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That's pretty normal, so it may well be the A/F that's messing up. But on the grounds that the MAF is both easier and cheaper, I think I'd try that first.
 

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Discussion Starter · #24 ·
Well i changed the MAF and performed the IAVL setup last friday and everything was fine until today. Today on my way home after about 140 miles since friday the check engine light came on with a P0172 error and my 3K studder is back. Up until this point this issue has not caused the service engine light to come on. I ordered a Denso 02 sensor at the same time so tomorrow i may swap the original MAF back in and install the new 02 sensor.

Speedometer White Light Plant Gauge


Speedometer Light Gauge Measuring instrument Font


These screen shots were from my ride home in 6th gear with the cruise set on flat ground.
 

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That's a generic rich code, a catchall the ECM throws when it can't figure out why the engine wants too much fuel. When it isn't from the MAF or from bad fuel, it's almost always from a bad A/F sensor (front O2).
 

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Discussion Starter · #26 ·
So does it make sense to put the original MAF back in along with the new primary 02 sensor? The MAF was $30 so im not worried about the $$. Which ever MAF ends up in the car the other one will be a spare on the shelf.
 

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Nah, swapping back seems pointless. You'll still want to run a new IAVL after you install the new A/F, though. They work together, that's why either one can affect the other and cause rich/lean issues.
 

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Discussion Starter · #28 ·
The only thing i was concerned about was the fact that ive been dealing with this issue for months and never had a SESL until i changed the MAF. I will try the new 02 but if theres any signs of an issue the original MAF is going back in.
 

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That sounds like a plan. Changing both at once won't prove anything anyway, it just makes it a two-body problem. Newton could have told you, in orbital mechanics you don't have a choice, but in matters where you have control, one body at a time is always the wise course. Because if you reach 3, you're in trouble. ;)
 

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Discussion Starter · #30 ·
And the saga continues... I ordered a Denso upstream 02 sensor which got delivered a week or so ago. I went to install it and found that the electrical connector was wrong which after a quick search revealed my Michigan car has Commiefornia emissions. So i packaged that 02 up and sent it back and ordered the right one. The correct Denso showed up today and after 5 min or so was installed. Welp....same problem, the 3K rpm miss or studder or hesitation or whatever you want to call it is still there. Im starting to think that the issue is one of the ignition coils but its not throwing a misfire code so im hesitant to buy a coil and swap one by one to see if it changes anything.
 

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When coils misfire only under load or elevated RPM, it's usually from an insulation failure. With Nissan COP's, that usually means a boot is leaking spark to the metal walls of a plug tube. That almost always leaves some sort of evidence on the boot or walls, give it a close look for carbon pocks or tracks. If you've had any leaky tube seals, the oil eventually makes the rubber porous, so suspect any coils that were exposed to oil before the others.
 

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Discussion Starter · #32 ·
I do or did have one tube seal that was very slightly leaky. I bought a kit to replace the tube seals but when i got the valve cover off i found that they were molded in and couldnt be changed.

If i order a coil is there a brand to buy or any brands to stay away from?
 

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There's an awful lot of China-cheap crap out there, stay away from all of it. Nissan's COP coils are virtually all made by Hanshin in partnership with Denso, so those two names are the only ones I trust when looking for discounts.
 

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PS - There's nothing wrong with China-cheap for rocker covers. I bought from these guys for my '04 and it was no-grief part for $31. They're getting $42 for yours:

 

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Discussion Starter · #35 ·
Ok thanks, ill see if i can find a Hanshin or a Denso. Good to know about the rocker cover, ill investigate that when i get into the ign coils.
 

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You're most welcome. I should add about the coils, I have a couple of customers who insist on NGK's. Neither of them has had any trouble, but two is a very small data sample. So draw your own conclusions, I personally stick with Hanshin/Denso.
 

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Discussion Starter · #38 ·
Well what i figured would happen happened, the coil didnt alter the performance of the car. I started at cyl #1 and swapped each of the existing coils with the new Denso coil one by one. So im back to the drawing board.
 

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Well what i figured would happen happened, the coil didnt alter the performance of the car. I started at cyl #1 and swapped each of the existing coils with the new Denso coil one by one. So im back to the drawing board.
Since you had a P0172 DTC, here are several other things that could cause misfires:
  • The camshaft position sensor or the crankshaft position sensor may be marginal. The best and cheapest fix for this situation is to replace both sensors at the same time; the reason for doing this is there is no way to determine which sensor is at fault with this type of condition. You can take your vehicle to a dealer/repair shop and they'll tell you there is nothing wrong after they go through with diagnostic tests because at that time the vehicle was running OK. You could end up spending $200 or much more depending on how much time/parts are used.
  • Incorrect fuel pressure. Tee-in a temporary fuel pressure gauge between the fuel feed hose and the fuel rail. The readings at idle should be 51 psi.
  • There may be a major intake system vacuum leak. To check the intake system for a vacuum leak, attach a vacuum gauge to a full vacuum source. With the engine fully warmed up, the reading at idle should be 18 - 20 InHg. At 3,000 RPM, it should be around 21 InHg. If readings are under 18 InHg, check the intake manifold nuts to make sure they are tight. The gasket may have failed; spray a water mist at the gasket to see if the gauge reading changes. Also check the intake plenum bellows at the throttle valve and at the MAF for cracks or loose clamps.
  • Dirty fuel injector(s). Run some good injection cleaner, like BG products 44K, through the system; give the cleaner about a week or two to do it's job.
 

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Discussion Starter · #40 ·
The only time i have had any codes was when i swapped to the replacement MAF, when i went back to the original MAF the codes did not come back.

Im off work till after the first so ill check out those things.

Thanks for youre thoughts
 
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