Date: 201309
Local time of day: 0601-1200
Location: ZZZ.ARTCC, US
Light: Daylight
Aircraft: MD-88
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Powerplant Fuel Distribution
Component problem: Design; Malfunctioning
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Confusion; Troubleshooting; Training / Qualification
Second reporter function: Captain; Pilot Not Flying
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Aircraft Equipment Problem Dissipated; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Took Evasive Action
Contributing factors: Weather; Procedure; Chart Or Publication; Aircraft
Primary problem: Ambiguous

Narrative: On descent; passing through approximately 24;000 feet; we noticed the left engine was indicating an extremely low idle condition.  EPR was 0.92; fuel flow was between 600-700 LBS; and N1 and N2 were substantially lower than the right engine.  I don't want to comment definitively on other indications; as I can't recall them exactly.  The FDR could be referenced.  The autothrottles and autopilot were engaged at the time.  I assumed control of the radios while the Captain referenced QRH.  The engine was not technically flamed out; N1 and N2 were too high.  I would classify it as a low idle condition.  However; this was the best (in our view) checklist to be run.  The engine did not re-light after complying with the checklist to step 2.  I then disengaged the autothrottles and moved the left throttle to its forward stop.  I wanted to see if there was a cable (mechanical) problem and to see if I could generate any increase in fuel flow or rotation. That was unsuccessful.  Step 3 involves bringing the fuel lever off and shutting down the engine.  The Captain suggested we attempt to cycle the fuel heat on the left engine before shutting it down.  I was comfortable with this; even though it was not part of the checklist.  The Captain cycled it; and within 20-30 seconds the engine spooled up and operated normally from there until the end of the flight.  We discussed this with Maintenance at the gate. From a systems perspective; it is too much to write in this narrative as to exactly what might have caused this.  I referenced the fuel system diagram; however; it is difficult to come to a conclusion without speaking with Maintenance as to what they found and/or pulling FDR data.  I will say this; however:  Our QRH needs to be reviewed.  The fact that an action not contained in our checklist saved us from shutting down an engine is a pretty clear indication that this is not a complete checklist.  Also; on a related note; 'INFLIGHT START'; needs to be addressed.  When would this ever be run?  Fire/Severe Damage prohibits relight.  A flameout or rollback allows a re-light attempt; however; the QRH never directs you to this checklist.  If step 1 is unsuccessful; it has you bring the throttle to idle and the fuel lever off in steps 2 and 3.    It is my philosophy that a QRH should be able to be run by a third grader; it should spell out EXACTLY what to do in an emergency -- period.  Checklists should be flowing and logical and lead you from one to the next at the appropriate time.  Counting on a pilot to rely on 'systems knowledge' and start trying things outside the scope of the QRH to solve a problem should only be expected in the most serious or unusual circumstances.


Second narrative: [This Report contains no additional information.]


Synopsis: A MD-88 engine rolled back below idle during descent causing the crew to consider an engine failure but upon activating Fuel Heat the engine returned to normal operation. Additional checklist items should be considered.