1994 Infiniti J30 engine vibration/piston misfiring

[Fini_Sent]

~130K miles

My '94 J30 vibrates noticeably, regardless if it's in P/N/D. It originally started about 2 years ago, and it would randomly vibrate every time it ran for a couple weeks, then not vibrate for a couple weeks. I've since had tune ups.

For the past couple months, it has not stopped this vibration. I also notice that when I accelerate, esp. in first and fourth gear, the car seems to struggle. I am due for an oil change, but I know that won't solve it.

Just wondering if anyone has any clue of what this might be. I have heard the J30 can be an upkeep pain, so I am trying to decide whether I want to repair it or look for a new car.

Thanks!

[GerryO]

CEL ON? Pulled any codes? One bad fuel injector? There's not much to tune up on a J30, what with no distributor/cap, plug wires or rotor. Platinum spark plugs should last 100K miles. When was the timing belt last replaced?

[yodawill2000]

Does sound like a clogging injector, but as Gerry said that would throw a Check Engine light when that cylinder was missing.

[driverdriver]

Ohm test your injectors(they should be in the 10-14 ohm range, anything below or above means you need a replacement) and check your ignition coil packs. Those two are usually the most likely culprit to engine vibration with acceleration problems.

If your getting a warning light, pull your codes from the ECU.

[Fini_Sent]

No CEL.

Re ignition coils: had 3 of them replaced 5000 miles back - def. a possibility.

Timing belt last replaced - not sure. Have had the car for about 35K miles and have not replaced it in that time.

Clogged injectors - good fuel additive I could add? Any other way I could handle it?

[driverdriver]

Timing belt is critical. If it hasn't been replaced, I would do it ASAP! The J30 engine is an interference type setup. When the belt goes, so does everything else. You would be looking at either a new engine or an engine rebuild.

[yodawill2000]

Ditto on the TBelt thing.Look under the front edge of the hood and see if it doesn't show when the belt was last replaced.

Redline SL1 is my injector cleaner of choice.

[Chillin014]

I had a similar problem, ended up replacing 3 or 4 injectors. Not a fun job. They never threw a CEL but the car ran horrible all the time. It fixed the problem though.

It still shakes at idle but I think I've got an exhaust leak as well.