i did a search,found some similar threads but none really like mine.I can feel a slight misfire until around 2500 and 3000 grand,then breaks loose,it goes away.(It feels like the car it is turbo somewhat) I replaced jus about everything. Personally i think i need a cat.I jus wanted to what you guys think!I have a 91 se manual with a 108k

 

cat is unlikely, a cat will usually cause problems at higher rpm because it is clogged.

you probably have 1 bad injector, nothing unusual about that.
unplug your ignition wires 1 at a time to see which cylinder isn't firing.

 

there all firing

 

is it intermitent? or consistant?

 

intermitent, but it can be pretty consistant at times

 

im thinking an injector, like internetautomar said, is possibly on its way out

how are the plugs and wires etc...

 

Ohm out your injectors if its intermitent. 10~11 ohms about. that should rule out the injectors with out any doubts. i had the same problem it was injector #6 then #4 then #1 and so it went, to make a long story of replacing injectors peice meal i learned its easier to do them all at once if you have the cash.

 

I'll put my money on that sorry *** epoxy ignition coil, Nissan loves so much! The part throttle load and higher manifold pressure really puts a strain on the ignition. Ground a test light and sweep your ignition wires just in case you've got a cracked spark plug boot that's leaking voltage. Other than that swap out the coil with another...I've eliminated those epoxy coils (2ea) on my D21 p'up and replaced them with oil filled coils and never ever had problems again...My 3rd gen is getting an ignition system control, a heavy duty oil filled coil and later some magnecor 8.8mm wires.

 

what do u mean by ''replaced just about everything''? wat includes in that? can u be specific?

 

If you're referring to my post no, just the coil. The epoxy coil are very intermittent when they're starting to go.

 

new plugs,wires,coil,fuel filter,cap,rotor

 

hows ur EGR's condition....? is it working properly?....

 

I've got the exact same thing going on (apart from my now dead tranny). I found a really good video posted by somebody (can anybody help with a link, can't remember) showing a faulty temp sensor that triggered fans, but it's on the same circuit as the throttle position sensor (sends info on eng. temp to ECU) and for me personally, it was the culprit of an intermittent rough idle that I initially wrote off as fuel injectors. Good thing not. This part, and cleaning the connector and sealing the backside of it with tape < 30 bucks.

 

my friend i think u jus answered my question. a few months ago,i had and issue with my fans staying on.I played around with the sensor it stopped so i didnt think anything of it.It happened again last month while i was workin on my car.It would be nice if some one had the link!

 

I had the exact same problem and it turned out to be corrosion on my injectors. The problem will come/go erratically, but eventually will worsen.

I second the vote to ohm-check your injectors. It might be a layer of corrosion on the injector's electrical connectors (especially if those rubber boots over the electrical connectors are cracked open.) This corrosion will cause high ohm readings (and proper reliable function of the injectors), despite there being nothing wrong with the injectors themselves. It results in the miss you can hear and feel.

The corrosion can be scraped off with something sharp, without removing the injectors from the car. Scrape until all fresh, bright copper color is visible. Some injectors are accessible without removing the intake or plenum, but some must have plenum / upper intake pieces removed to gain access. (At least, speaking from '89 max VG experience.)

 

I replaced injectors in each of my cars after periods of intermittent firing. I would ohm them.

 

Yes, check that sensor out again. I have a few cracked injector boots as well, so You may want to check/clean those too, as was mentioned by another member. You know how these things can compound and make trouble shooting challenging.

I left my car idling for 20 min outside a gig while I was speaking to the proprietors and somebody came in saying somebody's car was smoking out back. My car has NEVER overheated, so I thought this was odd. THEN, when I found that video online, I was like, wait a minute... overheating... fans... rough idle possible... HA!!! Anything but fuel injectors, please. I wish I had that link, I'm sorry. But it sounds like you know what I'm speaking of.

And if you still suspect injectors, well don't forget to try a few bottles of BG 44K in your tank. $$, but good stuff.