i've read through numerous posts on misfires and can't see to figure out why my path is misfiring. so i'll just tell my story and see if someone can help me out. There's no CEL the entire time. The car has 130k miles on it.
-- car misfires for an hour or two driving around 70mph under load. the problem goes away for a 1 month or so, i though it was bad gas.
-- a month later, the problem comes back but much worse. misfires at all speeds and it stalls out and won't start... i let the car cool down.. it starts for a little then dyes. it eventually just won't start at all.
*i replace the distributor cap and rotor - nothing
*i replace the spark plugs and the car now starts and runs but i still have the misfire at high rpms or under load at low rpms.
*i felt the fuel two fuel lines and i could definitely squeeze them while the car was running.. so i replaced the fuel filter (what a pain-in-the-a**)... didn't fix it. problem is still there
*i cleaned the MAF (it already looked clean).. nothing..
what should i try next?
Ideally, I'd like to:
1. measure pressure of the fuel lines,
2. check the intensity of the spark if thats possible to see if i have a bad
ignition coil
3. check the air-fuel to see if my MAF is working..
I just don't think i have the equipment to do those though.. are their simple ways to perform these tests?
Thanks
misfire on 99.5 path, please help
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GrilledCheese33
- Posts: 4745
- Joined: Mon Apr 04, 2005 3:29 pm
- Car: 2008 Nissan Xterra
1972 Yamaha R5
2017 Sea Doo Spark Trixx - Location: 386 FL
Re: misfire on 99.5 path, please help
Your next step should be to check into the ignition coil. After that I would look into the MAF and also oxygen sensors...
Re: misfire on 99.5 path, please help
Miss-fires
Bad:Spark, fuel, timing, injectors
Spark
Plugs, too wide, fouled, bad ground. Wires: leaking. Rotor:dirty inside or out, transistor: break down. Pulse generation:dirty
Fuel
Lack of fuel, atomization, mixture, pressure pump fuel filter air filter
Timing
Low speed vs. high speed, static vs. dynamic, rotor loose, base plate, slot windows out of time
Injectors
Fouled, bad spray pattern, delay, carboned
Since your vehicle displays intermittent miss-fires do the easy things first.
Fuel filter
Timing verification static and at idle and higher RPM to check advance.
With a timing light and built in dwell verify the spark sequence.
Re-gap or replace plugs
Inspect the HT wires to Rotor
Open rotor and inspect the components look for a dusty dirty film and clean
If above good then check out the compression of all cylinders
Do a leak down test
Check the injectors
What grade of gasoline are you using? The use of high grade when 87 is recommended is a trouble area because of carbon build up that will change compression, pre or post ignition
Bad:Spark, fuel, timing, injectors
Spark
Plugs, too wide, fouled, bad ground. Wires: leaking. Rotor:dirty inside or out, transistor: break down. Pulse generation:dirty
Fuel
Lack of fuel, atomization, mixture, pressure pump fuel filter air filter
Timing
Low speed vs. high speed, static vs. dynamic, rotor loose, base plate, slot windows out of time
Injectors
Fouled, bad spray pattern, delay, carboned
Since your vehicle displays intermittent miss-fires do the easy things first.
Fuel filter
Timing verification static and at idle and higher RPM to check advance.
With a timing light and built in dwell verify the spark sequence.
Re-gap or replace plugs
Inspect the HT wires to Rotor
Open rotor and inspect the components look for a dusty dirty film and clean
If above good then check out the compression of all cylinders
Do a leak down test
Check the injectors
What grade of gasoline are you using? The use of high grade when 87 is recommended is a trouble area because of carbon build up that will change compression, pre or post ignition
Re: misfire on 99.5 path, please help
thanks for the reply guys.
Thats a lot of good information..
i'm running around 89 octane i think (1/2 87 and 1/2 93 - does that equate to around 89?) .
I've already replaced the fuel filter and also the spark plugs.. so i guess i'm going to do the next low lying fruit next.. ohm out the wires, ignition coil, power transistor, and resistor.
from the manual, it looks like:
-ignition coil (primary) should be 0.5 to 1.0 ohm
-ignition coil (secondary) should be 12 kohm
-power transistor should be anything but 0
-resistor should be 2.2kohm
i've never mucked w/ injectors before.. can those be cleaned or do they need to be replaced.. and also.. are they hard to get to in my path?
Thats a lot of good information..
i'm running around 89 octane i think (1/2 87 and 1/2 93 - does that equate to around 89?) .
I've already replaced the fuel filter and also the spark plugs.. so i guess i'm going to do the next low lying fruit next.. ohm out the wires, ignition coil, power transistor, and resistor.
from the manual, it looks like:
-ignition coil (primary) should be 0.5 to 1.0 ohm
-ignition coil (secondary) should be 12 kohm
-power transistor should be anything but 0
-resistor should be 2.2kohm
i've never mucked w/ injectors before.. can those be cleaned or do they need to be replaced.. and also.. are they hard to get to in my path?
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asnorton44
- Posts: 502
- Joined: Mon Apr 26, 2010 3:43 pm
- Car: 2001 Infiniti QX4
- Location: Indianapolis, IN
Re: misfire on 99.5 path, please help
Do you have the 3.5 engine?
Re: misfire on 99.5 path, please help
no, i have the older 3.3asnorton44 wrote:Do you have the 3.5 engine?
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asnorton44
- Posts: 502
- Joined: Mon Apr 26, 2010 3:43 pm
- Car: 2001 Infiniti QX4
- Location: Indianapolis, IN
Re: misfire on 99.5 path, please help
I believe your engine does not have ignition coils then.
Re: misfire on 99.5 path, please help
you're right.. there's just one coil and it's part of the distributor assembly.. you're not supposed to replace just that part.. but some guys here have done it w/ success..asnorton44 wrote:I believe your engine does not have ignition coils then.
Re: misfire on 99.5 path, please help
What does your book recommend for gas, if 87 use that, if you get pinging, you may be carbon fouled.
Your injectors are probably OK.
Plugs need verification of gap with a wire gauge, not a flat, better to be smaller than bigger.
Your HT leads should be removed, the rotor cap and the plug boots. On a bench with a bright light look at every inch of the leads, look for carbon track, scrapes, roughness of the outer sheath. If any replace. Carbon track is hard to see but you may feel a raise of the insulation. If in doubt replace. If your HT leads have not been maintained every year by removing and cleaning, they may be breaking down dielectric-ally.
If your getting ignition at all leave your power transistor alone, but clean the slotted widow array at the bottom of the rotor. This triggering device is light initiated and if the light is blocked somewhat by a dirty environment, a miss-fire could be caused here.
Remember that miss-fires could be a cause of many smaller issues totaling a complete non firing of an ignition sequence. The particles of non combustion then travel into your cat and cause other problems.
You have been miss-firing a long time and a check of your exhaust gases might help with diagnoses...O2 sensors, knock sensors.
Keep a record of your findings, and what is you gas mileage like in terms of miles per gallon. If you are low your O2 sensors may be too slow to react properly
Your injectors are probably OK.
Plugs need verification of gap with a wire gauge, not a flat, better to be smaller than bigger.
Your HT leads should be removed, the rotor cap and the plug boots. On a bench with a bright light look at every inch of the leads, look for carbon track, scrapes, roughness of the outer sheath. If any replace. Carbon track is hard to see but you may feel a raise of the insulation. If in doubt replace. If your HT leads have not been maintained every year by removing and cleaning, they may be breaking down dielectric-ally.
If your getting ignition at all leave your power transistor alone, but clean the slotted widow array at the bottom of the rotor. This triggering device is light initiated and if the light is blocked somewhat by a dirty environment, a miss-fire could be caused here.
Remember that miss-fires could be a cause of many smaller issues totaling a complete non firing of an ignition sequence. The particles of non combustion then travel into your cat and cause other problems.
You have been miss-firing a long time and a check of your exhaust gases might help with diagnoses...O2 sensors, knock sensors.
Keep a record of your findings, and what is you gas mileage like in terms of miles per gallon. If you are low your O2 sensors may be too slow to react properly
distributor bearings are shot
i want to measure the resistance of the ignition coil and found that it wasn't that bad. 0.78 (primary) and 10.8k (secondary).
I dig a little deeper, took out the old ignition coil (which looked a bit rusty) and found shards of metal at the base of the distributor.
The shards of metal looked to be ball bearings that went bad since there were definitely a few missing. It was also pretty dry and definitely not lubricated.
This is starting to make more sense. I have noticed some grinding noise from the distro cap when I rev the car. That's probably the distributor rotor scrapping against the terminals because the bearing is shot. would a shot bearing cause this? Looking quickly at it, i didn't even see why the bearings were necessary...
Anyways, It doesn't look like there's a way to replace just the bearing.. so how hard is it to replace the distributor? do i need to use a timing gun afterwards?
I dig a little deeper, took out the old ignition coil (which looked a bit rusty) and found shards of metal at the base of the distributor.
The shards of metal looked to be ball bearings that went bad since there were definitely a few missing. It was also pretty dry and definitely not lubricated.
This is starting to make more sense. I have noticed some grinding noise from the distro cap when I rev the car. That's probably the distributor rotor scrapping against the terminals because the bearing is shot. would a shot bearing cause this? Looking quickly at it, i didn't even see why the bearings were necessary...
Anyways, It doesn't look like there's a way to replace just the bearing.. so how hard is it to replace the distributor? do i need to use a timing gun afterwards?
Re: misfire on 99.5 path, please help
New complete distributor should be a direct replacement.
If the tip of the rotor is actually touching and ripping into the carbon inserts in the underneath of the rotor cap you will soon need a rotor cap. With ground up bearings that circled bearing race was put on before the distributor shaft was assembled.
You take the complete distributor out of its engine mount hole, note where the top of the shaft points to, record that and pull out may take a twist.
With the whole thing out you can rebuild it from top to bottom if parts are available or get a new one complete, but i won't be cheap.
Distributors in my mind are serviceable entities, especially cleaning and lubricating.
If the tip of the rotor is actually touching and ripping into the carbon inserts in the underneath of the rotor cap you will soon need a rotor cap. With ground up bearings that circled bearing race was put on before the distributor shaft was assembled.
You take the complete distributor out of its engine mount hole, note where the top of the shaft points to, record that and pull out may take a twist.
With the whole thing out you can rebuild it from top to bottom if parts are available or get a new one complete, but i won't be cheap.
Distributors in my mind are serviceable entities, especially cleaning and lubricating.
new distributor replacement
ARKQX33V6 wrote:New complete distributor should be a direct replacement.
Distributors in my mind are serviceable entities, especially cleaning and lubricating.
Thanks, ARKQ.
So i plan on just buying a new distributor and replacing the old broken one. I haven't done one before but have done some quick reading and have some questions.
1. When i insert the distributor into place and i'm one teeth (spline) off, am i going to be able to notice that the rotor is in the incorrect position? basically, is being off one teeth one way or the other easy to tell if i have the new rotor/ distributor marked correctly?
2. TDC: which pulley do i turn with the wrench (what's socket size?)? and which pulley do i look for the tdc mark on?
3. Do i need to mark the distributor mounting position so i can mount the new one exactly the same?
4. Is it necessary to adjust the timing w/ a timing gun afterwards? (i'm hoping to skip this step)
Thanks,
Re: new distributor replacement
I took a look at some pictures of the gears on the distributor. There looks to be like around 16 or so teeth making it like 20 degrees or so per notch. This seems pretty reasonable.. to be able to tell 20 degree differences in the rotor position.egg998 wrote:
So i plan on just buying a new distributor and replacing the old broken one. I haven't done one before but have done some quick reading and have some questions.
1. When i insert the distributor into place and i'm one teeth (spline) off, am i going to be able to notice that the rotor is in the incorrect position? basically, is being off one teeth one way or the other easy to tell if i have the new rotor/ distributor marked correctly?
Thanks,
Re: misfire on 99.5 path, please help
So i plan on just buying a new distributor and replacing the old broken one. I haven't done one before but have done some quick reading and have some questions.
1. When i insert the distributor into place and i'm one teeth (spline) off, am i going to be able to notice that the rotor is in the incorrect position? basically, is being off one teeth one way or the other easy to tell if i have the new rotor/ distributor marked correctly? ***Before removing the existing rotor mark exactly where the HT lead distribution point is pointing. While pulling the rotor assembly out, leave everything in the rotor assembly but the rotor cap. With the now known position, retract the rotor assembly and watch the top HT movable switch to see which way it turns as you pull things out. Then place the new tower in the same relative position and when inserting it should turn to the marked position. If it does not, remove and turn it in the correct direction then try again. It may be a trial and error time for you but a direct replaced rotor tower must be in the same exact position. There may not be enough rotation of the rotor in the motor mount to account for timing adjustments. ***
2. TDC: which pulley do i turn with the wrench (what's socket size?)? and which pulley do i look for the tdc mark on?***TDC is on the main damper, but you do not need to know the timing to exchange rotors, make sure the new rotor faces exactly the same as the old one. Mark with tape and verify the existing markings and plugs line up with the new one. Be3fore inserting the rotor should be examined for lubrication where moving parts are located, shelf life may have dried it out**
3. Do i need to mark the distributor mounting position so i can mount the new one exactly the same?**Sure wouldn't hurt, the best thing besides marking everything is to take a picture with a digital camera***
4. Is it necessary to adjust the timing w/ a timing gun afterwards? (i'm hoping to skip this step)***Every time you mess with the rotor it makes sense to use a timing light, in fact if the engine works now time it before you pull the rotor. Although you have to see the marks, a chalk scraping across the indent markings will help you see the marks. I set mine a little different that stock, experiment...you just may get better gas mileage***
Never skip verifying the timing...never, and after you have the engine running, listen to the rotor with a stethoscope or a large screw driver to your ear, small noises can easily be large noises if not looked after.
Investigate the driven gear at the bottom of the rotor, look for flat spots, gear non mesh, shiny matings. The gear should have mating marks in the center of the gear suface, not top or bottom, the gear should rotate smoothly.
When the new rotor is installed completely clean up the led and notched segments and open and clean and maybe lubricate the bottom annually.
1. When i insert the distributor into place and i'm one teeth (spline) off, am i going to be able to notice that the rotor is in the incorrect position? basically, is being off one teeth one way or the other easy to tell if i have the new rotor/ distributor marked correctly? ***Before removing the existing rotor mark exactly where the HT lead distribution point is pointing. While pulling the rotor assembly out, leave everything in the rotor assembly but the rotor cap. With the now known position, retract the rotor assembly and watch the top HT movable switch to see which way it turns as you pull things out. Then place the new tower in the same relative position and when inserting it should turn to the marked position. If it does not, remove and turn it in the correct direction then try again. It may be a trial and error time for you but a direct replaced rotor tower must be in the same exact position. There may not be enough rotation of the rotor in the motor mount to account for timing adjustments. ***
2. TDC: which pulley do i turn with the wrench (what's socket size?)? and which pulley do i look for the tdc mark on?***TDC is on the main damper, but you do not need to know the timing to exchange rotors, make sure the new rotor faces exactly the same as the old one. Mark with tape and verify the existing markings and plugs line up with the new one. Be3fore inserting the rotor should be examined for lubrication where moving parts are located, shelf life may have dried it out**
3. Do i need to mark the distributor mounting position so i can mount the new one exactly the same?**Sure wouldn't hurt, the best thing besides marking everything is to take a picture with a digital camera***
4. Is it necessary to adjust the timing w/ a timing gun afterwards? (i'm hoping to skip this step)***Every time you mess with the rotor it makes sense to use a timing light, in fact if the engine works now time it before you pull the rotor. Although you have to see the marks, a chalk scraping across the indent markings will help you see the marks. I set mine a little different that stock, experiment...you just may get better gas mileage***
Never skip verifying the timing...never, and after you have the engine running, listen to the rotor with a stethoscope or a large screw driver to your ear, small noises can easily be large noises if not looked after.
Investigate the driven gear at the bottom of the rotor, look for flat spots, gear non mesh, shiny matings. The gear should have mating marks in the center of the gear suface, not top or bottom, the gear should rotate smoothly.
When the new rotor is installed completely clean up the led and notched segments and open and clean and maybe lubricate the bottom annually.
Re: misfire on 99.5 path, please help
Lots of good information there. Thanks again. I update with my experience after I finish. Hopefully this weekend if the part comes. I ordered a Richporter distributor from this online place i always use.ARKQX33V6 wrote:So i plan on just buying a new distributor and replacing the old broken one. I haven't done one before but have done some quick reading and have some questions.
I think it's fixed!
Here's my experience with the distributor replacement. I attempted turn the motor to TDC but couldn't get the socket over the cam bolt with the breaker bar attached. So I skipped that step and just marked where the distributor rotor was pointing with a sharpe and also took a picture with my phone. I also marked where the where the bolt mounted onto the distributor which wasn't useful and i'll explain later.egg998 wrote: Lots of good information there. Thanks again. I update with my experience after I finish. Hopefully this weekend if the part comes. I ordered a Richporter distributor from this online place i always use.
Removing the old distributor should be quite easy but I only had a 12mm wrench. The space is tight with a wrench. Ideally, you'd use a 12mm socket w/ a flex joint. Unbolt it making sure not to drop the bolt into the engine bay. Wiggle it a few times and out it comes. The connectors are always a challenge. I was able to get the big connector off. The smaller connector (ignition coil) came apart as well but I had to cut the distributor side of the 2 wires leaving it's connector mounted to the rusted metal bracket. The disconnected connector wasn't coming off easy.
I dropped the new distributor in. The first try, the rotor was probably 25 degrees off counter-clockwise. This is because the rotor turns ccw as you insert it. The second try was pretty darn close. You can definitely tell when the gears are engaged. The rotor will turn while you insert and then it won't move. I then attempted to line up the mount holes of the new distributor to where my old one was. This didn't work out. When i use the same mount location, the rotor wasn't in the correct place. I'm guessing it's not the exact same distributor so the mounts might not be exactly the same. Regardless, I thought the rotor position should be the same as the old one. This controls the timing. So i mounted it in a slightly different position than the old mounting position as to keep the rotor in an almost exact position.
The car now drives pretty solid without any misfiring. I think it's fixed. I'm thinking about skipping the whole timing thing w/ a timing gun (no flames please).
So my lessons learned: If you have misfiring, and you check the distributor, make sure to take apart ignition coil and check the bearings. Also, don't try to use a wrench to unbolt the distributor. And lastly, if you have to change the distributor, it's not too bad.