a couple issues..

When the engine is cold, it likes to idle at like 1200 for a while before it comes back down (longer than it should i think)
Then when the trans is cold, it shifts so hard from park to drive it feels like the tires are cheerping on the ground. But it only does it from park to drive (or reverse) not from first to second or on through the gears.

Another thing is when the car is at operating temp and is sitting idling, it miss fires and sometimes even throws a code.

I think the shift issue is because of a bad front motor mount (hockey puck one) and the high idle. Causing the engine to rock, but im not sure why its miss firing at operating temp. I put in a new pcv, plugs, coil packs, and wires. I also tried cleaning the idle air control valve with no luck.

Could it be a issue with the programming on the zzp pcm?

To keep in mind the car is cat less so maybe that's causing an issue? Also on a cold start up the supercharger sounds like its sucking in a ass ton of air until the idle comes down and it smooths out. Not sucking in a lot of air like a whine but more like there's a vacuum leak or something.

I have reason to believe its running to rich is because im getting pretty bad gas mileage.. like 20 on the high way bad.

Please help guys im so stumped!! thanks!

[Alpine_jake]

Just went and put in a brand new idle air control valve and it seems to be running better when its idling. I think the air sucking sound i was getting when it was cold was the idle valve not closing all the way because it wasn't working properly. Fuel mileage seems to be a bit better on the high way, right around 26.

It seems to be fixed as of now but i wont know for sure till i get to drive it some more.

[00Beast]

If you're getting 26 highway, then you're doing better than me...

[nos4blood70]

26 isn't too bad on the highway. As for hard shifting, is your front trans mount broken?

[Alpine_jake]

its not broke but its not doing too healthy either. my concern is why does it only do it when its cold? not cold out side but the trans is physically cold. im sure the motor mount isnt helping the issue but i mean it just slams so hard. hard enough to knock stuff around in my cup holder lol

when out for a drive a bit ago... idles fine now but same trans issue

a sticky valve in the valve body? just a had a trans flush done less than a week aho

[nos4blood70]

You mentioned you have a ZZP tune... They could have raised the line pressure in your trans. That would cause harder shifting. Before I had my shift kit, I had raised the line pressure and the trans would shift hard both when it was cold and when too hot.

[nubuilder]

Mine idles at 1200-1300 cold too.....I don't like it! Perhaps I should look into a new IAC.

Have you checked your trans fluid level?

[Alpine_jake]

Some times it does always shift a bit hard through the gears but i expected that to be from the tune.

Ill double check the fluid level to make sure its not too high. Even though it did the hard shift into drive before and after the trans flush.

Yeah nubuilder check out that iac it definitely seemed to help me out a bit bring the idle down faster. Before i changed it that was all i could here for a couple minutes was that supercharger screaming because that iac wasnt closing fast enough. now it only does it for like 15 seconds till the idle comes down and it smooths out.

[nubuilder]

I'll definitely have to check it then. Mine screams like crazy too. (I never did like that it idled so high)

[Monkeybiz]

Try cleaning your MAF, screen and the other sensor there (coned shaped). I just did that to mine, and I'm getting 35MPG, my harder than I liked shifting transmission smoothed out too.