We just finished putting the engine back together from a rebuild, and now a lot of fuel is exiting through the exhausts in the form of fluid and gas. We rev it to like 2k and the exhausts literally spit out fuel.

Injectors and fuel pump have been replaced. No other leakage.

We did find a few error codes: bad cam sensor (bank 1) and oxygen sensor (bank 2). I am going to buy replacements for these ASAP but I don't think this would cause such a huge amount of fuel going out unburnt does it?

Does anyone know what is going on? Pls advise.

Happy Thanksgiving, btw.

 

Cam sensor for sure.If you are running cats,they prolly are clogged or gone.

 

Man I hope you're right. I don't want any more headache. lol

I got non res TPs so that's one less thing to think about

thanks.

 

Keep us updated

 

Update:
Changed the cam sensors and the car is still having the same problem.

Diagnosis procedure: Took out the injectors, still attached to the fuel rails and see how they behave.
Observation: one of the driver side injectors gives out max voltage reading, spraying fuel at maximum pressure. This happens the moment the ignition is switched to On mode, flooding the cylinder.

Injectors are not grounded either.

Electrical specialist is looking at the wiring on the ECU connectors.

More to come

 

I always l thought unburnt fuel that exits into the exhaust will come out as fireballs and not.....well....actual unburnt fuel lol.

 

^lol. Not enough powah i guess.

Ok more update.

We eliminated all the possible causes. IE: we changed cam & crank sensors, o2 sensors, got new injectors, new fuel pump and most importantly... another engine harness from a currently working Z. We had a hunch the old one was grounded (even though tests showed no signs).

After all of these were replaced we are still getting the same issue.

Here you can see Injector #4 is fully opened the moment the ignition is in "ON".


So now the question... is there any possibility that the ECU is causing this?

Background on this ECU: This was reprogrammed and tuned by a popular VQ specialist based in Florida. I sent my old one so they can take a look at it and was confirmed, toast. So they gave me a used unit, got the NATS removed, "mail tuned" it with with Uprev and sent it to me back in Dubai.

I phoned up my buddy to bring over his Z tomorrow and test the ECU on his Z one more time.

I need some feedback on this guys. Help me out pls.

 

The injectors are connected to + voltage all the time & gets activated by receiving ground signal from the ECU. You said you replaced the injectors & they are fine, So that makes you left with either the harness or the ECU.



Looking at the diagram above, If ECU pin # 41 ( injector 4 ) is grounded all the time, Then most likely the ECU is fried, Use a voltmeter and try to take a measurement as close to the ECU pins as possible.

Good luck,

 

Thanks a lot for the input, amr.

I am not sure if the tech has done that but he did mention to me that all the wiring do not show any fault at all. We even swapped a full engine harness from a perfectly running car and got the same result.

The ECU was never used on any car after I got it from the shop in US. Since NATS is disabled we decided to plug the ECU in my buddy's perfectly working Z. As I have feared - his Z started blowing fuel out of the exhaust. It happens within 10-15 seconds after the car is started.

This really concludes that the ECU I was given is bad. I'm sending an email to the shop and hope they will let me return the unit to get a replacement.

 

That sums it up pretty well, But could it be incompatible ECU ( not a bad unit ) since the one you got is USDM and i think you and your buddy's cars are gulf spec ?!!!

I've always heard that you should replace the ECU with one that has the same #.

 

This was my very first question when I contacted the tuner, actually. THen I was promised that the ECU will work on any VQ35DE regardless of where it comes from because NATS is disabled (Uprev Osiris software).

Also, my buddy's Z was imported from the US lol. Mine is Gulf Spec.

I just sent an email to the shop in FL that sold me the ECU. I hope they replace it with a working unit.