300zx Stalling/Cutting out Whilst Stopping/slowing down!??

So for a while now I have been having this problem where my 300 will cut out while I am coming to a stop or slowing down?

I believe I have narrowed it down to the Throttle Position Sensor having a lot of green corrosion so I have given it a thorough clean and it seems to have helped a lot but I am still going to replace it in the next few weeks.

However it may run alright and not stall/cut out/hesitate/stumble/anymore or very rarely now that I have given it a good clean it seems to do it only when I have the AC on and Im coming to a stop or slowing down. Also if I turn the car off or it cuts out with the AC on and I try to start it again the car will have extremely irradic idle or just cut out again? Loving it! Haha

Any ideas of what this could be and how to solve it would be muchly appreciated!?

 

You've done well diagnosing & rectifying the corrosion issue with the TPS connection.
It's possible other connectors could be in a similar condition, CAS, Coil Packs, Injectors, CTS for example.
Check every connector you can find & verify its condition.
If the connectors break, due to ageing & being brittle, replacements are available.
Be careful with the wiring, too much flexing can cause a broken wire, it may be worth checking continuity after checks/repairs have been completed.

 

Thanks! I have been slowly and painfully learning about my Z. Haha

Yeah the weekend before I took off all the easy to see and get to sensors and cleaned them. Most are alright as the engine had been rebuilt a little while ago and some but not all connectors had been replaced but I still cleaned/sprayed then anyway. I still have to check most of the sensors you have listed so thanks for the heads up.

 

Are you running a POD filter on your intake? I used to have this issue on my old zed when running a POD, I went back to the stock intake box with Hiflow filters and the problem went away.

 

That would be a negative. Stock.
Although i was thinking about getting one.. You might of just changed my mind though..?

 

Just to add to my original post:
My 300 also surges. When I am sitting in the garage in neatrul I can push on the accelerator and take the Revs up to around 1900 (its just slightly below 2000) RPM and the car will start surging, the Needle will start jumping up and down. You can feel it throughout the car. As soon as you go past it slightly to say 2000RPM it will stop surging and run perfectly agian and same goes for sitting under that certain mark.

Any ideas?
Has or does anyone else Z do this?

It's a 1989 Z32 N/A Manual for anyone who wants to know.

 

Next thing I would be checking for is an air leak. Check all the hoses and clamps.

 

http://zhome.com/ZCMnL/PICS/hesitation/hesitation.html

 

Pull off the IACV and AAC valve and clean them. You may have a build up inside not allowing the valves to adjust quickly enough to keep your base idle steady when coming off the throttle.
Had a similar issue with mine.

 

My Z dogs that a couple of times due to having a series 1 PTU. Issue was fixed after series 2 PTU install. Hope this helps

 

Thanks for all the replies and ideas guys!

I will have to start seriously looking for the issue when I get time after Chrissy.

Thanks again!

 

Wasnt that a recall or something? So I get it for free right? Haha

 

Definitely been wanting to do this! Is there a good write up for this? In the tech section or something?

 

Only in US.

 

Oh of course! Haha

 

iacv idle air control valve

First things fist, have you checked the fuse for iacv? If not pull the plug from the Iacv unit, it is the top one the lower one is for air con idle up, turn the ignition on and check for 12volts on one of the 2 pins, actually should be battery voltage so around 14volts. If ok you need to check the Solenoid with the ignition still on plug it back in you should hear it click, if not pull the whole unit off and clean as previously mentioned. Good luck.
Just for information the iacv unit does more than just control idle I believe the ECU uses this valve to control some of the air fuel mix, the ECU does this by the earth side by giving timed pulses the shorter the pulse the less the valve opens, longer pulse will allow more air. Could answer the surge issue!

 

So this morning i found a hose that was disconnected. Hooked it back up and took it for a drive and it doesn't seem to make any difference to when it was disconnected...

I am almost certain my car stalling/cutting out is due to the TPS as it hasn't done it since I have it a good clean although.. I shouldn't say it hasn't because it only does it now when the AC is on. The car stalls while coasting with the AC on almost 6 times out of 10.

Plus the other thing is I have read the write up on how to adjust your idle using the IACV/ACC or whatever that screw is multiple times and I have followed it step by step multiple times but my idle does not change.. So basically the screw has no effect on my idle at all? The only way I seem to be able to adjust my idle is by adjusting the TPS.

At the moment my idle is sitting AROUND 700RPM with the TPS volts reading about 0.45 give or take however I would like to adjust my idle up just a fraction more.

 

Spent the whole day messing with my car.
Pulled the IACV off and cleaned it up put it back on and I am now able to adjust my idle.
Sprayed some carby cleaner through my Throttle Bodies.
Found a disconnected hose and reconnected it.
Found a crimped hose and moved it.

However I believe my FICD is stuffed as my cars idle becomes erratic when I turn my AC on and only seems to stall/cut out when coming to a stop or coasting with it on.
Would I be right in saying this?

Found a few other things wrong with other sensors and connectors and resolved them but it defiantly seems as though it has to do with the blue solenoid/connector sensor (FICD) thing.?

 

The TPS is only one of the sensors sending information to the ECU to control idle speed.
It is telling the ECU the position of the throttle butterflies, whether they are fully open, closed or some position in between & that is all it does.

The engine idle speed is specified at 650 to 750rpm for a manual, so if you have an idle speed of 700rpm (& it's a manual) the idle speed is perfect.

 

Oh thanks for the info. I had always read that was between 700-800RPM.
Is that for autos or just incorrect information?