Hello gents have a very strange issue with my 300zx. Its a twin turbo auto, 100k miles and has pretty standard mods (cone filter, decat, remap). I have just replaced turbos due to smoking and car was running fine. I have had this issue on and off since i have had this car. Basically it is very intermittent power loss. The car will run faultlessly fr a week in a row, then you turn the key and it takes half throttle just to move off. Feels like it is pulling a tank! Last time it happened i ran the car, had the issue. Then turned it off and on again and the car was back to normal completely.

At first it would only happen once a month or so but now happens every few days. The car is not misfiring at all however it idles slightly rough. Im going to check tps, install a new coolant temp sensor this week as well but im just interested in whether anyone else has had a similar issue to this and has any input. I have fixed numerous issues with the car and had hesitation issues before but the very intermittent nature of this problem is very confusing. Also forgot to mention this happens whether the car is hot or cold, and happens completely randomly

You hear about a lot of dead MAFs playing up like that. When it's doing it unplug the MAF and if it doesn't change, that'll be it.

 

It might not be fully dead just on it's way out or damp/wet on the hot wire.

Cheers tom i actually never thought that the maf could be intermittent. Ill try unplugging it when it happens again

hey,

not sure if you've seen this before...

http://twinturbo.net/net/viewmsg.aspx?forum=technical&msg_id=922678

 

I found it crucial to endure all connectors where secure and clean as well.. the MAF can be cleaned as well..

Hi there medallion thanks for that article. I have seen that and live by those rules haha. All the connectors are crimped and clean as ive had issues with misfiring in the past. Just so odd thats its so unpredictable

agreed... sometimes it's a nightmare tracing a very small fault.

 

so many possible contenders...

 

MAF, PTU, TPS, ECU, coil pack, fuel, earthing... etc... best of luck.

Thanks medallion. Do these symptoms sound related to the coolant temp sensor? Ive also noticed that the car doesnt idle higher rpm when first turned on, it just idles at normal 800 rpm from turning the ignition

I assume you mean the ECU temp sensor unit (two prong one).

 

if it works correctly it should be telling the ecu exactly that.. so worth a check, connectors, wire and connection to ecu.

 

http://www.karljapetre.com/z/ecu/

Basically it is very intermittent power loss. The car will run faultlessly fr a week in a row, then you turn the key and it takes half throttle just to move off. Feels like it is pulling a tank! Last time it happened i ran the car, had the issue. Then turned it off and on again and the car was back to normal completely.

 

Nothing wrong with the engine! whats happening is your autobox is going in to limp home mode and selecting third gear only, that why it needs more throttle to pull away and the feeling of dragging a tank, ignition off/on just resets the aufo box ecu. So what you have is an electrical issue with the gearbox, could be a simple low voltage at start up causing the issue as the ecu does not react well to low battery voltage. There are numerous things that can cause it but check your battery terminals and ensure its fully charged.

Failing that use the inbuilt diagnostic to see if there are any codes stored.

 

Jeff TT

Hell jeff, i remember when it first happened that it felt like pulling off in a high gear as the engine revs high but theres not much movement. I have literally cleaned and crimped everything in the engine, replaced a fair few sensors as well. Ill go and clean my battery terminals... just remembered that i get intermittent speedo cutting out as well, do u think it could possibly be the speed sensor causing both issues? Thanks for your input guys

Lol i meant to write hello jeff not hell:)

Its for sure a problem with the auto box going into limp home quite why is the next thing to solve, do you get any flashing lights from the power/auto when thE problem occurs at start up?

 

 

Jeff TT

Hi jeff. No i dont have any flashing lights on start up. However i just tested the box for codes and the light pattern corresponded to throttle sensor circuit failure. Is that the tps by any chance?

Hi jeff. No i dont have any flashing lights on start up. However i just tested the box for codes and the light pattern corresponded to throttle sensor circuit failure. Is that the tps by any chance?

 

Yes, to get a code means either intermittent open circuit or short, bad adjustment will not show a code.

 

Jeff TT

I guess thats a new tps then. Anyone have an idea on price? Would the tps issue materialise in any other way as well? Could it also be causing power loss which coincides with the autobox safe mode? Thanks again jeff

Also, would ppl recommended buying a new tps or are used ones ok

Tps are not expensive new around £50 but you will need to know if its actually gone or is a bad connection/ cable fault or even an old code, worth leaving the battery disconnected for a few hours to reset and try it all again.

 

Jeff

Actually mate you are 100% right. I forgot that i wiggles the tps connector while car was running and that probably threw the code. Ill reset it and try again but it probably wont come up again.

Hi guys i reset the ecu, cleaned up the terminals and earthing points and there are no error codes anymore. Took for a drive and it was fine, hopefully it was just a case of bad voltage. Might fit an earthing kit as i have a hks one somewhere. Do people think its better to install the earthing in sequence or spider style?