New built lt1 unhappy

[RollingD]

97 trans am m6

Just put this bad beast together finally with all sorts of bells and whistles
383 lt1 stroker, le2 heads 236/244 cam, 1.6 rockers, full exhaust, ported intake, 58mm TB, ram air, MSD ignition, pretty much everything is new and aftermarket. I got a tune from PCMforless as well. Lots of other unlisted parts but everything was well researched and compliments each other, it should be happy but it hates me.

After I put all this stuff together I was throwing like 4 codes or so. EVAP, one O2 sensor (no cats and back ones tuned out already), random misfire, and some other random thing.

The car does not run well at ALL. The symptoms are as follows: the fuel trim is overcorrecting on one side says my scanner, o2 sensor right? The car is hard to start, I usually have to give it gas and hold it for a while before it will hold an idle. Once it IS holding an idle I can rev it all I want and it will be fine. As soon as I take off and try to drive anywhere I have to give it a LOT of gas and feather the clutch to get moving. It tends to misfire pretty badly under load, seems to be only at low rpms. When I come to a stop its garunteed to slow rpms down to under idle and sputter and die if I don't hold them.

I did some looking into it and thought at first the EGR blockoffs were leaking, nope. I instead found out my D/S header was leaking from where I had it welded at the AIR fitting after I cut it off. Also when I had my scan tool hooked up the tac on the car was reading 1100 idle but its actually about 900 or so where pcmforless set it to. This reading is coming from the computer so my high idle theory was busted. Another wierd thing is that when before I had like 4 codes now I'm only reading 1 code, p1642 fan relays. That might be because I had a manual fan switch hooked up and the wires are connected to each other, fan kicks on and they all kick on, something like that. Where did my other codes go....I don't know. The other change I made that I don't know if it matters or not is the pcv valve. It used to get its vacuum feed from the front of the intake, going through a pipe to the valve in the D/S. Now the front port is blocked off, and I just put together two 90 degree elbows to get vacuum from where the EGR used to be, I did use the original pcv vacuum fitting though. Does the location matter?

Now I know that I need to get that hole in the header closed up, I'm gonna take it over tomorrow and have the guy try to weld it shut. But other than that....any ideas?

[big hammer]

i've read some sub-standard things aboot pcm for less tunes. but if i were you i would post this over on ls1 tech int the lt1 section. there is a huge lt1 following over there with some knowledgeable guys

[MrKid]

It sounds like the symptons of a rich mixture to me. Did you try changing that O2 sensor out?

[MurderedOutTA]

it could be your o2 sensors since you dont have them anymore. your cars computer is reading them and trying to adjust itself therefore its running to rich or to lean which could cause it to do that. what you can do is order what they call (dummy) o2 sensors, they will read right all the time and they are not to expensive either.

[cocobolo95]

You mentioned you have an exhaust leak. Did you fix it? If not an exhaust leak can mess with the fuel mixture.

[97bluebird]

I guarantee you that it is your tune, I has a pcmsforless tune in my car and it never ran right. It was doing the same thing, throwing codes for a non existant problem. I had to find a local guy to tune mine and now it runs pretty good, but it still runs pig rich.

[RyanJM]

Best bet is to do what I did when my car ran rich after the dyno tune. Go fine a local shop that that has a portable wideband 02 and does street tunes. After we redid my car most of the smelll went away and I have no cats so there is a some left. According to my friend who ownesthe corvette shop they had my tune way to rich and my plugs ended up having to be replaced and they were only in for 8k but that tune being so rich screwed everything up. Mail tunes are ok if you have some bolt ons but since your motor is so modded it would probably be better getting a local tuner so he can drive the car while tuning to make sure it's right and if you have issues you just have to go back to the shop so they can see it rather than tring to explain it.

[RollingD]

Well I did find something! I listened to some advice and checked out my tps sensor. I was unable to check the voltage on it because apparently my multimeter broke T_T But the scan tool I have tells me the % the throttle is open. I went over to the TB and opened it while watching the scanner and it didn't move from 0% throttle until I had moved it up a good bit from closed. According to Golen(those guys who build badass lt1) their 383's normally require more air at idle so I figured that was the same problem with mine. I adjusted the set screw on the TB until the tps gave a reading then backed it to JUST AT 0%. Now since my scanner isn't cool enough to read idle air counts I don't know if its right or not but I'll figure it out when I fire it up. I would have already done so but while I was fooling around in there I blew up the fuse for my water pump >_> and have no extras. Better I learn this lesson while the car is just sitting here I suppose. Yes there is still the hole in my exhaust and I'm probably gonna drive over and have the guy weld it tomorrow. I also found that the wires on my passenger side that go down to the o2 sensors are TOUCHING the headers. So...basically I need to get a new multimeter, test those wires to make sure they're still serviceable, and reroute and/or repair them. I'm hoping these three things are my problems and thats it, it'd make me feel all warm and fuzzy to know I didn't screw anything major up. I'm ok with a few simple mistakes like not adjusting my idle or overlooking some wire placement. I'll let you guys know how it works out.