88 civic running rich, stalling at idle, ideas?
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Honda-Tech Member
Joined: Nov 2003
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From: ca
88 civic running rich, stalling at idle, ideas?
The car is an '88 DX 4 dr D15B2 5-speed. There is a code 1 (O2 sensor) that shows up only after driving for at least 30 min. on the highway, and if the engine cools it usually takes +30min of driving before it will show again.
Probed the O2 pins on the ECU with a meter while driving, and the O2 sensor voltage appears to fluctuate correctly. Many crossovers 0.3-0.7V and quick response. The only thing that did not pass the troubleshoot from the Helms is when decelerating closed-throttle from +5000rpm, the voltage does not drop low to show fuel cut, it just hovers ~0.8V.
Pulled the O2 and bench tested it with a propane torch. All the way to +1.0V with the sensor under the flame, and immediately to 0.1 or 0 when torch is removed. So, reluctantly, the sensor was replaced with another universal Bosch, and no change.
Sometimes when coming off the highway after a long drive and the engine goes down to idle, it will stutter and stall, but start right back up. When this happens, the car is running very rich which is why it is stalling (smell of unburned fuel). Also MPG is down from ~37 MPG to ~30.
The plugs, plug wires, cap, rotor, and timing all check out fine, fuel filter was also replaced.
Unplugging the bottom injector (green one, Honda refers to as auxiliary injector) doesn't seem to help, but unplugging the top injector (brown) does eliminate the rich idle / stalling.
Replaced both injectors with different used ones, no change.
Fuel pump reads ~40 psi when primed with engine off, and ~35 psi at idle with FPR vacuum line connected. Fuel volume measured at FPR return line w/key on for 10 seconds is ~6 oz., Helms spec is 7.8 oz. minimum.
TPS, MAP, and 2-wire ECT sensors all check out within spec with car idling and off, engine cold and hot.
Replaced EACV, ECU, main relay with those from another running D15B2, still no change.
Any ideas?
Probed the O2 pins on the ECU with a meter while driving, and the O2 sensor voltage appears to fluctuate correctly. Many crossovers 0.3-0.7V and quick response. The only thing that did not pass the troubleshoot from the Helms is when decelerating closed-throttle from +5000rpm, the voltage does not drop low to show fuel cut, it just hovers ~0.8V.
Pulled the O2 and bench tested it with a propane torch. All the way to +1.0V with the sensor under the flame, and immediately to 0.1 or 0 when torch is removed. So, reluctantly, the sensor was replaced with another universal Bosch, and no change.
Sometimes when coming off the highway after a long drive and the engine goes down to idle, it will stutter and stall, but start right back up. When this happens, the car is running very rich which is why it is stalling (smell of unburned fuel). Also MPG is down from ~37 MPG to ~30.
The plugs, plug wires, cap, rotor, and timing all check out fine, fuel filter was also replaced.
Unplugging the bottom injector (green one, Honda refers to as auxiliary injector) doesn't seem to help, but unplugging the top injector (brown) does eliminate the rich idle / stalling.
Replaced both injectors with different used ones, no change.
Fuel pump reads ~40 psi when primed with engine off, and ~35 psi at idle with FPR vacuum line connected. Fuel volume measured at FPR return line w/key on for 10 seconds is ~6 oz., Helms spec is 7.8 oz. minimum.
TPS, MAP, and 2-wire ECT sensors all check out within spec with car idling and off, engine cold and hot.
Replaced EACV, ECU, main relay with those from another running D15B2, still no change.
Any ideas?
Honda-Tech Member
Joined: Mar 2009
Posts: 51
Likes: 1
From: naptown
Re: 88 civic running rich, stalling at idle, ideas?
convert to mpfi... check your fuel pressure with the regulator vacuum hose unplugged, it should be about 10 psi higher. Also smell that vacuum hose; if it smells like gas then the diaphragm has ruptured in the FPR.
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