Popping Valve cover to check for sludge

Hello folks,

My 2006 Sentra 1.8L with 103,000 miles isn’t maintained perfectly. While I got oil changed every year (less than 6000miles OCI), I am not aware of the oil used or the filter used. The car’s performance isn’t the top notch. It hesitates to accelerates, rarely speeds above 60mph, struggles to go uphill etc etc.

I have no idea how much the sludge in the engine can contribute to these issues. But if it does, I would like to check if there is significant sludge in the engine. I would like to pop open the valve cover to check it and to make peace with my suspicion.

I am asking here to check if this is a wise or a stupid idea or if there is any other way to find out.
If I do pop it open, should I be making Permatex gasket before putting the cover back on?

Thanks in advance.

Doesn’t sound like the car was kept maintained and perhaps many things got neglected.

More likely than not it is not a sludge build up but that causes the lousy performance, but in my opinion it is time to give it a good tune-up. Spark plugs, coils/wires, filter and fluid changes and everything else your user manual calls for. As far as a potential sludge buildup, you could get it flushed or do it yourself. If you decide to remove the oil pan get the proper gasket the car calls for and not anything “permanent”.

This year I started doing a lot of things because the performance was just getting on my nerves.

I changed Spark plugs, put the OEM ones. The mechanic said the spark plug coils are in good shape and no need to change. Replaced engine and cabin air filter, Flushed anti-freeze. In the process of changing transmission fluid. I am going to do 3 drains and refills. Have already done 2 drains and refills. Put High mileage oil with Mobil 1 filter. Will be changing oil and filter every 3 months for one year to clean out gunk, if it can do the job. The serpentine belt was changed 2 years ago.

I plan to change PCV Valve, clean MAF sensor but I am not too sure if I should try cleaning throttle body.

105,000 miles maintenance is as follows.

What else in the list above is easy DIY that can improve the performance? and what else should be left to a professional? Of course, I would like to know about sludge issue too, if it can lead to such awful performance of the car.

Thanks in advance.

So what happen when you go uphill and push on the accelerator? Does the engine rev up, but the car does not accelerate or does the engine sound fine and it just does not speed up? If the engine revs up as you push the gas, but the car does not accelerate, you could have a slipping transmission. If the engine sounds fine and does not speed up you could have a bad catalytic converter. I kind of doubt that because of the mileage, but if the car wasn’t maintained anything is possible. I assume there is no engine check light?

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No Check Engine Light.

The Engine does not rev up much but it does sound louder and feels struggling. Even if I push the accelerator, the car does not accelerate. RPM dial goes up but not the speed.

In either of those situations, what is my recourse?

The transmission fluid was never changed since I acquired the car in 2010 at 77,000. I didn’t know if one should do that as it was my first car. Not the smartest reason, but I really had no clue. When I drained the transmission fluid, it looked relatively clean, still pretty pink/red. Hence, I am in the process of changing the fluid. I didn’t flush it because at many places, I read it is not a good idea for high mileage transmission fluid change.

This is what auto manufacturer’s are now using in place of gaskets for valve covers/oil pans.



Your engine has a timing chain, so we can rule out having to change a timing belt.

Because the tach goes up, but the vehicle does not speed up, I would thing too that you have a slipping tranny. I would suggest that you take it to a good tranny shop and ask their opinion. Stay away from the chain Tranny shops that are advertized. Many of these have less than knowledgeable techs that every diagnosis is “You need a new Transmission”.
Ask your mechanic who he would go too.

The only thing that I would suggest is that you should have the throttle body cleaned, or if you are going to do it…be sure to use a “Sensor Safe” cleaner.

But you will never get a lot of pep out of a 1.8!!! The lack of pep could just be that one of the 4 squirrels has slipped off the little treadmill.



That indicates that the transmission is slipping. Unless you heard the transmission down shift?

In any gear, the engine speed should be directly proportional to the car speed. One goes up or down, the other has to match it.

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The engine needs to breath…change the air filter and clean throttle body because of carbon deposit buildup.Get a seafoam treatment…that will clean things up.

Assuming there is no driveline slippage, I’d suggest checking the air and fuel filters along with checking the catalytic converter for a restriction.

Sludge in the engine will not cause your car’s problems.

A worn out engine will cause problems like this but I’m assuming that’s not the case here.

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It sounds like you are taking the proper corrective actions to bring the vehicle back to life after a period of deferred maintenance. Good for you. The rpm thing, where it goes up but the vehicle speed doesn’t correspond, that’s a transmission problem, assuming you’ve got a conventional automatic. A proper service can sometimes fix that, which usually means to drop the pan, clean the bottom of the pan, sieve the old fluid for metal debris, new transmission filter, and refill with the proper fluid. If that seems to help doing it one time, drive a hundred miles or so, then try the same thing again. You could get lucky after repeating that a time or two, and the transmission slipping problem would be fixed.

If you feel the engine simply lacks power, with no check engine light and no diagnostic codes, and with a basic tune-up already done, start with these checks

  • engine compression ok?
  • engine air filter clean? bird nest or plastic bag stuck anywhere in cold air intake path?
  • any signs of cat problems? e.g. higher than normal intake manifold vacuum levels?
  • ignition base timing and advance curve check out ok?

As far as sludge, removing the valve cover is a good way to check for that. Often you can peek inside that area with a flashlight and a dental mirror just by removing the oil filler cap, so try that first. If you remove the valve cover, and that’s never been done before, best to install a new gasket. Check the factory service data as there may be a requirement for rtv placement at certain spots as part of the gasket replacement. Striclty follow the service data on the order to tighten the valve cover bolts , and the proper torque. Overtightening those be bolts is a common diy’er error, and can be an expensive one to make.

If the engine oil and filter has been changed every 6K miles, I doubt you’ll have much problem with sludge causing any problems, unless you have a variable valve timing engine.

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Thank you everyone. I need to think a bit on how I should get this worked out. Since the budget is tight and DW is not willing to spend much on a car that costs less than $3000, yet it needs to be kept for a few more years till things improve.

I changed air filters. I am little hesitant to clean throttle body as there are a few nightmare scenarios posted on the web. When you say Seafoam treatment, do you mean in fuel tank?

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Take a look at this about Seafoam to clean the intake and injection system

Keep in mind that unless you have the SE-R variant, Sentras are slow. All the maintenance in the world is not going to make a slow car fast. For that, you need to get into modifications, and you’ll want to really know what you’re doing with those because there’s a lot of snake oil out there which will drain your wallet and not improve your performance.

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It’s not much risk to use a cleaner like Seafoam for the intake valves and combustion chamber deposits, as long as it is used according to the directions. I’d hesitate to use it to clean the MAF sensor though, unless you have evidence there’s something wrong with the MAF sensor. If you aren’t getting lean or rich codes, suggest to leave the MAF sensor alone. If it gets damaged it can be an expensive part to replace.

I bought MAF sensor cleaner, but have heard you should buy throttle body cleaner to clean the throttle body due to some cleaners can ruin a protective coating, seafoam in gas, should be no problem

There are cleaning sprays specifically for MAFs. Seafoam or other harsh cleaners will destroy the MAF.

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If the car were mine, I’d connect a vacuum gauge to get an idea of what’s going on. There’s nothing easier and faster than a gauge to determine in seconds if the engine is getting weak or if there is an exhaust restriction.


Worst case scenario (if throttle body was extremely dirty with carbon deposits), you will get high idle and potentially engine code[s] related to this.

To reset, look for “Throttle Valve closed position reset procedure” and “Idle air volume self-learning” here: http://nissanhelp.com/diy/sentra/engine_codes.php

To read/reset codes, you might consider spending $11 for ELM327 type of adapter for Android phone/tablet or notebook: https://www.amazon.com/gp/product/B01BY2CK32/ref=oh_aui_search_detailpage?ie=UTF8&psc=1, use it with “OBD Auto Doctor” on PC/MAC or “Torque Lite” on Andoid.

I guess, I will need to take it to the mechanic to get these things done, right, or there is any other way to figure out. I don’t mind DIY if there is well-documented procedure.

You are right. Sentras are slow but when I notice same vehicle as mine running on highways at speeds of 60+, I definitely wonder something is wrong with my car. I am pretty certain that I can not run my Sentra at 60 or more mph safely, whereas I have gone about 90mph in Forester without any hassle. Something is definitely not working to its optimum level and I am trying to figure out what that can be. As I mentioned earlier, the mechanics I work with don’t find anything odd. So I have stopped arguing with them now.

This is interesting but to be honest, I didn’t understand what this work entails. If I get to watch the video performing this task, I will be more than happy to do it myself.

Oh man, I have royally crappy luck when it comes to OBD adapters. 3 of such adapters are sitting in the drawer right now and absolutely none of them work with Sentra. I paid for Torque app so I have the app, I just can’t find an adapter that will work with Sentra. No idea what is so novel abt this Sentra.

I am going to use cleaners specifically made for MAF sensor and throttle body. I do not plan to use Seafoam. I was planning to use it in the engine through brake vacuum booster line