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Discussion Starter #1
Hey ya'll! We all love our X's and I very much have for the past 14 years I've owned mine! But there us a problem that is looming over my head and I'm sure it is transmission related.

Recently, I had to change my AF sensors for the second time because the first time my mechanic recommended me to use Bosch and I foolishly agreed, and after the noticeable lack of power and extremely rich ratios, I researched and made the switch to Aftermarket Denso AF sensors. Everything changed in terms of power and correct readings. I had to reset the MAF and then I went ahead and cleaned it and the Throttle Body, changed to a K&N engine air filter, and I got new tires on the baby. Now it has a cleaner ratio and runs a bit smoother.

But the problem still remains that there is a groaning sound when accelerating and when I get weird acceleration going back and forth in rpms before 30mph and after that it is smoother unless I hit the brakes and then accelerate again. I managed to change the radiator and transmission fluid and filter before SMOD got too bad. Even with all of this, these problems still happen. I'm thinking the transmission is going, but I don't have any check engine lights yet or pending codes.

Any suggestions or experiences on this matter?
 

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Clarify " before SMOD got to bad"... I feel like that is a very small window.

did it have smod? how long ago? did it do this before?

Have you checked the PCV?

also look into the VIAS issue/ fix. I had to do that, I didnt notice a loss in power but over like 2200 rpms and around 30 mph you could hear the valve essentially opening and closing. it would cause me to let off the throttle. more annoying than anything, but i bet it could cuase power issues since it has somethig to do with the amnt of air pulled into the intake.
 

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Discussion Starter #3
Thanks for the reply @mtnbound !

So before SMOD got bad was essentially meaning that there was almost no contamination in the coolant when the radiator got changed, but at the same time, when the mechanic saw the transmission fluid, he said it looked very metallic and "unlike anything he has seen before" (sounds like he was trying to sell to me). My mom used the car before me, so she didn't make sure to do the required maintenance. I don't think the transmission fluid was changed for at least 4 to 5 years. After the fluid and filter was changed, people said the shifting was normal.

I haven't checked the PCV. I'll make you to do that and I have never head of the VIAS issue so I'll look into that as well!
 

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here's whats on my mind.. does the engine feel like its down on power, or does it feel like the truck just doenst want to " go" if its the later then i'd go with trans issues.

like can you rev it in nuetral and have it rev quiclly and failry high in the rpms, or does it feel like it doenst want to rev?
 

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Discussion Starter #5
So I'm leaning more towards it doesn't want to "go". I can rev it in neutral and drive, but I'll get a nice surge to 4.5k rpms at most and then it falls back to 1.75k to 2.25k rpms and struggles to go past it.

If I do have transmission problems, should I take it to a Nissan stealership? I know the SMOD cases caused for free replacement before 80k miles and then Co-Pay for after. That way, maybe it won't be too bad of a repair??
 

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Discussion Starter #7
I think what might be a good idea too, is to get it fully diagnosed for $120 to check the fuel filter because I have never replaced it before, or check spark plugs again because I had leaking problems that got fixed.
 

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Discussion Starter #8
Hey I just got a check engine light with the code p0442 which is a small evap emission leak. That is definitely part of the cause and now I'm looking towards that for the root of the problem. I'll definitely check the PCV
 

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Discussion Starter #10
Yeah that's what I'm thinking the fuel cap is not on right. It is aftermarket because I lost the OEM one, should I try to find a better cap?
 

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Discussion Starter #14
Lol I see! I made the drive back an 80 mile trip and it was struggling, but I don't think it's the transmission though. I shifted the transmission to multiple drives on the road. I think it might be more electrical than anything. But when I'm driving, it just feels like something is pushing the car back as it accelerates and makes it try harder. I'm going to test drive in the morning and see what the fuel trims and o2 sensor readings are.
 

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Do you get a blinking "A/T Check" light key on, engine off? The funny thing is there is an A/T light, but it only tells you of a problem key on, engine off. When the rig is running, the "Service Engine Soon" light kicks on to tell you there is an issue with the transmission. Damn near government level logic.

Edit: upon re-reading your top post, I see that you have a K&N filter you added at the same time as the Denso MAF, if the K&N was over oiled, there is a possibility that the MAF sensor filament has oil and dirt build up on it causing the surging you are talking about due to incorrect airflow readings. Clean the MAF with an approved MAF cleaner and see if the problem vanishes. It really sounds like a MAF related issue with surging and lugging, happened on a friend's Maxima, my Pathfinder, my first gen Xterra all at lower speeds, at or under 35MPH, you would have to floor it to keep the engine from stalling out or lugging hard feeling like the "loss of power" you allude to. It would take a while for the oil from the K&N to build up on the MAF sensor wire, and would present seemingly randomly now. Dirty or failing MAF will have your tachometer needle jumping more and more erratically as time goes on.

With the issues you have listed, it is hard to pinpoint exactly what the root cause may be, but logic dictates start with the cheapest thing to test and move onward with diagnostics. Check your ATF dipstick, cold radiator and reservoir for signs of residual SMOD (free diagnostic), check the color of your ATF as well, dark/burnt ATF may cause some loss of power, but not to the extent of the car bucking or surging/lugging typically, then clean the MAF ( I cannot stress enough using the proper MAF cleaner for the MAF, brake cleaner, etc will likely destroy it, that wire is like a delicate little flower. Look at it wrong even and it may die, well that may be a slight over exaggeration), drain the ATF pan and see if there is water/coolant contamination, if yes, drop ATF pan and valve body, clean thoroughly, then follow the steps I messaged you about fixing the TCM.
 

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Discussion Starter #16
Wow I never have heard of that before. I didn't understand why people kept talking about an individual A/T light, but I have not seen that at all, so it must be a power thing.
 
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