TROUBLE CODES - RUNNING SUPER RICH

[Jusepi97sx]

Hey all,

i was hoping someone could help me out or at least guide me in the right direction and see if i can make these repairs myself instead of having to go to the mechanic.

car - 97 240sx

symptoms - The car is running Super rich.. it's going thru gas like nothing.. 1/4 tank on like 20 min drives. the exhust tip is all black and heavy on the carbon. From time to time it wont' hold idle and stall. I haven't found a pattern to this, sometimes i'll do it when it's cold... other times after it's been running for long periods of time. Check engine light is on.

the trouble codes that come up are P0130 & P0171Could someone tell me what those are?!?

this issue has some history - i had the same problem about 3-4 mths ago.. got one of the 02 sensors changed. the idle is somewhat of a mystery too.. it comes and goes.. it just all seemed to come together now again and it didnt' pass state inspection.

Pls help, Thxs

[Jusepi97sx]

ok.,

so i searched and p0130 is the O2 sensor... the same one i had changed recently and P0171 says running lean!

1, It cannot be the O2 sensor again right?., could something else be acting up that makes the O2 sensor read wrong making the ECU read out that its the O2 that is faulty?

2. the car is running rich.. why would a code for it running lean read out!? i'm confused

help

[The Mic]

check you AIV, see if it's clean.

[Meantime]

He doesn't have an AIV on a '97.

Were you running rich before replacing the O2 sensor the first time?

[Jusepi97sx]

OK, now that i go thru all my records, i've changed the same O2 (bank 1) 2 times in the last yr and a half.. def. this is wrong

yes it was running rich before i changed it about a month ago or so.

i've also cleaned out the MAS w/ break cleaner.. tune up was done perhaps 20-30k (w/ complete plugs, wires, cap)

[Meantime]

Did changing the sensor temporarily allieviate the problem at all? Or no effect?

I had a similar problem about six months ago. Replaced the O2 sensor in May of '03 and about a year later the engine was idling high and running rich as heck. No CEL light ever came on. On a hunch I replaced the coolant temp sensor and it completely fixed the idle problem.

I'm wondering if there's not something else causing the engine to run rich and foul up the O2 sensor. Have you checked for injector leaks?

[Jusepi97sx]

yes.. changing the 02 the first time did alliviate the problem... altho i dont think i was getting normal gas milage.. it seems to work ok and the idle problem went away. then when the problem came up again a month ago, changing the o2 again fixed the problem, same characteristics on the car.

i've also changed the thermostat recently b/c the car was not heating up. i've checked the Throttle valvue voltage.. and it checked out okThe engine light was coming on/off (mostly on) recently as well.

i have not checked for injector leaks tho. I was also told my MAS could be bad, that this is commen on nissans..

[Meantime]

If the engine wasn't heating up to operating temp then it would be constantly running rich and idling high (cold start mode). How recently did you replace the T-stat? Before or after the last time you replaced the O2 sensor? Is the engine now reaching op-temp?

[Jusepi97sx]

I changed the thermostat b/c i noticed that the air coming out of the vents was not really hot when i would put it on max and highest temp. the gauge was reading normal... right in the middle. I also thought that the car was running on cold start mode constantly and changing the thermo would fix that.. i did this right around the time i changed the O2 the second time.. so a month or so ago.

Now the temp. of the air is better.. not really Hot Hot.. like it should i think.. it takes it too much time to heat up... but maybe this is my comparing it to other cars.

[Meantime]

Hmm. Definitely check for injector leaks, air intake leaks beyond the MAFS, vacuum leaks etc.

I have an S13 FSM at home and I'll check it tonight, the testing procedure may be a little different for your S14 but it should help you at least narrow down the possibilities.

[Jusepi97sx]

K, i'll take a look at those things... thanks for the help.. def appreciate it

[The Mic]

ah, do'h!

[Meantime]

Ok. Got the FSM here. Unfortunately there isn't a specific "Running Rich" diagnosis here - it groups them by symptoms, i.e. "Unstable Idle" or "Surge". So I'll go through and outline what the manual says for conditions similar to yours.

1) Check EGR valve for sticking. There's a rubber diaphragm under the mushroom-cap looking thing above the collectors. When the engine's running, reach under and press up on the diaphragm. Your engine should stumble and almost die. If it doesn't, your EGR has issues.

2) Check injectors. There is really 2 steps to this - first, determine if the injectors themselves are all working. This involves taking the distributor out of the engine and turning the CAS to see if the injectors make a "click". Pain in the *** and probably isn't the source of your problem; if an injector was out you'd be running rich regardless of the O2 sensor. Second step is to check for leaks. The easiest way is to warm up the engine, then shut it off and take out the sparkplugs and see if any are wet with fuel. If you want to take it a step further you can take out the injector rail, turn the ignition to "on" and see if fuel is dripping from any injector. Sometimes you can faintly smell an injector leak after the engine is off, depending on how large it is.

3) Check spark. Take out a plug and wire, put it against a ground and crank the engine. If it's weak, faint or inconsistent check the coil and ignition circuits, especially the grounds.

4) Check air regulator. This is a pain also since the regulator is tucked under the collectors around the AAC valve assembly. Pinch the hose (if you can reach it) while the engine is running. If the engine speed drops, something is wrong with the air regulator.

5) Check for air intake/vacuum leaks. You can use an aerosol spray like carb cleaner to find leaks around air hoses; the engine speed will change and/or you'll actually see the particulate move around the leak. I suggest something non-flammable.

Hope this helps you out. :/

[s13sr20chris]

pull the plugs and see if they are all black or just some of them.