89 PRELUDE HIGH NOX - Prelude Honda Cars & Trucks

Nox is created in the engine, and the hotter the engine the more Nox is created.Get your car to run as cool as you can,oil change.engine/rad flush,fresh coolant,tune it up etc.In addition a high nox number may be a sign that your catalytic converter needs to be replaced.The converter is where the nox gets neutralized. good luck

What causes High NOX Emissions


Thousands of technicians have faced the challenge of bringing a particularly stubborn application into compliance for NOx emissions. High NOx readings are a clear sign of performance issues somewhere in the system. The question is, where?
Among the potential causes of non-compliant NOx readings are:
Misfire condition
Malfunctioning or improperly adjusted EGR valve
Failed oxygen sensor
Leak in exhaust tubing upstream of converter
Excessive carbon deposits in combustion chamber
Improper spark advance
Blocked coolant passage
Overly lean air-fuel mixture
Damaged cold air duct
Failed or malfunctioning catalytic converter
Corroded or damaged engine sensor electrical connections

Please note that while a failed catalytic converter will contribute to high NOx readings, the failure in itself may have been caused by some other upstream performance problem. In all cases, it is crucial to identify the root cause of the problem before blaming the converter.

Case Study

Hi there:
I suggest check this links, according with the fuel system:
- Fig. 62: Vacuum hose routing-1989 carbureted Prelude (except California)
- Fig. 63: Vacuum hose routing-1989 carbureted Prelude (California)
- Fig. 64: Emission component schematic-1989 carbureted Prelude
- Fig. 65: Vacuum hose routing-1989 fuel injected Prelude


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My honda prelude 1989 runs speed and later it will be slow and cannot run again.

A high NOx reading can be caused by any conditions that make the engine run lean. Vacuum leaks will dilute the fuel/air mixture with excess air leading to lean running. Lean mixtures lead to high combustion temperatures which produce NOx.

A malfunctioning EGR valve will not recirculate enough exhaust gas to keep combustion temperatures in check. The primary purpose of this valve is to lower NOx emissions are high RPM. It does this by delivering some low oxygen content gas back into the intake stream to dilute the incoming mixture. By decreasing the oxygen, combustion temps are lowered.

By the same logic, a misfire can cause high NOx. If the fuel/air mixture is not burned, excess oxygen in the exhaust (catalytic feed gas) will cause a dramatic decrease in catalytic converter efficiency in reducing NOx

NOX is created when the internal combustion temperature gets to high.The egr system uses burnt exhaust gases to line to cylinder walls.The purpose of this is decrease internal combustion temperature therefore reducing the amount of NOX created.Would look to a possible egr malfunction usually they will trigger the check engine light but not always.The 4.3L has been known to have issues with carbon buil up in the egr and the egr pintle not open and closing properly.

is everything stock? and you have catalitic converter in place?

Stop by Schucks auto supply and have them run the codes. i'm sure there is a code if you cant pass emissions. your check engine light bulb is probably out.

and usually the first cause is the first o2 sensor.

well you didn't specify the year, make, and model of the truck you are asking about so this is the best answer I can come up with. Below is a list I found that says what vehicles are interference motors...

INTERFERENCE ENGINES WITH TIMING BELTS
ACURA
1986-89 1.6L Integra
1991-95 1.7L Integra
1990-95 1.8L Integra
1986-89 2.5L Legend
1992-94 2.5L Vigor
1986-89 2.7L Legend
1990 2.7L Legend
1991-95 3.0L NSX
1991-95 3.2L Legend
AUDI
1970-93 All Except 1970-77
1.9L & 1970-73 1.8L
BMW
1987-95 2.5L 325I 525I
1994-95 4.0L 740I
CHRYSLER
1993-95 1.5L Colt
1987-88 1.5L Colt
1992-95 1.5L Eagle Summit
1987-88 1.6L Colt
1989-92 1.6L Eagle Summit
1994-98 2.0L Neon Stratus
1990-95 2.0L Eagle Talon
DAIHATSU
1988-92 1.0L Charade
1988-92 1.3L Charade
1990-92 1.6L Rocky
FIAT
1974-79 1.3L 128 Series
1979-82 1.5L Stranda
1974-78 1.6L 124 Series
1974-78 1.8L 124 Series
1974-78 1.8L 131 Series, Brava
1979-82 2.0L Brava, Spider
FORD
1981-85 1.6L Escort, EXP
1981-83 1.6L LN7, Lynx
1984-85 2.0L Escort, Tempo
1993-95 2.0L Probe
1986-88 2.0L Ranger
1984-87 2.0L Lynx, Topaz Diesel
1985 2.2L Ranger
1989-92 2.2L Probe
1986-88 2.3L Ranger
1986-87 2.3L Diesel Ranger
1991-98 4.6L Crown Victoria
GM
1986-95 1.0L Geo Metro
1989-91 1.0L Firefly (CANADA)
1985-88 1.5L Sunburst (CANADA)
1985-89 1.5L Spectrum
1990-93 1.6L Prizm, Storm
1981-84 1.8L Diesel (CANADA)
1982-86 1.8L Buick Skyhawk
1990-98 1.9L Saturn
1987-88 2.0L Buick Skyhawk
1988-95 2.3L Quad Four
1985-87 3.0L Buick
1979-95 3.8L Buick
HONDA
1986-87 1.0L Prelude
1973-78 1.2L All
1973-78 1.3L All
1980-84 1.3L All
1973-78 1.5L All
1985-89 1.5L Civic
1988-95 1.5L Civic, CRX
1993-95 1.5L Civic Del Sol
1979-84 1.5L All
1985-87 1.5L CRX
1993-95 1.6L Civic Del Sol
1973-78 1.6L All
1980-82 1.6L All
1988-95 1.6L Civic, CRX
1984-87 1.8L Prelude, Accord
1979-83 1.8L All
1986-91 2.0L Prelude
1990-91 2.1L Prelude
1990-95 2.2L Prelude, Accord
1992-95 2.2L Prelude
1995 2.7L Accord
HYUNDAI
1984-95 1.5L Excel Scoupe
1995-98 1.5L Accent
1992-95 1.6L Elantra
1993-95 1.8L Elantra
1992-95 2.0L Sonata
1989-91 2.4L Sonata
1990-95 3.0L Sonata
INFINITI
1990-92 3.0L M30
ISUZU
1987-89 1.5L I-Mark
1990-93 1.6L Stylus Impulse
1987-89 2.0L Impulse
1981-87 2.2L Diesel Truck
1986-95 2.3L Truck Trooper
1988-95 2.6L Truck Rodeo Amigo
1991-96 3.2L Trooper Rodeo Amigo
KIA
1995 2.0L Sportage
MAZDA
1984-85 2.0L 626
1988-92 2.2L 626 MX6
1989-93 2.2L Pickup
1988-95 3.0L 929 MPV
MITSUBISHI
1985-95 1.5L Mirage Precise
1990-92 1.6L Mirage
1989-95 2.0L Galant Eclipse
1983-86 2.3L Diesel Pickup
1994-95 2.4L Galant
NISSAN
1982 1.5L Centra
1983-88 1.6L Sentra Pulsar
1987-89 1.8L Pulsar
1982-89 2.0L Stanza 300ZX
1984-95 3.0L Maxima 300ZX Pathfinder
PORSCHE
1976-83 2.0L 924
1976-89 2.5L 944 Series
1989 2.7L 944 Series
1989-91 3.0L 944 Series
1976-83 4.5L 928
1984 4.7L 928
1985-91 5.0L 928
1992-95 5.4L 928
SUZUKI
1985-94 1.3L Samurai Sidekick
1989-94 1.3L Swift
TOYOTA
1986-95 1.5L Tercel
1981-83 2.2L Pickup
1984-87 2.4L Pickup
1982-88 2.8L Celica Cressida
1987-94 3.0L 4-Runner
VOLKSWAGEN
1976-91 All Except 1.9 2.1L Engine
1990-92 1.6L Golf (CANADA) Jetta
1990-95 2.0L GTI Jetta GLI Passat
VOLVO
1991 2.3L Coupe 940
1986-94 2.3L 240 740 940

there is an adjustment bolt on the back side of the idler pulley . you just loosen up the nut on the front of the pulley , then turn the 12 mm bolt under the pump on the back side of the pulley.