02silverpathy Posted January 2, 2009 Share Posted January 2, 2009 (edited) Hi all! My 02 VQ is giving me small misses when driving under moderate load. There is a small mountain range nearby and I have now on 2 round trips over and back feeling a mild multiple missfire. ->The plugs are just at 10K old and are NGK Iridium IX. The vehicle gives no Service Engine light, however does not correct the problem on its own. --->The conditions are engine fully warmed up around 2500-2700 rpms, approx 28-32 deg outside. I use 93 octane 100% of the time and this is the second tank exhibiting the same behavior. ------>The only modifications are a short ram intake, coolant bypass on the TB, and PCV catch filter (currently empty). ~~~~I did NOT double check the gap on the plugs last year...I know don't flame me...I am wondering if this may be the cause, however why did it take until now to rear its ugly head?~~~~ The only other thought that I have is that the coolant bypass is allowing more cold air into the intake (which is unheated due to the bypass itself), and the ECU fuel maps are preset for this air to be heated by the intake manifold/throttle body...any Guru's out there for this one?? Edited January 2, 2009 by 02silverpathy Link to comment Share on other sites More sharing options...
BowTied Posted January 2, 2009 Share Posted January 2, 2009 Hi all!My 02 VQ is giving me small misses when driving under moderate load. There is a small mountain range nearby and I have now on 2 round trips over and back feeling a mild multiple missfire. The plugs are just at 10K old and are NGK Iridium IX. The vehicle gives no Service Engine light, however does not correct the problem on its own. The conditions are engine fully warmed up around 2500-2700 rpms, approx 28-32 deg outside. I use 93 octane 100% of the time and this is the second tank exhibiting the same behavior. The only modifications are a short ram intake, coolant bypass on the TB, and PCV catch filter (currently empty). ~~~~~~~~I did NOT double check the gap on the plugs last year...I know don't flame me...I am wondering if this may be the cause, however why did it take until now to rear its ugly head?~~~~~~~~~~~~ The only other thought that I have is that the coolant bypass is allowing more cold air into the intake (which is unheated due to the bypass itself), and the ECU fuel maps are preset for this air to be heated by the intake manifold/throttle body...any Guru's out there for this one?? Not a guru... just curious. What was the temperature? Was the fuel for each tank from the same fuel station? Was the altitude where you encountered the issue notably different than your typical driving? I really doubt it is plug gap. Link to comment Share on other sites More sharing options...
02silverpathy Posted January 2, 2009 Author Share Posted January 2, 2009 (edited) Not a guru... just curious. What was the temperature? Was the fuel for each tank from the same fuel station? Was the altitude where you encountered the issue notably different than your typical driving? I really doubt it is plug gap. Temp was between 22-25 on the last trip back over the mountains Fuel was from different stations The mountains (2) with a valley in between are just under 1900 ft each at their peak, so probably 100-150 less than that for the road. Additionally I have noticed this mainly on the mountains under load, however I hauled 4 people a distance of 160+ miles when I initially noticed and thought I was just kidding myself that there was a problem I had hoped it was the plug gap as that is an easy fix...I also still have my OEM laser plats. with 47K on them numbered per cylinder in boxes that I though about putting back in as a control for the problem--worst case of course. What do you think about the fuel maps for the "intake warmed" air that would occur after the MAF sensor gets its information? Having this air warmed would make the engine run rich and adjust from that point...VS. getting colder air than expected and having to fatten up? Do you think this is possible or does the ECU have limitless maps and can adjust 100% of the time?? The RPM is definately a factor--at low RPM there is nothing to feel and higher RPM these misses seem to disappear. Edited January 2, 2009 by 02silverpathy Link to comment Share on other sites More sharing options...
5523Pathfinder Posted January 2, 2009 Share Posted January 2, 2009 Have the ignition coils been replaced? Seen many a misfire issue and its caused by the coils, especially when hot. they wont always throw codes either. Link to comment Share on other sites More sharing options...
02silverpathy Posted January 3, 2009 Author Share Posted January 3, 2009 No coils replaced as of yet---I did read on a Maxima forum that they hook up DC-DC converters and boost up the coils output by 2 volts for a total of 16 and get great results. Is there a way to test a coils output/resistance (or is it capistance)? Link to comment Share on other sites More sharing options...
BowTied Posted January 11, 2009 Share Posted January 11, 2009 A buddy of mine had similar problems with a Jimmy every time he went this looong hil (escarpment) it would through a CEL which would cure itself later. I wonder if the altitude change is messing with a map sensor or something like that? Until you undo the bypass, or get a guru to chime in, I think it may be hard to troubleshoot. Part throttle is where you will have some timing advance... do you here any detonation/pinging? Thinking knock sensor here... Link to comment Share on other sites More sharing options...
nissandoms47 Posted January 11, 2009 Share Posted January 11, 2009 VQs take the double platinum NGK plugs. Try those and see what happens. Link to comment Share on other sites More sharing options...
02silverpathy Posted January 12, 2009 Author Share Posted January 12, 2009 No ping at all, no codes. It is def only under medium load...not during heavy load and not at crusing speeds. I bought the Iridium IX's to relieve some of the load required to fire a coil on plug design--their super fine point makes them easier/cleaner to fire...these plugs have been used for quite a long time in other small engines (ie. fork lifts)...unless I am confusing them with something else. Link to comment Share on other sites More sharing options...
BowTied Posted January 12, 2009 Share Posted January 12, 2009 How does a fine point make it easier to fire? The voltage the coil kicks out is relative to the gap opening I thought? I put regular NGKs, not platinium or iridium a year ago with zero issue - recent emission test scored zero on idle and drive for hydrocarbons. Now power issues or mis-fires. Link to comment Share on other sites More sharing options...
02silverpathy Posted January 13, 2009 Author Share Posted January 13, 2009 Right! With a finer point the area that the spark must leap from is now defined and aimed vs. a more round blunt end. This enables the Iridium to run a larger gap, or at least that is the idea. Link to comment Share on other sites More sharing options...
02silverpathy Posted January 21, 2009 Author Share Posted January 21, 2009 (edited) Ok tons of online butt time looking at the ignition system in this Nissan to find that other than a coil going bad it is posible that I have a small discharge leaving the spring of the coil pack and arching somewhere else. The answer to that is to remove the coil and put a dab of di-rlrctric grease in the end arounds the boot between it and the spring, and around the boot and where it meets the valve cover. I think that our valve covers are a fiber/plastic so there should not be any arching there, but it is worth a try! Updates when I get ballsy enough to go out in the cold! To add: so far I have seen no evidence that the Iridium plugs are a culprit of problem. I have not found that our VQ35 uses a waste spark ignition so there is only plug fire exiting the center electrode, no double pulse coming from the ground to center (which would cause a hesitation in fire since the Iridium is the harder metal and does not conduct as well as the ground electrode). If anyone knows differently, please tell me--I kept the OE NGK double plat plugs and can re-install them, they have 46K on them but they look great! Edited January 21, 2009 by 02silverpathy Link to comment Share on other sites More sharing options...
02silverpathy Posted January 25, 2009 Author Share Posted January 25, 2009 (edited) So the outcome is..... 1 coil pack, cylinder #4, was not tightened down when I did the plugs 10K ago (or the small bolt came loose) 1 driver side valve cover grommet is leaking oil into the spark plug tube,#6, fair amount of oil on the back of the plug for approx 10K miles 1 hose leading into the Sceptre intake pipe is completely out leaving an unmetered amount of air into the intake system The truck is running much smoother now, and I am wondering how much fuel I wasted over the last year with that plug not firing 100% correct the entire time...what a douchebag mistake! I added a few ground wires around the IM and TB, and one from the driver side head to the "frame" with plans for more in the future (read: warmer outside). I also took the time to clean my small filtered catch-can for the PCV system out and wipe the back side of the TB...and take a peak inside at those intake screws--all of the plugs were gapped within 1/2 sheet of notebook paper correct and showed completely normal signs of ignition burn---oil and tranny fluid 100% normal--must have been that coil pack--I'm a stupid douche. Edited January 25, 2009 by 02silverpathy Link to comment Share on other sites More sharing options...
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