Question about 1993 Cadillac DeVille

Open Question

93 deville 4.9 failed nox on smog we replaced

93 deville 4.9 failed nox on smog we replaced egr,02 sensor,cat.i srayed carb cleaner looking for vac leak car runs great nox was 1480 co 00 hc 21

Posted by on

  • Colin Stickland
    Colin Stickland May 11, 2010

    scrap it and buy a small car

×

3 Suggested Answers

GodBlessU
  • 3513 Answers

SOURCE: 1994 cadillac deville 4.9 engine fail smog check

Hi


Please check this link to get anid ea if your car failed smog check to troubleshoot your problem.


http://www.smogtips.com/six_things.cfm


Please get back to us if you have further query else please accept the suggestion.
Thank you for contacting fixya.com



Posted on Jul 18, 2011

ZJLimited
  • 17970 Answers

SOURCE: 1994 cadillac sedan 4.9 engine will not pass smog.

The HC is high because the CO is high, CO is caused by to much fuel being delivered. You will want to check the Oxygen sensor and make sure it is functioning properly. You will want to check the fuel pressures, including rest pressure. We have seen leaking injectors cause this problem. You will want to make sure the thermostat is working correctly also.

First thing to do is check over the sensors that control the fuel mixture as it sounds like you're runnign too rich. This could be due to a faulty water temp sensor. If this is the problem then the ECU (Engine Control Unit / aka computer) will be leaving the car constantly 'on choke' and not reducing the fuelling as the engine warms - so unplug the sensor and clean the contacts on both sides with some switch / electrical cleaner (not WD40) and inspect the wiring for any signs of damage to the insulation especially where it runs over other components and through the bulkhead

If the engine is running well and the state of tune and ignition timing is good (15 degrees BTDC) then most likely the converter itself is bad. Usually NOx readings will go down as HC and CO readings go up, and as a result it is extremely rare for a car to fail an emissions test with all three things if the Catalytic Converter is working properly.

A bad oxygen sensor can also cause a failure similar to this, but will usually cause HC/CO readings to be high (but NOx readings would be low), or the opposite - high NOx but low HC/CO readings. The O2 sensor is located in the exhaust manifold just before the bulge of the catylst and at the point where the 4 pipes join together.

Unfortunately there is no good way to test the Cat. Highly specialized equipment is necessary to do this, however a temperature test might clue you in to one that is bad.

After driving the vehicle for several miles, immediately check the temperature of the converter at the very front and the very rear of the unit itself. The rear should be at least 100 degrees (F) hotter than the front. If the two are close to the same temperature then it is proof the converter isn't working very well.

I have to note though that temperature testing is far from conclusive. I've seen converters that pass test with flying colors but still ended up needing to be replaced.

Aftermarket converters tend to be less effective than factory converters because they are not built specifically for your vehicle. Instead, a universal unit is welded into some exhaust pipes so that it will fit. Generally this isn't an issue, but if you live in a 'green' state such as California where emissions standards are very strict, it could pose a problem.

Keep us updated.

Posted on Aug 02, 2011

  • 5 Answers

SOURCE: 1992 cadillac sedan deville fail smog high nox. The cars runs fine already replace plugs cap and rotor injectors ?

Replace the catalytic converter with dealer part aftermarket such as carquest or napa are only designed to last about two years!and make sure egr system functioning properly also.

Posted on Dec 24, 2011

Add Your Answer

Uploading: 0%

my-video-file.mp4

Complete. Click "Add" to insert your video. Add

×

Loading...
Loading...

Related Questions:

1 Answer

93 Plymouth voyager failed smog with high NOX .I've replaced transducer and EGR . The EG R was used and works . No check eng lite on but did pull codes #34+43+55


Although I could not find those specific codes, the grouping centers on various faults to the oxygen sensor, which was my first guess when I read about the high NOX levels. My local Advance Auto stocks the Denso direct fit oxygen sensor (Part No. 234-4004) for the 3.3 liter V-6 for $50.

http://www.allpar.com/fix/codes/new-codes/oxygen-sensors.html

Sep 09, 2014 | 1993 Plymouth Voyager

1 Answer

1996 dakota 4 cyl. won't pass smog test nox is 225 over limits. Asked smog tech it has no egr. I replaced 02 senser ,flushed cooling system, used seafoam as directed on bottle. All those steps dropped nox...


any leak above the o2sensor can throw everything off down the line.
be it a intake or exhaust, sounds to me like you found your problem allready,Gary

Oct 24, 2013 | 1998 Dodge Dakota

1 Answer

1992 cadillac sedan deville fail smog high nox. The cars runs fine already replace plugs cap and rotor injectors ?


Replace the catalytic converter with dealer part aftermarket such as carquest or napa are only designed to last about two years!and make sure egr system functioning properly also.

Dec 24, 2011 | 1997 Cadillac DeVille

1 Answer

SMOG test passed ALL except "NOx" results were 696 Limit is 585. Any easy fixes ??


I've had good luck using CRC's "Guaranteed to pass" fuel system cleaner. Follow the directions exactly. It should bring all the smog numbers down--perhaps get your NOx number low enough.

If the EGR valve is not working properly, it will lead to high NOx. Check for a leaky vacuum diaphragm on this valve. It will not only keep the EGR from working when it should, but also lead to a lean mixture that burns hotter, thus generating even more NOx.

Check for vacuum leaks. Any extra air that makes the mixture lean will contribute to high combustion temperatures and high NOx--even if the EGR valve is working.

Finally, if those steps don't work, it could be your catalytic converter is getting old and inefficient. Don't be surprised if you need a new 'cat.

Feb 27, 2011 | 1987 Acura Legend

1 Answer

I took my daughters 1995 Nissan Altima for its two year smog inspection and it failed three times due to nox failure at levels around 1400. Back in march of 2009 I took it to a reputable shop and they...


Check the ports if there is any carbon,I doubt it,
but you got to look
I would make sure you don't have overheating issues
That is the cause of NOX (High Combustion Temp)
Check fuel pressure
Use synthetic oil in engine
Check PCV Hoses etc

Feb 06, 2011 | 1995 Nissan Altima

1 Answer

High nox fail smog test any remedies? 99


NOX is created when the internal combustion temperature gets to high.The egr system uses burnt exhaust gases to line to cylinder walls.The purpose of this is decrease internal combustion temperature therefore reducing the amount of NOX created.Would look to a possible egr malfunction usually they will trigger the check engine light but not always.The 4.3L has been known to have issues with carbon buil up in the egr and the egr pintle not open and closing properly.

Jun 07, 2010 | 1999 Chevrolet Astro

1 Answer

1992 dodge stealth failed smog test with high NOx reading at idle. passed perfect at high rpm , failed at idle. hat causes a high NOx reading?


NOX is produced when cylinder temperatures exceed 2500 f.
Your vehicle has 2 ways to directly reduce NOX, EGR system, and catalytic converter, and also the cooling system indirectly.
Take a look at the EGR system, vacuum lines, pipes, and make sure the diaphragm moves. Disconnect the vacuum line, then push on the diaphragm and plug the hole (from vacuum line) when you release the diaphragm there should be vacuum. Also you may want to take it out and give the EGR passages and EGR valve a good cleaning, with some type of carbon cleaner like carb cleaner.

Mar 10, 2010 | 1992 Dodge Stealth

2 Answers

2000 chevy s-10 2.2l engine fails smog check due to high nox at 15mph.


Possible carbon build up need to clean system depends on your mileage and condition of your engine watch also for possible bit of overheating during testing look for vacuun leaks.

Jan 07, 2010 | 2000 Chevrolet S-10

1 Answer

1990 Dodge Dakota Smog Issue


Question

PPM of Nox or Co or HC?????


The base of the EGR and the EGR air passage tube will collect carbon over the years.

Most car over 65,000 will fail Nox and has high CO because of the partly block passage.

The only way to clean to the air passage tube is with a lot of WD-40 or similar cleaner.

The EGR valve can be clean or replace under $68 ////gasket for around $3.

Make sure there is NO LEAK when you put the EGR valve back in place.


Please post what PPM is failing on reply.





Jul 06, 2009 | 1996 Dodge Caravan

1 Answer

Cant pass smog failed nox got 2032,allowed 695 95 bmw 318i


Since your car has no EGR valve, you have one of two problems. You either have a bad O2 sensor, making the car run lean, or you need a new Cat. Or, you've had a bad O2 for so long that it ruined your cat, and now you may have to replace them both. Either way, I'd highly recommend having a smog tech take care of this problem for you, since you have no access to a smog machine that will tell you if the repairs you've done have solved your problem.

Jul 02, 2009 | 1992 Oldsmobile Cutlass Supreme

Not finding what you are looking for?
1993 Cadillac DeVille Logo

Related Topics:

140 people viewed this question

Ask a Question

Usually answered in minutes!

Top Cadillac Experts

yadayada
yadayada

Level 3 Expert

70387 Answers

Colin Stickland
Colin Stickland

Level 3 Expert

22041 Answers

Jeff Turcotte
Jeff Turcotte

Level 3 Expert

6878 Answers

Are you a Cadillac Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides

Loading...