# Please help! Sentra 2001 power loss/stutter



## Dagolfer (Dec 5, 2013)

I am not very mechanical but I will describe what happen and hope that you can help me diagnose the issue so I won't have to spend more money.

My car is a 2001 1.8L sentra manual transmission. It's been a super reliable car until 2 months ago where I needed all the coils changed. Last week my car started to stall after it had warmed up and when I took my foot off the accelerator.

I took it into the garage and they diagnosed O2 sensors. I also got my spark plugs changed.

After the car developed a stutter and loss of power. 

I have since changed the MAF after going to autozone and getting a PO171 code
The symptoms are now as follows:

1)When cold the car starts up fine
2)As the car warms up it will stutter when the accelerator is lightly pressed
3)When the accelerator is pushed further the car will continue to stutter for 15 seconds then gain power.
4)When I get to my cruising speed say 55 mph and I am not longer accelerating the car will begin to stutter again
5)When I stop the car will begin to shake quickly (sort of like a snare drum cadence) and then will calm down a little but not quite to smooth.

That's pretty much it. I've checked for leaks in the hoses I can see(but I am not expert).

I am at a loss, but don't want to spend more money trying to find the issue instead of fixing it.

Please help!

Thanks


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## smj999smj (Jan 1, 2006)

I would do a cylinder leakdown test. The 1.8L's are famous for bad head gaskets causing misfiring issues and/or rough running.


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## Dagolfer (Dec 5, 2013)

I guess my main question is - before I brought the car in for the 02 sensor change I didn't have any of the symptoms I am having now. The car was running perfectly except for the stalling out at red lights or when I was making a turn.

Could the original 02 sensors have been masking the stuttering?


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## worthirt (May 21, 2013)

Dagolfer said:


> Could the original 02 sensors have been masking the stuttering?


They may have, but I doubt it. Something else may have gone wrong just agter they replaced the O2 and the computer relearned everything. It's also possible that you have another sensor that is bad. Go with what smj said, do a leakdown. Also I would clean or check your Idle Air Control valve (IAC) since some of your problems are happening at idle it may be getting gummed up, do the leakdown on the engine to make sure though.


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## rogoman (Dec 16, 2004)

Looks like maybe you've made some unnecessary replacements such as replacing the O2 sensor and the MAF. What was the reason for replacing the MAF? If you still have the original parts, consider putting them back on the car, then reset all the fault codes in the ECU. Drive the car and see what fault codes get set if any; post your findings here with the actual codes. 

Make sure the new spark plugs are NGK OEM types, not any other brands. Some Nissan engines tend to have problems with other brand spark plugs. Check for vacuum leaks in the intake system. The proper way to check for a vacuum leak is to 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.


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## Dagolfer (Dec 5, 2013)

rogoman said:


> Looks like maybe you've made some unnecessary replacements such as replacing the O2 sensor and the MAF. What was the reason for replacing the MAF? If you still have the original parts, consider putting them back on the car, then reset all the fault codes in the ECU. Drive the car and see what fault codes get set if any; post your findings here with the actual codes.
> 
> Make sure the new spark plugs are NGK OEM types, not any other brands. Some Nissan engines tend to have problems with other brand spark plugs. Check for vacuum leaks in the intake system. The proper way to check for a vacuum leak is to 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.


HI Rogman,

Thanks for the response from you and everyone else. The reason I changed out the MAF was due to the PO171 error code that I mentioned.

When I initially went in all that was happening was the stalling. I had no other issues with driveability or idling or stuttering. The garage (I really trust these guys, I once went in stating that I needed a new alternator and they tightening a few nuts and didn't charge me a thing) said that codes were saying bad 02 sensors. Since they never were changed since the car was bought I thought that might fix the issue (they changed all 4). I took the car home and the stuttering was noticeable the first time I hit the highway. I took it back and they replace the plugs with OEM replacments. Still a bad stutter. I gave it a few days to see if it was just a break in phase, but they the SES light illuminated.


I took the car into autozone and it said error code PO171. I did a quick check with my inexperienced eyes and couldn't see any holes or cracks that would cause a large vacuum leak the code suggests. 
My next step was to clean the MAF with MAF cleaner. That seemed to really give the engine a good boost, though it was still stuttering. I was thinking that if a cleaning improved performance, maybe a new one would fix the issue.

And here I am today. The car still stutters at low RPMS but does great when accelerating. at 55 or 60 mph when I am not longer accelerating it doesn't really stutter so much as I can feel a little hiccup in the power. The car still shakes a bit when I stop (after the car is warm), then it seems to stop shaking, then start shaking, then stop shaking.

What I am planning on doing this weekend, since I don't have the tools to perform the drop test is that I am going to clean the IAC. Do you think I can do this being so mechanically inexperienced? Should I check for anything else?

Thanks!


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## hadouken007 (Apr 14, 2011)

I was having all the problems u are car stalls and shutter and it shuts off at red lights was checking, changing everything nothing helps till I bought a new MAF on ebay from a trusted MAF maker for like 75 bucks now it runs right , u can't clean em u gotta get it new, THAT fixed everything for me been about a year now still works.

Sent from AutoGuide.com Free App


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## rogoman (Dec 16, 2004)

Dagolfer said:


> The car still stutters at low RPMS but does great when accelerating. at 55 or 60 mph when I am not longer accelerating it doesn't really stutter so much as I can feel a little hiccup in the power. The car still shakes a bit when I stop (after the car is warm), then it seems to stop shaking, then start shaking, then stop shaking.
> 
> What I am planning on doing this weekend, since I don't have the tools to perform the drop test is that I am going to clean the IAC. Do you think I can do this being so mechanically inexperienced? Should I check for anything else?
> 
> Thanks!


At this point it's probably worth cleaning the IAC. You should invest in some basic diagnostic tools like a scan tool, vacuum gauge and a cylinder compression gauge. Perform a compression test on all cylinders to determine the overall health of the engine. Like I said in my previous post, perform the vacuum test. Try to obtain an FSM for your car; they can be gotten from this web site:

Nissan and Infiniti Service Manuals


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## smj999smj (Jan 1, 2006)

A bad head gasket can cause damage to a front oxygen sensor and stuttering and the lean system code. Also, replacing the rear oxygen sensors if there was no code for them was a waste of money as they are only for monitoring the catalytic converter efficiency and have no affect and the engine management. If you can't find any vacuum leaks, I would proceed with the cylinder leakdown test. Just Google "Nissan 1.8L head gasket failures" and you'll see what a problem it is. Hopefully it is not your problem, but don't disregard the possibility just because the engine is not overheating or there is no sign of cross-contamination.


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## Dagolfer (Dec 5, 2013)

Question: I am causing any damage if my car stutters while I drive it? How much does a leakdown test cost?

Thanks!


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## worthirt (May 21, 2013)

It really depends on what the problem is. You may be casuing more damage, in the case of a head gasket, but if the problem is in your IAC or something like that, there is most likely no real damage being done. Personally until the problem is found, I wouldn't drive it.


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## smj999smj (Jan 1, 2006)

A shop would probably charge 1-2 hours for a compression and leakdown test. If you have an air compressor, you can buy the leakdown tester tool for $45.

Cylinder Leak Down Tester Cylinder Engine Cylinder Compression Lost Test Gauges | eBay


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## Dagolfer (Dec 5, 2013)

Another symptom has arisen that I didn't notice before. My gas mileage is really bad right now. I thought with a lean code that not enough gas was being pumped. I am also smelling a little bit of gas when shut the car off. I read this could mean a fuel leak. But could this also be because the car is reading lean that it is dumping extra fuel?

Does this diagnose the problem any more or is it still either an IAC or a head gasket in most people's eyes?

Thanks!


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## worthirt (May 21, 2013)

is there a check engine light on?


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## Dagolfer (Dec 5, 2013)

yes after I had the plugs and O2 changed the light was off. The light came on after the stutter got worse. So I went to one of the box stores and the scanner said the problems was PO171. I changed the MAF, but the car still has the problems stated above. I am going to try one last thing before I take it back in for the dropleak, etc. I want to try and clean the IAC, but I have no idea how to do this...is there a manual to show me exactly where it is and how to peform this cleaning?

Thanks!


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## Dagolfer (Dec 5, 2013)

I am going to have to take teh car in tomorrow. After driving at highways speeds ok for 3 days today the car decided to not want to go above 70 easily. I also lost a quarter tank of few over the course of 40 miles.

My question is:

what should I ask my mechanic to do tomorrow?

I am going to ask for the vacuum leak test. Should I ask for them to check out the IAC? I may do the leakdown test too.

Any insight as to what I should ask would be appreciated.

Thanks!


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## worthirt (May 21, 2013)

vacuum leak test and leak down defiantly, then go from there. if you add a fuel pressure check to those other two, the results will tell the mechanic almost everything he needs to know. don't worry as much about the IAC, I think that it isn't causing the problem of barely getting over 70 mph and using fuel like crazy.


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## Dagolfer (Dec 5, 2013)

UPDATE:

HI all,

Thanks for the help. Well I would say that the problem is mostly fixed, but there is still an issue with my car. After I took my car in to do all the tests. The mechanic said I had a bad O2 sensor and replaces. That basically fixed not having any power.

I still have problems that I am hoping you can help me with
Here are the symptoms:

1) Car stutters sometimes at low RPMS especially in 3rd gear
2) After the car warms up often get a really bad shaking when idling. After 10 seconds this is followed by a calm period, then repeats the cycle.
3) My gas mileage is still really bad I used to get 30-31 before this whole thing started, I am at around 24-25 right now
4) The mechanic I took it to said that my tail pipe is actually sucking in instead of blowing out.
5) When blowing the vents I can often smell exhaust.

That's it! I hope you can help.

Thanks! Happy New Year


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## worthirt (May 21, 2013)

Take your IAC off and clean it. Your idle issues may be coming from it.


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## Dagolfer (Dec 5, 2013)

Worthirt I really appreciate all the help you have given me. Would a dirty IAC cause all the issues I have?

Thanks!


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## Dagolfer (Dec 5, 2013)

Ok so the car just got worse. I don't know if it is the cold weather that just came in, but the car is stuttering worse than ever. 

My question is. Is it difficult to clean the IAC? I have looked all over the internet for a how-to but cannot find one. Can someone point me in the right dirrection?

Thanks!


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## Dagolfer (Dec 5, 2013)

Unfortunately the problem still has not been solved. 
I just cleaned the IAC. Here are the current symptoms

1) Horrible gas Mileage I used to get 30 MPH now I only get 20 MPH
2) 1st and 2nd gears are fine, but when I am at lower RPMS on 3rd and 4th gear the car still stutters, has very little power for 10 seconds then gets a big surge of power
3) Idle is better since I cleaned the IAC, but it still isn't as good as it was.

Does any one have any suggestions on what I should do next!


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## otto888man (Dec 30, 2013)

Have you checked for exhaust leaks? Have you cleaned the Mass air flow sensor? When was the last time you did a tune up?


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## Dagolfer (Dec 5, 2013)

otto888man said:


> Have you checked for exhaust leaks? Have you cleaned the Mass air flow sensor? When was the last time you did a tune up?


I've taken the car to the garage 4 times already. The last time I asked them just go from front to back. They said there were no leaks anywhere. 

I replaced the MAF a month ago and had a full tune up 3 or 4 months ago.


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