96_pimped_out

I finished up a fairly major upgrade all at once. I did heads, cam, ported intake manifold, injectors, rockers, new opti/plugs/wires, coil, electric water pump, and fuel pump. There might be something I'm forgetting, but the TB and MAF are both still stock.

The problem is that after the car runs for a bit (10-15 min) it doesn't want to run anymore. It doesn't run rough, doesn't hesitate/miss, etc. It just simply wants to die. If you rev it, it will keep running (at least for a bit) but if you let it drop down close to idle it will die. It's then difficult to start it back up when this happens.

I'm not entirely certain about this part, but it seems to be heat related. When I first started it, I had air bubbles in the heads and it heated up very quickly. It seemed to happen much quicker until I got the air bubbles out. It doesn't overheat at all anymore, so it now just takes longer.

If you let the car sit for an hour or two, it starts up and runs fine again.

I'm guessing some sensor somewhere, something that changes after the car runs for a bit. It's a '95 and I have an OBDI cable - is there some data logging I can do to troubleshoot? Anyone have any ideas where to start?

96_pimped_out

PS - Of course I got a new tune too, from PCM4LESS.

OBE1 95Z28

Double check all of your connections:

vacuum lines
coolant lines (overflow tube and steam tube connections at radiator)
sensor connections

My friend recently had the overflow tube and steam tube connections reversed on the radiator causing the system to overheat as it couldn't build up pressure.

96_pimped_out

I edited my original post, it's not overheating anymore. That was only when I had the air bubbles.

I don't really understand how the motor transitions from cold to warm, what sensors change, readings are supposed to be, etc so I was hoping for a place to start there?

OBE1 95Z28

The biggest change is when the engine goes from open loop running (preset air/fuel ratio stored in the PCM) to closed loop. Closed loop changes the air/fuel ratio during part throttle driving by the O2 sensor readings.

Eck

I'm having similar trouble with my car after cam/ignition work. Mine never was overheating and it's not dying, it just doesn't run as good when it gets hot. Let me know if you figure anything out...

stereomandan

Definately sounds like it happens when you hit closed loop. This is when a number of sensors actually start being used to control the engine. Are your O2's hooked up properly? Any wires not connected, or possibly pulled loose. Triple check ALL connections.

Good luck. Sounds like a fun project.

Dan

96_pimped_out

I bought new O2 sensors with the headers, but I did have a problem the first time I tried to run it after this build. The opti was bad, it loaded up, and ran ULTRA rich, misfired, etc. (Reason I replaced pretty much the entire ignition system)

I only ran it like that a few times for a few minutes though. Could that have been enough to foul out brand new O2s? I sure wouldn't have thought so...?

Dave89IROC

new headers? are they coated?

96_pimped_out

Yes, coated MAC mids, no cat, and some no-name but decent stainless exhaust that was on it when I bought it.

OBE1 95Z28

I have read several posts where newly coated headers can "foul" O2 sensors. Guys have replaced the sensors after the coating has had a chance to "cure" and their cars ran better.

Joe B

In addition to all the other recomendations.....Drilling out the existing IAC bypass hole between the lower section of the stock throttle body(behind the air foil if you have one) stopped mine from constantly wanting to die after the mods in my sig were made...things were really bad on mine after the car was warmed up at Idle, and when comming to a stop it would die and take forever to restart)......."To start" drill it out a couple drill sizes larger and see if it helps things at all, if not no harm done, if it helps, go larger one drill size at a time untill things are good......also open your throttle body blades a bit more to see if that helps things,and check and re-set your (CLOSED) TPS voltage to .67..........Joe

96_pimped_out

I'll check out the IAC and look for the bypass... I did take the TB apart and clean it during the build, I could have hacked something up there.

Also, I've found when I rev the engine my spedo goes up too. Not sure if this could be related in any way? I posted about it here: http://web.camaross.com/forums/showthread.php?p=3939381

stereomandan

Yeah, my O2's fouled with my coated MAC mids. Not sure if it was the coating burning off, or the ultracopper RTV used on the header gasket, or slip tube. I waited a few hundred miles, and put in new O2's. Sounds like you don't have that luxury though, if you can't drive it. My guess is it might be the combination of the O2's and something else. Maybe the IAC as mentioned.

Dan

96_pimped_out

I sure wish I would have found that juicy little piece of info... I would have left the old pieces of crap O2s in there for a bit!?

Ug... I fear your'e right, and it's another $100 down the crapper. I'll play with all of these suggestions tonight, see what I find...