Popping Valve cover to check for sludge

I suggest a vacuum gauge as a preliminary check because gauges are cheap and easy to use. They come with a user instruction sheet.
The only thing missing in the instruction sheets involves the test for a clogged exhaust as there are actually 2 indicators. The instructions only show one.

Usually the easiest place to tie in to manifold vacuum is to disconnect the fuel pressure regulator vacuum hose and connect the gauge to that.
The entire process of connection and testing should take no more than 5 minutes at best.

With a good engine and exhaust system the intake manifold vacuum will read in the 17-21 in hg range at warm idle. If you then bump the accelerator to an rpm of 2500 or so briefly, the vacuum will drop rapidly almost reaching zero. If the cat is clogged the vacuum at idle isn’t as high, and it doesn’t go as low when you bump the throttle. You’re Sentra should have no trouble at all accelerating to 60 mph. It might take you 12 seconds to go from 0-60 mph, vs 7-10 seconds in more powerful car is all. If you simply cannot reach or just barely rach 60 mph as your max speed, something is definitely amiss. You mentioned above the engine rpm seems to go up ok but the speed doesn’t correspond. Have you asked your shop to consider a slipping transmission as the cause yet?

Unless you are an experienced diy’er, it’s more economical to let your mechanic do those jobs for you.

I was using this specific ELM327 to read/reset codes on my daughter’s 2003 Sentra, usign both Android and MacBook, both worked fine.
I do have a bunch of adapters sitting in my drawer too, but all of them were able to read/reset basic set of OBD2 codes, I was trying to get to “Nissan extended codes”, this is where they all failed.
I could suggest you to make sure you do not have issues with OBD2 connector in your Sentra.

Performance-wise, I was easily getting to 75+ MPH on my daughter’s car, so if you get only get up to 60, you definitely have a performance issue.

Up in the thread it was a great advice about testing for the exhaust restriction and for compression: I would entertain these options first, before getting any further. Sentra’s engine has spark plugs easily accessible, so testing for compression should be very easy, you can rent the tool from AutoZone or Advance Auto

It is difficult to believe reaching 60 MPH is challenging and your mechanic has not noticed this. Does your engine reach 5000 RPMs when accelerating? Is there a reason you cannot press the accelerator to the floor? Are there several floor mats in the way?

I doubt that you will find a dead cylinder with a vacuum gauge, modern vehicle systems alert you of this before you will notice.

@ok4450 and @GeorgeSanJose Whatever both of you suggested flew way above my head, so just tell me what I should tell the mechanic in precise terms and I will just ask him to do it. I am not comfortable messing something I don’t understand.

I actually mentioned that the car struggles to go uphill and thats the time he commented, you are not driving a sports car. That time I didn’t have Forester to compare to, but since acquiring Forester, this problem ‘feels’ more pronounced.

@andriy.fomenko I will give a shot to this adapter as well. Hopefully, it will work.

@Nevada_545 I don’t remember ever trying to get rpm to 5000. When merging with the highway, it goes up to ~4000 but once I speed up, it comes down to whatever the number is, around 2000. Next time, I drive on the highway, I will record a video so that I am sure that I am giving correct information.

Thanks everyone for commenting.

Unless you have a confirmed diagnoses, I would be reluctant to tell the mechanic what to do. Keep in mind, none of us here have seen or touched your car. It’s one thing to tell the mechanic that you had suggestions from others and what he thinks about it, but just directing him/her to do something can be very costly and no guaranty that it improves your car’s performance.

How about finding a different mechanic shop that is more open minded?

Repeating my previous post:

RPM dial goes up but not the speed[/quote]

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.

Get the transmission checked would be my #1 priority.

Note: does not apply to a CVT transmission.

Fuel filter probably clogged. Spark plug wires leaking voltage. Distributor advance sticking.

Mscullin, the problem was posted eight months ago. The original poster (OP) has likely either solved the problem or traded the car by now. Long ago, actually.

For some odd reason, which we’ve discussed here before, this site’s format seems conducive to the resurrection of old threads whose problems were posted and have likely been solved long ago, sometimes years ago.