1994 Nissan Sentra won't pass smog. What to do first?

Asked by Mar 11, 2017 at 11:19 PM about the 1994 Nissan Sentra Limited (1994.5)

Question type: Maintenance & Repair

The car was given to me after it was involved in a minor accident. It hwas
current on smog and reg. but dmv requires smog for owner transfer. I put
new radiator plus over flow tank, hood fenders etc. It runs great but failed
smog. I had oil changed, trans. flushed, fuel filter repalced but 2nd test
failed. Getting costly as they are charging me $70.00 test. All cars built
before 1996 are costing more and coupons are not applicable. Any advice?

5 Answers

List the reasons that the smog shop failed the car. The song shop should have given you a printout showing why the car failed what does their paper work say? You need to start there by posting the reason the car failed.

17,815

New Air filter, Evap & charcoal canister system good? The EVAP system may be venting fuel vapors into the engine when it is not supposed to, causing high hydrocarbons. Put a new or bigger catalytic converter on it(wait until car is has been ran for a while as cat need to be hot to work, make sure all spark plugs are good and plug wires too, any ignition parts up to par. Use Gasoline Additives to clean the internal engine & fuel injection (do well in advance as you do not want to be burning off excess carbon during a smog test). Fix all Vacuum leaks. Clean PCV valve. Make sure the check engine light is off before your appointment. Warm up your vehicle before testing. In colder weather this may take a few minutes longer. Use Premium fuel(still may have additives but you want the cleanest fuel possible). Wait until any fuel cleaners or additives are gone from the tank. Clean or replace or check for issues with your exhaust gas recirculation system (EGR). You want your car to burn up any extra fuel so plugs/wires/distributor cap & rotor button/timing set correctly/EVAP working/fuel injectors clean/new air filter/ ALSO make sure throttle body/air cleaner and those sensors are cleaned (look up each on net to see how to clean them).

17,815

First and foremost, make sure your catalytic converter (cat) is hot before you go to emission testing. A cat is just a honeycomb of metal that becomes so hot it burns any left over fuel the motor was unable to burn. In order to incinerate the left-overs, the cat must become extremely hot. The best way to ensure your cat is hot, is to cruise your car down the highway for 15 to 20 minutes before you go to test the vehicle. The exhaust temperature is the hottest during light throttle cruise. Running the car down the highway will heat soak the cat, to ensure it will “lite off” during testing. A good old fashioned top end de-carb is always a good idea before emission testing a vehicle. If you can get a full injector purge, that is best. Simply adding BG’s 44k to the gas tank and sucking a bottle of de-carb through a vacuum line also works well. The carbon in a motor becomes hotter than the normal parts of the motor, which can lead to detonation, misfire, or high NOX due to elevated combustion chamber temperatures. Check your cooling system. A faulty cooling system can cause pre-detonation, and high nox. Let your car cool down, and make sure the coolant is full. Low coolant levels can cause multiple problems. As recommended here replace your radiator cap every spring.

17,815

https://shadetreespeedshop.com/how-to-get-a-car-to-pass-emission-testing/

17,815

Also copy & paste above URL:

Your Answer

Sentra

Looking for a Used Sentra in your area?

CarGurus has 1,751 nationwide Sentra listings starting at $1,987.

Postal Code:

Nissan Sentra Experts

  • #1
    L_R
    Reputation
    1,340
  • #2
    Doran Harney
    Reputation
    1,290
  • #3
    Tom Demyan
    Reputation
    1,060
View All

Related Models For Sale

Used Nissan Altima
70 Great Deals out of 1,275 listings starting at $2,750
Used Toyota Corolla
162 Great Deals out of 3,413 listings starting at $2,394
Used Honda Civic
307 Great Deals out of 4,113 listings starting at $1,494
Used Toyota Camry
42 Great Deals out of 1,593 listings starting at $1,700
Used Honda Accord
62 Great Deals out of 1,114 listings starting at $748
Used Hyundai Elantra
156 Great Deals out of 3,443 listings starting at $2,490
Used Nissan Maxima
29 Great Deals out of 324 listings starting at $3,976
Used Hyundai Sonata
45 Great Deals out of 1,292 listings starting at $1,781
Used Volkswagen Jetta
98 Great Deals out of 2,140 listings starting at $1,600

Used Cars For Sale

2017 Nissan Sentra For Sale
452 listings starting at $14,498
2016 Nissan Sentra For Sale
22 Great Deals out of 194 listings starting at $11,888
2015 Nissan Sentra For Sale
23 Great Deals out of 135 listings starting at $9,495
2014 Nissan Sentra For Sale
47 Great Deals out of 241 listings starting at $7,495
2013 Nissan Sentra For Sale
28 Great Deals out of 291 listings starting at $7,380

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.