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Old 07-30-2010, 01:07 PM   #1
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Passing Emissions with 1990 Chevy 454 Class A RV..???!!!!

Just bought an RV for a great deal and figured I'd need to do some work on it as it had a loping idle and none of the appliances would function without battery or generator so got it home and got started.

Everything on this rig was pretty dirty but after cleaning, lubing, new batteries it turns out almost everything works great. I had to rewire the rear air conditioner as somehow the romex wiring in the wall was shorted together. . . weird! Anyhow I have everything working.

List of what I've done:
Batteries $160.
Tires $1150 ... installed at my home
Complete lube. Oil, trans, chassis, differential and coolant $50.
Converted Dash AC to R134a from R12 $50.
Tune up= Plugs, wires, cap, rotor, air filter and pcv valve $50.
Timing adjusted to 10 degrees advance.

The loping idle has gone away and I did find a disconnected vacuum hose to the carb which I replaced.


PROBLEM!!
I took it to emissions and it failed TWICE on the HC (hydro carbons) at idle and load.

Before the first test, here is what I did:
Replaced plugs and wires and did all fluid changes.
I checked the Egr valve and it is functioning properly (holds 10" vacuum indefinitely and rpms drop significantly when vacuum is applied in place of vacuum hose).
HC reading first test: Loaded 392, Idle 509

Before the second test I replaced the pcv, air filter, rotor and cap. I also advanced the timing to 10 degrees.
I then added 3 bottles of rubbing alcohol to the gas tank and here are the reading on the second test: Loaded 748, Idle 781.

It might be important to note that the idle and loaded limits are 300.

So all my efforts to pass had the effect of doubling the hydro carbons emissions.

Anyone have any advice on this? Should I mess with the timing?
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Old 07-30-2010, 02:57 PM   #2
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Did you try a infrared remote thermometer to see if the cat is working?
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Old 07-30-2010, 03:08 PM   #3
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thermometer

Thanks for that info.
I have a ir thermometer, never thought of using it on cat converter.
What should I be looking for?
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Old 07-30-2010, 03:21 PM   #4
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If I remember correctly advancing the timing actually works against you when smogging. When my son had his old Mustang smogged we set the timing at about top dead center it was totally gutless and we had to set it while waiting to be smogged but it passed with flying colors. As soon as the test was done we had to advance the timing to drive it home.
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Old 07-30-2010, 03:32 PM   #5
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I think the max temp on a cat is 1000F. It starts it's afterburning process at 600F (inside the cat). I'm not sure what the outside case temp. should be but you might compare it to a working cat.
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Old 07-30-2010, 04:08 PM   #6
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Set your timing back to factory specs, too much timing causes you to fail right away. Do you have a carb? If you do it is more than likely partially to blame for your troubles. I have two carb set ups, one for smog and one for power. If you know how to build carbs, do a good rebuild, floats included. Also check the throttle shafts, the bores in the carb body wear out and you wil have to bush them.
J
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Old 07-30-2010, 05:21 PM   #7
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You really have 2 carbs that you switch out? lol. That is awesome!
It does have a carb that I am not too familiar with. There are no mixture adjustment screws or idle screw. It has electronic...?injectors?... that spray gas in from the top. I'd really prefer not to mess with it since it seems to be performing and is controlled by the system without any adjustment screws.

I WISH I knew what factory specs for timing were on this thing. Anyone?

Also, I can't see the timing teeth marks in the grooves, it's just too hard to get a good look at it. There's a large V groove and then 3 smaller v grooves to the right and one small v to the left. This is of course looking down and from the BACK of the engine since I'm in the cabin of the motorhome crankin my head under the dash 2" from the spinning fan!!!! Yikes, that's how you work on motor in one of these things isn't it? Anyhow, I have it set at the tip of the peak between the 2nd and 3rd v on the right which I am guessing is 10 degrees.

I'm thinking maybe I'll set it to TDC, where it runs crappy, and run it through one more time to see if I can squeek by before I invest in the cat converter. Anyone have any input on that?
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Old 07-30-2010, 06:52 PM   #8
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If you can see the harmonic balancer when under the coach looking at the motor hand crank the motor until the grove is lined up with TDC. Make sure you aren't 180 degrees out, can check that by pulling the number 1 plug and putting thumb over hole and determining if on compression or exhaust stroke. Once you've got it to TDC then take something to mark the harmonic balancer in an area that you can see when under the coach. I usually use white out and mark a line across the balancer and onto the engine. Now you have a new reference point for TDC and can adjust accordingly.

If it was me I'd go as close to TDC as you can and still keep the engine running since your first attempt was close to passing. Are you trying to smog the vehicle in California if so I feel your pain.
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Old 07-30-2010, 10:26 PM   #9
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Quote:
Originally Posted by woodstockaz View Post
You really have 2 carbs that you switch out? lol. That is awesome!
Yep, in California you do what you have to to keep them running. Sounds like you have fuel injection. After you get the timing set, take a good drive, get the engine god and warmed up and go straight to the smog station. You need somebody who REALLY knows how to pass old GM stuff.
I had a guy but he moved and I can't find him, so I had to go
multi-carb.
J
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Old 08-02-2010, 04:34 PM   #10
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SOOO FRIGGIN PISSED!!!!!!!

Spent a couple hours this mornin replacing the Catylitic Convertor. Set the timing back to "factory specs" which apparently is supposed to be 6 degrees advance and ran it through emissions.
SO JUST TO RECAP That's new spark plugs, wires, distributor cap, rotor, O2 sensor, catylitic convertor, 3 bottles of alcohol in tank, all 8 cylinders reading 143-146 psi on [COLOR=#0072bc !important][COLOR=#0072bc !important]compression [COLOR=#0072bc !important]test[/COLOR][/COLOR][/COLOR]

AND IT FAILED AGAIN!

GOOD NEWS is that it finally passed the load test for hydrocarbons, but the idle test is WAY TOO HIGH!! The Carbon Monoxide on the idle test jumped real close to failing too which was a surprise.

Wits end..........................................
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Old 08-03-2010, 02:11 AM   #11
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Quote:
Originally Posted by woodstockaz View Post
SOOO FRIGGIN PISSED!!!!!!!

Spent a couple hours this mornin replacing the Catylitic Convertor. Set the timing back to "factory specs" which apparently is supposed to be 6 degrees advance and ran it through emissions.
SO JUST TO RECAP That's new spark plugs, wires, distributor cap, rotor, O2 sensor, catylitic convertor, 3 bottles of alcohol in tank, all 8 cylinders reading 143-146 psi on [COLOR=#0072bc !important][COLOR=#0072bc !important]compression [COLOR=#0072bc !important]test[/COLOR][/COLOR][/COLOR]

AND IT FAILED AGAIN!

GOOD NEWS is that it finally passed the load test for hydrocarbons, but the idle test is WAY TOO HIGH!! The Carbon Monoxide on the idle test jumped real close to failing too which was a surprise.

Wits end..........................................
This may help you out.
http://www.autoshop101.com/forms/h56.pdf
J
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