P0172 DTC For 98 Civic D16Y7 Engine

  • 1998 HONDA CIVIC
  • 195,000 MILES
Initially had a rough/surging idle problem, cleaned throttle body, injectors are good, new spark plugs, IAC valve good. Car idles fine but running conditions are crap. Loses power at seemingly random times. Finally ran diagnostic tool and came back with P0172 System Too Rich (Bank.1). Previously threw a P1456 But that has since gone away and not returned. Freeze Frame Data is as follows

Throttle Position: 9.8%
Engine RPM: 1261
Load Value: 19.6%
Map Sensor: 21 KPA
Coolant Temp: 197 Degrees F (Water Pump issue [resolved])
Intake Air Temp: 109 Degrees F
Short Term Fuel Trim (1): o.O%
Long Term Fuel Trim (1): 3.9%
Short Term Fuel Trim(3): -100.6%
Long Term Fuel Trim(3): -100.6%
Speed: 34 MPH
Fuel System: Open 1
Fuel System 2: N/A

I am absolutely stupified and don't want to spend more money replacing parts that don't need it. I almost threw away $170 on an IAC valve that I didn't need. Please! HELP!
Do you
have the same problem?
Saturday, September 1st, 2012 AT 11:34 PM

1 Reply

2. If DTC P0172 (system too rich) is set, check for:
? Fuel pressure regulator clogged or stuck closed.
? Clogged fuel return line.
? Leaking fuel injector.
? Fuel octane level less than specification.
? Deteriorated primary HO2S 1.
? Insufficient EGR system flow (D16Y5 engine).
? Leaking or stuck open EVAP purge control solenoid valve.
? Valves incorrectly adjusted.

Repair as necessary. If no problems are found, go to next step.

3. Check fuel pressure. See FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES article. If fuel pressure is okay, go to next step. If fuel pressure is too high, check fuel pressure regulator and fuel return pipe.
Repair as necessary. If fuel pressure is too low, check fuel filter, fuel pump, fuel feed pipe, and fuel pressure regulator. Repair as necessary.
4. On all models except D16Y5 engine with M/T, start engine and run at 3000 RPM with no loads and transmission in Park or Neutral until radiator fan comes on. Using scan tool, check primary HO2S 1 output
voltage. If voltage does not stay at less than 0.3 volt or more than 0.6 volt, go to next step. If voltage stays at less than 0.3 volt or more than 0.6 volt, replace HO2S 1.
5. On all models, using a vacuum pump, apply vacuum to EVAP purge control solenoid valve from intake manifold side. On D16Y7 engine, EVAP purge control solenoid valve is located at right side of engine,
below air leaner to air tube connection. On B16A2, D16Y5 and D16Y8, EVAP purge control solenoid valve is located below fuel injector rail cover. On all models, if vacuum does not hold, replace EVAP purge
control solenoid valve. If vacuum holds, check valve adjustment. On D16Y5 engine, check EGR system. On all models, if no problems are found, replace fuel injectors.
Check the evap for working right and check fuel pressure. Cold be a clogged return or egr passage due to temp outside and if you did a lot of short hops.
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Saturday, September 1st, 2012 AT 11:54 PM

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