Motor Pulses -- 93 240sx

[Xero]

general yes, so I'll try to explain it as best as I can.

When I'm accelerating is when I notice it the most. I'll go through 1st, shift at 3k like always, but around 2k-3k, it kinda pulses, like, there's power, then none, then again, almost like it's missing, which it very well could be.

It happens in all gears, and I've also notice it at freeway speeds.

After I got to work today, I put my foot on the gas without it in gear, and revved it a little, just enough to get it to go up a few hundred.

If I held my foot perfectly still revving it, (1000 or so rpm) I could hear it pulsing up and down a few rpm, I'd say plus/minus 25-50rpm. It wasn't constant. It'd be constant, then pulse, then stay constant for a couple seconds, then pulse again. At about the same speed as when I noticed it when accelerating.

So...it's not rpm dependant, and it doesn't do it at idle either. Idle is "usually" solid at 750, though sometimes it'll be down at 600, sometimes up at 800. When I'm coasting, it likes to sit at 900-1000 till I stop and put the brakes on, then it drops down to 750. I don't know if that's just in the computer, though.

On monday, I thought I smelled fuel when I got to school after it had died coming off the freeway, but I didn't smell any on Tuesday.

Things I've replaced:water temp sensor (OEM Nissan)TPS & about a foot and a half of TPS wiring on the harness side. (OEM Nissan and NAPA shielded wire)wires/cap/rotor/plugs (NGK/NAPA/NAPA/NGK)O2 Sensor (Bosch)Short EGR vacuum hose that seemed crackedcleaned AIV and throttle body

I think that's it, if you need more info, ask.

thanks

--Justin
Modified by Xero at 1:12 AM 4/6/2005

[NISTECH]

Justin,Is this the stock KA in your car? If so I am a bit stumped as it looks like you have replaced all the items I would have suggested as being the possibility.Except the air flow meter which I would rather you test first before just throwing it at the car.

[Xero]

yes, stock car.

Where would one go to get the MAF checked?

It does have an aftermarket coil (MSD) which I'm gonna check the wiring on, but I wouldn't think a random pulsing would cause that.

I've also got some injector seals which I might replace since I have them, but once again, I wouldn't expect it to pulse.

[NISTECH]

if you have a volt meter you can test it yourself. or you can take it to a dealer and have them test it.

[PhopsonNY]

I had a similar problem with my s13 hatch, but it seemed to go away when replaced the o2 sensor.

I don't know, isn't the 93 OBDII which would mean it has 2 O2 sensors, before and after CAT.

good luck

[NISTECH]

no 95 is the first obdII vehicle, full on OBDII didnt appear till 96. And even then the second o2 is not used for engine control.

[initial_d_s14]

i had that happen in my 95, are you sure all the vacuum lines are intact, all my problem was one vacuum line, the line that goes from intake tubing to valve cover.

[Xero]

what was wrong with this tube? was it allowing air in? It may very well be that rubber boot thing that that hose goes in to, I had a feeling that was cracked at the neck.

[initial_d_s14]

on mine it had just completely come off of the intake piping, when i slipped it back on, bam, started running fine again.

[Xero]

well, got some new symptoms.

driving down the highway, 70mph in 5th, bout 3000rpm, I push the throttle down it doesn't go anywhere. There's, like, no power at all. I can hear it get louder, but nothing else happens.

Also, when it does that (since it's kinda intermittent, it cleared up after a couple minutes, actually) when I change throttle position, not necessarily to WOT, but just increase throttle, it takes a good half second before I can actually feel the increase in power. It's like tip-in retard, only way worse. It seems like a MAF issue to me, but I thought I'd just throw out the new symptoms to see what everyone else thought.

[NISTECH]

is your butterflies in your runners closing/operating properly?

[Magnes]

Did you check the trouble codes?

Also, what was the last service you did on the car, what changed recently, and what was the last problem that was fixed?

What happens at WOT, or steady throttle at high RPM? (Wondering if it's a fuel delivery problem)

[Xero]

there are no trouble codes, and there have never been trouble codes in the 3 years I've had the car. It's always had something wrong, though. I change one thing, it performs well for a day then something else tweaks.

at WOT, it's choked, like there's no power.

It used to do the power jump at 5500rpm like alot of 240s do, but it hasn't been doing that the last couple times I revved it, but there's still no power.

At lower rpms, if I'm at a steady throttle, it'll delay when I increase throttle, but at higher rpms it usually just goes, but it going it's all that fast.

[NISTECH]

make sure your are opening and closing when you throttle it. if they are staying closed the intake air is not getting to the cyl fast enough. When you goes it they should open so the intake air has a shorter path.

[Xero]

I will check the vacuum line (I thought it was vacuum line based, or is it a solenoid?) for the butterflys saturday.

[NISTECH]

it is controlled by a vaccum line but you want to make sure they rotate under the proper conditions. with vaccum they should pull closed when vaccum is released they should rotate back.

[Xero]

okay, at Idle I see the arm down, the second I twist the throttle they arm flips up, I let the throttle back down and it rotates back down. So the butterflys are working.

When I was leaning over there, I could smell a faint exhaust smell from the EGR valve. Any ideas on that? Or is that normal? I thought I had smelled fuel a couple weeks ago, but I haven't smelled it since.

[NISTECH]

check your BPT hose and see if it is split open. If it were it could have a very slight feel of hesitation, but not drastic.

[NateDogg]

ANY UPDATES, XERO??