I have an 2005 G sedan with just under 92,000 miles on it. In June the Service Engine Light came on with a code of P0300 and after taking it to a mechanic they determined that Fuel injectors #5 and #6 both went bad on me. I had both injectors replaced and didn't have any other issues until this weekend. My SEL came on again, showing the P0300 code and this time I decided to take it to the Infinti dealer to have them diagnose the problem, and this time it's Injector #4 has gone bad. The dealer then tells me that Infinit recommends replacement of all fuel injectors at once to ensure proper resistence is maintained or it could cause more injectors to go bad...

Common sense tells me this is bull**** and that more than likely age/wear was the contributing factor to the demise of #4 and that it would be more prudent to just change #'s 1-4 and leave 5-6 alone as they are practically brand new.

Any knowledgeable advice on this dilemma is greatly appreciated.

 

If three have failed already, chances are the rest will fail shortly. I would replace 1-4.

 

Generally, if one injector has gone bad, the remaining injectors can become overfueled in order to compensate for that 1 or 2 underfueled ones as the "closed loop" O2 system attempts to maintain what they refer to as stoiciometric ratio. In an effort to maintain this ratio, other injectors can be damaged by being pushed to their limit for en extended period (what your dealer was likely referring to) and it may not show up right away.

It may be that this is what's slowly happening in your system, and as suggested by herrschaft, you may have no choice but to replace the others so that in their potential failure they don't damage the new ones.

By the way, do you know what may have caused their failure (clogged injection filter, coil windings overheat, mechanical or body joint leak, etc.)-- it may help in preventing the problem from reoccurring.

Good luck and I hope this helps

 

Thanks for the response....Now I have already decided that I am defintely replacing #'s 1-4, but based on what you said above would you recommend changing #'s 5 and 6 as well, or is that overkill since they have only been in a couple of months?

 

Just make sure they are the exact same type/model as the 5-6 and you should be OK. Sometimes shops use 'equivilant' parts while the dealer will use genuine parts...you don't want to mix.

 

Injectors 1-4 were replaced and the car is still misfiring ...FML!!!!!!!!

So now it's either back to the dealer for another $560 in diagnostics or to try another shop....

 

What a nightmare this is becoming!

Things to consider up front on your won:

1) Go to Autozone and see if they can spot a code-- free service that costs $50-75 at the dealer.
2) Be aware that false codes can pop up when your engine is rough.
3) Look at you vacuum hoses for any broken or dilapidated ones. A hissing/whistling sound or broken hose that makes no noise can result in your car losing vacuum which can cause the engine to run rough and misfire. Have someone put pressure on the gas pedal and look for hissing sounds in your engine bay, that's the quickest/easiest way most of the time. Most leaks occur at the ends, so this is the 1st place to look. If all vacuum hoses check "ok", then you can...
4) Borrow a pocket IR thermometer laser temperature reader and check each exhaust manifold temp. After the engine has heated check the temp of each cylinder on the exhaust manifold-- the cylinder(s) with the lower temp(s)will be your culprit(s). Generally, it only takes one misfiring cylinder to make it look like everything is out of sorts.
5) What you're doing is basically chasing a signal (which is what one does in electronics to finds a source point for a problem).
6) While engine is idling, do you hear a rhythmic clicking sound from each injector. You can use a stethoscope for this-- I actually own one just for these kinds of problems? Injectors with no sound or a sound that seems off kilter will be the ones to focus on.
7) The rest will likely require a mechanic unless you have all of the equipment. Most mechanics will begin to test for ignition system problems at this point, fuel pressure, compression test, etc.

Good luck and I hope this helps,
Isa

 

**Update** I took my G into a Nissan service center near my house to see if they could make heads or tails of this issue. They ran some test and my air to fuel ratio is completely out of wack. They tested the MAF and it's coming up as being bad so they are going to replace it and go from there. Wish me luck...

 

Well a bad MAF would be a serious prob. indeed...hopefully that is all it is. But it is not usual for a MAF to just go bad...it could be part of a chain of events, ect.

 

MAF sensor has been replaced and surprise, surprise the engine is still misfiring. The dealer is saying the engine is running lean and the tech is currently suggesting to replace the plugs which I just did back in June. His explanation is running the car lean may have caused the plugs to go bad and you wouldn't be able to tell by looking at them.... Sounds like yet another shot in the dark to me....

PS. They ran another compression test and it showed slightly lower compression on cylinder #6.

 

The only time I had a misfire was when the coil pack was loose on #6. I'm not an expert, but I'm sure you would be able to tell if a spark plug was bad. Curious to see what the problem is.

 

Hey Deadwrong, it might just be me... but almost sounds like there is something clogging up the injectors, one by one. The filter in the injectors is very fine, and any crapp that gets stuck in it would surely cause a reduced amount of fuel resulting in your lean condition.

The dealer obviously wants to make money by selling you ALL NEW injectors, when it could very well just be at a earlier point in the lines. Its just a random statement off the top of my head, but maybe one of your fuel filters is bad? And since your MAF was replaced yielding the same results, I would also turn towards the coil-pack harness and check for any corrosion that might cause a resistance towards a spark plug. :/

Just my 1 cent (because 2 cents would involve a concrete answer). Good luck bro.

 

Ghos7, I believe you may have hit the nail on the head. Here's some back story in 5/2009 some douche put sugar in my gas tank, I never started the car because there was a pile of sugar on the ground by the gas tank. Due to this incident the fule filters, senders gas lines were all replaced and the fuel tank was emptied and cleaned. I started having issues with failed injectors in 11/2009. After the last work I had done in 10/2010, I have been going back and forth with my insurance company for them to look into whether or not the poblems are related. I finally convinced them this January to authorize the Nissan dealership Im working with to look into the issue, but of course the dealer claimed they couldn't troubleshoot the injectors that have already failed and they insisted on doing another fuel injector replacement (my third). The replacement was done less than 2 weeks ago and surprise,my check engine light came on again today and I'm getting misfires yet again....Now hopefully I can finally gert someone to dosome realtroubleshooting and figure out what the hell is going on here....Until my next update....

 

I would research the bad injector why it was gone bad. Do you still have the old injector?