Hello all,l am having yet another problem,when I start the car it idles around 900 rpm,but after 30 seconds or so the revs keep droping down to 500rpm until it nearly conks out,also the car doesn't seem to rev up when I turn on a/c,lights,etc.anyone know what might be wrong?Also I have a diagnostic cable if that might help.thanks guys.

If you can hook it up that will help a lot. The air idle system on these cars is a bit faffy. It could a number of things, mass airflow meter, throttle position etc or it could just be a large air leak in intercooler/inlet pipework.

Perform a boost leak test and then move forward.

If you can hook it up that will help a lot. The air idle system on these cars is a bit faffy. It could a number of things, mass airflow meter, throttle position etc or it could just be a large air leak in intercooler/inlet pipework.

Perform a boost leak test and then move forward.

 

Hi thanks mate for your reply,Can i do a boost leak like in this video or will i need a air compressor?thx

Compressor is best mate.

Compressor is best mate.

 

To be honest, for a significant leak, that crude smoke test is actually a very good idea! For minor leaks you would probably need a bit more pressure behind the smoke in order for them to become apparent. But yes, a compressor, a quiet environment and a bottle of snoop is always a good bet.

To be honest, for a significant leak, that crude smoke test is actually a very good idea! For minor leaks you would probably need a bit more pressure behind the smoke in order for them to become apparent. But yes, a compressor, a quiet environment and a bottle of snoop is always a good bet.

 

With the symptoms described in mind that’s a fair point Joel.

Please be careful not to over pressurise the system though, I believe 5-6 psi will suffice.

Above that and you run the risk of damaging seals etc'

So guys a update i found 7 leaks doing a leak test and fixed them,but still the car doesnt run right while idling,when i turn the car on the rpm does be at 900,but then drops to 500 and less nearly dying out,only when i turn on the a/c does it stay at 900 rpm,also i am getting a Coolant Temp Sensor(code 13)I dont understand why i am getting this code as i put in a new sensor around a year ago,Does anyone know what the problem might be and also will this fault make the car run poorly.Also guys what size of pipes are these as a need to order new ones.Thanks all

https://www.google.com/search?q=300zx+boost+pipes&source=lnms&tbm=isch&sa=X&ved=0ahUKEwizhuKvlq3bAhXL_KQKHckNDrMQ_AUICigB&biw=1254&bih=705#imgrc=EDdXKu8CtxgeBM:

Check the connection of the coolant sensor as they can get dirty (green) clean and reconnect.

Well that certainly would of been helping. You need to sort the coolant sensor fault, I think the error is sensor circuit rather than sensor alone, a dodgy connection is likely as Gary says. Check the throttle position sensor is functioning correctly. And ensure the yellow plug on IACC is clean and secure. You really ha e to ensure the components that contribute to the sale speed are correct first. Once that’s sorted you can then adjust the idle screw. If you just go at the adjustment first you will not fix anything.

Thanks guys for your replys,i have sorted out the coolant sensor fault,bad connection,so i let the car tick over and when a just below 500rpm the reves jumps up to around 620 and back down to under 500rpm

Yeah, as Stephen says, there are a few moving parts in idle speed. The physical throttle bodies (don't touch) idle screw on the iacv and the tps comes into it too.

 

I think those hoses are 4mm and 6mm.

 

ASH are a bit average in quality, but fine for vac hose

 

http://www.autosiliconehoses.com/silicone-hose-shop/performance-silicone-hoses/vacuum-silicone-hoses.html

 

These are quite handy too. Better than a screw in a bit of hose.

 

http://www.autosiliconehoses.com/silicone-hose-end-caps-2-pack-blanking-plug-bung-4mm-to-32mm.html

 

Cure all vac leaks, clear all codes, comfirm your injectors and things are all firing. Then follow the wiki guide on a tps and base idle set up.

thanks guys

Ideally you need a conzult to setup the base idle properly but as Tom says, you can do it with a basic multimeter but you do have to be sure that you have cured all the leaks because if you set it up with a leak, you’re just masking a problem.

Have you tried a different MAF? Mine was doing weird things last week, wouldn't tick over nicely, dropped revs until it cut out. I had to rev it to keep it alive etc. I changed the maf from the other car and it runs like a dream now...

Quick question guys,should the timing change much while reving the car from 15 degrees btdc on idle,also what rpm should idle be?Also would i be better taking out the IACC or leaving it in the car do a ohm test?

https://www.youtube.com/watch?v=gKLOxygj04A

Yes, timing will advance in relation to RPM.

When setting at 15 deg' btdc, make sure that everything is up to running temperature.

You can test the IACC in situ, however, it wouldn't harm to remove it and give it a good clean given the symtoms.

You will most likely need a new gasket mind.

Thanks mate

I will try and clean it in situ and check voltages,my car is running like this guys in this video but idles fine with a/c on,lol at the end i feel like that

I possibly went a bit ott when I wasn't happy with my idle. But I did a plenum pull. I found all sorts of things that weren't quite right. None of them a big issue by themselves but all added up to be a problem.

 

I rebuilt my iacv assembly. Seapped the loom for a wiring specialties one. Fitted a s2 ptu. Replaced the injectors. Cleaned the throttle bodies. Removed the egr. replaced the pcv valves as well as other stuff. 02 sensors... It just tidied up (as it was then) 24 years of things going brittle and black.

 

It ran better afterwards and I learned a lot about my car.

Found the thread.

 

Just look at the pictures

 

https://www.300zx.co.uk/forums/showthread.php?179020-Extreme-makeover-engine-ancillarys-in-a-month

Well guys i found a leak at the balance bar,and car is running alot better,TPS is at between .46 and .48 volts,but my acc is at 45% on consult software:confused1:

Well guys i found a leak at the balance bar,and car is running alot better,TPS is at between .46 and .48 volts,but my acc is at 45% on consult software:confused1:

 

Is that 45% when the engine is up to operating temp?

Is that 45% when the engine is up to operating temp?

It is mate

Are you getting the throttle closed switch activate?

As Joel and others have said, it is important to get things up to temperature and things like the TPS/Timing etc' set correctly.

With regards to the ACC being at 45%, that may well improve once you set the base idle.