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Discussion Starter #1
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1997 Sentra GXE 4dr, automatic, AC, 123K miles

- Bought new.
- Replaced all spark plugs & wires after 4 years (28K miles) due to mis-fire in cylinder 1
- Oil/Filter changed every 3000 miles or 4 months
- Air filter changed every 2 years
- drive belts changed every 40K miles
- coolant replaced after 105K miles
- starter motor, alternator replaced at 90K miles
- battery replaced every 5 years
- Both CV boots replaced at 90K miles

- at 123K miles, did a major tune up due to rough ride (cylinder 3 misfire & Service Engine light turned on)
-replaced spark plugs, wires, distributor cap, rotor, PCV valve, fuel filter, oil & filter, air filter
- Flushed (drained) and filled ATF 3 times (12 qts)

Car runs smooth now and passed enhanced smog test (SF bay area).

HC and NOX emissions have been going up every time smog check is done (at test only stations).

CO2 and O2 levels didn't change over the years - remain at 14.7 (CO2), 0.2 (O2)

HC went from 9 ppm at 15mph, 3 ppm at 25 mph to 63 ppm at 15 mph and 36 ppm at 25 mph.

NOx went from 178/89 at 15/25 mph in 2009 to 346/201 in 2011.

CO went up from .01/.01 to .21/.13 at 15/25 mph in 2011.

Questions:
1. what can I do to reduce HC and NOx emissions - even though the car passed smog this year, I'd like to do any other maintenance needed to reduce the emissions now and be prepared to pass smog in 2013 :)

2. AC stopped working a month ago -- blows hot air, fuse inside the car looks OK. What do I need to check.

My Sentra has been dependable, gives good mileage (32 hwy) and I'd like to keep it running for another 100K miles.

Appreciate your comments, help.

rsnissan
 

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If you ran the car with a misfire, there's a good chance you've done damage to the cat running it like that. Cat's don't like to be fed raw gas (i.e. due to a misfire). But since, apparently, you haven't had a Cat Efficiency code yet, that might not be the case.
Past that, I don't see anything about checking the timing (lots to do with emissions and power) or doing a compression check (overall engine health).
 

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Discussion Starter #3
jdg, thank you very much for the response!

>> If you ran the car with a misfire, there's a good chance you've done damage to the cat running it like that. Cat's don't like to be fed raw gas (i.e. due to a misfire).

I didn't drive the car for more than 15 miles after the misfire. I was worried about damaging the catalytic converter and so immediately replaced spark plugs, wires, distributor cap, rotor, fuel/air filters, auto transmission fluid (drain/refill a few times as suggested in this forum) etc.

>> But since, apparently, you haven't had a Cat Efficiency code yet, that might not be the case.

I think I may have dodged damaging the Cat by not driving the car with misfire (thanks to the posts on this forum, I knew it is not a good idea to do so)

>> Past that, I don't see anything about checking the timing (lots to do with emissions and power)

I need to check with the mechanic if he adjusted timing (idle as well run). I requested a "major tune up" and the mechanic replaced all the parts mentioned above. It didn't occur to me to ask him if he checked/adjusted timing.

>> or doing a compression check (overall engine health).

didn't do so.

Subjectively, my wife reports that the car runs a lot smoother and accelerates well now than before the tune up.

How much can I expect to pay for checking/adjusting timing (if not done before as part of "major" tune up), and for engine compression check? This is in SF bay area. A reasonable ball park estimate is OK. I don't want to be taken for a ride :)

thanks again
 

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I didn't drive the car for more than 15 miles after the misfire. I was worried about damaging the catalytic converter and so immediately replaced spark plugs, wires, distributor cap, rotor, fuel/air filters, auto transmission fluid (drain/refill a few times as suggested in this forum) etc.
That's all it takes...depending. 15 miles on the highway could mean 10 minutes of hot and heavy engine revs, or could mean an hour of stop and go city driving...either way, doesn't take much to poison a cat, especially if it's old in the first place.

I think I may have dodged damaging the Cat by not driving the car with misfire (thanks to the posts on this forum, I knew it is not a good idea to do so)
I'm betting against the "dodging", but anything could happen.

I need to check with the mechanic if he adjusted timing (idle as well run). I requested a "major tune up" and the mechanic replaced all the parts mentioned above. It didn't occur to me to ask him if he checked/adjusted timing.
While you're checking on the timing, ask the guy if he knows how to do it "right". You can't just loosen the distributor and tweak it like the old school engines. You have to follow a specific procedure. Don't do it right and the engine will likely run like crap.

didn't do so. (i.e. compression check)
A lot of info to be had from a properly performed compression check.

How much can I expect to pay for checking/adjusting timing (if not done before as part of "major" tune up), and for engine compression check? This is in SF bay area. A reasonable ball park estimate is OK. I don't want to be taken for a ride :)
thanks again
Couldn't tell ya. Don't live there. If they're like the rest of the clowns in the world, they'll likely soak you for a few hundred $$$ to do a full tune up and diagnostics.
 

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If your getting 35 mpg, passing emmissions and the car is running smooth, personally, I wouldn't waste my time or money on a compression test. As far as adjusting the timing, you shouldn't have to pay anything as it should have been performed as part of the major tune-up; check with your mechanic. Typically, the ignition timing never has to be adjusted on these vehicles unless something was replaced, ie timing chain, distributor, cylinder head, etc. The high NOX could be an indication of normal carbon buildup. I would suggest considering having a top engine cleaning performed, ie Motor Vac or a similar system. Making sure the EGR port is completely clear would be another suggestion.
 

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Discussion Starter #6
Hi jdg, smj999smj: thanks a lot for your help.

> As far as adjusting the timing, you shouldn't have to pay anything as it should have been performed as part of the major tune-up

I've read the "definitive guide" on how to adjust timing and will ask my mechanic if he did check/adjust timing and if so, how. He was referred by friends who have used him for many years - he is said to be very reliable. BTW, my 2011 smog report shows ignition timing as "10 BTDC" and it used to be "8 BTDC" in 2009.

> I'm betting against the "dodging", but anything could happen.

Since there is no Cat malfunction indication, is there a way to test the Cats or should I just replace both Cats? It is probably going to cost a few more hundreds of $$$ and will have to wait a couple of months.

> Typically, the ignition timing never has to be adjusted on these vehicles unless something was replaced, ie timing chain, distributor, cylinder head, etc.

None of the mentioned items were replaced. Distributor rotor, cap, plugs, & wires were replaced as part of major tune up.

> The high NOX could be an indication of normal carbon buildup. I would suggest considering having a top engine cleaning performed, ie Motor Vac or a similar system.

I switched from non-branded gas to Chevron Techron and added Techron after the major tune up. Was thinking of trying LucasOil fuel system treatment or SeaFoam (many of forum members don't seem to think they are useful. I'll try them anyway :)

> Making sure the EGR port is completely clear would be another suggestion.

Will check that. BTW, PCV was replaced as part of the major tune up.

thanks again. you guys rock!
 

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Swapping out the dist. cap and rotor could, in theory anyways, change your timing a little bit if the tolerances on the old parts and the new parts didn't match up (i.e. old rotor was off just a tad to one side, the new rotor is off just a tad to the other side, that sort of thing), but I wouldn't think it would cause enough of a change to matter.

On another semi-related item, how does the engine sound on a cold start? Does it sound a bit like a diesel? With 123K miles on the engine, it just might be time for a new upper tensioner, which also, in theory, could move the timing around just a bit. The upper tensioner is another common "issue" with these engines. Check the stickies for this particular forum section to read all about it.
 

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Discussion Starter #8
jdg, smj: thnaks for your suggestions. Was busy during the week to talk to my mechanic. Finally caught up today.

While you're checking on the timing, ask the guy if he knows how to do it "right".
He said he checked timing after rotor/cap/plugs/wire replacement and it was good. He describe the procedure which sounded similar to the definitive posting in this forum. ["sounded similar" because I didn't have a print out with me when I talked to him].

Aside: I am happy to have finally found a very good mechanic who is also honest. I've friends who bring their luxury cars to him for the last 10+ years and he treats my sentra and altima as well as he treats those.

Making sure the EGR port is completely clear would be another suggestion.
Got the EGR port cleaned today. It wasn't very dirty - don't ask me why not :)

On another semi-related item, how does the engine sound on a cold start? Does it sound a bit like a diesel? With 123K miles on the engine, it just might be time for a new upper tensioner, which also, in theory, could move the timing around just a bit. The upper tensioner is another common "issue" with these engines. Check the stickies for this particular forum section to read all about it.
I didn't know how diesel sounds :) Did a google search and listened to some "diesel sounds" and the description that it sounds like a sewing machine and then listened to my car on multiple cold starts. I don't hear any "diesel sound". The suggestion about checking upper tensioner is a good one anyway and I'll keep that in mind - since my car has 123K miles already. Also asked my mechanic about it. He immediately said that from the sounds of the engine he doesn't suspect anything wrong with it the upper tensioner.

In any case I asked him to look at it when he was changing "front crank seal" today. He didn't find any sign of upper tensioner wear when he had access to that area. I had quarter sized oil drips in my driveway and he found oil coating on the passenger side and as mentioned in one of the stickys, it turned out to be front oil seal leak, which is fixed now.

If your getting 35 mpg, passing emissions and the car is running smooth, personally, I wouldn't waste my time or money on a compression test.
I've already spent a few hundred dollars doing major tune up, front oil seal replacement, and A/C recharge. AC started blowing hot air after 14 years of service :) and since it is wife's car, has to be fixed pronto, no?

The high NOX could be an indication of normal carbon buildup. I would suggest considering having a top engine cleaning performed, ie Motor Vac or a similar system.
Used Chevron Techron concentrated on one tank of gas and Lucas "Deep Clean fuel system cleaner" on the next tank of gas. The exhaust used to smell bad (like rotten eggs) before the major tune up and fuel treatment. After the tune up + fuel treatments, the smell is gone. I also held a clean rag about 2 inches from exhaust (on cold start and after 30 minutes of highway driving), the rag has no oily residue (just water vapor) nor black soot. The mileage has gone up to 34.4 MPG from 32 just before all the work, in mixed city/highway driving).

jdg, smj: even though I am not a DIY'er, I really appreciate your help. you guys are MVPs of this forum!
 

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Aside: I am happy to have finally found a very good mechanic who is also honest. I've friends who bring their luxury cars to him for the last 10+ years and he treats my sentra and altima as well as he treats those.
Hell...somedays that's all a guy needs is an honest Joe to hook 'em up.

Got the EGR port cleaned today. It wasn't very dirty - don't ask me why not :)
Clean gas? :)

I didn't know how diesel sounds :) Did a google search and listened to some "diesel sounds" and the description that it sounds like a sewing machine and then listened to my car on multiple cold starts. I don't hear any "diesel sound". The suggestion about checking upper tensioner is a good one anyway and I'll keep that in mind - since my car has 123K miles already. Also asked my mechanic about it. He immediately said that from the sounds of the engine he doesn't suspect anything wrong with it the upper tensioner.
Sewing machine is pretty close to how a bad upper tensioner sounds.

I had quarter sized oil drips in my driveway and he found oil coating on the passenger side and as mentioned in one of the stickys, it turned out to be front oil seal leak, which is fixed now.
That new seal will probably last another 100K+ miles.

The exhaust used to smell bad (like rotten eggs) before the major tune up and fuel treatment. After the tune up + fuel treatments, the smell is gone.
That might be temporary if only due to the extra additives. "rotten egg" smell is usually a sign of a cat that's been poisoned and is on the way out. You can't restore a bad cat. Hope for the best, but you might want to start looking around for a new one or saving up for a new one.
 

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That might be temporary if only due to the extra additives. "rotten egg" smell is usually a sign of a cat that's been poisoned and is on the way out. You can't restore a bad cat. Hope for the best, but you might want to start looking around for a new one or saving up for a new one.
Will do. Probably in a few months. I've heard conflicting opinions about using Nissan cats vs Magnaflow. Should I stick with Nissan OEM Cats? BTW, it is a 97 model and I believe not a 3-way Cat, introduced a few years later. Also, it is CA model.
 

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Will do. Probably in a few months. I've heard conflicting opinions about using Nissan cats vs Magnaflow. Should I stick with Nissan OEM Cats? BTW, it is a 97 model and I believe not a 3-way Cat, introduced a few years later. Also, it is CA model.
Everything from about the mid-80's and up is a 3 way cat...well, almost everything...but at least all the passenger cars are. Personally, I'd stick with OEM, but that's just me. And since it's a CA model, I'd especially stick with OEM...unless the Magnaflow has a CARB number and is a certified replacement.
 

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It's been almost 2 years since my last post and it's time for smog check. So, changed synthetic oil and filter, air filter, filled up as usual with Chevron gas + 12 oz Techron concentrate.

In 2011, HC went from 9/3 ppm at 15/25 mph in 2009 to 63/36 ppm at 15/25 mph. The car barely passed HC emissions at 15 mpg since the limit is 64 ppm.

NOx went from 178/89 ppm at 15/25 mph in 2009 to 346/201 ppm in 2011.

So, expecting to fail smog test this year, I took the car to my trusted mechanic and expressed my concern about not passing smog this year. He spent about half an hour with the car, adjusted something (he said "air") and charged me too little IMO to report here. I saw him test the EGR (applied vacuum and the engine stumbled) but he didn't remove it or clean it this year.

Took the car for smog test and it passed with flying colors! The emissions now are similar to the ones 10+ years back.

HC: 27/12ppm at 15/25mph Nox: 51/41ppm at 15/25mph

No problem with the CATs and no major expenses. yay! I thought I'd report back. Thanks for all the suggestions :)

rsnissan
:newbie:
 
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