1. Fuel System:
* Stale Fuel: This is the most likely problem after a year of sitting. Ethanol in gasoline attracts water, which can separate and clog injectors or damage the fuel pump. The fuel may also simply be gummed up. Drain the fuel tank (safely, following proper procedures), replace the fuel filter, and add fresh fuel with a fuel system cleaner.
* Fuel Pump: The fuel pump could have failed due to age or sitting. You should check the fuel pressure. A low or no fuel pressure reading indicates a pump problem.
* Fuel Injectors: Clogged injectors are possible due to stale fuel. A fuel injector cleaning might resolve this, or they may need replacement.
* Fuel Pressure Regulator: Could be leaking, reducing fuel pressure.
2. Ignition System:
* Battery: A dead or weak battery is a common cause of poor performance. Start with a battery check.
* Spark Plugs and Wires: Old spark plugs and wires will misfire, leading to poor performance. Replace them.
* Ignition Coil(s): A failing ignition coil can cause misfires in one or more cylinders. Check for cracks or damage.
* Distributor (if applicable, though unlikely on a LT1): While the LT1 is electronically controlled, problems with the ignition module or crankshaft position sensor can cause similar issues. These are less likely but should be checked if the above steps yield no results.
3. Transmission:
* Fluid Level and Condition: Check the transmission fluid level. It may be low, or the fluid itself might be degraded after sitting for a long time. If the fluid is dark brown or smells burnt, a transmission service or even rebuild may be necessary.
* Transmission Filter: Should be replaced during a transmission fluid change.
* Torque Converter: Possible internal failure, though less likely to manifest as just poor acceleration. More likely to cause slipping or other transmission-specific problems.
4. Other Potential Issues:
* Intake Air Leaks: Check all vacuum lines and connections for cracks or leaks. Air leaks disrupt the air-fuel mixture.
* Mass Air Flow (MAF) Sensor: A dirty or faulty MAF sensor will throw off the air-fuel mixture. Cleaning or replacement may be necessary.
* Throttle Position Sensor (TPS): A faulty TPS provides inaccurate readings to the engine computer, affecting performance.
Troubleshooting Steps:
1. Start with the easiest and most likely: Fresh fuel, new fuel filter, and a check of the battery.
2. Check fuel pressure: This will quickly pinpoint fuel system problems.
3. Inspect spark plugs and wires: Replace if necessary.
4. Check transmission fluid: Level and condition are crucial.
5. Consider a professional diagnosis: If you're not comfortable tackling these issues yourself, a mechanic with experience with LT1 engines can run diagnostics to pinpoint the problem more accurately.
Don't assume it's just one thing. The combination of age and prolonged sitting likely means multiple systems need attention. Start with the basics, systematically checking each system, and keep good notes of your findings. A methodical approach will help you diagnose the problem and get your Z28 back on the road.
