I'll try to make this as short as possible but I believe in giving as much info so you know where I am at with this.

Engine Info

have an '88 Camaro with a newly rebuilt and modded 3.4L
Major mods are a crower cam:
Intake: ------266 ------lift----.435
Exhaust:-----260-------lift----.420
Intake Centerline: 112

Ported, polished intake
Enlarged Intake( 1.85)/exhaust (1.58)valves
57mm TB
19LB Ford injectors

Other minor mods but I listed only the major. Have also installed
an underdrive crank pulley, Accel coil and ESM, etc.

Computer is stock --- This I realize could be an issue later

Also the passenger side ehaust manifold has the O2 sensor accomodation instead of at the 'Y' junction below. Don't think this
is a problem but good to know, anyway

Problem

Misses at idle when in closed loop

Some details:
When first starting at cold open loop, everything appears and sounds normal. Smooth idle, etc. This car has a 'Cold Start Valve' so it is operating normally when engine is cold.
As soon as closed loop takes over, and assuming "Cold Start Valve" turns off or is totaly out of the picture , idle problem occurs along with sever pinging. I checked the timing and it is presently set at 8 BTDC. But previously I had experimented with different settings to see if it would cure this problem, but to no avail.

JFYI, no SES light at all. No codes or strange SES on off scenarios. When I drive the car, it runs great!! Although I am hesitant to really nail the accelerator due to this problem. The idle is set at about 1000 RPM and if it weren't for the miss, woud be pretty smooth. When I put in gear idle maintains, so the IAC appears to be working OK.

I'm not sure at this point what to do. I suspect it could be a bad injector but I don't have the tools/equipment to trouble shoot this
if it were suspect. These injectors were sent out for rebuild to "Maren Fuel Injectors"(sp).

Anyone with ideas or suggestions? Can the ECM be scanned for getting more details about what the engine is doing and what measurements are being thrown to the computor?

Also, is there a shop in the Northeast I can contact that will take the car in for diagnostics ( I live in the Long Island area)?

Thanks for your help.

 

While I'm no expert on the 3.4L, I suspect it's not that much difference in this case.

Idles fine while cold, but won't idle right in closed loop? Check the O2 sensor, but I suspect it's going to all be in the prom that's still stock and this set up is no where near stock if I read it correctly.

 

vernw, forget to mention that all sensors are new except MAF and
I believe the MAT. You may be right about the ECM.

 

I actually saying the PROM as in you probably need to burn a custom DIY one.

I've also seen new sensors (and spark plugs) that were bad right out of the box.....