[warpspeedmrsulu]

Hi all,

I hope I can get some feedback on this really bizarre issue I've been having with my Z. It's an '03 (thus all the headaches) Performance model. The car has started demonstrating this really odd behavior which I'll attempt to describe as accurately as possible. When the car is cold, it starts and idles perfectly--but when you pull out onto the road and begin to accelerate, it becomes apparent that the car is not accelerating to it's full potential (not even close). There is no sputtering or hesitation, the car even seems normal for the first few seconds, but then power just stops coming. It almost acts as if it is registering the first inch of accelerator pedal depression, but no more. Once you hit this acceleration 'wall', the car behaves as though you are not depressing the gas any more, even if you floor it. The result is very slow, steady acceleration you'd get if holding the gas pedal in the exact same position for an extended period of time.
As the car warms up, the problem manifests less and less. When the car begins to respond, if you floor the gas, you may initially get no additional power (as before), followed by sudden surges of power which start and stop, until eventually the car may seem to run normally besides the occasional lack of power. I took it to the dealer and they are having a hard time diagnosing the problem. First they replaced the throttle body, but that did not correct the issue. Now the tech at Nissan says it has to be either the main computer or the computer wiring harness--but this doesn't seem right to me...why would the behavior an electronic component change as the car warms up? Also, there is no Check Engine Light, and the computer is not throwing any codes. I'd hate to buy an expensive computer only to find the issue is not corrected. PLEASE HELP!
WarpSpeedMrSulu is online now Report Post Reply With Quote

 

[warpspeedmrsulu]

350z-tech, you have let me down!

 

[Ronin Z]

My guess would be the ECU (or maybe a sensor).

Your Z's ECU is capable of switching between multiple ignition and fuel curves based on various criteria such as air temperature, coolant temperature, throttle position and so on. If one of the many sensors is feeding the ECU bad information (or the ECU is not reading the information correctly) strange behaviors can result.

-Ronin Z

 

[warpspeedmrsulu]

Wow. And then I get a response from the legend himself. Ronin, do you think the fact that the problem seems to dissipate somewhat over time, or as the car heats up, would seem to incriminate a sensor more strongly than the ECU itself? I'm desperately trying not to resign myself to the probable fact that the only thing I can do here is replace the ECU, and if that doesn't work, start going after various sensors, one at a time, until the issue is resolved? That would suck.....bigtime.

Thanks again for your time.

 

[Ronin Z]

To be honest, I'm having a little trouble understanding the exact nature of your problem, but here's my take on it...

As you are doubtlessly aware every aspect of your engine's performance is controlled be the ECU. The ECU makes it's determination of how to adjust the fuel and spark curve based on the information it's getting from the endless array of sensors. OK, with a scanner, the shop can look at all of the data that is coming into the ECU in real time. It should become readily apparent if a bad sensor (let's say coolant temp sensor) is sending intermittently bogus data.

If you do have a flakey sensor, then what is happening is that data is so bad that the ECU can't use it. So the ECU would resort to "limp mode". But if the ECU was going into limp mode, it would recognize this as a fault and trigger the nice warm glowing Service Engine Soon light. Since you made no mention of getting a light, whatever is going on the ECU doesn't see anything wrong... which would lead me to think the ECU has tanked. Either that, or you have wickedly heinous grounding issue somewhere.

Those things aside, could be a MAF sensor issue too...

Good Luck
-RZ

 

[fstrnhm]

Are you back on 350Z-tech Ronin?

 

[warpspeedmrsulu]

I've got a new symptom! I'm now getting intermittent dashboard lights that shouldn't be there, but no check engine light. I'll typically get the 'VDC OFF' and 'SLIP' lights which will illuminate and stay on until the car is restarted--this seems to happen more often when the car is cold. I'll also intermittently get the 'BRAKE' light even though the parking break is not engaged...I'm assuming this is consistent with a problem with the ECU?

 

[idrm350]

The previous problem you mentioned could be the cam position sensor, I believe.

The "BRAKE" light is likely unrelated. It might be due to low brake fluid level in the reservoir due to normal pad wear, you should check the brake fluid level.

 

[warpspeedmrsulu]

The previous problem you mentioned could be the cam position sensor, I believe.

The "BRAKE" light is likely unrelated. It might be due to low brake fluid level in the reservoir due to normal pad wear, you should check the brake fluid level.

Thanks for the response!

Hmmm...do you think a shotty cam position sensor could account for the 'VDC OFF' and 'SLIP' lights as well?

 

[idrm350]

It can but normally, you get a check engine light along with them. Check out this thread:

http://www.350z-tech.com/forums/123-maintenance-repairs/68989-car-wont-start.html

The cam position sensors on our engines seem to fail quite often and produce frightening symptoms as they do so. The sensor can send intermittent signal causing periods of normal operation, periods of limp mode (probably what yours is doing) operation, or it just plain won't start.

Your best course of action is to gingerly drive it to an auto parts store (O'Reilly, Kragen, Napa, whatever you have) and ask them to scan it for codes (should be free). Diagnose from there using the wonders of the interwebs!

 

[willy]

...the BRAKE light comes on for reasons other than just brake problems... for example, I had a short in my alternator wire that threw the BRAKE light... It can possibly be caused by random missfires...

 

[warpspeedmrsulu]

...the BRAKE light comes on for reasons other than just brake problems... for example, I had a short in my alternator wire that threw the BRAKE light... I can't possibly be caused by random missfires...

Oh--you just reminded me of two other symptoms I have...sometimes the car doesn't start--this has been happening a little more frequently lately. Sometimes, you turn the key and nothing happens--electronics all turn on fine but it doesn't turn over, makes no sound--nothing happens. Other times it makes this weird whooshy-grinding type noise but doesn't start, but if I just try it a few times it will start completely normally after a couple tries. UGH...this car has been nothing but trouble.

 

[willy]

weird... also note I meant it 'CAN' not 'can't'... The starting problem I've heard before, something about the sensor that senses when the clutch is fully depressed...

 

[idrm350]

weird... also note I meant it 'CAN' not 'can't'... The starting problem I've heard before, something about the sensor that senses when the clutch is fully depressed...

That's true, your starting problem could be that. There is a button/switch on the clutch pedal that allows the car to start when the clutch is depressed. That could be going bad.

 

[pueblopete]

Not to stir up an old thread. But I have the same problem and was wondering what was the outcome of this?

 

[richardun]

I'm having this issue too. @pueblopete, @warmspeedmrsulu... what was the issue? Care to pay the knowledge forward?

 

[teclen124]

Hi all, I hope I can get some feedback on this really bizarre issue I've been having with my Z. It's an '03 (thus all the headaches) Performance model. The car has started demonstrating this really odd behavior which I'll attempt to describe as accurately as possible. When the car is cold, it starts and idles perfectly--but when you pull out onto the road and begin to accelerate, it becomes apparent that the car is not accelerating to it's full potential (not even close). There is no sputtering or hesitation, the car even seems normal for the first few seconds, but then power just stops coming. It almost acts as if it is registering the first inch of accelerator pedal depression, but no more. Once you hit this acceleration 'wall', the car behaves as though you are not depressing the gas any more, even if you floor it. The result is very slow, steady acceleration you'd get if holding the gas pedal in the exact same position for an extended period of time. As the car warms up, the problem manifests less and less. When the car begins to respond, if you floor the gas, you may initially get no additional power (as before), followed by sudden surges of power which start and stop, until eventually the car may seem to run normally besides the occasional lack of power. I took it to the dealer and they are having a hard time diagnosing the problem. First they replaced the throttle body, but that did not correct the issue. Now the tech at Nissan says it has to be either the main computer or the computer wiring harness--but this doesn't seem right to me...why would the behavior an electronic component change as the car warms up? Also, there is no Check Engine Light, and the computer is not throwing any codes. I'd hate to buy an expensive computer only to find the issue is not corrected. PLEASE HELP! WarpSpeedMrSulu is online now Report Post Reply With Quote

My guess is there is carbon build up ..may i suggest a good fuel injection clean and also gas treatment...i looked for what particular gas treatment for the Z and its a red canister that starts With a T...but long story short the carbon build up is whats causing it. Spray your maf sensor with the sensor cleaner just follow instructions....and maybe spray some seafoam in a vacuum line and watch all the carbon smoke aways thru the tail pipe..garantee your car will breath better