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Discussion Starter #1
I have been having a random misfire at WARM IDLE with my 2002 nissan xterra V6 3.3L non S/C. I had three codes after I have replaced the timing belt, Water pump, and all belts... the codes were:
1) knock sensor code
2) O2 sensor code
3) random misfire code
4) Idle Air Control Valve code

The car has 217000 miles on it so I figured I would do it a solid and make it like new :). Changed the spark plugs, spark wires, rotor, rotor cap, removed all intake crap to change the knock sensor because of the code and put new gaskets, cleaned the crap out of the Idle air control valve, cleaned the upper intake planium and replaced the fuel filter. Prior to all this I replaced the radiator, all radiator hoses, and the thermostat. After changing everything I gave it an oil change and new oil filter along with a new air filter. Ran B-E-A-utiful for about a mile or two basically until the car was WARM. THEN IT WENT BACK TO A SHAKY IDLE AND MISFIRE CODE BUT ONLY AT IDLE!! AHHHHH ITS DRIVING ME NUTS!!!! SOMEONE PLEASE HELP ME!!! I'm seriously about to blow the dang thing up but I cannot afford to do that and buy a new car because i'm poor. If you find anything out or already know what the fix is the PLEASE PLEASE TELL ME I NEED HELP. help me please I BEG YOU!

I appreciate it.
 

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could be a dirty MAF sensor or a vacuum hose that was not put on properly or is cracked. if it's just a small misfire at idle then it isn't that bad, no need to blow the thing up.
 

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Discussion Starter #4
I have read a lot about this same problem and no I have not replaced the whole distributor. But I will give that a try.
- I don't know about the vacuum I don't hear any whistling. I suppose a leak could still be there though.
 

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- take off the dist. cap and the rotor, remove the "dust" shield within the rotor and check for metal debris first, this is a free inspection which could locate the issue for you
- when I removed my cap and dust shield i had a lot of metal bits that were the result of a chewed up dist. bearing
- replaced the bearing for $5.00 and car runs like a champ
- mine was the same issues, once normal operating temperature was reached, it would start to misfire, buck, not rev past 3K rpm
 

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Discussion Starter #7
Update.... I checked the distributor and bearing seems fine. I spoke to my uncle who is a retired master mechanic. He said it is most likely the the EGR valve. When the car gets to a certain temperature air seeps into the vacuum hose at the top of the EGR valve to maintain a steady idle and if there is any blockage from the exaughst Circulating through the EGR valve then it can restrict air feeding into the planium (he used high tech words to describe it but had to dummy it down a bit for me). Once the car is warm and it does the misfire thing again then I should unplug the vacuum hose at the top of the EGR valve and that should stop the misfire. If it does then the EGR is my problem I should clean it or get a new one. I'll let you know what happens because currently it's not doing the misfire and the check engine light is no longer on and all codes are clear.
 

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Update.... I checked the distributor and bearing seems fine. I spoke to my uncle who is a retired master mechanic. He said it is most likely the the EGR valve. When the car gets to a certain temperature air seeps into the vacuum hose at the top of the EGR valve to maintain a steady idle and if there is any blockage from the exaughst Circulating through the EGR valve then it can restrict air feeding into the planium (he used high tech words to describe it but had to dummy it down a bit for me). Once the car is warm and it does the misfire thing again then I should unplug the vacuum hose at the top of the EGR valve and that should stop the misfire. If it does then the EGR is my problem I should clean it or get a new one. I'll let you know what happens because currently it's not doing the misfire and the check engine light is no longer on and all codes are clear.
Good stuff! Let us know how it turns out, I would love to see if this was the issue
 

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I had the same problems with mine........Through an online discount parts dealer I replaced my wires, distributor cap and rotor all with Genuine NGK parts. I also replaced my spark plugs from the original NGK PFR5G-11 plugs to a hotter longer lasting approved plug for the Xterra NGK BKR5EIX-11 IRIDIUM Plugs. After replacing these few parts the vehicles started, idled, accelerated, back to idle at lights/stop signs PERFECTLY with "NO" fluctuations at road speeds/accelerations and idles from then on...NEVER AGAIN!!, air condition on or off, just like it rolled off the showroom floor, yes that great!...........BUT my computer light came on and gave me three new codes and my heart dropped.......Though it ran perfect it would never pass inspection....The computer codes were, 1) the engine knock sensor...my engine did not knock and I wasn't about to pull the top of the engine off to replace it...2) catalytic converter both left and right forward that actually attached to my engine manifolds on both sides..3) oxygen sensors............I tried and tried resetting my computer light seeing how well the engine was running, but it would come back on after about three days.

You can do this by yourself but I needed my truck to pass it's inspection................SO....I took it into the dealer I purchased the vehicle from.......They told me they removed and bench tested the oxygen sensors which they can do with a hand held volt/ohm style meter and they tested good, I told them to NOT TOUCH THAT KNOCK SENSOR!........I gave them approval to replace the two catalytic converters with new original model converters and install the oxygen sensors that tested good back in and run the vehicle and check it on the dealer's engine computer................THE LIGHT STAYED OUT!!! without changing the knock sensor and oxygen sensors.......just the catalytic converters......(Don't try all these methods of trying to clean the converters out by putting additives or other liquids into the converters thinking this will clean them out.....IT WON'T....the converter interiors are not designed/made to do this type quick fix which is NEVER a fix.)

Like I said, the part changes in the first paragraph in a couple hours and make your engine purr like new....BUT IF your perfect running engine gives you THREE NEW CODES, (knock sensor, oxygen sensors, catalytic converters) and you need that computer dash light out, change the two forward converters on both sides by yourself if you have the time and skill or take it in to have it done and make sure they DO NOT screw with the oxygen sensors and for sure the knock sensor unless they keep the light on after replacing the converters......that's all they replaced on mine, light stayed off after dealer put road time on the vehicle required to break in the converters and to tell the vehicle's onboard computer that they are indeed functioning correctly.
The dealer passed my vehicle's yearly inspection.............I used a dealer because they will do what the customer says if you appear knowledgeable, yes they are expensive.....I don't trust drive in garage mechanics, vehicle computers etc...... sorry. CEK
 

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I had the same problems with mine........Through an online discount parts dealer I replaced my wires, distributor cap and rotor all with Genuine NGK parts. I also replaced my spark plugs from the original NGK PFR5G-11 plugs to a hotter longer lasting approved plug for the Xterra NGK BKR5EIX-11 IRIDIUM Plugs. After replacing these few parts the vehicles started, idled, accelerated, back to idle at lights/stop signs PERFECTLY with "NO" fluctuations at road speeds/accelerations and idles from then on...NEVER AGAIN!!, air condition on or off, just like it rolled off the showroom floor, yes that great!...........BUT my computer light came on and gave me three new codes and my heart dropped.......Though it ran perfect it would never pass inspection....The computer codes were, 1) the engine knock sensor...my engine did not knock and I wasn't about to pull the top of the engine off to replace it...2) catalytic converter both left and right forward that actually attached to my engine manifolds on both sides..3) oxygen sensors............I tried and tried resetting my computer light seeing how well the engine was running, but it would come back on after about three days.

You can do this by yourself but I needed my truck to pass it's inspection................SO....I took it into the dealer I purchased the vehicle from.......They told me they removed and bench tested the oxygen sensors which they can do with a hand held volt/ohm style meter and they tested good, I told them to NOT TOUCH THAT KNOCK SENSOR!........I gave them approval to replace the two catalytic converters with new original model converters and install the oxygen sensors that tested good back in and run the vehicle and check it on the dealer's engine computer................THE LIGHT STAYED OUT!!! without changing the knock sensor and oxygen sensors.......just the catalytic converters......(Don't try all these methods of trying to clean the converters out by putting additives or other liquids into the converters thinking this will clean them out.....IT WON'T....the converter interiors are not designed/made to do this type quick fix which is NEVER a fix.)

Like I said, the part changes in the first paragraph in a couple hours and make your engine purr like new....BUT IF your perfect running engine gives you THREE NEW CODES, (knock sensor, oxygen sensors, catalytic converters) and you need that computer dash light out, change the two forward converters on both sides by yourself if you have the time and skill or take it in to have it done and make sure they DO NOT screw with the oxygen sensors and for sure the knock sensor unless they keep the light on after replacing the converters......that's all they replaced on mine, light stayed off after dealer put road time on the vehicle required to break in the converters and to tell the vehicle's onboard computer that they are indeed functioning correctly.
The dealer passed my vehicle's yearly inspection.............I used a dealer because they will do what the customer says if you appear knowledgeable, yes they are expensive.....I don't trust drive in garage mechanics, vehicle computers etc...... sorry. CEK
That is the right way to fix the problem . How many miles ? and what was the cost ?
 

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Discussion Starter #11
Mine no longer has the codes for oxygen sensor, idle air control valve (which I cleaned), or the knock sensor (which I replaced) but two days ago the engine light was blinking again. Which again is a *random misfire code*!!! Ugh! Lol. But my uncle called me back and told me to check the pressure in each valve to see if all is equal. So I got a pressure tester and will let you know what I find. Thanks for continuing to help yall
 

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I know it has been a long time since I updated this but my problem is fixed. Perhaps when the rotor was replaced last or when the timing belt was done the distributor was off a tooth and was far too advanced. Readjusted the distributor and that made a difference. Also, I found a vacuum leak on the plastic intake in-between the ridges connecting to the upper intake planium. There where two fairly large cracks there and when the car gets to operating temp and those expand it would let air out. Those were not noticeable cracks until I flexed the plastic to fit a seafoam tube in there. So be aware if you have the same problem I did. Your problem, like mine, could be hiding in the cracks.
 
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