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Posted on Jan 02, 2017
SOURCE: troubleshooting code po301
The MAF will not cause a miss on just one cylinder, here are the things that will, low cylinder compression, defective fuel injector, intake manifold vacuum leak at the gasket, and of course ignition system problems.
Posted on Dec 18, 2008
Check the fuse to the injector. If it is out or got wet, it could mimic these conditions. let me know what happens. I have an 85 model.
Posted on Jan 15, 2009
Just had one of these with a maxima, the code is multiple random misfire, when a misfire occurs, to start is do the basics, replace the plugs, check fuel pressure, clean throttle body, and coolant is topped up. also I have seen if the O2 sensor is not working correctly is can cause a misfire, you will need a scan tool to look at what the O2 sensor is doing, o rby back probing the sensor (don't damage the O2 sensor wires). If it wires replace them as well, if it has coils they usually dont give that code if one fails, it will pinpoint that a certain coil if one fals.
Posted on Oct 02, 2009
The black soot on the plugs means that you are running extremely rich. The fuel injectors ma test good electricly, but they are notorious for leaks. The spider-looking thing sandwiched between the plastic intake plenum and the intake manifold gets cracks in it's "legs" and leaks fuel ito the plenum area. The fuel pressure regulator is also housed in this same assembly. if the diaphram in the regulator gets a pinhole in it, it also leaks fuel into the plenum area, causing all kinds of erratic idleing, black smoke from the exhaust, and will cause your fuel trims to drop into the negative 20s.
There is a technical service bulletin covering this subject. This procedure outlines the steps required to replace the existing Central SFI Fuel System with a new MFI (Multiport Flexible Injection) Fuel System.
It is removing the injectors which are all housed in the center body of the injector assembly and replacing them with a new version where the injectors are located where the ols "poppets" used to be in the intake manifold ports. The picture below is for a V-8 engine that is covered by the same TSB.
The poppets and the pressure regulator are available individually to fix your existing fuel injection system, but I gave up on that after replacing several poppets only to have them come back in a few months with another popet line broken. I recommend replacing the whole assembly with the new and improved version. My customers have told me after doing this that the engine never ran that smooth when it was new.
The GM part number for the new injector assembly for your V-6 engine is 12568332 it is also now available at several aftermarket parts outlets.
As for the timing chain solution posted by doodieman200, all I have to say is that I have enough fingers on one hand to count all of the failed timing chains I have replaced on these engines. If you don't have a cam/crank sync code, the timing chain has definitely not slipped a tooth.
Posted on Oct 18, 2009
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