Hey guys!! So I have a 2004 G35 AT coupe and I just put a 2006 sedan engine in it. I replaced the water pump and timing chain sprocket, guides, and tensioner. I also added ART pipes, and DC Sport headers with new updraft O2 sensors. I hooked the engine up and it cranked, but sounds rough and the idle is extremely low and dies within seconds. I've checked all my hoses and connections, and there is no codes being thrown so I am at a loss at what the issue could be. It smells rich in gas after it tries to run. Any help would be appreciated. I've tried to clean the MAF and Throttle body but nothing makes a difference. i have also tried ECU reset procedure, throttle body idle air volume relearn procedure, throttle body close position relearn procedure, and accelerator position relearn procedure but nothing seems to work. The car immediately dies if I give it any gas and the rpm never increases. I'm at a total loss on what to do next.

 

Try putting the original engine back in.

Telcoman

 

Im no genius , but i have the 07 G35 6spd rev up motor and i know 05-07 is the rev up , im guessing your running that same ECU for the 06 motor right ???

 

I'm using my original 2004 coupe Automatic ECU, which I thought would work fine because the "new" motor is a DE from an automatic sedan, not a rev up

 

Did you replace EVERYTHING including fuel rail/injectors, throttle body, etc when you did the motor swap or was it just a long block? Sounds like a fuel management issue, probably a big vacuum leak somewhere.

 

I used my old throttle body, upper and lower plenums, cool packs, valve covers, and intake. But the fuel rails and injectors are from the used engine I swapped. It smells like gas after it turns over so I know the fuel pump is working and the car has half a tank of gas. Maybe I'll swap the injectors and see if that helps.

 

Another idea, and it's a pita to check, is an improperly aligned cam/crank/chain. If it runs as bad as you're saying then it's something major and shouldn't be too hard to find. Lot of teardown though, how SURE are you that the cam timing was correct when you installed the new chain? If you're off by one tooth on the sprocket it's not going to run.

 

So I've been tinkering all day and I found a hose from the intake to the valve cover that was pinched. I straightened that out and the car now will run roughly and is less prone to stalling, idles at 400rpm. No smell of exhaust or gas. I haven't checked the injectors yet. When I put new water pump, guides, crank sprocket, and tensioner on the camshaft lobes were facing inwards like they should be for the exhaust stroke and all the timing marks lined up. I took reference pics of the chain and made sure everything was exactly how it was before sealing it all up. In retrospect I've got that 2% doubt since I'd never done anything timing related, but I'm pretty positive I didn't get it off by a tooth. Also I never touched the cam chains

 

I think if you're engine was out of time it would also set off a code.

Do you have a scantool or vacuum gauge? See what your vacuum is while running. I think it should be around 22hg and when I had a huge vacuum leak it would fluctuate. You also want to monitor your long-term and short-term fuel trims. Short-term should be constantly changing, close to 0, and +-10% of each other. Long-term should also be close to 0 and +-10% as well, but should slowly change.

Try unplugging the MAF and monitoring the same data. It should default to very rich condition and set some codes.

Are you sure the idle relearn took? I know when I had to do it once it took forever to get the sequence correct.

How about the engine harness? I don't know if it would cause a problem, but I know on some vehicles they make slight changes that can cause issues.