I have done a LOT of reading and a lot learning about the VG30 and I found no answer for this one and yes I have read the posts!!! I have read through over 600 threads from 2004-now and and not a thing....

Okay 87 turbo 300zx... Part 1) only in the morning 50`F or so overnight, I have a hard time starting... I have to crank it for 10 sec. or so, it will hit on a cylinder or two, if I push on the gas a little or all the way, it won't even try???? Most of the time on the 2nd try it will start with a little rough idle for the 1st 5-10 sec. Keep in mind, I can park the Z all day 9 hours or longer in 50-60`F and it will start just fine. So now it's running... for the 1st 3 minutets or so it almost acts like it is backfiring only under load... but the boost/vac gauge shows no sign of that... but it idles fine... ... after that no more ...??backfiring??... or loss of power.

Okay on to Part 2) ater warm up... at no given time as I'm driving, it seems like I lose 2 cylinders... BIG loss of power... and sometimes it will hit on all 6 like a bat out of hell... 1 second all good and the next it runs like and then it runs great.

If you need HELP just leave a post...

 

welcome to the site.

the first part, what you describe as "backfiring", sounds like it is probably the Cylinder Head Temp Sensor (CHTS). there are quite a few threads on that, read up and see if it sounds like your issue. how many miles are on the car? could your turbo be going bad?

 

OOOOh I did read a lot on CHTS... now I know what CHTS stands for... Thank you for that... I look into that...

 

and teh second one (though i doubt this is it but worth checking) sounds like my Z32 when it was loosing compression in one of the cylinders. also another cause of soemthing like this is simpled connections, mainly you fuel injector connections or injectors in general, you can run a resistance test on tehm to see if they are normal. though i dont know how many ohms Z31 injectors should be at with them unplugged. i know teh Z32 though is 14ohms

 

I don't think that's it, I'll get a lean/rich gauge and see if that will help me out... it acts like...???... under heavy loads... like the 1/4 mile... or regular driving... I took off 2 plug wires and at any time and as fast as 2 seconds it could happen 2-4 times or 0 times or stay running like I unplugged 2 wires... don't know??? This makes it bad if I need to eat a 5.0 or some other v8 car lol...

 

have you checked your cap, rotor plugs and wires?

 

thats teh other option to ^^^ as well as checking the timing, timing will cause a miss when you get on it.

 

first...do not get a narrowband o2 gauge if you plan to measure the air/fuel mixture.
second...checking your a/f ratio is not going to help you find the problem

since you said, you think youre missing a few cylinders, try to find out which ones arent firing. if the engine doesnt bog down if you remove the spark, then youve found the bad cylinder. check all your connections for that cylinder. try swapping wires. test your injectors.

 

This is a newer eng. with less than 50K with 178-185 per cylinder and the tune up has less than 500 miles on it and the timing is good with a new timing belt. At idle it runs great... only bogs down when driving... I unhooked the EGR hose, so lets see if that helps... seems to bog down more the hoter it gets or the longer it runs. So it's hard to find out if it is missing without a dino. I have an IR temp gun but I need to take off the hood and hold on for the ride LOL... By the way... Thanks for the help/info...

 

I was thinking if I got an air/fuel it would let me know if it was loading up or leaning out on fuel... and after I get it all working this would help me keep it in check... thanks... good idea or??? something better???

 

so, is this a j-spec engine?

was the timing checked when the belt was put on? you know, you can drive the car for a while, and then stop and check the temp. or, you could just look at your temp gauge. a car on the dyno runs hotter than a car on a road. theres less wind

a narrowband o2 sensor doesnt do much more than flash some lights. if you want to get accurate a/f numbers, get a wideband o2. or some engine software

 

Tuned up with genuine Nissan parts (rotor & cap)? It is my experience that nothing else quite runs right but Nissan parts.

New spark plug wires? Plug wires can get hot, break down, and begin leaking electricty (arcing). If the juice don't get to the plug, it don't fire.

Speaking of plugs, if you're not firing on a cylinder, or two, the condition of the plugs should give you a clue concerning which cylinders are misfiring.

Have you ran the ECU codes? It may have a story to tell you.

 

I have Nissan cap/ rotor... 8mm wires new... ngk plugs new... I'll pull the plugs and see if 1 or 2 of don't look the same... I don't know if it's the same cylinders that bog down... or a loss of fuel... it acts like the timing changes like the car thinks it is in idle mode then drive mode... it's really fast on how it changes.

and for the timing it's all on the #'s... I'll check it again... I was just saying that if I had a dino, I could check more things out becouse I could have the car under load.

???so, is this a j-spec engine???? Thanks from TurboZ87.300

 

Soooooooo let me be the 1st to say I got the loss of power fixed. The bolt under the rotor was loose and was letting the hall plate move.... now I'll work on the hard to start thing...

Hope this will help you on you z31...

 

I have an 84 300zx na and I have the same problem with starting it in the morning/cold temps. When i read what entropy said about the chts i started reading through threads to try and find the answer but i didn't, maybe i didnt read enough but i am not sure where the chts is located. i have a chiltons manual but i cant find anything about its location in that either. sorry for the agrivation if i am just over looking the obvious.

 

The CHTS is behind the timing belt cam driver side... below or under the distrubutator and hard to get to... but I to have read alot on this... some say NO this isn't it and alot say that this is it... lol I don't know... ... I'll figure it out one of this days... It's only hard to start 1st thing, so the rest of the is fine not only that, but you have one shot to get it right for the day LOL I have a parts car so I'll trade em out and see... Thanks