98 maxima misfire

[T2urtle]

alright guys i need another look at this, hopefully you guys can give me ideas.

1998 nissan with 118k, it has coil of plug system. last i change plugs was either at 60k or 80k with NGK v-power

my dad complains about a noise from the muffler about a month prior then
i have fault P0306 - misfire on #6

i had a couple used spare coils i bought. so i threw that in along with all new plugs while i was at it. cleared fault and about 15 mins of idling the car has a minor shake and i hear the exhaust noise my father speaks of. Its like a little drummer in the back. It sounded like back fire to me. I go to the front of the engine. I hear a swoush type of noise similiar to water and coolant flowing near the throttle body but it goes with the tune of the exhaust noises.

The car wasn't shaking insanely due to a misfire but it acted like it was missing. I drove it around the block and i didn't notice power lost or horrible shaking. pulled the car back in. i disconnected each coil one by one and each made the car shake A LOT MORE and the exhaust drumming beat faster. I did the same with the 3 front coils cylinder 2,4,6 and same results.

I go head and think maybe its just a bad coil again. this time i swapped a known good one (cylinder 4) into 6 and vice versa hopeing to get the fault jump to 4. NOPE results remain the same. cylinder 6 only. I ohmed the 3 front injectors and 3 front coils. everything was within range of each other and specs. specs for the injectors was 10-14 ohms and i had 11 on all 3 and coils only had to have something there and not OFL. which was present.

I dont know what to think here. My thinking is it has to be the injector, plug or COIL since its the only independent thing in the cylinder. A vac leak would cause mulitple cylinder misfires or least one under load, this is missing at idle same with a EGR sticking close/open.

nothing is adding up to me. maybe fresh eyes and brains can give me some troubleshooting steps.

 

[LTC8K6]

Swap injectors?

 

[T2urtle]

i hear i need to replace an O-ring on both if i do swap them. and they are a pain to remove out of the rail, most people who take them out break them.

Am i thinking right here. since its only 1 cylinder, plug, coil, injector and maybe i should check compression on it but that should be it? shouldn't it? Car has power, decent amount at that. Possibly bad injector only at idle hence why it ohmed out OK ?

I want to look into that throttle body noise but i dont think its relavant to my misfire. Its not a obvious misfire at all. i can only feel a soft shaky so maybe 1 out of 5 cycle type of misfire. if there such a thing.

 

[StageLeft]

If you replaced all the plugs and you then put in a known good coil into six and the bad six into four and are still misfiring on 6 you can be sure it's not a coil or plug.

 

[T2urtle]

understood that, part of the reason why i did it. my thoughts now are aside from the injector to look at what else could be the cause?

My father drives the car daily, doesn't care too much. he brings up concerns about the car with me and tells me to get to it when i get a chance. I want to go in with a game plan but all i have left now is the swap injectors.

I have spares of those as well =) But i'm putting #4 injector into #6 to make things a lot easier for me.

 

[StageLeft]

I think replacing the injector is a good idea. Then when the light comes on again the moment of truth is which cylinder it's for.

 

[kevman]

another vote for the injector. its a PITA job from what I understand.

 

[Viperoni]

On Maxima's, misfires are 95% of the time injectors or coils. Sounds like you got a bad injector, and it's just about time too, based on your mileage.

Best way to remove them is to get a high quality #2 sized Philips screw driver, spray down the injector with a penetrant (liquid wrench works well for me) to get the pentrant in the screw threads, and after taking off the top of the injector, keep spraying penetrant around the rim of the injector so it helps loosen the rubber O-ring. I recommend having at least 2 screw drivers on hand; 1 small and a couple of later ones to help you pry up the injector. You may need to apply a bit of heat to the fuel rail around the injector, I did so with a hair dryer and some caution.
Make sure you drain the fuel rail VERY well before you start, unless you like gas in your eye (I don't).

 

[T2urtle]

drain fuel rail.... fastest way i can think is pull the fuel pump fuse and crank for a bit... or is there a test port on the rail i can just use to piss out the fuel/pressure it has in there?

can i use any general injector o-ring? IE buy any single o-rings at autozone for a buck or so, I feel they should be about a buck.

 

[Viperoni]

drain fuel rail.... fastest way i can think is pull the fuel pump fuse and crank for a bit... or is there a test port on the rail i can just use to piss out the fuel/pressure it has in there?

can i use any general injector o-ring? IE buy any single o-rings at autozone for a buck or so, I feel they should be about a buck.

I pulled the fuse and cranked. Make sure you crank for a while after the engine dies.

I bought Nissan o-rings, about $2 a piece IIRC.

 

[AMDMaddness]

I know on my Pathfinder I could get my multimeter down to the injector and measure the coils resistance, Compare it to the others. Mine was wide open so it shows 0ohms. Injector failure on the nissan V6's is all to common.

 

[T2urtle]

^ i posted i measured the 3 front that i can reach easily which are 2,4 and 6 all were 11.x ohms and specs were 10-14ohms. but i'm still switching up the injectors when i get some o-rings and when my father brings me back the car

 

[T2urtle]

ok ok finally got a the car for a couple of hours.

i drove it around and it was fine, exhaust still made that drumming noise. I cleared faults last time i had it. check faults today pull P300 random misfire and the P1320.

i went for the quick kill, replace cylinder 6 fuel injector since it was the only single cylinder misfire fault i had. swapped in a used one, same results. Now i had to play the mix and match game. previously i ruled out the coil, since i swapped 4 and 6 with each other and 6 was still the problem. this time around i put the orginal injector 6 into cylinder 4, injector 4 into 6 and for shits and giggles coil 2 into cylinder 6. started it up same stuff. but no faults, it was misfiring. You can feel and hear it. idle nicely 650-770.

drove it around for about a mile, drove decent. power still there didn't feel it miss at higher RPM. came back in the garage and pulled faults. P0306 cylinder 6 misfire. I'm somewhat out of ideas at this moment. P1320 didn't show up.

P0306 shows up as "PENDING" on my ELMSCAN scantool.

 

[LTC8K6]

A code P0306 may mean that one or more of the following has happened:

Faulty spark plug or wire
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector
Burned exhaust valve
Faulty catalytic converter(s)
Running out of fuel
Poor compression
Defective computer

A code P0300 may mean that one or more of the following has happened:

•Faulty spark plugs or wires
•Faulty coil (pack)
•Faulty oxygen sensor(s)
•Faulty fuel injector(s)
•Burned exhaust valve
•Faulty catalytic converter(s)
•Stuck/blocked EGR valve / passages
•Faulty camshaft position sensor
•Defective computer

 

[LTC8K6]

Don't forget to check the wiring going to the coil and the injector.

 

[exdeath]

So you've ruled out injector and coil, but I didn't see that you checked the plug for fouling or correct gap.

To go any further without guessing and praying and throwing parts/money at it, you really need a scope. I'd suggest looking at ignition primary and secondary, injector voltage and current, and crank and/or cam position signals. One of those WILL look out of place when the misfire occurs.

Even if the injector and coil are good, you could have a faulty driver in the computer or a problem in the harness, and that will all show up on a waveform trace.

You might also run a comparative compression test to check for a valve problem. That exhaust drumming sounds an awful lot like it could be a compression leak through the exhaust valve on #6, as fuel ignition/backfire in the exhaust is not guaranteed or consistent enough to cause steady "drumming".

The misfire code is logged when the computer doesn't see the appropriate feedback in the primary waveform coming back from the ignition module during a commanded ignition event, or when the instantaneous crank speed does not increase. Many things can cause that and be completely unrelated to the ignition system.

 

[exdeath]

can i use any general injector o-ring? IE buy any single o-rings at autozone for a buck or so, I feel they should be about a buck.

They only need to be a fuel/oil graded nitrile rubber type O ring.

 

[T2urtle]

i did check the plugs but not the gap.

cylinder 2 and 6 only, while i swap the coil i pulled the plugs as well. cylinder 2 the good cylinder has a light white coat on it. wear as cylinder 6 has a darker coat. Nothing was dripping wet or anything like that. Both plugs were not crazy looking in any way. I might pick up a spark plug gapping tool sometime this week and check it out.

 

[exdeath]

i did check the plugs but not the gap.

cylinder 2 and 6 only, while i swap the coil i pulled the plugs as well. cylinder 2 the good cylinder has a light white coat on it. wear as cylinder 6 has a darker coat. Nothing was dripping wet or anything like that. Both plugs were not crazy looking in any way. I might pick up a spark plug gapping tool sometime this week and check it out.

The dark color is normal, it's carbon from fuel contamination as a result of the misfiring.

Take a spare plug that is not fouled, and plug it into #6's ignition lead/coil pack and use some insulated pliers/vicegrips to secure the side of the plug to something metal on the engine (leave the old plug in the cylinder unless you want a lot of noise and fuel everywhere).

Observe for strong thick orange/blue consistent spark at the electrodes for about a minute (ideally you'd want to scope the secondary and get an actual voltage). If you have no problems here, swap the plugs. If the problem goes away then recurs, you have an issue with fueling that is fouling the plug and causing the misfire (even if it's dry, the carbon residue from the fuel can provide an alternate path for the spark and prevent it from jumping the gap reliably, and generally the plug is considered ruined).

Also do that compression test. It takes 5 minutes and that rapping sound in the exhaust is concerning.

 

[earthman]

You need to start with basics. Check compression. This could be a worn or burned valve. If it's that or a vacuum leak, they are more noticeable at idle and tend to disappear under load. A bad plug, wire or coil would be much more noticeable under load than at idle. You could also have a cracked head or leaky head gasket causing this as well.

 

[T2urtle]

UPDATE TIME

Ok here is the run down.

Car now only is showing P0306.

I measured resistance between spark plug signal wire at the coil to the ECM all were about 1.6 ohms.

ohmed the injectors to be at 11.x all in the same while warm as well.

i did the compression test on the front 3 cylinders which are 2,4,6. all 3 were in the 175-180 area.

Checked and confirmed right spark plugs and gap was corrected per the NGK website. I got the right ones copper plugs and gap to .44

I swapped all coils with a friend's car who has a working car W/O a CEL.

In the end i still got misfire on cylinder 6, P0306. The idle is dropping sometimes into the low 500's but mostly stays in the 650 area. I've played with idle screw and nothing helping. The idle air control valve is going crazy i guess its trying to compensate for the misfire.

One thing i did notice was that there was a tiny bit of oil leaking from the valve cover gasket where cylinder 6 is. But that is just a valve cover, i dont think it can a cause for a misfire but there is a leak. Spark plug tube seals on the other hand were all clean and dry. Coils and plugs when removed was clean and dry.

What do you guys think? :dunno:

I'm out of ideas about ready to turn it over to someone.

 

[exdeath]

So everything looks good in theory but still having issues. Compression good, you've used good plugs, coils, and injectors and you're still getting a misfire. What about the harness and connector to the coil pack, ignition controller (part of the computer usually), injector driver (also inside the computer) etc?

Only thing left that you can really do is start scoping signals. Something is wrong somewhere that you can't see or resolve by throwing working parts at it. If it's an issue with the crank/cam position sensor, ignition controller, computer, or harness, you'll be able to compare all cylinders through several cycles and see a slight difference on a scope when it starts misfiring. You can also get a crude comparison of the mixture in each cylinder by looking at the firing voltage and slope of the burn line on an ignition trace in the event of a fuel related misfire, see late coil dwell or bad driver grounds, etc.

Random intermittent misfires are probably one of the most difficult problems to troubleshoot, especially at home without the aid of an engine scope. Really need to see what the engine and computer are seeing and figure out WTF. Otherwise try tapping on the edges of the computer, or wiggle wires and spray down various connectors with a water bottle and see if you can get anything.

That's one drawback of individual injectors and per cylinder ignition components; some can act erratically and the engine still runs. When you have single units that are global that begin to fail (eg: one ignition coil), it usually downgrades to a no start issue which is infinitely easier to troubleshoot.

 

[T2urtle]

yes in theory i've thrown parts at it that i can. I've ruled out all the small cheaper repairs. the whole harness looks good. The harness on the ECM side is facing the pass footwell, rarely does my father shuttle people around.

everything is controlled by the ECM AFAIK.

i'm currently looking for a shop to take this car to. Hoping they dont charge me up the butt.

I really thought the wiring was bad but resistance was all same at 3 cylinders at the coils least. I didn't look at the injector wire resistance tho. Now that i think about it. One last thing for me to check.

A friend of mines wants to throw a ECU at it. But i dont think its the problem.

 

[allanon1965]

There is alot to be said for testing resistance when under a load, or hot and cold....Injectors can and do show good cold, but fail when heated up by the engine running..the injectors need to be checked when hot..

The p1320 is Ignition signal fault-primary (primary ignition signal fault) this being on the module side of the ignition....not the secondary side(plug boot, spark plug)

there is a TSB for Wire chaffing issues...
Classification:
EC97-018b

Reference:
NTB98-008b
Date:
September 16, 1999
Subject:
1995-99 MAXIMA EGI HARNESS WIRE BREAKAGE DIAGNOSIS AND REPAIR PROCEDURE
APPLIED VEHICLES:
1995-99 Maxima (A32)
SERVICE INFORMATION
If a 1995-99 Maxima has any of the following incidents:
MIL "on",
Engine no start, or
Other system malfunctions such as A/C mop, A/C idle up mop, rough idle, oil pressure light mop,
The cause may be wire breakage in the engine control harness where it bends over the right rear of the engine next to the right strut tower (see Figure 1). See the symptom charts for possible diagnostic trouble codes (DTCs) or specific symptoms that can cause one or more of these incidents.
This repair procedure may apply to your MIL "on" DTC symptom if it is specifically listed on the charts. Note that for each DTC or symptom listed there can be more than one circuit to check using the following procedure.
Only incidents and circuits listed on the attached chart are applicable to this bulletin. All of the incident possibilities are circuits contained in wiring that pass through the bend in the engine control harness.
A kit (P/N 24299-0L725) containing a harness protector and four clips must be installed to prevent
additional wire breakage.
SERVICE PROCEDURE
Diagnosis Procedure - MIL "ON"
Use this procedure when the vehicle has come in with the MIL "on" and a DTC stored in Self-Diagnosis memory.
1. Use CONSULT to display Self-Diagnosis Results.
2. Compare the DTC displayed by CONSULT to the DTC Charts (Chart # 5 1, 2, 3 and 4).
3. CONSULT can be used in Data Monitor mode as a preliminary check. Monitor the operation of the system indicated by the DTC.
4. Check for intermittent open or short circuits by aggressively wiggling the EGI harness side to side and up and down at the specified harness bend (see Figure 1) while watching the results on CONSULT Data Monitor. If the applicable monitored value changes or a DTC sets when you shake the harness then wire damage has been confirmed (see NOTE 1).
5. Use the correct year service manual Trouble Diagnosis for the DTC displayed together with the DTC chart to identify the wire color and pin location for the circuit in question.
^ If the wire color code is listed on the DTC chart, perform continuity check A.
^ If the wire is identified as "shielded wire" on the DTC chart, perform continuity checks A and B.
6. Perform the indicated continuity check(s) on the wire(s)for the circuit in question to isolate the short or open to the incident wire(s). It may be necessary to shake the harness as outlined in step 4 to verify intermittent conditions. Ohmmeter values should not change while shaking the harness (see NOTE 1 below).
^ If an open circuit is confirmed in a color-coded wire, perform the repair procedure.
^ If the open or short is confirmed in a "shielded wire," replace the entire harness.
NOTE 1: If you cannot confirm an open or short circuit with CONSULT, it is necessary to perform the continuity check outline in steps 5 and 6 above. If you cannot confirm an open or short in the specified wire(s) as they pass through the indicated harness bend with the continuity check, this bulletin does not apply.
Diagnosis Procedure - Non MIL Symptom
Use this procedure if the vehicle symptom is listed on the Vehicle Symptom Chart (Chart 5).
1. Verify the symptom in question is listed in Chart 5.
2. Refer to the system wiring diagram in the correct year service manual together with Chart 5 to determine the wire colors and pin location for the circuit in question.
3. Perform continuity check A on the wire(s)for the circuit in question to isolate the short or open to the incident wire(s).
4. Check for intermittent open or short circuits by aggressively wiggling the EGI harness side to side and up and down at the specified harness bend and performing the indicated continuity check(s). If ohmmeter values change while shaking the harness the wire damage has been confirmed (see NOTE 2 below).
^ If an open circuit is confirmed in a color-coded wire, perform the repair procedure for color-coded wires.
NOTE 2: If you cannot confirm an open or short circuit in the specified wire(s) as they pass through the indicated harness bend, this bulletin does not apply.

This being said, there are updated coils for this car and testing indicates 77' F to be the test temp, but personal experience has shown this to be a misleading test at that temp. If the harness is ok, then injectorsare the primary suspect , given the p1320 code.

if it were mine, it would get 6 new updated coils from nissan....there is a known problem with these coils, which is why they were updated and why you dont replace just one.