Axel

iTrader: (3)

I'm losing a huge amount of power. No computer codes. It's not the spark plugs, not the coils, not the y-pipe. This is a 2000 5 speed SE.

According to the dyno, there's a big sudden loss at 3500-3800 RPMs both in TQ and HP.
I know VI kicks in at 5000. Anyone know if anything kicks in at 3500-3800?

Here's the dyno:

Sprint

iTrader: (10)

those are some weak numbers.. the only thing i can think of with a dip in dyno chart like that is clutch slippage..

Axel

iTrader: (3)

No, no clutch slippage either unfortunately (I wish it were that simple)

RedbeardMax

i have 95 auto and have slightly better dyno...

something's wrong with your max for sure.

Axel

iTrader: (3)

That's an understatement

The dealership is clueless. Heck, everyone's clueless about this issue. If at least the computer spat out some kind of code.

Oh, and it's worse now than it was when the dyno was run 3 weeks ago.
Soon I'll be slower than a Geo Metro...

IceY2K1

iTrader: (3)

Do you have an OBD-II scanner or know someone who does?

You should consider getting one from www.obd-2.com to help find out more details.

I need more clues before I can give a diagnosis. Good luck!

Axel

iTrader: (3)

The dealership did all that and nothing came up. The car thinks it's running just fine. That's the problem. The symptoms are loss of power and the dyno is the only thing that shows where the power loss is. There's nothing else to point anyone in the right direction...everyone is clueless due to the lack of symptoms.

IceY2K1

iTrader: (3)

1)What EXACTLY did the dealership do?

2)Is it possible for you to take it to another dealer?

3)Have they hooked up a Consult-II and test drove it?

4)Do you have ANY modifications?

5)What does the power loss feel like? Surging? Slow revs? Smooth as butter power just not as much? What?

More details of what is happening might help.

SteVTEC

whoa! That is one fcuked up dyno chart!

Things that make you go Hmmmmmmmm...

What happens at 3800rpm on a VQ30DE-K? Is it some sort of closed-loop => open-loop ECU operation crossover? I suspect something in the ECU. Either a blown sensor or something like that that somehow is not tripping any codes. It would have been interesting to see what your A/F curves looked like on the dyno. Does the car suddenly get EXTREMELY rich (ton of black smoke spewing) right at 3800rpm?

Anyhow, since everything looks A-okay before 3800, I'd say it's definitely something electronic related.

njmaxseltd

iTrader: (19)

I notice you have a CAI, when is the last time you cleaned the air filter? I've heard a couple of guys on here talk about how quick that filter gets dirty.

SteVTEC

dirty filter would not explain how the engine runs fine before 3.8k, but like shia after 3.8k.

Axel

iTrader: (3)

The CAI is quite new. The problems started happening prior to the CAI though. Just not as noticeable. It's been gradually getting worse.
Would an electronic thing cause a gradual degredation? I would think it'd be instantaneous no?

Sigh...I've received a lot of advice anywhere from electrical (ignition) to fuel delivery to ECU, to exhaust to CAI (the list goes on). The problem is that no one seems to have ever experienced something like this before. In the end, it looks like trial and error is the only way to go.
Maybe I should swap out the ECU with a similar 2000 5-speed...?

JeffesonM

iTrader: (5)

that would help narrow down the list of suspects

IceY2K1

iTrader: (3)

OK, I'll ask ya again.

Did Nissan hook up a Consult-II and DRIVE the car? Yes or no?

I wouldn't normally suspect the ECU, but since there are no codes I don't know how that could happen without something being out of spec..

Axel

iTrader: (3)

Yes they did, they hooked it up and drove the car with me in the car. They ackknowledged the power loss immediately (hard not to notice). However, since the computer showed no errors, they don't have much to start with. They contacted Nissan Tech line (or whatever they're called) and even faxed them the dyno graph shown above. I'm calling back this afternoon to find out if they've gotten anywhere although I doubt they did. (Last time I called they hadn't.)

IceY2K1

iTrader: (3)

Ok, well that helps IF they know what the hell their doing, which I'm not buying just yet.

With a Consult-II they can and SHOULD have monitored ignition timing vs. rpm/load and injector pulse width. Plus, 02-sensor and MAF readings. These would pretty much eliminate the MAF, knock, and 02 sensors.

I'm thinking you've got a bad injector(s), but I would think that would throw a code. Maybe not, I'll check my ESM tonight.

Otherwise, my guess is malfunctioning coils that crap out above 3800rpms, but you said they check them.

Dave B

First off, your VIM is not working which seems to be a major problem with the 2000-2001 plastic manifold. There's a reason Nissan went back to a cast manifold in 2k2. Notice how your power stops at 5600-5700 and then falls off? Power should travel straight to 6500rpms.

Second, there is something majorly wrong because even from the start at 2100rpms, you should be making over 170fwtq and 70fwhp.

A shadetree mechanic can test the coils, check the vacuum, and verify that nearly every sensor on the car is working.

To test the coils you must remove each one and test the resistance with a voltmeter. A voltmeter can test the knock sensor, O2 sensors, etc. The only downside is that you've got a 2000 and Chilton's only makes manuals for the 95-99. I don't think much changed in the way of sensors between 95-01. You should be okay with the 95-99 manual.

Vacuum can be tested using a simple vacuum gauage connected to the vacuum line on the fuel regulator. Vacuum should be steady at 16-22Hg at idle and drops when the throttle is opened. If the vacuum bouncesit or reads low or doesn't drop with throttle application, you've got problems.

$15 Chilton's
$15 voltmeter
$30 vacuum gauge (MityVac model)

= $60 and you can check nearly every system on your car and save a TON of money and dealership aggrevation.



Dave

Sly

Does your 2K have Cali emissions or fed-spec? The NLEV (cali-spec) VQ30DEK intake manifolds have a "swirl control" valve that activates at around 3200 rpm. Below 3200 rpm it's partially closed to create a swirl in the combustion chamber and burn fuel more efficiently. But after 3200 rpm it's supposed to open fully. It could be stuck closed, causing a restriction and screwing up the intake efficiency. BTW, this is a different valve from the "power" valve that activates at 5000 rpm and is on all VQ30DEK manifolds.

Axel

iTrader: (3)

Unfortunately in this case, I have a fed spec...that was a good suggestion though.

IceY2K1

iTrader: (3)

Have you checked your flex section on the Budget Y-pipe?

I believe they don't use the mesh inner lining, but just incase I'd check it.

Axel

iTrader: (3)

Yeah, it's not the y-pipe, that's already been checked...

NotNew!!NewSN!!

Well im gonna say the things in the past that have shown the same dyno's.

Clogged Cat
Knock sensor

Both of those have shown the same type of dynos.

Axel

iTrader: (3)

The y-pipe has been disconnected from the main cat. The main cat and the y-pipe were visually inspected and the car was driven with the main cat disconnected. Although it was loud, the car had the same loss.
As for the knock sensor, wouldn't that show up in a computer code..?

IceY2K1

iTrader: (3)

How was it driven with the main cat disconnected?

FED emission Maximas have an O2-sensor after the main cat and it would throw a check engine light. Are you sure they drove it? Was this when you were in the vehicle?

dwapenyi

iTrader: (3)

I'd check coils, plugs, and maybe your VIAS is stuck open in high rpm mode, un-like the others I've seen here who've had theirs stuck in low rpm mode.

DW

IceY2K1

iTrader: (3)

If that was true, I would expect the low end to be crap, but the top end to be fine.

I suspect if it's the VIAS the valves are stuck partially opened just enough to allow the air to travel through the longer runners(less resistance than shorter) until ~3.8K, but then the turbulance causes resistance and the air starts to travel through the short AND long runners. So, the short and long runners are partially flowing.

Just a GUESS of one theory of what MIGHT happen, because otherwise if the power valves failed in the fully closed or open position, we would see that in the dyno.

Jeff92se

iTrader: (82)

Just a note: Just because there are no codes, doesn't mean all the sensors are working correctly. I think we need to get past that one.

A fubar'd vi sounds like a possible cause. I would say a lazy 02 sensor also. How's your mileage? Worse after the power loss? It's too bad you didn't get the wideband 02 sensor option on the dyno test.

I think those obd-II readers are cool and fairly inexpensive. It might show your a/f, ingition timing and injector pulsewidth?

IceY2K1

iTrader: (3)

Any agreement/disagreement on a clogged/stuck/faulty injector?

If the injector is not producing fuel, what would happen? The bank of cylinders would be read by the 02-sensor as lean, right?

If so, then the ECU would add fuel enrichment until the 02-sensor was happy and the other two cylinders would be WAY rich causing the power to drop, right?

Jeff92se

iTrader: (82)

Hard to say becuase I don't he's mentioned how his car is running nor has he removed the plugs to see if any are black/wet/odd colored.

From what I read, I think the dealer just scanned his ecu for codes. I don't see where they actually sat there and looked into the injector pulse-width/ignition timing/02 sensor. In fact, maybe his detonation sensor is reading something other than knock and is pulling the timing back.

Axel

iTrader: (3)

The plugs have been changed. The original plugs were fine.
As for everything else...who knows...

Would all your suggesting cause the dyno to show up like an EKG?
Low power with a smooth curve is different than low power with a continuously spiky curve. Am I making any sense?

IceY2K1

iTrader: (3)

http://forums.maxima.org/showthread....ed+fuel+filter

IceY2K1

iTrader: (3)

A clogged fuel filter!?!?!?!

How many miles do you have and WHAT maintenance have you performed and when?

I'm going to figure this one out damn it!

Jeff92se

iTrader: (82)

Well Ice's link had more detail. But there isn't any detail about what the timing is doing and what the injectors are pulsing. I'm leaning towards the VI right now. Anyway to rig it open to see if the high rpm power comes back? Thing is I think I've read that the flaps inside the manifold get stuck either way. Dunno. Costs 0 to try. Just zip tie it open.

Axel

iTrader: (3)

33,000 miles and regular scheduled maintenances as per Nissan's recommended service intervals. This is the first issue in 3 years I've encountered with the car.

Jeff92se

iTrader: (82)

Where did you get your brake lines for your 300z upgrade? /Thanks

IceY2K1

iTrader: (3)

Hmmmn. Did you ever get the fuel pressure tested?

My bet is fuel delivery somehow, either the injector(s), fuel filter, or maybe even the pump.

Once they test it maybe we can get somewhere.

dwapenyi

iTrader: (3)

I thought the 5th gen Max does not have a replaceable feul filter.

DW

IceY2K1

iTrader: (3)

Looks like we do:
http://catalog.nissan-auto-parts-sto...e=NI&year=2001

Axel

iTrader: (3)

From Nissan dealership (the entire brake kit was provided by the dealership).

Axel

iTrader: (3)

They claim they can't test the fuel pressure.
It's a little confusing. Nissan Tech wants to know the fuel pressure but the mechanics say they weren't given the proper tools to test the fuel pressure for a 2000. Sounds weird to me but this dealership isn't the type to give me the runaround so...?
In any case, they asked me to come back in so I'm going over on Friday. Hopefully, they'll be able to get further with this.