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Old 08-16-2019, 09:02 AM   #61
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Re: 2008 Nissan Sentra Stumbles at 3000 RPM


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Originally Posted by raylo32 View Post
Tell me about it... Same here. I just replaced the aftermarket backup camera in my Tacoma yesterday. It was a Pioneer that I put in with a JVC head unit 10 years ago. I had since changed out the head unit to a Pioneer a few years ago and the camera was still good. But it died about a year ago. Now I am retired no excuse to let it go.

It could maybe have been a simple job if I had got another Pioneer cam but for some reason I picked an Alpine. Looked like a better cam. Tried splicing it in but no video. Turns out the Pioneer cam's power supply was putting out lower voltage (3.5V) than the Alpine (6V). Maybe that's why the Pioneer cam "died"?? I dunno.

So I had to do the full monty to install the new power supply and extension cable to the camera... rip out the head unit, pull all the dash panels, remove the driver's seat, etc. Up, down, crawling around and under... last night I felt like I went ten rounds with Mike Tyson.
Buddy that wore me out just reading that. I bet you were tired and wore out after all that. Your luck sounds about like mine.
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Old 08-16-2019, 09:17 AM   #62
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Re: 2008 Nissan Sentra Stumbles at 3000 RPM


I got the rear catalytic converter yesterday along with the MAF sensor and gas cap. The front cat is supposed to be here today. It looks like the rear cat they sent is the wrong one. The flange only has two bolt holes and the one coming out of the front cat has 3 bolt holes. That may not be where the rear cat goes but since they cut the pipe and welded a straight pipe in, I have no clue how it actually goes in there. I think they may have cut the flange out along with the rear converter.

I have looked all over the internet trying to find how a stock exhaust for 2008 Sentra SE-R Spec V with a 2.5 200hp engine looks like. I have found diagrams of exhausts but the one under the car looks nothing like that.

I guess I need to contact Rockauto and see what they have to say about the cat. The strange thing is they only had one style rear cat and this is it.

Question, It states that I have to use premium unleaded, what will happen if I use regular octane gas? I am old school mechanic and not familiar with these newer cars. Will it mess up my converters?
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Old 08-16-2019, 09:31 AM   #63
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Re: 2008 Nissan Sentra Stumbles at 3000 RPM


Jim, you got an SE-R? That is the hot rod version certainly not a little old lady's car. Good chance whoever had it modified it a lot so who knows what you will find. As far as octane, no, using regular won't hurt the cats. But it may allow the engine to knock which could damage the pistons and such if it gets bad enough. Most modern cars have knock sensors that automatically dial back timing to protect the motor if that happens. Then alls you'd see is a tad less performance and mpg. But I am not sure how Nissan does this. If I were you I'd compromise and use mid grade at least.


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I got the rear catalytic converter yesterday along with the MAF sensor and gas cap. The front cat is supposed to be here today. It looks like the rear cat they sent is the wrong one. The flange only has two bolt holes and the one coming out of the front cat has 3 bolt holes. That may not be where the rear cat goes but since they cut the pipe and welded a straight pipe in, I have no clue how it actually goes in there. I think they may have cut the flange out along with the rear converter.

I have looked all over the internet trying to find how a stock exhaust for 2008 Sentra SE-R Spec V with a 2.5 200hp engine looks like. I have found diagrams of exhausts but the one under the car looks nothing like that.

I guess I need to contact Rockauto and see what they have to say about the cat. The strange thing is they only had one style rear cat and this is it.

Question, It states that I have to use premium unleaded, what will happen if I use regular octane gas? I am old school mechanic and not familiar with these newer cars. Will it mess up my converters?
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Old 08-16-2019, 10:36 AM   #64
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Re: 2008 Nissan Sentra Stumbles at 3000 RPM


Octane is an anti-knock agent, added to HIGH COMPRESSION engine fuel.

Using lower grade fuel, only hurts performance, and might allow knocking on acceleration.

Which could damage your engine, So trying to cut back on the octane requirements is a judgement call on your part.

You could try a mid-grade, to see how it performs, then the "regular" grade, and decide if you want to continue using the lower grade fuel.

Go to the Nissan dealer, to ask if they have a diagram, in their parts department for the exhaust system.

I used to get printouts from my local dealers, when I was confused on how parts were supposed to fit.

Turned out that many times some "doofus", has rigged things that were not factory parts.


ED
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Old 08-16-2019, 11:44 AM   #65
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Re: 2008 Nissan Sentra Stumbles at 3000 RPM


Ray, I do use the higher octane gas, I was hoping I could use the lesser cheaper gas. (not the real cheap places to buy gas) The low octane gas right now is $2.08 a gallon where the high octane is $3.00. That little car is eating gas like crazy right now, I just hope after getting all the new parts on it will improve the gas mileage. I won't use raceway or walmart gas, it causes too many problems for me.

Quote:
Originally Posted by de-nagorg View Post
Octane is an anti-knock agent, added to HIGH COMPRESSION engine fuel.

Using lower grade fuel, only hurts performance, and might allow knocking on acceleration.

Which could damage your engine, So trying to cut back on the octane requirements is a judgement call on your part.

You could try a mid-grade, to see how it performs, then the "regular" grade, and decide if you want to continue using the lower grade fuel.

Go to the Nissan dealer, to ask if they have a diagram, in their parts department for the exhaust system.

I used to get printouts from my local dealers, when I was confused on how parts were supposed to fit.

Turned out that many times some "doofus", has rigged things that were not factory parts.


ED
Dern Ed, that is cool, why didn't I think about going to the dealer and getting that information. That is why you make the big bucks. lol


I remember back in the OLD days, we could put a water injector on the car to cut back on the pinging. I didn't think about the knock sensor may kick in if it started pinging. This engine has a 10.5:1 compression ratio compaired to the standard 2.5 of 9.5:1. I wouldn't let the engine lug so heavy it would ping before downshifting anyway, just an old habit from the old days of high compression engines pinging in a strain. Back in the old days, 10:1 was stock compression ratio in most cars.

After all these years, I just looked up why the pinging would hurt an engine, I see now why it would.

1. High compression ratio: Due to high compression ratio, sometimes a secondary flame front is formed starting from piston head or any other hot spot if present, which collides with the flame front generated by the spark plug. In short due high compression ratio, preignition takes place leading to knocking issues.
It can be resolved by reducing the compression ratio if a VCR(variable compression ratio) system is used.
2. Due to the presence of a secondary hot spot: Due to long hours of running the engine, unburnt/partially burnt carbon particles get deposited on the piston head, screw threads, regions around the valves, etc. These deposited carbon particles act as ignition source when the compressed fuel-air mixture is on the verge of burning (no spark, primary flame front not yet started). Thus before the actual start of the primary flame front, a secondary flame front starts travelling in an opposite direction, cause a collision and hence knocking.
it can be resolved by cleaning the engine cylinder(s) and all the carbon deposits must be surely removed.
3. Due to the overheating of the engine: If the heat of combustion chamber is not efficiently dissipated, then there is a significant rise in the temperatures of the combustion chamber parts such as piston head, valve heads, spark plug and threads of spark plugs screw and other similar parts. Due to this rise in temperature, these all overheated parts act as ignition sources and start multiple flame fronts, which collide and cause knocking.
It can be fixed by fixing/improving/modifying the engines cooling system and use coolent if possible.
4. Due to the low speed of engine: Due to low engine speed, there is a sufficient ignition lag, which gives enough time for a secondary flame front to get formed leading to the knocking.
If the speed of the engine is increased sufficiently, this issue can be resolved. Another alternative can be "advancing the spark timing". This will reduce the ignition lag and hence the knocking.
5. Knocking characteristics of the fuel: The fuel to be used in the engine should be tested for it knocking characteristics (octane rating) in a standard engine setup and a good quality antiknocking fuel should be used in order to get rid of this issue.


Ed this dealer we bought the car from keeps saying a little ole lady had the cats gutted and cut off and a straight pipe replaced. He is trying to cover his butt. What he isn't thinking about is, he sold the car knowing this. He is dragging his feet getting the title to the court house also. If he doesn't get on the stick I am going to turn him in.
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Old 08-16-2019, 11:45 AM   #66
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Re: 2008 Nissan Sentra Stumbles at 3000 RPM


Stay with the better gas, it doesn't take long to destroy a high compression engine
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Old 08-16-2019, 05:27 PM   #67
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Re: 2008 Nissan Sentra Stumbles at 3000 RPM


Dern Ed, that is cool, why didn't I think about going to the dealer and getting that information. That is why you make the big bucks.

above quoted: Send all you can spare, and we'll be even.

I personally do NOT fix anything, until I have a clear title "in hand".

I hope that you don't get ripped off, putting money and parts into this thing.

Yes; get on their behind, like ugly on an ape, and get a clean title.


ED


PS, I once melted all the pistons into a puddle in the oil pan, running one too hot.

So do use the best gas that you can get, without preignition (knock) happening.
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Last edited by de-nagorg; 08-16-2019 at 05:30 PM.
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Old 08-16-2019, 11:00 PM   #68
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Re: 2008 Nissan Sentra Stumbles at 3000 RPM


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Originally Posted by de-nagorg View Post
Dern Ed, that is cool, why didn't I think about going to the dealer and getting that information. That is why you make the big bucks.

above quoted: Send all you can spare, and we'll be even.

I personally do NOT fix anything, until I have a clear title "in hand".

I hope that you don't get ripped off, putting money and parts into this thing.

Yes; get on their behind, like ugly on an ape, and get a clean title.


ED


PS, I once melted all the pistons into a puddle in the oil pan, running one too hot.

So do use the best gas that you can get, without preignition (knock) happening.
Ed, I am one of the easiest going guys you will find, but if he rips us off, he will never know I am an easy going guy.

You talked me into it, I will use the high octane gas.
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Old 08-19-2019, 04:23 PM   #69
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Re: 2008 Nissan Sentra Stumbles at 3000 RPM


Here is the latest skinny. I have put the converters on, new MAF sensor, new plugs, new gas cap and a new 02 sensor. It has cleared all codes, I double checked to see if there were any codes pending, nope clean as a whistle. Not one single thing has changed, the longer I drive the car the worse it gets, very little power. It does get better gas mileage believe it or not.

The next move is to recheck all ground wires and see if that helps. I am at my wits end, I don't have a clue where to go next. Any suggestions?

I have read online anything from relearning the throttle body, to regapping the plugs closer, to replacing the crankshaft and camshaft sensors also replacing the knock sensor. If it isn't spitting a code, I don't know where to go next.
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Old 08-19-2019, 04:58 PM   #70
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Re: 2008 Nissan Sentra Stumbles at 3000 RPM


Jim: have you ran a compression test on this engine, it's beginning to sound like you have a dead cylinder.

Dang, I hope not.


ED
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Old 08-19-2019, 05:24 PM   #71
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Re: 2008 Nissan Sentra Stumbles at 3000 RPM


This thread has been going awhile so I don't recall, did you pull the original plugs and read them? If you replaced them did you pull them again to see if one or more looked abnormal (wet with oil, fuel, etc)?

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Jim: have you ran a compression test on this engine, it's beginning to sound like you have a dead cylinder.

Dang, I hope not.


ED
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Old 08-19-2019, 06:59 PM   #72
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Re: 2008 Nissan Sentra Stumbles at 3000 RPM


Quote:
Originally Posted by de-nagorg View Post
Jim: have you ran a compression test on this engine, it's beginning to sound like you have a dead cylinder.

Dang, I hope not.


ED
Ed, I haven't done a compression check yet. I don't think it is a dead cylinder, this little car will burn the tires off when it is cold and runs so smooth it is unreal. It only bogs and jerks some when it get warm, the warmer the worse the power loss. I am just baffled.

Ray, I haven't taken the plugs back out to check them out. The Champion plugs the dealer put in were clean as a whistle all looked like they were new and just put in.

On top of all this, the Pathfinder AC totally quit, with the compressor running it is blowing warm air. I believe the compressor is shot. I have a reading of 67 on the low side and 125 on the high side with outside temps of 94 with humidity over 40%, rpm at 1500.

I think there is an open valve in the compressor letting high pressure bleed back into the low pressure side. Remember the needle on the high pressure gauge was fluctuating like crazy a while back. The AC would work after being on a while and then it took longer and longer to cool at all, then finally no cool air. I did notice that the schrader valves are leaking ever so slightly, but never the less, they are leaking.

Is this ever going to end, we are broke now so things will have wait on the AC.
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Old 08-19-2019, 11:21 PM   #73
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Re: 2008 Nissan Sentra Stumbles at 3000 RPM


Jim: humor me, check the compression, then get out your timing light, and check your timing .

Yes I know that I am going "old school", on this, but you gotta start from the beginning to find this bug.

Report back on the timing observation.


ED
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Old 08-20-2019, 08:14 AM   #74
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Re: 2008 Nissan Sentra Stumbles at 3000 RPM


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Originally Posted by de-nagorg View Post
Jim: humor me, check the compression, then get out your timing light, and check your timing .

Yes I know that I am going "old school", on this, but you gotta start from the beginning to find this bug.

Report back on the timing observation.


ED
Bill, I will get out there in a little while and I will check the compression while I have the plugs out checking them. I don't have a timing light any more. I do still have a dwell tach though. lol I plan to take every ground wire loose, clean and reconnect today. I plan to pull all the electrical fittings and check to see if any are fouled or not connected well.

Just had a thought, I wonder if heated air will foul the MAF? The fresh air intake will not stay on for the MAF to draw fresh cooler air. It is drawing hot air from the engine compartment. I will fix that today as well. I know the MAF is heated but maybe too much heat is bad for it to operate properly. I guess I will find out.

One other thing I have noticed, the positive clamp on the battery isn't tight enough to keep the terminal from turning by hand, I will see about making that fitting tighter also. I don't see how that could be the problem but at this point I am grasping for straws.

Ed this car has a timing chain and I am told it lasts the life of the engine but I have sen chains wear out in the past so I don't see how this one can be any different. No way will I pull that cover to just check it though, that is a major project.

The title of this thread is a little wrong, the car doesn't just shimmy, bog down or jerk and jump at 3000 rpm as I thought, it does it at all rpm. I have noticed if I really pour the coal to it when it jumps and jerks, it will go on but it seems like the engine really doesn't like that. I don't want to mess around and foul out these new converters.

I appreciate all your help, I just don't know what to do next. I will let you know what I find today.
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Old 08-20-2019, 08:44 AM   #75
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Re: 2008 Nissan Sentra Stumbles at 3000 RPM


Jim,


Go to bottom of this link.
https://x.nissanhelp.com/forums/alti...eleration.html

There is a list of service bulletins about the stumble. Seems tobe common.


Going thru some of the posts seems like Nissan doesn't have a remedy.
May be time to cut bait.


bg
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