Possible Misfire at 3.5-4K rpms? - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

spikevyxel · 11-13-2006, 11:00 PM

I have a 95' basically stock 240sx and over the course of the past 2 years i've had the car, there was occasionally a dip in power around 3.5 to 4K rpms. I kinda shrugged it off as a slight misfire, but since it wasnt very consistent i didnt really think much of it. This past week however there is a consistent and very noticable loss of power at those RPM's ranges. It seems to have happened the day after i took it to the track where it was pretty much raged upon. Seemed fine driving it home.

Any ideas or things that i should check please let me know.

Currently running Bosch Platinum +4... put in about 4 months ago.
91 octane
approx. 80K miles on motor

thanks in advance

punxva · 11-13-2006, 11:29 PM

this usually is caused by problems with the maf, or the sparkplug wires

spikevyxel · 11-13-2006, 11:34 PM

So since the spark plug wires look fine (NGK) its probably the MAFS?

I guess if it is the MAFS, it wont be that big of a deal. I plan to turbo in the next month and i'm getting a Z32 MAF.

Is there anything else that it could be? Distributer? TPS?

thanks for the reply

punxva · 11-14-2006, 07:51 AM

yea you could also check timing, but 240's mafs usually go out and do this, just check the voltage per the fsm

Wykydtron · 11-14-2006, 08:14 AM

Timing can be a major roll, have someone check it with a timing gun.

A couple of things I would assume, all of the above and:

11 years later, when was the last time the fuel pump was changed? There's a slight possibility that it's factory. Shouldn't it be changed every 2 years or so? I would dig into any recipts that may have came with the previous owner.

Temperature Sensor, everyone thats loves there KA knows about this issue. If the TS goes out, it will wack out the readings. When tested, a faulty TS read can read from -40 to ____ blah blah blah, something retarded. When you change the TS, you'll notice an improvement in throttle response!

Faulty injectors, I wouldnt assume this right off the bat. Chances are they are absolutely fine. If you decide to swap these out, get SR injectors and buy an SAFCII.

spikevyxel · 11-14-2006, 09:53 AM

A-Tech... you bring up a good point. I'm pretty sure the last owner didnt replace the fuel pump and i sure didnt either. I already got a Walbro on order. I did however replace the TS about a month ago. As for injectors, i already got a nice set of 480cc wait to be put in with turbo.

Punxva... Timing is set correctly( TPS... IAVC and such) however i never checked the voltage from the MAFS or any other sensors. I want to hit myself for not checking voltages on the sensors. thanks

Thanks guys for the responses. I guess i'm kinda lucky that all the stuff that it could be is the stuff that i'm replacing anyway.

robertftw · 11-14-2006, 03:58 PM

change the plugs, use ngk plugs people that i talk to that used those bosch plugs have problems with misfiring ( i dont know my self never used them thats just what they say). plugs are cheap, did you look at the old plugs?

dct223 · 11-14-2006, 04:02 PM

i agree in using NGK plugs... bosch platnum +4's dont do jack shit, its just marketing, my car ran better with NGK's

spikevyxel · 11-14-2006, 10:59 PM

Ok then... thanks for the replies and the comments.

I will switch to NGK's in a couple weeks. I'll prolly end up going to a colder plug for peace of mind.

11-13-2006, 11:00 PM	#1
spikevyxel Join Date: Oct 2005 Location: Az Posts: 27 Trader Rating: (0) Feedback Score: 0 reviews	Possible Misfire at 3.5-4K rpms? I have a 95' basically stock 240sx and over the course of the past 2 years i've had the car, there was occasionally a dip in power around 3.5 to 4K rpms. I kinda shrugged it off as a slight misfire, but since it wasnt very consistent i didnt really think much of it. This past week however there is a consistent and very noticable loss of power at those RPM's ranges. It seems to have happened the day after i took it to the track where it was pretty much raged upon. Seemed fine driving it home. Any ideas or things that i should check please let me know. Currently running Bosch Platinum +4... put in about 4 months ago. 91 octane approx. 80K miles on motor thanks in advance

11-14-2006, 08:14 AM	#5
Wykydtron Zilvia Addict Join Date: Oct 2006 Location: Skykomish, WA Posts: 909 Trader Rating: (0) Feedback Score: 0 reviews	Timing can be a major roll, have someone check it with a timing gun. A couple of things I would assume, all of the above and: 11 years later, when was the last time the fuel pump was changed? There's a slight possibility that it's factory. Shouldn't it be changed every 2 years or so? I would dig into any recipts that may have came with the previous owner. Temperature Sensor, everyone thats loves there KA knows about this issue. If the TS goes out, it will wack out the readings. When tested, a faulty TS read can read from -40 to ____ blah blah blah, something retarded. When you change the TS, you'll notice an improvement in throttle response! Faulty injectors, I wouldnt assume this right off the bat. Chances are they are absolutely fine. If you decide to swap these out, get SR injectors and buy an SAFCII. __________________ @schassis.eddi

11-14-2006, 04:02 PM	#8
dct223 Nissanaholic! Join Date: Nov 2003 Location: hella NORCAL! Age: 39 Posts: 1,664 Trader Rating: (4) Feedback Score: 4 reviews	i agree in using NGK plugs... bosch platnum +4's dont do jack shit, its just marketing, my car ran better with NGK's __________________ Sfourteen

11-13-2006, 11:34 PM	#3
spikevyxel Join Date: Oct 2005 Location: Az Posts: 27 Trader Rating: (0) Feedback Score: 0 reviews	So since the spark plug wires look fine (NGK) its probably the MAFS? I guess if it is the MAFS, it wont be that big of a deal. I plan to turbo in the next month and i'm getting a Z32 MAF. Is there anything else that it could be? Distributer? TPS? thanks for the reply

11-14-2006, 09:53 AM	#6
spikevyxel Join Date: Oct 2005 Location: Az Posts: 27 Trader Rating: (0) Feedback Score: 0 reviews	A-Tech... you bring up a good point. I'm pretty sure the last owner didnt replace the fuel pump and i sure didnt either. I already got a Walbro on order. I did however replace the TS about a month ago. As for injectors, i already got a nice set of 480cc wait to be put in with turbo. Punxva... Timing is set correctly( TPS... IAVC and such) however i never checked the voltage from the MAFS or any other sensors. I want to hit myself for not checking voltages on the sensors. thanks Thanks guys for the responses. I guess i'm kinda lucky that all the stuff that it could be is the stuff that i'm replacing anyway.

11-14-2006, 03:58 PM	#7
robertftw Zilvia Member Join Date: Sep 2006 Location: florida Posts: 148 Trader Rating: (8) Feedback Score: 8 reviews	change the plugs, use ngk plugs people that i talk to that used those bosch plugs have problems with misfiring ( i dont know my self never used them thats just what they say). plugs are cheap, did you look at the old plugs?

11-14-2006, 10:59 PM	#9
spikevyxel Join Date: Oct 2005 Location: Az Posts: 27 Trader Rating: (0) Feedback Score: 0 reviews	Ok then... thanks for the replies and the comments. I will switch to NGK's in a couple weeks. I'll prolly end up going to a colder plug for peace of mind.