Cadillac Seville / Cadillac Eldorado Forum Discussion, '94 Seville SLS High HydroCarbon output in Past Cadillac Vehicle Discussion; so much for trying to make a nice pretty chart for you....lemme know if you cant follow that and I'll ...
After talking to the mechanic about a possible vacuum leak, he's still leaning towards a bad cat. Not heeding the advice of the mechanic, I've tried to identify vacuum leaks with a can of carb cleaner (disengaging the tps sensor first..dont ask) but Im afraid I couldnt tell between a vacuum hose or any other hose so may be missing something...otherwise, not able to find a leak. Wouldnt a bad cat get some kind of error code if it went bad?
One symptom/issue not mentioned before; if I fill the tank more than 1/2 full, a strong fuel smell permeates the cabin...eventually going away. Problem with the evap? And would that cause the HC's to be high at idle?
Another "issue" is intermittent hesitation at various accelerations, like a cylinder cuts in and out whenever it wants to. Even though I ohm'd the coils and all seem to be in range, after lifting the hood and staring at things like a deer caught in headlights, I notice a rapid clicking sound coming from the 6/7 coil. Idle's smooth...not necessarily "cadillac smooth" but smooth enough for the girls I go out with.
I've had a p030 and a p070 code, but cleared them and they havn't come back yet. The p030 came back once after some above average driving, cleared it again and it hasnt come back since. Could either of these codes (I know what they are) have anything to do with high HC's at idle?
Saw you involved in another post on another site called Caddyinfo.com. The conversation went something like this:
"The rest of the EGR must be cleaned out, too."
"REST of the EGR? All that needs to be cleaned is the pintle valve."
"This is a 1994, with the EGR passages under the intake manifold through trenches in the heads. Over about 100,000 miles they fill up and clog. In the 1995 and up Northstars the EGR passages are metal hoses external to the heads but they still need to be cleaned out once in a long while."
"Oh! The "mouse holes". I thought you where talking about the valve, but Angela's is a '96"
So I cleaned my EGR's pintle valve, but knew nothing about mouse holes. Is that something I should have cleaned out to reduce the H/C output? And if so, how does one clean out the mouse holes?
You see those black rivers of carbon in these pics. Those are the EGR passages on a 94 engine. The "Mouse holes" are in between the EGR valve and these "rivers." It might be a pain in the butt to clean them out. It took me almost 2 whole cans of carb cleaner and some pipe brushes to do it.
Finally got the car smogged and passed with flying colors. After avoiding a new cat converter the whole time, it turns out the old one was just dust inside the case. After the mechanic took it off, he came over, tipped the cat converter on its end and "ash" just came out. Installed a new cat, took it to get it smogged and the hydrocarbon output went from 112ppm (max 100 allowed to pass California smog test) to 5ppm. Roughly $320 out the door. Now its time to replace the front hub/bearings. Lets see how cheap I can do this....
'94 would be a "ASM" or dyno test, codes don't matter as long as the stuff out the pipe is clean.
If it fails for HC and CO both it is usually a weak cat, especially when the numbers are that close.
Most things that would cause it to fail a dyno test will be noticeable driving like a misfire. When people get failed emissions tests it is amazing to watch how many parts they just throw at the thing trying to get it to pass.
Vacuum leaks won't usually create an HC problem, it will drive the engine lean. HC is unburned gasoline which only shows up when you don't have enough oxygen to burn the Hydrocarbons.
Oh and EGR is for NOx, or oxides of Nitrogen. It has little to do with anything else unless it sticks open then it can cause some gas reading problems but most of these have pintle position sensors and would set a code for EGR position error.
Glad to hear you got it through, what kind of cat did you put on it?
In the 21 years that I worked on emissions in a Caddy/Olds dealship I've found that when cars 'JUST FAIL' by a little on both H/C & C/O it was the CAT. I know it's not what you want to hear but that's probably what you'll find at the end of all your other solutions.
pfk, you need to buy your converters somewhere else.
The installer is required by law to warranty that catalyst to work for 5 years.
See EPA regulations.
They are installing the wrong one, or a cheap one.