Newbie with transmission problems

[RICKY77]

I recently bought a 1991 300zx na. After changing an injector I hydrolocked the engine, I was going to rebuild the original engine since it only had 85000 miles but went with a Jdm engine and trans combo from zoon at dallas jdm. engine and trans looked great on arrival, put in new clutch pressure plate, throwout bearing, slave cylinder and clutch master cylinder. also replaced timing belt, thermostat, and water pump on engine. It is running great and shifting fine until it warms up. When it warms up it feels like i am pulling a trailer or something is holding me back. When i shift gears the motor will rev up but the car just doesnt seem to respond like it should, again like im pulling something, the motor will also start to die when i put it in neutral coming up to stop when this happens (i think that might just be an o2 sensor). I have adjusted the clutch at the pedal and master cylinder, so i dont think the clutch is slipping. I just wanted to see if any of you guys have any ideas or tips. This is my first Z-car, I have wanted on for 20 years and cant wait to get it back on the road. It is an amazing machine.

[300ZXttZMAN]

Welcome to nico!

I am going to move this to the Tech section.

[NolimitZ32]

When I read your title I was going to suggest you don't hang out in those kinds of bars

Does the car idle correctly? is it throwing any codes or engine lights? have you checked your timing?

[RICKY77]

The car does idle correctly, and it isnt giving any codes. I had to swap the throttle position sensor from my old motor because the jdm version wasnt compatible with my ecm. In order to do this i had to swap my throttle body on the driver side because the tpm mount is different. The car idles great and runs perfectly until it gets to operating temperature thats when it feels like you are pulling a trailer. It will still idle if i dont let the rpms fall to fast when i hit the clutch. If i put the car in neutral and the rpms drop, its like it tries to rebound from dropping but just cant. The whole thing is confusing me, It runs and shifts to good to be a major problem I just have to find it. I was hoping maybe someone has experienced this.

[NolimitZ32]

My money is on a vacuum leak.

I have never heard of the TPS and ECU not matching up. All OBD1 cars if in stock form should have interchangeable ECUs and TPSs

[RICKY77]

It could possibly be a vacuum leak. The balance tube on the jdm engine did not have a nipple for one of the vacuum lines to connect, like the adm engine had. I had to splice in a T. Do you feel like it is a vacuum leek causing my bogging problem? After about 5 minutes of driving it feels like the E-brake or something is on, motor id running fine, just wont really go. This is my firs z32, i have always wanted on just finally got one and I know you guys have alot more experience than me. I am just a weekend mechanic, pharmacist by trade. But the ECU would not recognize the JDM TPS, kept gassing the cylinders. First off none of the connectors matched up, went to put the ADM TPS on the JDM engine and it wouldnt bolt up, totally different, even in size. It was actually pretty difficult to get the JDM engine in. I was told all I would have to do is swap out the wiring harness, but that wasnt the case. The people at dallas jdm were great though, motor is in great shape and I received the engine 4 days after placing the order. I was very nervous after hearing all of the JDM horror stories.

[NolimitZ32]

Its USDM not ADM and I have no clue what the hell is oing on with your engine because mine is a JDM swap and everything is interchangable, the only difference between JDM and USDM is the oil pressure switch is on the opposite side. Maybe you got a OBDII late model engine, I've never seen one of those. as for the vac leak as I said I'd bet on it because thats how mine behaved when it had a massive leak, couldn't get it to idle, drove sluggish as a snail. Get a hold of if you have the money or build if you have the time an emission smoke machine, they are like the absolute greatest thing ever, makes finding a vac leak almost too easy.

[RICKY77]

Sorry I meant usdm. I'll see if i can get some picks of the tps because they are definitely different and how they mount to throttle body is different as well. Actually almost all of the connections were different. I feel sure it is a vacuum leak after a little more research. car runs great just sluggish once gets to operating temp, but still running fine, exccept for idling. I have found some vacuum line diagrams online and a friend that owns a junk yard just got one in, same year just an automatic. I can rob some sensors and vacuum lines from his car. what is an OBDII engine? Thanks for the suggestion with the smoke machine.

[NolimitZ32]

No need to be sorry, I'm just trying to enlighten. An easy way to check if its a vac leak is to disconnect the MAF while the car is running and warmed up and see if the idle stabilizes, then go for a light drive around the block (you will be in limp mode so it wont go above 2500RPM IIRC) but it should pull somewhat normal up to 2500. Also it may be a bad MAF if it's not a vacuum leak. OBDII is On-Board Diagnostic phase 2, introduced in 95 and made a requirement for all new cars sold in the US market, in 96. The 300zx was last sold on our shore in 96 but was on sale in Japan till 99 so there could have been other changes to the electronics that I don't know about (though thats not likely, I've studied these cars extensively). AFAIK only the Injectors, the PTU, and the CAS were ever changed.

[RICKY77]

Thanks again for all your help. I just can't wait to get it back on the road. Which I'm driving it now. It runs perfect and pulls perfect until after about 5 minutes, then it still runs fine it just feels like brake is on or something.

[NolimitZ32]

No problem, GL, let us know if this doesn't solve it.