93 240sx : Misfiring

[hondacivicsipower]

Alright, after months of trying to fix this problem.I've had it.My car misfires every now and then usually after a decent warm up.Here is what was changedAccel Wires 8mm NEWNGK plugs NEWOEM Nissan Cap and Rotor NEWMy car is a 93 and has the infamous MITSUBISHI DIZZY, the rare one.My question is this, I have a feeling it is the external coil.Could the external coil cause me to misfire?I've pulled my new plugs and they are normal, look grayish white.I know they are normal, all my cars have always been like that.However, I've come to the conclusion.It has to be my dizzy, external coil, or a bad injector, which I'm not sure, but anybody care to explain.Where can i get some injectors, and are they hard to replace?Because I am pretty fed up

[NISTECH]

Grayish to white indicate a lean condition. Lean condition can be caused by many things. O2 is primary to a lean condition, a small vaccum leak, a plugged injector. the best way to diagnose for a lean condition is to use a DSO and tap into the O2, test the O2 first to make sure it is working properly if its ok asses weather the O2 readings are on the lean side. Another good way is to use a consult and moniter alpha readings if they are high then car is definitly running lean. Haveing a lean condition can cause a slight missfire.

[hondacivicsipower]

The car just passed inspection with the sniffer so I know it can't be running leanIn terms on injector, is there a place where I send it to that can fix it?I am 90% sure this is the problem,

[NISTECH]

do you have the print out from the smog station? if so post all the numbers. With those readings I can mathmatically figure out if the car is running lean. Just be cause it passed smog does not mean it isnt slightly lean.

[hondacivicsipower]

no i don't as i threw it out after i passed smog in august.Since these injectors are so much dough brand new, I got to wait and go to a junk yardthe 93-07 altimas have the same side feed injectors, so that is what I am going to hit up when ig et a chance to go to a u pull itthanks and i'll updateany info on how to pull the injectors?I know i need the gasket from advance,i'll pick those up in advance

[slipnfall]

NISTECH: (sorry to threadjack 'sipower, but free bump for you ) What are considered high alpha readings? I am having misfirings at 40-50MPH steady speeds, and have a CONSULT datalog from while this is occuring. I'm just not sure what are normal Alpha and Base #'s. Durring long durations of the EGR 'op(cruising), narrowband is fixed on lean. Timing is reading 47*, but factoring base of 20*, puts it around 27*

[NISTECH]

Alpha readings should be between 91 and 109. target is 100. In alreality your readings should hover between 95 and 105. occasional blips to one side or the other outside that range are ok. but at steady speeds you should be in the realistic 95 to 105 range. Anything that locks in a range bringing it over 105 makes it lean and rich hanging below 95.

The emissions control people are on this new trip of using lambda something mercedes has been using for years ,nissan has been using it and calling it alpha for many years. I was asking for his emissions test numbers to enter in a lamda calculator to determine if his car is running lean or not. The lambda calculator basically takes all the pollutans out the pipe and breaks them down using a scientific approach to add up all the elements coming out the pipe to determine if the car is running rich or lean. If my lambda value is less them .98 the car is running rich, if its greater then 1.02 it is running lean. This is primarily used to determine if a cat is bad but also to tell us what the engine is actually producing. If say I had a car failing smog and my lambda total was within the .98 to 1.02 range I know my cat it the cause of the failure. If my reading was out of that range I know the cat is not the main source of the problem. However depending on how long the car has been running like this the cat could be damaged. Cats dont go bad unless a condition exists or did exist that took it out. A lean condition will overheat a cat and melt it down [litteraly thermal melt down] If a car is running to rich it will plug up and coat the substrate which prevents it from combining molocules of oxygen to carbons. On a three way cat the front half splits molocules by releasing oxygen from nox. this oxygen is captured in the 2nd half of the cat to beused for the combination with the carbons. If you coated or melted down that aint gonna happen. So in many cases people throw cats at a car to get it to pass smog. Yea it might work this time around but the next time, if the source of the problem hasent been fixed, your right back to square one.

[slipnfall]

Thx for the response; in my log file I have a readings which falls within your expected range of values(95 to 105). Seems I'm OK there. But then I also have an 'oxygen' reading which varries from (low as 5, but from memory i'm not sure what the high end is). These number vary greatly.

Rather than continue here I will start a new thread in Nis/Inf engineering later tonight so we can discuss this further. I'll upload my log file to maybe shed some light on this.

Cheers,Jamie

[slipnfall]

NISTECH: You may find the above mentioned post here:zerothread?id=142660

Thx for your time.Jamie