Tackdriver

Ok, here is the deal, I hope somebody can help.
My truck just had the "snap test" done.
It failed the "opacity" part.
I had 68.x percent, max is 40.

Here is the deal. Truck runs fine, I dont want to change a thing. How do I get the opacity back to where it should be? Or is this a dealer only thing?

It is a 98 12 valve, BTW.

All help is appreciated.

Tackdriver

whoops!! wrong forum, sorry about the mix up!

RATTLINRAM

Gotcha moved. ;D

vssman

We need to know more about the truck. Has it been BOMBed or is it stock? Has anyone ever touched the AFC? Did you go through with the boost signal line hooked up to the AFC (I'd try disconnecting that if your pretty close to stock).

Don M

The snap test is a booger to beat. What modifications do you have done to your truck? I have some ideas to help lower the soot output.

Don~

Tackdriver

Ok,
I just flunked another smog test. This after having the guy at the exhaust place put on about a thousand dollars worth of things.

The failure mode is a score of 68 on the opacity test, I am allowed 40. It is a snap test. They gave the last test to me free as they said there was too much smoke for the equipment to work right.

When I first got it 3 years ago, it was straight piped.

So I took it to Midas and they put on a combo muffler and cat. That was yesterday, and today it failed the opacity test again.

The truck (I have been told) has a modified pump. I dont know if it is a TST kit or what, but it runs really well.
Never had any problems until now.

Im sorry I cant be more specific about the pump, but I bought it used. I also replaced the air filter and ran a full tank of diesel that had ATF mixed in it.

Will the star wheel help?

At this point I am very put out by the ordeal

Any assistance is appreciated.

Tackdriver

Vssman
I just looked at the lines coming off the AFC housing.
There are two.

A small one and a larger one that ends up and the wastegate of the Turbocharger.

Did you mean the little or the big?

They both seem to T into the same place

Thanks

MCummings

Sorry you spent all that money on the exhaust. Can you take it back? Depending on the muffler, it probably increased your EGT, and hurt spoolup time (unless a straight through design), the Cat, definatly is hurting performance.

Does your truck have gauges? This can help us determine how much your truck has been modified.

Probably all you need to do is slid the plate all the way back, and tighten up the AFC, alot.

Another trick, is to put something, that might appear permanant, say a piece of wood (2x4) under the carpet to keep the truck from seeing WOT.

The reason your truck smokes is because the injection pump has been modified. No need to run ATF (which is bad for the pump, and injectors), or replace the airfiler (unless it's dirty). You need to turn the fuel down. it seems like the truck has been setup for some good throttle response which almost always leads to more smoke at initial throttle application on the 12V's.

If you aren't familiar with the work done to the pump, or how to do the work, any specialist diesel shop should be able to slide the plate back, or atleast, tighten up the AFC.

Don_M could help you with the procedures as I have only done it once or twice, and it's hard for me to get all the sizes of wrenches correct. (Although, it is a fairly easy process).

Hope this helps,
Merrick

banshee

Tighten the star wheel all the way down... that should do the trick. It'll make the truck doggy off the bottom, so count the turns or clicks so you can set it back.

John

Rebel

Sliding the AFC housing all the way to the rear will also help get rid of any preboost smoke.

kd460

Ran accross this thread last evening. Maybe the info here will help you out some. Good luck, Kevin

http://forums.tdiclub.com/showflat.p...31&fpart=1

dingo

good luck smogging yur truck. I didnt know that they required that in AZ. it sucks. Thats part of the reason that I sold my 78 k5 and bought my ctd, no smog checks on diesels

midwestdually

dont go spending money when everything that you need to do to your truck is going to be FREE. also...NEVER take anything to MIDAS.

Forrest

I wonder if twins are more susceptable to failing this test.

vssman

Sorry for the delay in getting back. The boost signal line goes from the intake to the rear (toward the firewall) of the AFC. It comes off at an angle toward the engine and back of the truck. This hose allows boost (when you make some) to push the AFC lever away from the 'fueling lever' that is riding on the plate. Essentially as long as the AFC see no boost it will limit your fuel. There are a bunch of other adjustments too. The big round 'bell' on the rear of the AFC has an adjustment screw right smack in the middle (It may be covered by a metal cover). Unscrewing it a turn or two will lower your initial fuel amount. Tightening the starwheel spring toward the rear of the truck will limit the amount of fuel just after initial amount and before boost. This adjustment is not needed if you disconnect and plug the boost signal line - or try pinching it. If all else fails, take the AFC off and look for a number stamped on the top of the plate. Don't loosen the plate, just look for a number stamped on top. If it's a TST plate, it will have a number on it and you'll be able to determine what you have from that. Is the test at a local garage or a state run place? If it is a local place ask the guy to take it easy on how fast he slams the pedal to the floor. The block of wood trick sounds good too. This time I'll make sure to have the 'notify of replies' box checked.