1991 Nissan 240SX



August, 11, 2008 AT 9:26 PM

Engine Mechanical problem
1991 Nissan 240SX 4 cyl Two Wheel Drive Automatic 190000 miles

I recently replaced all 4 fuel injectors on my 240SX (4 cyl w/double overhead cam).

1) after installing re-built injectors, upon start up, billowing grey smoke. Before replacing the injectors I tried to de-carbonize using cleaner through a vacuum tube, so I thought it was left over cleaner. After about a mile, the smoke cleared up and I drove it about 5 miles. Ran great.

2) about an hour later, next start up, flooded. Eventually started, drove about 5 miles, lost power to the point where I could not go over 50 mph. Took next exit to get home after about 2 miles. It stalled at the end of the ramp and could not start. Towed home.

3) pulled injectors. The lower o-rings were damaged. I had lubricated them with oil when I put them in, but did not use silicone. Probably it. Heavy gasoline smell in the oil. Changed the oil which was very diluted with gas. Maybe 1 or 2 quarts.

4) replaced o-rings on new injectors, plenty of lube, they went in very smoothly. Idled great, after the engine was under load, more grey smoke. Pulled injectors and o-rings were intact.

6) reinstalled the old injectors to get back to a baseline. Lubed properly and they went in smooth, same smoke once engine put under load. That really puzzled me.

7) pulled the spark plugs. There is a fine layer of dry carbon covering them. No oil at all. All 4 looked exactly the same. Plugs were put in new with injectors. Now I am really puzzled.

Checked water, OK. Don't think it is a head gasket. Tailpipe is wet, but does not smell like oil or antifreeze. Smoke is not black or white, just grey and smells fuel rich. Plenty of exhaust pressure, so I think converter is ruled out, maybe. Perhaps the damage to the o-rings allowed so much unburned fuel to pass through the exhaust that either the converter is fouled, or the O2 sensor is fouled, causing an extremely rich condition. I cannot tell because the car will not work with my OBDII code reader. I guess it could be another fuel component, but I wouldn't think it would fail at the exact moment I replaced the injectors. Also, if it were rings, I would think the plugs be oil fouled and most likely they wouldn't all be coated so evenly. No oil back to the air filter, so I think the PVC valve is OK. Something must be telling the fuel system to dump fuel, or maybe I am not getting the injectors sealed properly. They feel like they are in there pretty good and I am almost certain that they are going in without damaging the o-rings. Also, I didn't see any damage to the sides of the fuel rrail. I was very careful getting them out. Any thoughts are much appreciated.



6 Answers



August, 12, 2008 AT 7:29 AM

I am no expert but I know a few things. I had to clean my throttle body butterfly and I used a throttle body/ carb cleaner after doing that my car started fine I shut it off then it would not start I had to let it sit for about an hour, the cleaner must have flooded it. I am wondering if when you lube the injectors if that is mixing with the fuel cuasing the smoke. Becuase the smoke cleared up after a while correct? But i'm not sure if it would be an o2 sensor becuase if you car is running rich wouldnt that tell the sensor you are getting too much fuel? But I could be wrong. How does it idle? Is it at a constant RPM or does it vary?



August, 12, 2008 AT 8:21 AM

When I had replaced the injectors the first time, it flooded. After I replaced the o-rings it did not.

The injector lube couldn't possibly create the smoke I am seeing. Like throwing wet leaves on a fire.

The smoke only clears up after idling a while. What you said about the 02 sensor makes sense.

The idle is right on the money. Does not vary. I have not cleaned the throttle body as it looks like a pain to get to. But a good idea regardless. I have not checked the EGR either, don't know if that would cause any problem like this though. Thanks for responding, any more thoughts would be appreciated.



August, 12, 2008 AT 12:46 PM

Just a tip for cleaning the butterfly on the throttle body, have a rag under it so when the fluid that gets sprayed in doesnt run out and land on the engine. Also I just used a rag to wipe out hte inside which worked pretty good. But I probabaly should have used a Q-tip to get around the seal of the Butterfly. COuld there be something in your exhuast like a bees nest or something that could be smoking. My uncle bought a rx7 that had been sitting for a while and there was a bees next in the cat and when he started it smoke came out untill he removed the hive.



August, 15, 2008 AT 12:04 PM

Does the trans have avacuum line to it? Could be sucking ATF causing the smoke



September, 18, 2008 AT 4:05 PM

2CarPro Jack,

The trans does not have a vacuum line to it. I crawled under the car and could not find a vacuum line or vacuum modulator. I confirmed by consulting the shop manual. It appears that there are only electrical connections.

Any other ideas?




September, 18, 2008 AT 7:05 PM

Need to get it on a scanner to watch the o2 sensor, the pulse width on the injectors to see what is going on, you could guess what it is all day long, now it is time to actually watch the injection work. No leaks in the air intake tube between the MAF and the engine?

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