AndrewPearce11

I have an issue with my 96 z28. The engine was rebuilt about 1500 miles ago with these mods:
bored 30 over
Head work done- Intake 2.02 Exaust 1.6
new cam- lift 480, dur in 208 dur exhuast 214
114 lope center, 6 degrees advance
AC pump delete
EGR Delete
AIR Delete
Mid length headers
K and N Air intake
Series 80 flowmaster
11 to 1 compression.

Now the problem is when I am running the car it want to die, The only way that I can keep it from dying is the feather the throttle. It only does this when the car has been warmed up. After the issue happens I let the car rest for a minute then I turn it back on and everything is fine for a few miles before it happens again. I checked the fuel pressure and the car runs at a steady 35psi, which i know is a little low. I Had the gauge hooked up to the engine when it began doing the problem and the fuel pressure did not change. It stayed at the 35.
So what do you guys think it is? could it possibly be a dying fuel pump? Opti spark? I wouldnt think it would be a opti since it seems to fire just fine. Im open to suggestions.

Injuneer

If 35psi was the reading with the vacuum compensation line on the fuel pressure regulator, that is normal. The pressure should be 43.5psi (acceptable range 42-47psi) with the vacuum line off the regulator. Additionally when driving the car, the pressure should rise or drop depending on what is being done with the throttle.

Have you scanned it for codes? Who tuned it for the heads and small cam?

How old are the O2 sensors? Sounds like the problem may be linked to the PCM going into closed loop when the engine warms up - typically 3 to 4 minutes after startup.

AndrewPearce11

Ok Ill start there. I had RPM performance in Indy tune it but I do not think they did a very good job. All they did was tell me how badly built the engine was and when I got it back it seemed that they really messed up the shift points. I no longer have an over drive and all the shift points are really messed up. The engine is not throwing any codes that I can see. RPM told me they would turn off my check engine light that was caused by the cat delete, so I think something fishy happened there. Know of any good people close to Indy that would tune a 96? The only people I can seem to find are people that tune the LS engines. RPM also left a cable that can connect my laptop to the car in my car. How hard is it to tune it myself?

Injuneer

Are you basing "not throwing any codes that I can see" on the absence of an SES light, or have you actually scanned it for codes? There are codes, including some for the trans, that don't turn on the SES light. Code readers for OBD-2 are cheap. Auto parts stores will scan it for free. If you have someone scan it, write down the exact numerical codes.

Heat soak can affect both the ICM and the optical cam position sensor module in the Opti. Can start fine, run fine cold, then have issues as those components heat up. But if that's the problem, they would set codes. But the fact it starts having problems after only driving a few miles seems more likely related to O2 sensor problems.

You need software to tune. What software did RPM use? There is tuning software available for the OBD-2 LT1 (JET DST, LT1_Edit), but it's expensive, and there's a significant learning curve. There are mail order tuners, but they are getting harder to find, at least good ones.