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Hey gearheads! 05 sentra on trial lol

My 05 Sentra runs amazing except for about a minute when it starts LOL. New alternator really helped and the camshaft positioning sensor and crank PS I’ve also been changed. There are no codes showing up and no lights on the dash. What it’s doing is coughing so to speak LOL when it starts it revs high and almost stalls repeatedly about 20x really quickly and then it starts idling but hesitates if you try to drive away but when it warms up it’s great all day long and you can start it and stop it and it works perfectly. Throttle position sensor? I tried switching mass air flow sensor as well and this did not improve anything. Anyone have any ideas? Please and thanks

Sounds like the fuel/air ratio is wrong when it’s running open loop, before the oxygen sensor warms up.
I would look for a vacuum leak, leak in the air intake hose between the MAF sensor and throttle body, or a dirty MAF sensor.


Hey Smith
Thanks for the suggestion. The master air flow sensors are both looking very clean. I switched one from my other 04 Sentta which has become a parts car. Butt yes I think you are correct about the beginning idle problem. Question is why is it doing that? I will go down right now and check for a leak n let u kno. If I took a video of it starting n doin its wierdness can i post it on here so u can hear?

Sure, we love to hear weird sounds.

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I agree with @circuitsmith and his idea to check for a vacuum leak. These rubber hoses get brittle and rot after 10 years or so and one can easily have a crack. Inspect all the vacuum hoses carefully, sometimes the cracks are hard to spot.


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I missed this on my earlier read.
More possibilities: head gasket seeping coolant into one cylinder or same with a fuel injector.
Then it takes a minute to clear out.

Try this: start it cold, let it run for just a couple seconds, then take out the plugs and have a look and sniff at them.

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Good morning guys. Thanks so much for your input. Yes I checked all the hoses and from different angles and checked the connections and the hose clamps and the everything under the sun LOL. Everything looks clean and fine. Call the mechanic this morning and he said it needs to generate some code and I just have to keep starting it until the check engine light comes on so that the computer will spit out a code and tell us what the problem is. I’m going to try that but I have my doubts because I think it would have turned on a check engine light by this point. As far as the fuel being injected in early that makes sense but it sounds like the whole engine wants to shutdown as opossed to just 1 or 2 cylinders. Are you saying sniff the plugs to see if injectors are all sending fuel in early?

Here is a link to the video i took this morn so u can c n hear wut its doin…Plz leme kno if the link is fine
Thx doods

link does not work for me

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I’m inclined to think you have a leaking injector. It leaks gas down over night so it is running too rich on first start in the morning. Have someone look at the tailpipe on first start to see if there is a big puff of black smoke as it starts.

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Thx doods ------- Seriously - What is wrong with ( Thanks in advance )

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To be honest I usually find it off-putting when regulars give new users a hard time about spelling/grammar/etc, but… This was a little over the top. We’re busy people, @amadrummer - help us help you by not making us have to dust off an English-to-Teenager dictionary. :wink:


I have been there, done this same thing. The car would start and run terrible with a miss and smelly fumes from the exhaust that reminded me of an old two stroke boat motor. It would run great after a few minutes and unless left sit for several hours, it would run great the rest of the day. I fought with this problem for months until someone suggested I remove and clean the grounds, especially the sensor grounds.

This didn’t take long. I used fine steel wool to get them good and shiny and also made sure the mating surfaces were cleaned up too. I then used a rag soaked in carb cleaner. After dry, I applied silicone grease and re-assembled. They didn’t look that bad but had somewhat of a patina on them compared to clean. You wouldn’t have thought this would have made a difference but I guess it did as the problem went away and never came back.

One thing you mention is no check engine light. I had the same exact issue. I have seen other cars where corroded grounds or battery cables cause random check engine lights where it is never the same code twice. I clear the code and it comes back with something completely different the next time. These are my two experiences with iffy grounds. You either don’t get any codes or they are completely random.

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You could try a dose or two of something like Seafoam or some other product that says it cleans fuel injectors. Read the label, and don’t use more than it says to use. You might get lucky, or like most of us, it doesn’t work, and you have to clean the injectors manually or replace them.

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Merci beaucoup fellas
Your input n expertise is much appreciated.
Same off and on atart today then ran like a top all day. Took it for the daily code check haha and it showed canposition sensor but we alredy hada new one in last week so he said com back when the chek engine light lights up. So i ask my friend who teaches for ICar and he said clean the throttle body and check the wires to the mass airflow sensor.
I will let u know the next step tomorrow

Check wiring and connector to the cam position sensor.

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YES! Check your sensor connectors and any associated ground points as I mentioned above. Focus on anything related to the crank position sensor first of course. You may have replaced a perfectly good cam position sensor with a bad connection somewhere. Odds are it is getting bad input from the sensor and will not run at all if this gets bad enough.

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Thanks again guys.
CPS is new. I took it off and cleaned it and check the wiring. It looks great. I took off the throttle body and clean everywhere I could and used break cleaner. Cleaned a little bit of the oil residue from

Cleaned a little bit of the oil residue from the engine head overflow pipe connects to the air intake. There was just a little bit of residue there. I checked all the vacuum hose routing and everything looks clean and sounds. Mass air flow sensor wiring looks good too. I will see if it starts nicely later on today and tomorrow morning without the coughing. Thanks again and I’ll let you know

Unbelievable. I put a small piece plastic film as a shim in between the camshaft position sensor and the engine and it works fine LOL unbelievable. I saw a post on YouTube about this and apparently it’s a major problem with either the design of the camshaft position sensor for the manufacture of the CPS. Go figure. Now I will try to start it in the morning and see if it does the coughing or runs normally. I’m serious it was just a very thin piece plastic film. Stay tuned the saga continues LOL