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Discussion Starter · #1 ·
Hey guys new to the forum and have a serious issue with my 1st GenX. Bought it with low compression on 5 and 6 and did an engine swap car fires up and idles fine but pulls a P0300 code nothing else have new cats new O2 sensors and new almost everything in the X. The scanner is recommending new fuel injectors which I have new #5 and #6 injectors I have a mid on cylinder 3 and 6 as when I pull the plugs there’s spark but no change in idle. I even swapped the injector between 1 and 3 and cylinder 3 continues to misfire. I don’t have much electrical experience but when I unplug the fuel injector still no change. It runs decent stop and go but on the highway it won’t hit much more then 55 mph is there anyone here that can help I’ll be switching the fuel injectors out tomorrow morning.
 

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Hey guys new to the forum and have a serious issue with my 1st GenX. Bought it with low compression on 5 and 6 and did an engine swap car fires up and idles fine but pulls a P0300 code nothing else have new cats new O2 sensors and new almost everything in the X. The scanner is recommending new fuel injectors which I have new #5 and #6 injectors I have a mid on cylinder 3 and 6 as when I pull the plugs there’s spark but no change in idle. I even swapped the injector between 1 and 3 and cylinder 3 continues to misfire. I don’t have much electrical experience but when I unplug the fuel injector still no change. It runs decent stop and go but on the highway it won’t hit much more then 55 mph is there anyone here that can help I’ll be switching the fuel injectors out tomorrow morning.
From what you are saying I wouldn't be chasing injectors but ignition from the distributor. Lot's that can go wrong on that front in the Gen1. Have you inspected the internals of the distributor for signs of wear? They are famous for bearing failure on the main shaft.
 

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Discussion Starter · #3 ·
I have 3 different distributors I’ve been swapping and checking bearings are good 1 is brand new one is a Nissan Xterra and one is a frontier dizzy from the JDM engine I swapped into it.
 

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I have 3 different distributors I’ve been swapping and checking bearings are good 1 is brand new one is a Nissan Xterra and one is a frontier dizzy from the JDM engine I swapped into it.
So I have to assume that changing the dizzy hasn't moved the problem at all. P300 code is for random misfires. You say you have pulled plugs with no change in idle. That would make you suspect the plug or wire in that case was bad if the idle didn't change. Are the plugs and wires new? Do you have a plug wet with fuel on the suspect cylinders? Is your ignition timing set per procedure at 10 BTDC?
 

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Discussion Starter · #5 ·
So I have to assume that changing the dizzy hasn't moved the problem at all. P300 code is for random misfires. You say you have pulled plugs with no change in idle. That would make you suspect the plug or wire in that case was bad if the idle didn't change. Are the plugs and wires new? Do you have a plug wet with fuel on the suspect cylinders? Is your ignition timing set per procedure at 10 BTDC?
 

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Discussion Starter · #6 ·
Yes new plugs new wires Just got to the X so I’m going to retime again and drop the dizzy did a timing belt water pump and tensioner about a month ago every dot aligned including belt marks. going to pull number three plug right now but the odd thing is not only is there a no change when pulling the spark plug wire but no change when pulling fuel injector plug for number 3 so swapped the number one and number 3 injector and still number 3 misfire. Does this sound more like an internal timing issue I.e. timing belt unfortunately?
 

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Yes new plugs new wires Just got to the X so I’m going to retime again and drop the dizzy did a timing belt water pump and tensioner about a month ago every dot aligned including belt marks. going to pull number three plug right now but the odd thing is not only is there a no change when pulling the spark plug wire but no change when pulling fuel injector plug for number 3 so swapped the number one and number 3 injector and still number 3 misfire. Does this sound more like an internal timing issue I.e. timing belt unfortunately?
Do you have access to a compression tester gauge that you can screw into the #3 plug hole? Have to wonder if the valves are both closed on the compression/firing stroke. Does the plug in #3 look like it's been firing or is it just wet with fuel?
 

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Discussion Starter · #8 ·
Alright so number 3 plug is firing not wet with fuel but definitely carboned number one plug is wet with fuel got the live data numbers at idle and 2000 rpm’s fuel trim seems low here’s the stats
 

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Alright so number 3 plug is firing not wet with fuel but definitely carboned number one plug is wet with fuel got the live data numbers at idle and 2000 rpm’s fuel trim seems low here’s the stats
Not seeing any diagnostic stat data here. I'm thinking you are seeing fairly big negative numbers for fuel trim on #3. Ideal numbers in theory are near to zero.
 

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Discussion Starter · #11 ·
So taking a Nord light on the plug for cylinder 3 my switch wire white/green is staying hot I would assume the same for 6 is there a ground someplace for the injector harness that can cause a live ground on 3/6 for do I start taking the harness apart
 

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Discussion Starter · #12 ·
So I think I found the problem here with engine running I’m not getting a pulse with the Nord light on cylinder 3 while cylinder 1 and 5 the switch side of the plug pulses while not running the switch wire stays hot as if the cylinder is just staying open on the injector hence dumping fuel into cylinder 3 any thoughts on tracing this switch wire to injectors 3 and 6 or could it finally be a pcm issue at this point
 

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So I think I found the problem here with engine running I’m not getting a pulse with the Nord light on cylinder 3 while cylinder 1 and 5 the switch side of the plug pulses while not running the switch wire stays hot as if the cylinder is just staying open on the injector hence dumping fuel into cylinder 3 any thoughts on tracing this switch wire to injectors 3 and 6 or could it finally be a pcm issue at this point
Wow. Sounds like you are on to it there. That's a new one on me so I don't know where to point you for that injector pulse fault.
 

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Discussion Starter · #14 ·
yup an engine and all new parts later the issue is two open circuit wires running to the ECU so I’ll do a pin out test on them tomorrow and see hopefully A critter just chewed them and I don’t need a new ECU. But anyone reading this with a similar issue test the pulse of the injector connectors pulsing light means that you’re good with signal two solid lights means fuel dump and boggy running because too much fuel. My problem is two random misses p0300 code nothing else new cats new engine new o2 sensor new distributor new timing belt water pump crankshaft position sensor tps sensor new ignition harness new MAP and the problem is wiring.
 

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yup an engine and all new parts later the issue is two open circuit wires running to the ECU so I’ll do a pin out test on them tomorrow and see hopefully A critter just chewed them and I don’t need a new ECU. But anyone reading this with a similar issue test the pulse of the injector connectors pulsing light means that you’re good with signal two solid lights means fuel dump and boggy running because too much fuel. My problem is two random misses p0300 code nothing else new cats new engine new o2 sensor new distributor new timing belt water pump crankshaft position sensor tps sensor new ignition harness new MAP and the problem is wiring.
Good tip on the injector pulse test for sure. Glad you are on scent and hopefully near to the successful end to that journey!
 
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