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Ok, so now you want to warm up the engine, make sure fuel system 1 says CL instead of OL, and watch shrtft1 and longft1. The sum of those is your total fuel trim, the percentage of fuel that the ecm is adding or removing based on how the o2 sensor is reading the mixture vs what the sensors are estimating it should be. In park or neutral, that sum should be +/-10%. If you just cleared any codes or disconnected the battery it will have to be driven to reset these values. Get readings at idle, then hold rpms at 2500 for say 15 seconds and note if the % goes closer to zero, further, or stays the same. Graphing function is very helpful here.

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Discussion Starter · #22 ·
System set at CL. In Park: ShrtFT1 = -6.5, LongFT1 = 9.4. Hold at 2500rpm, LongFT1(%) = 0.0, ShrtFT1(%) =-6.3.
While hold at 2500 rpm, error code P0301 came up. While the car at park engine vibrate, put in drive, rpm at 800, engine vibrate more. Interesting that I can smell exhaust or strong unburned gas from the front.
 

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The data shows it running rich at idle and getting better off idle and up. That means it can't be a vacuum leak or bad fuel pump. A injector balance test would rule out leaking injectors. Did it do this before your maintenance work?


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Discussion Starter · #25 ·
I am not sure, if the car vibrate before maintenance work or not, it was February, so cold, didn't pay attention. cold snap kills the alternator. First thing was alternator die, changed. After that the car chock (drop to 400rpm and back to normal) at breaking, this drove me to do maintenance work because it's due. Changed spark plug, injectors, all 4 coils, PCV, EVPR, valve cover gasket, O2 sensor, of course air filter. After all these things changed, the car run without error code except vibration. At the light I pushed to neutral to avoid low rpm, it throw P0301. I think I am down to one or two things left here, very close to find the true issue. How to do injector balance test? I may rinse the cylinder 1 with Marvel next, Throttle position relearn, will this help?
 

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If you have a misfire on that cylinder then that's what you have to address. I wouldn't waste anymore money on chemicals to try to fix this.

I'd start by doing another compression test. I do not believe that restore brought that cylinder up 70psi. There was too much of a difference there for that to be the fix. I believe that you will find that it's still too low to be contributing properly.

If you still want to do the injector balance test, which I would not until after compression, you'll need a fuel pressure gauge and either a bidirectional scantool, or one of these tools...


I have that one in case one of my scantools can't do the test on a vehicle. It precisely pulses the injector and when that happens, fuel pressure drops a very specific amount. You do it on each injector, recording the readings. Do it three times on each injector and compare results. There shouldn't be more than like 1 or 2 psi drop difference. More indicates a leak, less than the average indicates restriction.

Really just do compression next. If you want to know where it's leaking to, a leak down test will tell you. Once there is low compression, most people done care where it's going and just put in a used engine.

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