Need help with emissions

[moondog52]

Ok, well I finally have my '89 240sx running after being parked for 3 years in the Phoenix heat. But it failed emissions ... both CO and HCs were about double the minimum standards.The car has 142k miles on it ... all stock and original.

Here's what's been done ...

- new fuel pump- new fuel filters (I had one near gas tank too)- rebuilt fuel injectors (Pythons)- new battery

There was a small amount of old gas in tank, 2 gals. maybeI filled the tank with regular (could not get premium this last weekend because of gas shortage in PHX). So I figure the octane was a bit lower than 87.

Now at that point it was running like it used to ... seemedhealthy so I ran it thru emissions.

Ok it failed, so then I installed ...

- new plugs (Bosch Platinums) gapped at 0.40 inch- new spark plug wires (Bosch)- new distributor cap and rotor- new O2 sensor

When I started it up it ran like cr*p! Tried resetting ECU by disconnecting battery for 5 to 10 minutes.ECU mode 3 code said engine temp sensor bad (13)After 3rd ECU reset ECU code said Air Flow Meter bad (12)

Found corosion in MAF connector, so I scrapped ALL connectorsclean (injectors, etc.)

On 5th ECU reset it finally ran ok for about 2 minutes then died.

After 6th ECU reset it all started working ok ... mysterious!

Applied off-road octane booster to tank (supposed to add 7 points).

Drove it around for a while ... watching ECU green led flash rapidly ... engine pings when I stomp on it.

I'm going to check the timing next, and replace the engine temp sensor (for the ECU).

Anything esle I should do? The MAF is so expensive, I hope I don't have to replace *that*.

If I add a stock replacement K&N filter, will that help emissions?Should I reset the ECU after installing it?

Do you *really* have to disconnect the battery for *hours* to reset the ECU???

Any suggestions would be appreciated ... I'm so close, have spent so much time and money on this thing

- Brad in the Arizona monsoon season ... worst time of the year to be working on your car!!!

[NISTECH]

have the smog shop run a cat efficency test on your convertor. a good smog tech will know how to perform this test. you mention your co and hc is double what is acceptable. how is your nox emissions? or do they even do dyno testing in arizona? worry about your co emissions first after that is resolved then go after hc. co indicates a burn in the chamber therefore it is burning the fuel but it just has way to much fuel burning so it is not transfering to co2. there is not enough o2 present to make the bond of 2 oxygen molocules 2 one carbon molocule. which the cat plays a large part in. if the cat does not have enough storage space left to hold oxygen molocules it will not be able to perform the thermal reaction necessary to combine the two.

[moondog52]

Thanks for your partial reply. It's not very likey that the CAT is the problem as the car was running great and passing emissions until it was parked becuase of the leaky fuel injectors. Also, CATs usually clog over time and this engine shows no sign of an air restriction.

In answer to your question about the NOX results, that part passed just fine 1.77 out of 2.50 and yes they do a dyno test.

Are you able to shed any light on my other questions?

Is there any service I can do to the MAF other than clean the electrical connector? What about the sensing wire? Is it accessible and can it be carefully cleaned with a Q-tip and alcohol?

What about the engine temp sensor error I saw for a while during the ECU resets? I plan to instal a new one anyway because I understand that as they go bad their resistance does not drop enough and it make the ECU think it needs to enrichen the gas.

What about the K&N filter? If I add that will it improve the air flow and help emissions? Will I need to reset the ECU again after that?How long do you *really* need to disconnect the battery for an ECU reset?

[NISTECH]

okily dokily i will try to cover all your questions this time sos not to be scolded next time. 1. there is no cleaning procedure in the factory service manual for cleaning the air flow meter. the flow chart clearly explains if it is not with in spec to replace it.2. you probably have an intermitten circuit for the CTS or a bad CTS.3.Nissan does not recommend oiled filters due to they contaminated the air flow meter and cause them to burn up. a. probably will have no effect on your air flow unless your old air flow is filthy. b. no4. You do not need to disconnect the battery to clear the codes. you follow the procedure listed in the service manual by turning the switch in the ecm through the five modes till you get back to mode 1. Did I miss any????

[moondog52]

I do appreciate you taking the time to answer each of my questions.

I realize the manual does not have any info about servicing the MAF unit ... I was looking for some "real world" experience. I have electronic equipment that says there are no user servicable parts inside, but that doesn't stop me from doing it anyway because of my electronic knowledge. I understand enough about how the MAF unit works to know that if the temp sensor wire is not brought up to proper temp to burn off deposits and over time it will build up deposits anyway, that it would make sense to try to clean that wire with the proper solvent ... I'm betting that's the primary reason for failure of the unit. If you haven't gone there nor wish to that's fine ... I'll let you know if I learn anything more about that (if you're interested). MAF units are extraordinarily expensive in my opinion for what they are.

As for the K&N filter ... of course Nissan does not support them. if they did, I'm sure they would be installing and selling them. But again ... in the real world ... people use them on all makes and models of vehicles with great success. Except for those that over oil ...

So you don't feel that a K&N would improve emissions. Ok ... we'll see I guess 'cause after talking to some others that have experimented with this they say they saw a marked improvement in the reduction of HC and CO numbers. Again I'll let you know the results if you are interested.

I don't quite understand your response about the ECU reset ... I'm not just interested in clearing the codes, as I understand it for the ECU to properly read a new O2 sensor you have to reset via removing power so it can properly recalibrate ... is this not so?If so, then my question was, should I reset after putting on an air filter like the K&N which will change the air flow and all related to it. Also, the part about how long the power disconnect needs to be ... seems to me that a few seconds or minutes should be sufficient ... where's all this talk on the board of it needing to be hours coming from? What has your experience been?

Finally, yes the CTS will be replaced ... sounds like a logical candiate for causing a rich mixture and high emissions.

Thanks again for your time ... I appologize if my trying to be specific is not something you are used to.

[p00t]

for bad running condition check MAS wiring, and if you have to try cleaning it with carb cleaner, but be careful this may damage it.

for emissions maybe your EGR is stuck/clogged? try pressing the underside of it, should take alittle bit of pressure to move the diaphram but should be smooth. also when pressed all the way up the engine should want to die.

fill up on premium mobil if possible before taking the test.

[NISTECH]

I realize the manual does not have any info about servicing the MAF unit ... I was looking for some "real world" experience.

I have pleanty of "real world" experience. I have been a nissan tech for the last 8 yrs. My current level of certification is engine specialist! We dont clean air flow meters we replace them. As far as oiled filters go. Nissan had their own oiled filter for years the old factory red one was oiled. But Nissan has realized what it was doing to air flow meters and discontinued it 2 yrs ago. So do what you gotta do and let me know how it goes.

[moondog52]

Thanks p00t ... egr valve is ok. Still a shortage of premium gas in the Phoenix area due to a pipeline break almost 2 weeks ago.Regular is running about $2.25/gal still That's why I had to add the octane booster ... I'm planning on going thru emissions again this Friday.

Nistech ... so, do you do a ECU reset after replacement of the MAF or the O2 sensor? Is my understanding that the ECU does a sensor check and recalibration upon a reset correct? How long does the power really need to be disconnected? Seconds? Hours?

Please don't get upset about my asking the questions you haven't addressed again ... I'm just trying to get these questions cleared up.

BTW, I spent 13 years as a mechanic starting on the line and ending as shop machinist. Primarily Volkswagen and Porsche. Gave it up in '83 ... 20 years in electronics and computers now.My finger nails are much cleaner these days

[NISTECH]

drive the car for five miles after installing parts all will be re calibrated.

[moondog52]

As a final followup to the thread I started ... I was able to find time to run the girl thru emissions today. I set the timing at 15 deg BTDC to give me an edge. I ran a 20 mile test drive b4 taking 'er in. PASSED with flying colors! All the numbers were very low. I think I'll leave the timing at 15 deg for now ... accel seems perfectly adequate. After I run a tank or two of premium thru I 'llbump it back to the stock 20 deg. I'm considering doing the Seafoam thing.

I had installed a new K&N stock sized air filter, and did one more CPU reset today. Oh, and I did do an oil/filter change with 1/ 2 quart of Lucas added.

Frankly the car drives better than it did when I first bought 'er in '95, now with 142K miles on the engine.

I'm glad to have my 240 (legally) on the road again

Today was a good day !