# 1999 Sentra shaking, bucking on all rpm after a heat soak



## rowlandyin (Feb 5, 2007)

Hi, guys, I am new to this site, I am fixing a 1999 sentra for a relative. I got some weird weird problem. The car is completely normal when cold. I can start it, it idles, I drive it for 30 min on freeway. It is completely normal. There is no service eng light. Then I park it for 20 minute. And come back to start it, first thing I notice is it take longer to crank before starting. Once it starts, it idles low. And the car shakes, I give it gas. It will go up to 2-2.5k rpm but no more, rpm fluctuates all by it self with me holding the gas pedal steady. I floor the gas, it still stays in same rpm range but just shakes and bucks a lot more. While this is happening, service eng light is not on. I put a spark tester on number 1 cable, I can see healthy sparks. Then it gave me a code 68, probably because I did the spark test. It seems it only happens after a heat soak. The longer I let it sit, the more normal it acts. After letting it sit a day. I can start and drive it like this has never happened. The distributor is replaced with a rebuilt unit from autozone about 1 year ago. Plug wires are brand new. And plugs are good. I have cleaned the negative battery cable really good. I am very puzzled. Can anyone help? really appreciated. I have searched some posts. I think I will check coolant temp sensor next.


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## oliverr87 (Sep 23, 2005)

easy. if you can't rev over 3000 rpm, then it's your MAF.


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## rowlandyin (Feb 5, 2007)

if it is MAF, why doesn't it give me a code 12? if I don't get CEL, can I assume crank sensor, MAF, coil are all OK?


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## WiZzO (Jun 15, 2005)

you definatly want to go ahead and check your MAF, i remember when mine messed up it didnt give me a CEL but i changed it and my car was fine...i just think its funny how your car only does it when its hot...which almost wants to make me believe that it's also something else. not exactly sure what though :/


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## azkicker0027 (May 31, 2002)

if you can, go and try another known good MAF from another vehicle to isolate this component as faulty. a MAF from a dealer is about $400. 
but wouldn't a faulty MAF cause a no start condition even when cold? or maybe the heat compromises the circuit board inside.


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## WiZzO (Jun 15, 2005)

just go to a junkyard and get one for free  lol i'm not going to say that that is what i did or anything but yea newayz, as far as i know a bad MAF shouldn't stop your car from starting... it should just stop it from reving past like 2.5k rpm... i live in south florida where sometimes it gets really hot here and i've still never had a problem like that so i doubt that the heat is affecting the circuit board.


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## rowlandyin (Feb 5, 2007)

thank you guys for this info. I saw some oil dripping out of that rebuilt distributor I got from autozone, so I am taking it back to get another rebuilt one. I will keep you posted.


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## rowlandyin (Feb 5, 2007)

Looks like the problem is oil in distributor. I got a rebuilt one from autozone 1 year ago. I still have the life warranty. If it was not for all these posts here I wouldn’t have guess a bit of oil was a big deal. I saw some wet spot under distributor cap. when I took a look at inside of cap, it was clean except for that little channel at the bottom, I can see oil. The rotor was clean, the big plastic cover was clean. The oring that seals the cap has swelled up from soaking in the oil I can see spark arcing thru my spark tester. So I had assumed distributor is ok. I guess the problem probably came when the car is parked, engine heat vaporizes oil and it somehow foul up the cam sensor. And as the engine cools off, the oil vapor somehow escapes. And the engine fire up like normal again. 

Btw autozone honored the life time warranty without questions, they didn’t even look at my receipt that I have kept, they just punch in my phone number, saw my purchase in the database, and order one for me. 

I took the time to advance the timing some, I can’t see the timing mark. I was just going to advance it until it pings and back off since I am running 87 octane gas. I am close to the end of slot on the distributor, but the car still doesn’t ping. I wonder if I have done anything wrong??


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## WiZzO (Jun 15, 2005)

wow... that is a very interesting problem, would've never thought of that  ummm as far as you advancing your timing... you should definitely want to use a timing light... you know, for your motors sake lol and if your doing it to gain more power, you should start using premium gas and you can safely advance the timing to 12 degrees WARNING:!!! ONLY ADVANCE IT THAT MUCH IF YOU ARE USING PREMIUM GAS! LOL!! but other than that congrats on finding out the problem... and see... you did it all on your own, i'm proud of you haha


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## vind (Feb 18, 2007)

Hi,
I got the similar problem with my 1999 Nissan Sentra car. My car problem was It starts and rpm goes down and it shakes. What I used to do is I hit the gas pedal for 1 or 2 min and go. The car never stalled. 

I visited several mechanics and finally went to a Nissan Dealer, they rectified it. They RESET the BASE IDLE and and did 3M FUEL INJECTOR SERVICE. The car is fine for 5 months. Hope this information will help you.

And now I am facing another problem from the past 1 week. The car is shaking while I stop at "stop signs" or "Signal lights". 

Could some one please suggest me what to do?

Thanks,
Vind


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## rowlandyin (Feb 5, 2007)

When the problem occurs, can you stabilize rpm with gas pedal? If so, then it is not distributor. 
do you have same problem when cold? if the problem is worse when you first start up. I think it is IAC. you need to spray some solvent into the IAC

if the distributor cap looks oily. It is best to change it. It makes a huge difference. My problem is all fixed with the rebuilt distributor.


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