* Starting Enrichment: Older fuel-injected vehicles often have a system where the computer provides a richer fuel mixture (more fuel) during cranking to aid starting. The TPS signals the computer about the throttle position. If the TPS is malfunctioning or sending incorrect signals, the computer may not recognize the engine is in the starting condition and therefore doesn't provide the necessary rich fuel mixture. Flooring the throttle might be accidentally triggering a workaround within the system.
* Failed TPS: A faulty TPS can send inaccurate or no signal at all. This can cause a variety of starting problems, including this one.
* Wiring Issues: A break or short in the wiring harness connected to the TPS can also lead to intermittent or incorrect signals reaching the computer. Corrosion is common in older vehicles.
* Computer Issues (Less Likely): While less probable, a problem within the engine control module (ECM) itself could also be the culprit. This is usually diagnosed after checking the simpler TPS and wiring.
Troubleshooting Steps:
1. Check the TPS: This is the most likely culprit. You'll likely need a multimeter to check the voltage output of the TPS at various throttle positions. A repair manual for your specific year and engine will show you the correct testing procedure and voltage specifications. You can also visually inspect the TPS for damage or loose connections.
2. Inspect Wiring: Carefully examine the wiring harness connected to the TPS for any signs of damage, corrosion, or loose connections. Repair or replace any damaged wiring.
3. Clean the Throttle Body: A dirty throttle body can sometimes interfere with the TPS's operation. Clean it thoroughly with a throttle body cleaner.
4. Check Fuel Pressure: While less likely related to the gas pedal issue specifically, low fuel pressure could contribute to starting problems. A fuel pressure gauge test is recommended if the above steps don't resolve the issue.
5. Professional Diagnosis: If you're not comfortable performing these tests yourself, take your truck to a qualified mechanic specializing in older vehicles. They'll have the tools and expertise to diagnose the problem accurately.
Flooring the gas pedal is a workaround; it's not a solution. Addressing the underlying TPS or wiring problem is crucial to ensure reliable starting. Remember safety first – disconnect the negative battery terminal before working on electrical components.
