Failed Inspection - High Nitrous Oxide

1986 volvo DL wagon, 4 cylinders --no idea what the engine size is.

Any suggestions on an inexpensive fix for this problem?

Reply to
Larry Winkler
Loading thread data ...

CA SMOG2?

High NOX implies lean mixture or too high temperature burning, at any rate. I've had trouble with my '88 740GLT and my '93 Toyota on NOX. Replacing the 02 sensors, general tune up (plugs, cap, rotor, oil change, air filter change) _AND_ new cats got me under the limit for both cars. But just barely.

Generally speaking the SMOG techs may have some suggestions. Take the car to a good exhaust shop and ask them to test the cat - they'll put it on a rack and check the temperature before and after the cat. IRRC the temperature after the cat should be about 2x what it is just before. They shouldn't charge you for this.

-K

Reply to
Kelsey Cummings

On Sun, 13 Feb 2005 11:11:42 -0500, Larry Winkler was reputed to say:

Du a full tuneup - new air filter, check the mixture, the timing, etc. That will get it as low as it's going to go without mechanical work.

Then... here's a sugegstion... may work, may not...

I had a 1979 Ford F250 truck that just barely didn't pass on the first try. The tech told me to come back in a month and in the meantime run at least four tanks of Shell premium gas through it (35 gal per tank) plus a couple of bottles of fuel injector cleaner (even though the truck has a 4-barrel carb). I had been running cheap Arco regular exclusively.

It passed with a bit of room to spare.

YMMV

Mike

Reply to
Mike

DO YOU LIVE IN JERSEY? MY 96 850 DID THE SAME THING, DIDNT DO A THING TO IT RAN IT THRU AGAIN AND IT PASSED. ITS ALL A SCAM. KELLY

Reply to
Kelly

What's interesting in Illinois is that instead of actually testing the emissions from the tail-pipe, they just do diagnostics via the OBD-II connector.

Beverly

Reply to
Bev A. Kupf

Those engines have an ignition system that "over advances" ignition timing at part load. This is done in search of better fuel economy, but ends up doing not much more than raising combustion temperatures which causes NOx formation. On the windshield washer bottle is mounted the ignition computer. Disconnect the vacuum hose and plug it, or if the emission shop will get excited about a disconnected hose, put a ball bearing inside the hose and put it back on. This will cause the timing to run at the full throttle setting at all times, and I'll bet you won't notice any fuel economy change.

Reply to
Mike F

What if you have an older car such as mine with no OBD-II?

Reply to
James Sweet

Just heard from a friend that a dealer in Marin has been having 3 brick cats installed on older Volvos (with 2 brick cats) when they hit a car that is in otherwise good shape but can't pass smog for high NOX.

I don't think you are alone on the high NOX problem.

-K

Reply to
Kelsey Cummings

Mike, I also have high nox problems ('83 245) and have been looking for a fix to get it to pass (CA) smog. There's an article on brickboard that describes what you're suggesting. It talks about a "control unit transducer" and plugging a line to it. I looked all over the net (and in my manual) and couldn't find a picture/description of the unit so I could find it and plug the line... If this is the same as the unit on the washer bottle, thanks for identifying it! Is the vacuum line you refer to on the side of the unit, toward the front of the car? Now, on to my dilemma. First time I had it smogged, it passed the pre test. Took it two blocks over to the test station. The tech at the smog station noticed this vacuum line disconnected, hooked it up and the car failed. (pinging badly I might add) I plugged the line and reconnected it and that causes the motor to ping so much I'm afraid it's going to burn a piston. undrivable. Why (if you know) would the motor run fine and pass smog with the line disconnected and unplugged but rattle so much with it plugged? I'm tempted to cut a hole in the line where it's not visible, just to get it to pass.

Reply to
Clay

What you're looking at is the correct thing. The only thing I can think of is that you managed to trap a vacuum inside the transducer, which would put the timing on impossible advance at all times. As long as there's full ambient pressure trapped in there you should be fine.

Reply to
Mike F

Mike F wrote: > What you're looking at is the correct thing.

Thanks Mike. I thought about what if the plug leaked and pulled a vacuum in the transducer then didn't let it equalize. We'll try it again & check for a good seal... What do you think about tossing 10% methanol in the tank for the test?

Reply to
Clay

Methanol will help reduce combustion temperatures so it can't hurt.

Reply to
Mike F

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.