Failed smog...I'm shocked

[skippy3k]

I just took my 95 LWB in to be smogged and it failed. I've never had a vehicle fail smog before. It failed on excessive HC's at idle. The max is 100 and I got 190. At 2500 rpm, my HC's were 65 (with the max being 180) so that was fine. All other tests passed as well. A little Google-magic tells me that HC's are Hydrocarbons and refer to unburnt fuel.

The truck is new to me, so I don't know the history of it. The only thing I did prior to taking it in was changing out the spark plugs to plain old NGK's, changed the oil to Mobil 1 synthetic and Seafoamed it. The cap, rotor, and plug wires look new. The previous owner replaced one catalytic converter, but the other is stock.

After it failed, I looked closer at the engine. I cleaned the stepper motor and found that the air cleaner intake is missing 1 of 2 clips. But I wouldn't think that would have caused the problem? I went to check the timing with my trusty Craftsmen Inductive timing light, but damned if I can figure out what this "degree" junk you guys are referring to. I see the timing mark and the notch on the pulley, but I don't know how to determine if something is 8 degree BTDC or 800 degrees BTDC. I thought there would be reference points indicating 1 degree, 2 degree, etc.

Any ideas? Could the timing be off so little that it would fail?

 

[az_max]

stuck or dirty injectors?

 

[Drillbit]

Does it seem to run alright? You could always get one of those cans of magic mojo that will make you pass. Otherwise i would check the injectors, o2's and maybe your maf. Does your CEL light up when you turn the car on? If not they might have busted the bulb to mask a earlier problem.

 

[MUSKYMAN]

was the car fully hot at the time?

had it been taken out for a good highway drive before testing?

yaking it out for a real good highway drive will often burn off any fuel left in the cats and then it will test leaner at idle.

if its only been chugged around town then started and driven to the test site that can sure result in high HC's at idle.

 

[skippy3k]

Well, Drillbit and Musky brought up some good points.

Drillbit - Yes, it seems to run alright, though I am comparing it to my P38 which ran a whole heck of a lot smoother. In other words, I don't have much to compare to. But I can compare it with my neighbor's 94 LWB this weekend and see. As for the CEL, that occurred to me too after I posted. So I went out and found that it does NOT light up. I suspect the bulb is burnt since most of the other dash lights are burnt out. But if I have a fault, then that should help the troubleshooting.

Musky - No, it wasn't driven that much prior to testing. My wife actually took it in today and the test site is about 2 miles from the house. This came up during some of my Googling, but I discarded the theory as being too simple. But now that you mention it again....

 

[skippy3k]

Check that. The CEL light works fine. You gotta start the engine to see it.

 

[MUSKYMAN]

take it out for a good long highway drive then take it in for a retest...I bet it will pass

 

[Bannon88]

Run the hell out of it, let your engine hit some higher RPM's for a bit, really heat things up a bit to blow off the carbon deposits.

 

[Drillbit]

And just to be sure you are running high test aren't you?

A good hard run on a full take of 94 octane wouldn't hurt. If you have time to run more than a tank through run some injector cleaner but DO NOT go for the test with injector cleaner in your tank

 

[landrovered]

You could tune your maf sensor to lean up the mixture, the rover v8 runs very rich to allow the extra fuel to combust in the cats. I would suggest that your cats are going out. I retuned my MAF sensor because I run cat-less and it is amazing how much better it idles and runs. Go to the RPI website for information on how to tune the MAF. It is not hard.

 

[Chris-St Louis]

Do you have all 5 of your gas readings. That woudl really offer a bunch of insight.....

I wouldnt adjust the maf just yet. The car was make to pass emissions on the factory setting..

I thought you were leaving Dweb?

Oh yeah.... You didnt want me around anymore..


Well, good luck figuring it out.

 

[landrovered]

Tuning the MAF can be temporary, you could reset it after the test.

 

[MUSKYMAN]

Tuning the MAF can be temporary, you could reset it after the test.

what voltage value are you tuning to?

 

[landrovered]

For cat models it is 1.5v for non cat it is 1.0v, I have my 110 running at 1.25 and my RRC running at 1.35.

Linky... http://www.v8engines.com/carbs-2.htm

 

[ptschram]

New plug wires, cap, rotor, oil change, set timing (it's not that hard, BTW-the scale is on the pulley, not the cover).
Get everything back to factory specs and you'll likely be fine.

Run it hard

 

[skippy3k]

Chris, how long were you waiting to pull that one out? :applause: I like Tech Chris. It was General Chris that was wearing thin.

But for what it's worth, here are all the numbers. There weren't any NO percentages listed.

At Idle (674 RPM)
CO2%=7.7 O2%=8.8 HC (PPM)=190 with max being 100 CO%=.5 with max being 1.0

2567 RPM
CO2%=14.7 O2%=.20 HC (PPM)=65 with max being 180 CO%=.44 with max being 1.1

From what I understand, a high HC at idle and an acceptable HC at higher RPM's could indicate a vacuum leak as well. Also, I Seafoamed it a day or so before the test. I wonder if remnants of the Seafoam could have caused problems? Either way, I'll run it hard before the next test...the problem is I get charged each time it fails. I feel like I am gambling.

As for the timing question, just how do I determine the degrees? Is it a function of my timing light? I've only used this light on my older (pre 1970) vehicles.

 

[skippy3k]

set timing (it's not that hard, BTW-the scale is on the pulley, not the cover).

That might explain it. My pulley is pretty rusty and corroded. I'll take a wire brush to it and see what I find.

 

[Chris-St Louis]

http://www.discoweb.org/forums/showthread.php?t=33395&highlight=emissions

First read this...

Second, let me take a look at your numbers in aminute (on a call)

Third, Actually, Wasn't waiting really, it hit me in a moment of genius!

 

[landrovered]

Damn Chris you know your combustion chemistry, I am impressed. You go boy!

 

[Chris-St Louis]

Awe Shucks! You're making me blush. Actually, I can thank the Tree huggers for making me lean such a excellent diag tool.

Keep in mind, a gas engine makes the least EMISSIONS (Not Power) at 14.7 to 1 Air to fuel.

At Idle this truck is enjoying a 24.58 to 1 A/F Ratio! WOW! Holy crap is that running lean.

At load, it is at 14.62 to 1 A/F. Little rich, but not bad at all.

I think California uses IM240, which loads the engine at high RPM for a more accurate reading.

Being that it is SO high at Idle, and in spec under load.... I htink you are hunting down a Vaccum leak. Hoses? Intake? If your intake is leaking coolant already, might was well replace it. It will give you a chance to check all the hoses...

I think y ou have a HUGE vaccum leak! Good hunting!