rough idle, poor MPG, fuel injector replace
09-26-2012, 03:57 PM
#1
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Thread Starter
Join Date: Feb 2005
Posts: 59
rough idle, poor MPG, fuel injector replace
'95 Maxima. gas mileage had dropped from normal 18 MPG city to 13 MPG city. rough idle. hesitation on accelerating from zero. Check engine light on. codes: 4-3 (knock sensor), 7-1 (multi cylinder misfire), 10-5 (EGR...). i'll write for novice.
first step: i wanted to check each of the six ignition coils. pulling off the wire at connector on coil indicated noticeable difference in idle sound only when the middle front or middle back coil was unplugged. (couldn't notice a change in idle when any one of four coils (passenger front, driver front, passenger rear, driver rear) was disconnected i switched the passenger front coil with middle front, then driver front coil with middle front. each time when the middle front wire was disconneted, the idle slowed indicating all three front coils were good. i skipped (testing) the rear coils at this point).
second step: i wanted to check each of the three front fuel injectors. pulling off the wire at connector on each of the front fuel injectors. passenger front injector showed no difference in idle sound whether wire was connnected or disconnected. disconnecting middle front injector slowed idle, disconnecting driver front injector slowed idle. now i had suspicion passenger front fuel injector was bad. next i tested restistance between the two leads on the fuel injector body. using a cheap volt meter set to ohms x 10, passenger front injector read no continuity. middle front injector and driver front injector each had continuity (meaning little resistance). now i was ready to buy one new injector.
went to pepboys and tested a new fuel injector with the volt meter. showed had continuity (meaning little resistance).
to replace the fuel injector i did not release fuel pressure (others have suggested to do so). engine had been off for 30 minutes. did not remove fuse. did not disconnect battery. simply unscrewed the metal cover over the injector, placed a screw driver horizontally six inches away and a few inches higher from the injector as a lever so i could use another screw driver to pry up one edge (slot on each side) of the plastic top of injector (had put the screws into the holes as others have suggested to use for leverage but mgiht not have been needed). the injector popped up and some gas also shot up several inches. placed new injector into the slot. placed the metal cover over the injector and tightened two screws to push the injector down. attached wire. car started. reset the check engine light. idle seems smoother now. will learn if MPG is up to 18 city next time i need to buy gas.
first step: i wanted to check each of the six ignition coils. pulling off the wire at connector on coil indicated noticeable difference in idle sound only when the middle front or middle back coil was unplugged. (couldn't notice a change in idle when any one of four coils (passenger front, driver front, passenger rear, driver rear) was disconnected i switched the passenger front coil with middle front, then driver front coil with middle front. each time when the middle front wire was disconneted, the idle slowed indicating all three front coils were good. i skipped (testing) the rear coils at this point).
second step: i wanted to check each of the three front fuel injectors. pulling off the wire at connector on each of the front fuel injectors. passenger front injector showed no difference in idle sound whether wire was connnected or disconnected. disconnecting middle front injector slowed idle, disconnecting driver front injector slowed idle. now i had suspicion passenger front fuel injector was bad. next i tested restistance between the two leads on the fuel injector body. using a cheap volt meter set to ohms x 10, passenger front injector read no continuity. middle front injector and driver front injector each had continuity (meaning little resistance). now i was ready to buy one new injector.
went to pepboys and tested a new fuel injector with the volt meter. showed had continuity (meaning little resistance).
to replace the fuel injector i did not release fuel pressure (others have suggested to do so). engine had been off for 30 minutes. did not remove fuse. did not disconnect battery. simply unscrewed the metal cover over the injector, placed a screw driver horizontally six inches away and a few inches higher from the injector as a lever so i could use another screw driver to pry up one edge (slot on each side) of the plastic top of injector (had put the screws into the holes as others have suggested to use for leverage but mgiht not have been needed). the injector popped up and some gas also shot up several inches. placed new injector into the slot. placed the metal cover over the injector and tightened two screws to push the injector down. attached wire. car started. reset the check engine light. idle seems smoother now. will learn if MPG is up to 18 city next time i need to buy gas.
10-26-2012, 11:50 AM
#2
Newbie - Just Registered
Join Date: Oct 2012
Posts: 1
'95 Maxima. gas mileage had dropped from normal 18 MPG city to 13 MPG city. rough idle. hesitation on accelerating from zero. Check engine light on. codes: 4-3 (knock sensor), 7-1 (multi cylinder misfire), 10-5 (EGR...). i'll write for novice.
first step: i wanted to check each of the six ignition coils. pulling off the wire at connector on coil indicated noticeable difference in idle sound only when the middle front or middle back coil was unplugged. (couldn't notice a change in idle when any one of four coils (passenger front, driver front, passenger rear, driver rear) was disconnected i switched the passenger front coil with middle front, then driver front coil with middle front. each time when the middle front wire was disconneted, the idle slowed indicating all three front coils were good. i skipped (testing) the rear coils at this point).
second step: i wanted to check each of the three front fuel injectors. pulling off the wire at connector on each of the front fuel injectors. passenger front injector showed no difference in idle sound whether wire was connnected or disconnected. disconnecting middle front injector slowed idle, disconnecting driver front injector slowed idle. now i had suspicion passenger front fuel injector was bad. next i tested restistance between the two leads on the fuel injector body. using a cheap volt meter set to ohms x 10, passenger front injector read no continuity. middle front injector and driver front injector each had continuity (meaning little resistance). now i was ready to buy one new injector.
went to pepboys and tested a new fuel injector with the volt meter. showed had continuity (meaning little resistance).
to replace the fuel injector i did not release fuel pressure (others have suggested to do so). engine had been off for 30 minutes. did not remove fuse. did not disconnect battery. simply unscrewed the metal cover over the injector, placed a screw driver horizontally six inches away and a few inches higher from the injector as a lever so i could use another screw driver to pry up one edge (slot on each side) of the plastic top of injector (had put the screws into the holes as others have suggested to use for leverage but mgiht not have been needed). the injector popped up and some gas also shot up several inches. placed new injector into the slot. placed the metal cover over the injector and tightened two screws to push the injector down. attached wire. car started. reset the check engine light. idle seems smoother now. will learn if MPG is up to 18 city next time i need to buy gas.
first step: i wanted to check each of the six ignition coils. pulling off the wire at connector on coil indicated noticeable difference in idle sound only when the middle front or middle back coil was unplugged. (couldn't notice a change in idle when any one of four coils (passenger front, driver front, passenger rear, driver rear) was disconnected i switched the passenger front coil with middle front, then driver front coil with middle front. each time when the middle front wire was disconneted, the idle slowed indicating all three front coils were good. i skipped (testing) the rear coils at this point).
second step: i wanted to check each of the three front fuel injectors. pulling off the wire at connector on each of the front fuel injectors. passenger front injector showed no difference in idle sound whether wire was connnected or disconnected. disconnecting middle front injector slowed idle, disconnecting driver front injector slowed idle. now i had suspicion passenger front fuel injector was bad. next i tested restistance between the two leads on the fuel injector body. using a cheap volt meter set to ohms x 10, passenger front injector read no continuity. middle front injector and driver front injector each had continuity (meaning little resistance). now i was ready to buy one new injector.
went to pepboys and tested a new fuel injector with the volt meter. showed had continuity (meaning little resistance).
to replace the fuel injector i did not release fuel pressure (others have suggested to do so). engine had been off for 30 minutes. did not remove fuse. did not disconnect battery. simply unscrewed the metal cover over the injector, placed a screw driver horizontally six inches away and a few inches higher from the injector as a lever so i could use another screw driver to pry up one edge (slot on each side) of the plastic top of injector (had put the screws into the holes as others have suggested to use for leverage but mgiht not have been needed). the injector popped up and some gas also shot up several inches. placed new injector into the slot. placed the metal cover over the injector and tightened two screws to push the injector down. attached wire. car started. reset the check engine light. idle seems smoother now. will learn if MPG is up to 18 city next time i need to buy gas.
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