P0172 DTC For 98 Civic D16Y7 Engine

CHRISTOPHERWAYNETIDWELL

MEMBER
1998 HONDA CIVIC
AUTOMATIC
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!

1 Reply

HMAC300

MECHANIC
48,601 POSTS

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.