Ok so bought a 1991 300zx Twin Turbo Manual recently and the issue I am experiencing is at first I thought it was only when warm it would limit RPM to 2.5k and lose all power. After that it would either stall or return to 900rpm and if I put it in gear it would stall or not allow me to go over 2.5k rpm. If I leave it all night or a couple hours I can drive it for 5mins no issues at all. But the moment I have to hit a stop light after that amount of time it will do this cycle. I normally pull to the side of the road and turn off the car and wait a while before trying again. Some times Ill get lucky and be able to start right back up to no issue or try 50 times till it will let me pull away again. Just recently It has been to the point where I can let it sit and it will start doing this on cold start. It will also pulse in RPM or bounce when this is happening. Im sure I have left a detail or two out so please ask more questions if need be.

I have poked around at the TPS, when I tested it the reading was .49 so I adjusted it to .44/.45 However when throttle is fully open it peaks at 4.3 on the multimeter.

I will be trying to check the MAF tonight but not sure how I will go about it.

Background of the car is its had a top end rebuild from a blown headgasket from prior owner. But he stated the issue was happening way before that. It has 740cc injectors installed, Z1 eprom chip, greddy boost controller, nearly all new piping and hoses from Z1 installed, its pushing more than 14psi as I can see on the aftermarket boost gauge I think 16psi and it has had the PTU relocation done and a couple of deletes as well like HICAS with an NA rear.

If anyone out there can help me track down whats wrong that would be great. I can get the job done mechanical wise just detailed explanations are key with me or explaining like im 5 works as well. Things I think it can be is a limp mode or MAF issue. I ruled out TPS but it still could be bad because a couple people said it should open to 5.0 not the 4.3. But I need your guys help and legit would forever be grateful. Please for the love of muhala help me out. The car is a beast for the limited time I can drive it. Love it.

It seems to absolutely be limp mode, nothing else would specifically limit the RPMs so precisely. The question is what is causing the limp mode, sounds like it actually could be MAF related. The FSM has a great troubleshooting procedure that you can use even on tuned vehicles. Check the link in my signature and follow the troubleshooting procedures.

NolimitZ32 wrote: ↑

Tue Apr 13, 2021 5:12 am

It seems to absolutely be limp mode, nothing else would specifically limit the RPMs so precisely. The question is what is causing the limp mode, sounds like it actually could be MAF related. The FSM has a great troubleshooting procedure that you can use even on tuned vehicles. Check the link in my signature and follow the troubleshooting procedures.

Alrighty so I did some tests and when it was having a fit I unplugged the MAF sensor and the car kept running. I believe that signals that it is bad so I will start there and see if it changes. That FSM was spot on. Love it and thank you for the info. Hopefully this does it, I ordered the MAF from Z1 and will arrive by thursday so fingers crossed.

I help when I can, please do me a favor and post your results when you've resolved the issue for posterity.

Ok so with TPS, Boost Leak Test and a new MAF sensor from Z1 the car runs like new. I think the major issue was the MAF and I highly recommend replacing it when having idle issues after cold start. Z1 has the cheapest alternative to your local dealer. $250 at the time of writing this when my local dealer wanted $780 for it. Thats bonkers and I would not recommend getting it aftermarket if you have a TT just incase something happens with tunes or something. So All in all thank you NolimitZ32 for replying and for anyone lurking make sure to swap out your MAF. No begins my journey with a z32TT and im excited!