1994 nissan rough idle and loss of power, whats up? Details inside

September 11, 2012 5:14 PM

Having idle/loss of power problems with a 1994 Nissan Sentra. Whats your diagnosis?

Changed Distributor cap/rotor - no change

Changed fuel filter - it was pretty plugged - black sooty looking fuel came out of old filter. Car works for 1 day, woo hoo, and then starts with the same again.

Change out fuel filter again thinking maybe I got a rusty gas tank (Old filter is fine, nice clean fuel inside) - no change

Today, I am going to change the spark-plugs.

Other things:

Exhaust smells slightly rich perhaps, exhaust seems typical

I added injector cleaner crap awhile back (after the problem) and have run engine much since

No engine code


If the spark-plugs don't work. What do you think it might be?

posted by couchdive to travel & transportation (13 answers total)

First thing to check is your ignition module

The link is just from a quick google search.
posted by snsranch at 5:45 PM on September 11, 2012 [1 favorite]

It's an answer for a 1992 model, but the checklist here is another good place to start: vacuum leak, fuel pump weakness, etc.
posted by jquinby at 6:11 PM on September 11, 2012 [1 favorite]

Old-car repair tip; if you change the rotor, distributor or spark plugs, then you change all three.
posted by halfbuckaroo at 6:19 PM on September 11, 2012 [1 favorite]

This sounds like my ford ranger when it needed a new fuel pump.
posted by shortyJBot at 7:05 PM on September 11, 2012 [1 favorite]

I'd be tempted to say fuel pump too. Running with a clogged filter often screws up the pump because of the extra load of forcing fuel past the restriction.

There should be some checks you can find online and do for fuel pump strength, but they usually allow you to check flow rate or pressure. Not the two together, which can often be where the issue lies.

if you change the rotor, distributor cap or spark plugs, then you change all three.

QFT. Also, change the spark plug leads at the same time. It's rarely money wasted.
posted by Brockles at 7:57 PM on September 11, 2012 [1 favorite]

Have someone sit in the backseat and see if they can hear the fuel pump acting funny while you drive.
posted by twblalock at 10:03 PM on September 11, 2012 [1 favorite]

Could it be a Mass Airflow Sensor? I had a similar problem with a 1995 Nissan Maxima, and the exhaust smelled like unburnt gasoline.

I can't remember if the check engine light was on at the time, though.
posted by Betafae at 11:43 PM on September 11, 2012 [1 favorite]

thanks much everyone! This gives me some new leads.
posted by couchdive at 4:00 AM on September 12, 2012

The better place to ask this question would a Nissan Sentra forum, such as Troubleshooting section of AllSentra.com. I have no experience with that particular forum, but I've gotten great advice from a similar forum for my Hyundai Elantra.
posted by Doohickie at 8:14 AM on September 12, 2012 [1 favorite]

Another possibility is bad gas. It's not common, but gas turns into varnish as it oxidizes, and maybe what you pumped had been sitting neglected in the underground gas tank. If this problem started multiple fill-ups ago, from different gas stations, then you can rule this out . But if it started after your most recent fill, then consider trying to gas-up at a different station.

But I do like the fuel filter for this.
posted by Sunburnt at 10:15 AM on September 12, 2012 [1 favorite]

I had a '94 Altima SE [purchased in 1995] which racked up almost 230,000 before I sold it.
I did all the work myself.

Offhand I'd guess you need a distributor. There's a sensor built into it which goes bad and that you cannot change without replacing the entire distributor. I replaced mine twice. The 2nd one came from a salvage yard.
posted by who squared at 12:00 AM on September 13, 2012

ah yes, Who Squared, thinking of the the cylinder position sensor. Just replaced the distributor on my Acura for the same reason.
posted by couchdive at 2:13 PM on September 17, 2012

Well, if anyone is still following this...Changed fuel pump and no change. Bummer. Looking at other options posted

...or god forbid, I actually take it to the only mechanic i trust in town who is both awesome and very grumpy.
posted by couchdive at 7:28 PM on October 4, 2012