My J30 is only running on 4 cylinders

[davidawggg]

I have a 93 J30 with 95K miles, I have owned it for the last 9 years. It was running like a dream, but then out of nowhere it dropped 2 cylinders, I believe #2 and #3, now runns rough on only 4 cyls. Spark plugs are fine, no check engine light on, ECU give 55 code, which I think means all is well. It has 1/2 tank of fresh gas. This happened all of a sudden. any thoughts?

[yodawill2000]

Have you tried to move a coil from a dead cylinder to a working one to see if the problem follows ??

Bizzare your not getting a code with a misfire like that.

Could be Coils, Injectors or Spark plugs.

Almost forgot .. WELCOME TO NICO !!!!

[texml69]

did you do anything like a tune up on it before this started ??

[driverdriver]

Ohm test your injectors. One or more may have failed (which is a normal age related thing). You should get a reading of 10-14 ohms per injector. Anything below or above that range indicates injector failure.

It could also be an injector coil as Yoda's indicated. Do an ignition coil swap test.

[davidawggg]

Thanks for the replys, switched the coils, no change. I checked the Ohms of the fuel injectors on the dead cylinders and got Zero, then I checked it on a good cyl and got about 12 ohms. Is the timing or something that would make the injectors read zero ohms in the timing sequence of firing? Or are you supposed get a consistant reading regardless?

[1994 infiniti j30 190+]

on the cylinders that you got 0 ohms on that means your injectors failed and need to be replaced. and doing it on this engine is a pain but you can do it yourself just takes a while. and your supposed to get a reading when you check for ohms no matter what. as driverdriver said having them fail is just age related, i had it happen to me on mine and ended up not doing it and then they all started to go together and that was when i was at the point your at, running on 4 cylinders. so i would reccomend relacing all them at once. and thats weird your not getting codes, usually you get codes for something like that.

[GerryO]

and thats weird your not getting codes, usually you get codes for something like that.

CEL should turn ON too, even as they first fail intermittently and soon after once and for all.

[1994 infiniti j30 190+]

and thats weird your not getting codes, usually you get codes for something like that.

CEL should turn ON too, even as they first fail intermittently and soon after once and for all.

yea that what i had go on for me sometimes the injectors worked and sometimes not and the light would go on and off so much. so hearing his light isnt on and hes getting no resistance on those two is weird and has maybe a bigger issue. try disconnecting the injectors that got zero resistance and see if your light turns on. it should.

[driverdriver]

My CEL never came on when mine failed. The Ohm test simply revealed it and the tell tale rough idle and lack of power.

[davidawggg]

Thanks for all your input, The 2 injectors were bad, I used the cheat method to replace them (die grinder so I didn't have to pull the plennum. I did goof and for got to run the fuel ut of the rails before I pulled them and the gas leaked onto the pistons, so at 1st starting attemp I hydo locked, so I pulled the 2 plugs and cranked until the gas came out of the spark plug holes. But it got worse, Still wouldn't start. I thought maybe something broke when I hyrolocked. Pulled the timing covers, due for a timing belt after 17 years anyway. At that point I discovered I blew the fuel injection fuse. Fixed that, new timing belt, still wouldn't start, then realized I didn't have the connector on all the way for the spark pulser coils....Problem solved running now. Now to replace the power steering rack that is dripping on my driveway..........

[yodawill2000]

Good deal.
As you mentioned draining the fuel pressure is always the first step.
Glad you didn't bend a piston rod ,!!

[davidawggg]

Probably a good thing the fuel inj. fuse was blown, or it may have tried to start and I would have bent a rod.................