Hi, I have a 2003 G35 sedan. Engine went bad and shop installed a 2004 Engine. Do not know if computer was changed or needs to be. Car ran fine for a week. Now it runs fine to 40mph but does not go any faster. Sometimes it will do higher speeds but for most part it does not go over 40MPH. Trying to find out if they use same computer? Could this be a computer failure and if so what computer do I get? Or is this Tranny problem? Any help or guidance to get my car back at 100% would be greatly appreciated!
Thank You

 

Sounds like the shop forgot to plug something in all the way, take it back.

 

The shop that did the work should be figuring this out. Sounds like the engine is in limp home mode.

 

I had the shop in New York do it. You know a friend of a friends shop. Well I had the car shipped to Florida where I live. After using it for a week or so this happened. So I can not bring back to shop unless I want to pay 1100 to ship it back. So If possible can I get some help with this.
Thank You

 

Scan the ECU for codes. It's possible the ECU is throwing a code but your CEL isn't lightning up on the dash. Bring it to any auto store they will scan it for free

 

Have you checked under the hood to see if any plugs have come loose?

 

I am not familiar with this car. Where do you suggest I start looking for loose plugs. Any guidance is greatly appreciated.
Thanks

 

Any of the electrical connections you see. Everything you think would need to be unplugged then plugged back in during an engine swap. You'd be surprised how often a loose connection is overlooked. I swapped a 455 into my '77 Cutlass. Was sure we'd double checked everything. Turned the key and nothing. No lights, no start, nothing. Next morning I was poking around and saw a single wire hanging down. The wire went to the starter. Connected it, my car fired up immediately. So check things like the plugs on the cam/crankshaft position sensors, MAF sensor, etc.

 

Just took car out for a drive after changing plugs. Noticed I could do 60 or 70 but RPMs would be at 4-5000. Also I had to take it easy to give it a chance to shift to go that fast. So not shifting well. Put my code reader I recently purchased and had a code P1716. Please suggestions on what I should do. I googled and it said something about Turbine sensors. Needing a new tranny. Before I do this just want to verify this with you guys first. Again, I want ot thank you all for such great help you been.
Thank You

 

Well, there's 2 of those sensors that are both part of the valve body. You can at least check the level of your tranny fluid with the car warm and running. Or, drop the pan and check for metal flakes. Usually it seems that the lower gears are under the most stress and are the first to go. As much as I hate the dealership, I would get the car over to one so they can hook it up to consult 2. They can at least hook it up to review live data on anything that is going on in the transmission, check fuel/air, or any other related sensors. Or you could buy NDS2 and review the tcm data and I could compare it to mine