ByThaBay

Hello all,

First some background on the car. It was flooded back in 2010 in fresh water and the engine hydrolocked. I put in the following new parts:

Known good engine and automatic transmission from a 2003 350z
All new gaskets and seals
New water pump
new supsension (most of it)
new brakes
all new fluids
new spark plugs
new belts, etc.

The problem I have is that the car does not want to accelerate. The RPMs rise very slowly, even in neutral, compared to how they should rise when compared side-by-side with another Z. There are no codes stored and all the monitors are set.

I checked all the sensors as best I could and everything matched up fine with the donor car (ie, throttle sensors..). Ignition timing is at 18 and idle speed is at 650 rpm in Park.

I tried replacing the throttle body with a few different units, that didn't make a difference. I also replaced the mass airflow sensor with another good unit.

I'm pretty much out of ideas at this point. The car will maintain any rpm just fine and will cruise down the highlyway, but it takes like 30+ seconds to get up to the correct speed because the engine rpm goes up so slowly - like the ECM is telling the transmission that I am at WOT, but only manages to tell the engine to accelerate at 25% effort.

I am thinking it's a bad ECM - any ideas?

JaE35z

iTrader: (11)

Look into replacing knock sensor and harness

ByThaBay

rechecked both knock sensor and harness and both check out ok

ByThaBay

I am considering trying on a different set of cats... would I see a catalyst efficiency error if my current cats are clogged up?

Philly_G35

Have you tested/changed the Accelerator Pedal Position Sensor. Mine went in my G35 Sedan and the symptoms were similar.

ByThaBay

Yes, I looked at that sensor and it appears to be functioning properly based on the graph representation. Also, when I drive the car, the transmission shifts at the right points given the position of the gas pedal. Basically I can give it 1/3 throttle and it shifts normally, if I give it WOT, it accelerates like it's 1/3 throttle but transmission shifts at the WOT shift points, just takes forever to get to those points with engine speed remaining high for long periods of time in between as car picks up speed.

ByThaBay

I've ruled out a transmission issue as well due to the fact that the engine behaves the same even in neutral. revving at 1/3 throttle vs WOT produces same effect.

ByThaBay

I went to try on a new set of cats last night, only to find that one of my donor cats has one of the studs seized and I couldn't get it out. I'll probably have to drill the stud out if I want to use that cat. In any case, I already had my old cats out, so I took at look at them and they both looked like new - no issues on either the inlet side nor the outlet side.

Still no check engine light , all monitors are ready.

Philly_G35

I don't recall if I ever went WOT to remember the shift points. My dash turned into a Christmas tree when mine failed so I was able to pull a code. I also tried the Accelerator Pedal Reset and Throttle Position Reset procedures before I ordered the part.

When I was in neutral it didn't seem like it would ever reach red line when I revved the engine, the RPM's climbed very slowly.

Good luck solving the problem.

ByThaBay

I was looking at my VVT tonight and I don't think it's working right...

ByThaBay

I think I figured out why my VVT is not working and there is no check engine light on. Simply put, the ECM is not trying to turn on the VVT. The condition for the CEL to come on is only monitored if the ECM is trying to use the VVT. When the VVT is not in use, there is no reason to check the condition for the CEL. I believe the ECM was shorted out during the flood incident and this is causing it to NOT enter the section of programming where VVT is activated and monitored.

Ordered a new ECM, will post results once new ECM is installed.

ByThaBay

Looked over the VVT, looks like it is working after all.. but throttle is certainly being restricted. Tried a new ECM today but it didn't fix the problem. Checked fuel pressure at idle and under load, checked out ok. I've been reading some strange posts about LED tail lights causing similar issues (ie, throttle cut without warning) - perhaps the lo jack installed in the Z is confusing the ECM or maybe the aftermarket head unit is causing an issue?