Bucking infiniti j30

gasoline
filters
catalytic-converters
exhaustsystems
valves
leaks
transmissions

#1

Ok I am having a major problem here and I need help asap. I recently purchased a 1993 infiniti j30. It has some issues but the price was right. Shortly after I bought it the car started to buck while going up hill when it was under load. It wasn’t very bad and if I give it gas (quickly press the pedal down and release it) it will shift gears and the bucking will stop. There is a slight lag when I press on the gas. It will go forward slowly for a second or two then pick up and go. That just happens when I’m stopped. Also when the car is in first gear and I press the gas the fan turns on and the more I press the gas the louder the fan revs. The bucking problem has gotten a little worse since I got the car. Its starting to buck a little on straight roads now. At first I thought it was my transmission so I went and had new fluid and filter replaced with lucas tranny fix. ( the old fluid was pretty black ) that made it shift smooth but the bucking was still there. I took it to have the trouble codes ran and it came up code 01 revolution sensor. So I shelled out 400 bucks to have it replaced and still no change. I then started to think it might be a tuneup issue or a coil so I had the coils tested in each spot and none of them were bad. I then gave it a complete tuneup with bosch platinum plugs and ngk wires. Still no change so I had etech fuel injector cleaner put in through the gas and vacuum system to clean out my engine as well as changed the fuel filter. Still no change. I had recently discovered an exhaust leak above my catolitic converters so I thought they might be clogged up. I just had them cut off yesterday and had straight pipes put on. The lag is a little less but I have less power now and my exhaust pipes are rattling. STILL NO CHANGE IN THE BUCKING. I’m starting to think I may have a vacuum leak somewhere but I don’t know. I’ve done everything I can think of to fix this problem. PLEASE HELP ME!


#2

Has anyone checked the oxygen sensors?


#3

Yes. I had a mechanic test the o2 sensors. He said they were working fine. I’m gonna replace them anyway the next time I get paid.


#4

" At first I thought it was my transmission so I went and had new fluid and filter replaced with lucas tranny fix. ( the old fluid was pretty black )" That could still be the problem, but let’s hope not.


#5

I really need some help here guys. I really don’t know what this problem is. I’m going to change the o2 sensors this weekend but it could be another sensor or a crack in a vacuum hose somewhere. I would appreciate any advice.


#6

Actually, it seems that this problem is beyond your mechanics.
Have you checked the fuel pressure, after changing the fuel filter? Check the fuel pressure in Drive, engine at 2,000rpm, for two minuets.
Is the air filter clean? If not, replace it.
If you’re unsure there is a vacuum leak, check the engine vacuum while it’s running with a vacuum test gauge.
The code 01 for the “revolution counter” was probably for the vehicle speed sensor (vss), mounted on the transmission, wasn’t it? Did the code 01 come back?
The “bucking” (misfire) can be from a fuel/air or spark problem. An ohms check on an ignition coil isn’t of much use. A bad coil can pass that test. A better test is to pull the spark plug wire and attach it to a spark plug tester which clamps to the engine. Then, crank the engine and watch the spark.
The (radiator?) fan runs when the engine is cold, and the A/C is OFF? If yes, the engine coolant temperature sensor, or is wiring, or the fan relay, could be faulty.


#7

I am pretty positive that your problem is your Crank Angle Sensor. I have an Infiniti J30 as well. Mine is a 93. Search it on this forum, It’s going to be called Betcha Can’t Answer This Question. If your symptoms are like what is described in my post, replace your CAS. IF not, there are plenty of helpful suggestions where people have replied on my post. The CAS for my car was only 140 bucks. Don’t replace your O2 sensors unnecessarily. For my car they are like 200 dollars for them.

Mike