DRIVEABILITY Symptoms Versus Fuel Quality (Engine Systems Functioning Properly): Notes
PROBLEM SYMPTOM TABLE - DRIVEABILITY
| DRIVEABILITY SYMPTOM | FUEL QUALITY - CAUSE |
| Excessive spark knock | Octane number to low |
| Hard cold startes | Volatility too low Contamination |
| Garage stalls and/or tip-in hesitation | Volatility too low Contamination Intake Valve Deposits* Low fuel level |
| Poor cold performance | Volatility too low Contamination Low fuel level |
| Surges, Chuggles, Lack Of Power, Sluggish, Cuts Out and/or Misses | Contamination |
| Rough/Unstable Idle | Intake Valve Deposits* Contamination |
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NOTE:
* Intake valve deposits may result from unburned heavy-end hydrocarbons and lack of dtergent additives. Another brand of gasoline with the proper detergent additives may correct the problem.
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Diagnostic Hints
- Start diagnosis by verifying complaint. Keep vehicle overnight before verifying a cold driveability problem.
- Remember that the symptom(s) may indicate a fuel delivery/pressure or fuel control problem. Use DTC codes in the SELF-DIAGNOSTICS - 2.2L and/or SELF-DIAGNOSTICS - 3.0L .
- If engine is functioning properly, suspect fuel volatility/fuel quality.
- Determine if customer is using premium grade fuel. If so, suggest trying a different brand of fuel or regular unleaded fuel except when a premium-grade is recommended because of operating conditions. Some premium grade gasolines may actually cause cold engine driveability problems because of their lower volatility in the warm-up range. Inform customers that it may require more than one tankful of a different brand of fuel to correct a fuel quality problem.
- Determine if customer has old fuel in tank. If so, the volatility may be too low because the "light-ends" have evaporated.
- Consider the possibility that an unseasonable cold snap has made fuel volatility wrong for the weather.