Toby85 Posted February 21, 2014 Share Posted February 21, 2014 Hi, I've recently been having problems with my '04 350Z GT, running slightly off and throwing the engine management light on. The fault was found to be code P0300 - random misfire. Next I ran a compression test - results as follows; 1 - 165 2 - 170 3 - 160 4 - 175 5 - 170 6 - 170 So, although there is a 15psi difference between cylinders, I don't believe this is enough to cause a real concern - engine is 207,000 miles used! I next compared the way my car sounded to the way a good Z sounded, and it just sounded a little off - not a misfire, just not quite silly like it should be. When disconnecting the coil packs one at a time, it made an obvious difference. Next we plugged it in to a diagnostic reader and the only thing we found off was a lambda reading. The results were as follows (obviously these were fluctuating slightly); 02 1B1 - 0.295 02 2B1 - 0.290 02 1B2 - 0.590 02 2B2 - 0.330 So, obviously one lambda is showing a huge variation, I imagine a rich mixture due to a cylinder not firing but it could also be a faulty lambda? Also, which lambda is this? If anyone could offer any advice on what to look at next I'd really appreciate it - I'd imagine either an injector, coil pack starting to degrade or faulty lambda. Thanks in advance for any advice offered! Regards, Toby Quote Link to comment Share on other sites More sharing options...
Keyser Posted February 21, 2014 Share Posted February 21, 2014 I'm going with plugs - when were they last changed? Week spark - check engine earths are good. Or faulty coil pack/s Try that to start - what software you got? I can run piston checks on mine, were are you based? 15psi at 200k not that bad really Quote Link to comment Share on other sites More sharing options...
Toby85 Posted February 21, 2014 Author Share Posted February 21, 2014 Plugs are spanking new, made no difference! Just had a fresh full service. Good shout on earth straps - where are they on the Z? Any idea which bank of cylinders is in fault from the O2 readings above? I have no software - a mechanics friend brought his diags gear over! So you can isolate the problem to each cylinder? How does it work that out? I'm based in West Midlands, near Burton on trent. Thanks Toby Quote Link to comment Share on other sites More sharing options...
Sam Mcgoo Posted February 21, 2014 Share Posted February 21, 2014 +1 on what Keyser says. Ref your o2 voltages, strange as it seems I think that's normal. Every time I check mine, sensor 1 bank 2 is approx twice the voltage of the others. There's an old thread here showing others having the same findings - http://www.350z-uk.com/topic/48249-long-term-fuel-trim-question/#entry828744 What are your fuel trims saying on the OBD2 reader? Is one bank drastically different to the other? Quote Link to comment Share on other sites More sharing options...
Toby85 Posted February 21, 2014 Author Share Posted February 21, 2014 How odd, but very useful information! Wonder why that is?! All were fluctuating fine anyway so looks like this is ok, one more ruled out! Thanks! Quote Link to comment Share on other sites More sharing options...
Keyser Posted February 21, 2014 Share Posted February 21, 2014 Basically I can turn the spark off 1 piston at a time, if you can get or borrow a spare coil pack you can work your way round the engine to check that. If you don't have an earth kit (aftermarket) the main one is left hand side of the engine near the power steering pump, as a test a jump lead from the plenum to the battery earth terminal will do. Also check the battery terminal but I would think you would have starting problems if they were bad. O and this bad boy http://www.350z-uk.com/topic/73878-car-wont-start-after-rebuild-help/#entry1099337 Caused me some issues so worth a check Quote Link to comment Share on other sites More sharing options...
Toby85 Posted February 21, 2014 Author Share Posted February 21, 2014 Oh, and no idea of fuel trims - sorry! Quote Link to comment Share on other sites More sharing options...
Sam Mcgoo Posted February 21, 2014 Share Posted February 21, 2014 (edited) As suggested, I would start by getting a known working coil pack and swapping it out one at a time. Have you checked for vacuum leaks? Do you have much oil in your spark plug wells? With your mileage it could well be an injector starting to die, but there is no easy way to test that quickly. Have a look at the spark plugs you removed. How do they look? is there any that stand out as being a different colour then the rest? OBD2 readers can be had for cheap on ebay now days and are well worth owning. Edited February 21, 2014 by Sam Mcgoo Quote Link to comment Share on other sites More sharing options...
Toby85 Posted February 22, 2014 Author Share Posted February 22, 2014 Keyser - thanks, I will make all given advice a priority! I'll update with progress. Regards, Toby Quote Link to comment Share on other sites More sharing options...
Toby85 Posted February 22, 2014 Author Share Posted February 22, 2014 I'm in the process of obtaining a replacement coil pack to start. I haven't yet had a thorough check of the inlet tract for leaks but will do. Are there disposable gaskets sealing the plenum/TB/inlet manifold or are they reusable? Spark plug bores are bone dry and the removed plugs looked very healthy, a nice pale brown light coating. I guess it takes a while to remove the injectors so trying to isolate the problem would be a nightmare - guess it would be easier to replace the whole set?! Thanks Sam, Toby Quote Link to comment Share on other sites More sharing options...
Keyser Posted February 22, 2014 Share Posted February 22, 2014 If you do get to changing the injectors give me a shout I have a complete fuel rail with injectors from an 03 car was crashed engine was good. Good luck with it hope it's something simple. Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted February 22, 2014 Share Posted February 22, 2014 Presuming yours is a JDM car? sensor 1, bank 1 and 2 are the primary lambda sensors and these are the ones used by the ECU to control fueling, yours seem OK but it will obviously depend on the conditions during the test, bank 2 are the cat monitor lambdas and in my experience the engine will run quite happily without them, (just throw a CEL) I would be looking at plugs, coil packs and associated wiring, you right a misfire will result in odd lambda readings, usually a false lean, Quote Link to comment Share on other sites More sharing options...
Toby85 Posted February 22, 2014 Author Share Posted February 22, 2014 It's a UK car, early GT. Plugs are new, next is coil pack going cylinder to cylinder to find the issue (hopefully)! I'll clean all the connectors while I'm there and also clean the earths. Cheers, Toby Quote Link to comment Share on other sites More sharing options...
Toby85 Posted February 26, 2014 Author Share Posted February 26, 2014 Just an update - I got hold of a spare good cool and swapped it across all cylinders - made no difference. Checked all earths and cleaned, also added more - no difference. Couldn't find any vac leaks. Am now at the stage of changing injectors - I've got 3 good ones and I'm swapping 1 bank at a time. They don't look the same as the originals but I've read they are all the same specs, just the manufacturer varies. I'll update tomorrow with any findings! Fingers crossed... Quote Link to comment Share on other sites More sharing options...
GT4 Zed Posted February 26, 2014 Share Posted February 26, 2014 Good luck mate. Hope you find the cause for this issue. I've got a full set off OEM injectors in vgc if you need them. Just be meticulous and check all systems 1 at a time. Quote Link to comment Share on other sites More sharing options...
Sam Mcgoo Posted February 26, 2014 Share Posted February 26, 2014 Hope you get it sorted. Quote Link to comment Share on other sites More sharing options...
Toby85 Posted February 27, 2014 Author Share Posted February 27, 2014 Not the injectors either. At a complete loss now! Quote Link to comment Share on other sites More sharing options...
Toby85 Posted February 27, 2014 Author Share Posted February 27, 2014 I have noticed that the rev counter seems to pulse slightly when the revs rise or fall rather than move smoothly as I'd expect, it's not jumping above or below where you'd expect but just doesn't move smoothly - like I said, just moves in little pulses Quote Link to comment Share on other sites More sharing options...
Toby85 Posted February 28, 2014 Author Share Posted February 28, 2014 So yesterdayi took off and cleaned up both am position sensors and the crank position sensor which has now thrown the code 0345 - it still runs as before but with this new code so I must have disturbed something. I'm loathed really to keep throwing money at random sensors - I might just give it to a local specialist and let them investigate Quote Link to comment Share on other sites More sharing options...
Toby85 Posted March 12, 2014 Author Share Posted March 12, 2014 Ok, this issue is resolved - thought I'd update the thread to help others having this infuriating code! So, after paying for coil packs and injectors which did nothing and after much fruitless investigation it turned out to be something hugely simple - a dirty connection. Summary; Symptoms - general rough running but reliable starting and no stalling. Bogged down under heavier throttle. No obvious miss from a single cylinder. Intermittently flashing engine management light, sometimes going in to limp home mode. Diagnosis - error code P0300 only. Solution - cleaned electrical connections using flushing action with electrical cleaner. Ended up being one of these three; - Variable valve timing control solenoids - both connections filthy - Multiplug connections from battery positive terminal (no idea what for) - showing signs of corrosion I started the car after these and it was like a different car. Night and day! To anyone else having these issues - start here before anywhere else! Quote Link to comment Share on other sites More sharing options...
Sam Mcgoo Posted March 13, 2014 Share Posted March 13, 2014 Glad you got it sorted! Quote Link to comment Share on other sites More sharing options...
samsniss350z Posted March 13, 2014 Share Posted March 13, 2014 Hey Toby I'm glad you got things sorted out, I wouldn't be surprised if more owners were to suffer this problem after the wet winter. I was really surprised to see just how good your compression figures are after 207,000 miles as according to Nissan 180 to 195 PSI are really good figures for a strong and the minimum safe figues are142PSI, anything below and you're lookng at a rebuild so wth your lowest figure of160PSI you have a fair way to go before the dreaded rebuild. Again congrats on your fix. Quote Link to comment Share on other sites More sharing options...
Scully Posted March 15, 2014 Share Posted March 15, 2014 Glad you solved the problem, it's threads like this that I like as it will stick in your mind for diagnosing future problems on zed's and other cars for that matter. A shame you spent out for just a bit of cleaning really but must be a load off your mind. Quote Link to comment Share on other sites More sharing options...
Toby85 Posted March 15, 2014 Author Share Posted March 15, 2014 Cheers! Yeah I'm really glad it's running sweet. I only just got the car as a project and this was the real underlying 'problem' with the car, amongst plenty of other niggles. Almost all sorted now and just flew through the mot without an advisory! Just goes to show that with regular servicing mileage seemingly can have marginal wear on the car! It's been family owned since new by 1 owner who used it to commute on the M25, then once yearly got it MOT'd, serviced and washed by Nissan - and that was it! Was a little battle scarred when I picked it up but shows very little for it now it's had a little TLC and pampering! Only jobs left are sat nav blank (another thread in here), clicky rear axle/s (to be sorted soon), gearbox oil change (although seems fine) and potentially a wheel bearing starting to grind a little! Quote Link to comment Share on other sites More sharing options...
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