[Gymbo]

I have a 1991 Nissan Makima SE with an automatic transmission. It has 215,000 miles and was purchased new by my parents. After starting it up last Wednesday evening it ran rough. After a stop and restart it ran fine. I started it the next evening after work and it has ran rough ever since.

I have played around and by unplugging one spark plug wire at a time, I have determined that it is the driver's-side front cylinder, which I think is #6. When I unplug that wire, there in no change in how it runs, when I remove any other plug wire the car runs worse. I changed the spark plug and plug wire, which didn't fix it, but at least eliminated them as possibilities. There is spark coming out of the wire end when the engine is running. The rotor and cap are new as of last fall and look fine.

My next candidates are:
Injector
O2 Sensor
Mass Airflow Sensor

The car still revs and runs pretty well, just rough.

I have run a can of Seafoam through it seeing if that would clear out the fuel system.

The car also has an exhaust leak I can hear in the back of the engine, I haven't torn it down to figure out where yet, I am thinking it's probably a manifold stud?

Any thoughts on what my problem is and/or what I should check next?

Thanks in advance.

 

[internetautomart]

it's probably an injector.
just buy a new one and be done with it.
Internet Auto Supply <- good source for injector

 

[Gymbo]

Thanks for your response. That was my guess, based upon reading other threads on the forum.

How difficult is swapping out an injector?

Thanks again.

 

[internetautomart]

it's tough but not impossible. you could have to swap a motor..

 

[Moms93NissanMaxSOHC]

Not bad, just get the right injector

Just got done with my fuel injector replacement(sohc motor), its not too bad to change the injector, however, you will need the 2 upper intake gaskets at a minimum, the other possible issue I had was most of the rubber under the hood is very hard and prone to crack if moved and twisted. I ended up replacing 2vac lines, but i only raised the upper plenum, I did not remove it as it is not nessicary, just wedge a 4x4 block of wood under it. Overall its not a bad fix but because nissan sold me the wrong injector(green/yellow), I get to do it all over again, I will probably try to reuse the intake gaskets though.

So, if anyones wondering, you cant mix the different injectors, unfortunitly I was not aware that there would be a need to design 2 different injectors for the same friggin engine! Anyone know the difference between the two? Which is the high pressure version?

 

[Gymbo]

I got lucky and the problem cleared up after running some Techron through it...so I didn't have to swap injectors. Glad to hear your injector swap went ok.