Still problem with missfire HELP!!!

[Sdavne]

i posted earler about a misfire that i though was intermitten but recently it had not bin intermitten. it is all the time. i have a 1990 300zx n/a 2+0 alot of people told me to change the coil packs and i did and found the coil that was bad. i changed the coils and the same problem happens. what i uncovered by switching the coils is the front left coil has a weeker spark to it. (the sound sounds less week spark than all the others). so far i changed the plugs to NGK and changed the fuel filter and changed coils.. i heard it could be an injector but the injectors are all newish 20,000 miles and i also heard it could be an O2 sensor but i am not throughing any codes and i heard that OBD1 is useless and really hard to figure out the problems. and my check engine light is not on. this problem started to be intermitten and has gotten worse to the point when i drive it let it sit for a couple miniuets, when i restart it it idels really rough and runs really bad like it feels like i am running on 4 cylenders with no acceleration and if i start it and give it no gas it will stall out... please help!! i need ideas on what to do. i do not know anything else to check i aslo heard about the timming belt was changed about 20,000 miles ago as well but i do not think that all the sudden this would happen, it would be fine and that start happinging and then get worse but it use to be intermitten. please help....!!!! scott

[NORCAL300ZX916]

have u considered maybe a vac leak? the stalling when u give it gas sounds like it since u have already swapped the fuel filter and the injectors are not too old. Also have u tried to find a dead cylinder by pullin the plug on the injectors one at a time while the car is running to either kill it or hear the difference in one or two to single them out as the problem. i was having a similar problem it was also obvious to me because i could hear it from the passenger side of my exhaust so thats where i started. my problem turned out to be a dead injector. but a dead sparkplug coil or ptu could also be the problem. hope this helps.

[Sdavne]

yeah i tryed the vacume leaks i sprayed carb cleaner all over and did not find anyhing, i resealed the balence tube with that make ur own gasket thing but nothing changed.. and if it was a dead cylerder what would i have to do fix it...

[NORCAL300ZX916]

yeah i tryed the vacume leaks i sprayed carb cleaner all over and did not find anyhing, i resealed the balence tube with that make ur own gasket thing but nothing changed.. and if it was a dead cylerder what would i have to do fix it...

start the car, and pull either coil wires or injector wires one at a time(replace it before removing the next one) till u get one that doesnt change the idle. that will be the cylinder thats not firing or getting fuel. then once u find which one is not doing anything then u can the ohm test your injector and compare it to one thats functioning correctly. i think its like 16 ohms i believe, but dont quote me on that.lol if none of your cylinders are dead i would look at the ptu. i didnt know this until matt from driven authority told me but alot of the jdm ptus were recalled it looks like a silver heat sink on the left of the timing cover.

[evildky]

so lets stop guessing and actually troubleshoot the car
step 1, check codes
step 2 verify that the car is idleing on all 6 cylinders (unplug each cop 1 at a time it should cause the idle to dop or car to die, if nto that clinder isn't working, and we'll find out why next)

let us know what you find

[NORCAL300ZX916]

yea what he said!!!! hahahaa
was i right on the injector ohms???

[Sdavne]

i did all that except the injectors, i did not pull the wires, i thought i found the cylender that was missing because i pulled the wire and there was no difference to the idle so i replaced the coil. and still it is missing, and when i pulled the coil out with the car still on the spark on that coils sounds weeker than every other coil, the injectors are aftermarket and are 330cc i think.. but i will check, and they oinly have about 20- 30k on them. and how do you check the injectors ohms?

[Sdavne]

oh and no codes are being pulled up and i do not have a check engine light on either, oh and i am not sure if it matters but i have an ingin intake with hard pipes and the wire that is connected to the throtle bodies islike really loose and i can just pull it off with a light pull but when i go that there is no change to the engine? not the idle control wire the one that is accually connected to the right throdle body... not sure if this has anything to do with it and the bad cylender that i though was the coil(the one that does nothing when i pull the coil) is if you are looking at the engine from the front, the front left one.

[evildky]

330cc injectors? aftermarket ecu to match?

"the spark sounded weak"?

the cylinder taht made no difference when you pulled the cop wire, this is where we need to look but we must determine if it's lack of fuel or lack of spark

to ohm the injectors you just use a standard multimeter and hook to each side of each injector they should all be around 12-14 ohms, anything higher or open is a bad injector

if the injector checks out and you have a known good cop and plug (easy enough so swap them with a different cylinder and see if the problem moves) then a dead channel on the ptu would be the next suspect

[NORCAL300ZX916]

if the injector checks out and you have a known good cop and plug (easy enough so swap them with a different cylinder and see if the problem moves) then a dead channel on the ptu would be the next suspect

i was about to post that and bam its already there! good call man!

[Sdavne]

no the ecu is set for the injectors the plugs and 93 octane... but i will check the injectors and see what happens.