Smog Check Question

[1987Comanche]

This isn't for my MJ but this seems like a good forum for my question. I have a friend struggling with smog check on a newly acquired '88 Dodge Ram 318 TBI (by Holley, of all people), 727 torqueflite. The smog pump is gone but, then again, so is the small (1/2"?) pipe that would feed air into the exhaust pipe. It came from a state that could care less about emissions.

Anyway we tuned it up (plugs, wires, cap, rotor, air filter, fuel filter, etc) and he took her in. He passed everything except NOx with results as follows:

 

HC: 15.5PPM, limit 155

CO: 0.01%, limit 1.9%

NO: 2002.9, limit 1508 (FAIL)

CO2: 15.2%, no limit

 

The truck runs well and doesn't exhibit any indications of having EGR problems (part throttle detonation or random stalling from a stuck EGR valve). I suggested the O2 sensor next. Any other ideas??

[Jeep Driver]

Move.

[whowey]

Two quick questions.... how far south are you?? and what kind of fuel is he running??

 

The smog pump injects air into the exhaust stream ahead of or at the cat to help burn up unused hydrocarbons. The HC burning process can cause the NOx levels to be crazy...

 

Here is a quick article I found that explains some ideas better than I can.

 

http://www.nichols.nu/tip766.htm

 

Its related to Porche... but smog is smog...

 

One thing to note.. that injected systems always run a tad leaner than carbed ones.

 

BTW.. Holley made the TB units on at least some of the magnum V-8's. My ZJ has one.

[1987Comanche]

Truck is running Ohio emissions test and originally came from NC. It's running regular 87 Octane and I suggested looking for 93 octane oxygenated fuel. Would octane booster be a better idea than the Guaranteed to Pass stuff they sell? The engine is clean (old plugs looked great) so really it's a matter of trading NO for higher CO and HC. I have plenty of room on both of those. BTW cat is brand new.

[randomguy310]

i used to live in socal, a friend of mine would add 1/2 of tank of methenol to what ever car he was going to try to get to be smogged and he swears by it,

[dasbulliwagen]

Since when did Ohio have tailpipe emmissions checks? And if that truck was in North Carolina before, depending on the county it came from, it should have had at least an emmissions tampering check... which it should have failed.

 

And high Nox is usually caused by high combustion temps, which is usually held in check by EGR... so maybe the EGR is stuck closed or unhooked as well. Good luck.

[1987Comanche]

Don't know when Ohio started tailpipe sniffers. This is the first of his vehicles that's needed the sniff check.

I'll look into EGR. From what I can tell bumping the timing back should help clean up the NOx too. HC and CO will go up and he'll loose some power but it can be reset as soon as the E-check is over. I'm just not sure how far to retard the timing to hit the sweet spot.

State inspection (NC, NY, PA, etc) is just a money maker, nothing more. That truck was NC legal and I'm sure it was lick-n-sticked more than once along the way. NY was even worse. It's amazing that vehicles with no doors (just vapor barrier and windows) are street legal and pass "safety" inspection. FL got rid of state inspection in 1982 and I felt safer driving through that state than living in NY.

[xjrev10]

Move.

[carnuck]

Retard timing 5 degrees and NOx will drop like a rock.

[1987Comanche]

Retard timing 5 degrees and NOx will drop like a rock.

 

Exactly what I needed to know. Thanks :clapping:

[carnuck]

One heat range colder on plugs often helps too. I put NGK BKR6EK plugs in my '87 and pass the Etest here in Seattle without a cat or EGR (they are there, but non-functional) The plugs also got rid of the ping monster