300zx misfire..
 

i just recently bought a 93' 300zx convertible. when i bought the car i knew it was gonna need some work, it had a slight miss when i had first bought it so i figured changing the spark plugs would fix that, changed the spark plugs and now the miss is still there. sometimes when i start the car car it idles around 200-300rpm, but doesnt stall out. if i rev it, then it will go up to 900-1000 and stay there. at idle it still has a vibration and feels like a bumby and rough acceleration all the way up to 3000rpm, any ideas on what it might be?

Check ecu codes http://www.ttzd.com/tech/diagnostictech.html
Check coil packs
Injectors

whats the easiest way to check the coil packs and injectors?

first things first check the codes if no codes:

swap coilpacks see if the miss gets worse....if it doesnt probably not them...you can also ohm test these i believe but i dont know the specs.

Injectors can be tested using a multimeter i think ok specs are somewhere around 10-15 ohms

for the codes how do i know what blink means what number?

scroll down to that grey chart in the link i sent you its towards the bottom of the page...

example.....3 slow blinks followed by 4 fast blinks is code 34 which is det sensor circuit.
code 55 5 slow blinks and 5 fast blinks mean there are no codes in the system....

make sure to follow this step closely if you turn it twice you may reset the codes and not no if anything was in there and get 55
6. Turn 'diagnostic mode selector' (pot on side) fully clockwise. Wait at least 2 seconds, then turn pot fully counter clock-wise. The ECU is now in Diagnostics MODE II

alright thanks, ill try to do this tomorrow and let you know what i get

k just ran the codes and got back code 53. which is o2 sensor right, says it could be my o2 sensor harness and connector, o2 sensor, fuel pressure, injectors, intake air leaks. which one is most likely?

most likely the o2 sensor itself......but probably not whats causing your miss

when i move the wires around that are connected to my injectors the car seems to studder and miss more or run better depending on how i move the wires. any chance my wires just need to be replaced? or is it my whole injector?

try cleaning them

http://www.300zxclub.com/showthread.php?t=153696

either 02 or Injector wires could be starting to fray if the idle changes when you wiggle them.

Are you seeing any corrosion issues? If so I'd go about cleaning the connectors first. If not I would peel back a bit of the wire casing and check for corrosion in the wire itself.

These cars are old, I hate to say that but they are. Corrosion can cause all kinds of havoc in these harnesses. I would check all of the other advice you have been given as well.

If it comes down to needing coil packs, I have a set at my house I could sell pretty cheap.

Good luck and let us know what you find.

^This

if youre a member on 3zc this thread will help you...If you're not a member sign up
http://www.300zxclub.com/showthread.php?t=153696

Thanks Eric. I forgot where that write up was and was too lazy to go find it.

yeah i tested my coil packs and at least 3 are bad, i pmed you about yours

k so far with the car ive replaced the spark plugs, cleaned injectors as well as connectors, replaced soil packs with brand new ones. car still has a miss... now what?

*coil

Well, assuming that all wiring is fine, according to the Suck, Squeeze, Bang, Blow theory. The next simplest idea would be fuel related. Check the specs on your injectors and ensure that they are in fact all in working order.

You said earlier that you noticed a change in performance when you moved wires. That tells me that it has to be electrical in nature. Do you notice it on one injector more than another? Can you manipulate the wires so that the miss goes away? Perhaps the wiring is shorting out or has a bad ground. Check and make sure the harness isn't rubbed through anywhere or anything obvious like that. Find the common ground and check and clean that as well.

I'm just trying to think of things that might cause it that wont cost a fortune to fix right now.

Hope it helps.

clear your codes take the car for a spin again and check them again.

It could be anything....Injectors are known to fail on the 90-93's you can test them with a multi meter they should ohm out aroun 10-13 ohms each