Darwin

G'day.
I bought a 2003 manual 350z track (100,000 miles) a while back and it had this issue when I bought it - I thought it would be an easy fix but it turns out not.
The car pulls fine to approx. 3,500 rpm and then it was like hitting a brick wall - it just did not want to pull through that.
Mechanic number 1 - advised no codes. New plugs fitted. One new coil pack fitted. New MAF fitted. New fuel pump and assembly fitted. Electrical connector fixed on one o2 sensor - car still ran the same.
Mechanic number 2 - advised no codes. Had it on the dynatune for some time. Replaced fuel pressure regulator. Car runs a little better but at 3,500 rpm instead of hitting a brick wall it just slowly ….very slowly wanders up through the rev range. He wants to do some expensive mod on fuel pipes and fuel rail. I understand that may deliver more fuel but am concerned the underlying problem may still be there.
I don't know an awful lot about cars (my son does although he likes his S13, 14 and 15) and really don't want to take it to the one Nissan dealer within 2,000 miles as I have had a bad experience with them before so was hoping someone might have some suggestion of what to look at next.

jv350z

iTrader: (6)

Turn-on the car. Hold-down the "accel" (top) button on the steering wheel, and hit the "on/off" (middle) button once. Release buttons. Give it some revs.

Hopefully big smiles!

Darwin

Thanks for responding.
I have just gone out and tried that and taken it out for a run. It is just the same.
When the car is under no load, it can rev happily to red line, its just when its being driven.

jv350z

iTrader: (6)

I was hoping you were on a "valet" map. Look up UpRev map switching. But it sounds like you're dealing with a different issue. Good luck.

Darwin

Update.
I ended up taking it to the Nissan dealer. They had it for 2 days - and had no idea.
Having got her back home I have changed the 2 cam sensors and the crank sensor - still the same.
Think I will try the oxygen sensors next.

Darwin

Oh - the only thing the dealers did note was the plugs had a brown deposit and they asked if I had been using an octane boost. I havnt and the plugs have done less than 500km

ajpasa

Back to the valet stuff. Does it matter what key you are using in this case? Just a thought.

Darwin

I ended up changing cam and crank sensors - no change.
Changed fuel from 98 to 95 octane - ran slightly better so I let the wife drive it. After a month it broke down and threw an error code for accelerator pedal sensor - changed it, no difference.
That did get me to thinking about the fuel system so yesterday changed throttle body and did an ecu reset..... SUCCESS.
While I think the ecu is still doing a little bit of learning, the car is running almost perfectly.
Thanks to those who posted with suggestions.
Happy wife...….happy life!

03ztrackfun

@Darwin, I'm experiencing what I believe to be the exact same symptoms your car was displaying. Oddly as bad as the car runs during medium to high load acceleration no CEL codes have been tripped. For my Z after a few drive cycles from when the drivability issue first occurred the car finally tripped a CEL code p0455. I began searching out the component related to the EVAP Large Leak p0455 code and found a faulty Evap Vent Control Valve, replace the faulty EVCV and the CEL went out after a couple drive cycles however there has been no improvement in performance, I've had several more drive cycles and still no CEL code tripped.

Were you able to confirm your Throttle Body was faulty before replacement or you just gave it a shot and luckily it worked? Has the issue remained fixed and the ECU all caught up with the re-learn?

Thanks,
Rich

Darwin

I just took a guess at the throttle body and purchased a used one off ebay.
It did give a massive change in performance although still not completely right.
Its my wifes car and I havnt driven it since - she drives at a speed where cyclists would probably overtake her.... and as such she has no complaints.
However, my son drove it a couple of weeks ago and he reckons the same issue is starting to crop up again.
I have had no codes so that really stuffed me with diagnosis.

So, can't really help much..... I hope you get yours sorted - let me know how it goes.

03ztrackfun

Thanks for the incredibly quick and courteous response. I'm trying to not just "throw" parts at the problem until it goes away... that gets expensive and frustrating. I agree, not getting a CEL is difficult to understand. Perhaps since you went with a used TB the replacement is beginning to suffer the same fate.

I'll report back when I have useful info to contribute.

03ztrackfun

Problem resolved, Firstly I removed and properly cleaned the throttle body and MAF sensor, which did not correct the issue but that was needed for maintenance in any case. Based on what happened with Darwin I'm thinking something has failed with the throttle body but before I go that route I just kept having a hunch could be exhaust related. I disconnect the Y pipe at the rear flange to the converters and found the passenger side catalyst element had come dis logged and turned long ways blocking exhaust flow. I fought with it for a couple hours and was able to remove the catalyst element completely, started the car and gave a few revs to blow out dust, reconnected the Y pipe and took for a test drive... wham, all the power is back. Didn't have to spend any unneeded money.

Darwin

Great news..... perhaps I should have another look at mine. Thanks for the update

03ztrackfun

Darwin, absolutely take a look. Give proper care in removing the Y pipe flange bolts mine were rusted all to heck. Heated them cherry red with my MAPP gas, gave them a few solid whacks with a hammer, then fitted the socket and with a breaker bar the nuts came off super easy; even was able to reuse the flange gaskets