Hi all. New here but lurked many times. Appreciate the efforts of all contributors! Our ride is a 1991 Z28, 5.7 TPI. Factory performance rear axle (rear disc brakes). completely stock. It's been a pleasure to have and drive. I wrench on everything I own and am electronically connected so to speak. My very similar problem to what I see on the forums here is a rough unstable Idle as soon a CLOSED LOOP is achieved. Start cold and she runs (Idles) pretty well until closed loop and then the jet engine sound (IAC OPENING UP) gets really loud. Even without the monitoring hardware, I can tell its going rich and the ECM is commanding the IAC to open wide open to try and get the mixture back on track.
Things already done:
1227730 ECM swapped (I have 4 )
Plugs
Wires
Cap
Rotor
Spark is strong (Yes I got bit....)
O2 sensor
Ignition timing is stable for a 150000 mile car. It's not jumped a tooth anyway
MAP and TPS functionally verified( unplug one or the other and engine still controls timing. SERVICE ENGINE SOON LIGHT comes on. Unplug both and engine almost DIES if butterflies are opened a little.
EGR (which was bad by the way. Applied vacuume caused no movement and you could breath through the port on the valve
)
Injector inspection including removal, pressurized front and back flushing, leak down testing and spray pattern verified.
Fuel pressure tested (Guage will be on the car until it runs right...)
Fuel filter
Fuel pump
Intake manifold re-torque ( All but one were super tight. One was just tight (got about 1/8 turn).
I have been reading that this may be caused by a bad MEMCAL unit, which I only have ONE of (The original) The other ecm's I have were from other vehicles and not Camaros.
Heres the questions
1. Am I right in thinking maybe the MEMCAL and how often does this happen
1. Any other checks I can make that I might have missed?
2. Best suggested place to get another stock MEMCAL?
3. Suggesttion on where to send these MEMCAL units I have to get them reprogrammed as a 1991 Camaro.
Okay so I wrote it all down in one spot here so I can remember it and am going to fish around on the site for good info but anyone willing to comment/help out would be greatly appreciated. Thanks in advance to all you Camaro fans!
Oh yeah and valve guide seals cured the mosquito-fog-on-start effect really well!
Links or comments appreciated!
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