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Discussion Starter · #1 ·
I've got a 98 Vulcan pwrd Wagon with 170k and it runs pretty well. I notice a very very slight miss at idle (very slight) and a little less power than my sedan had, but other than that no real performance issues.

How do I know if the rotten eggs is the cats or if it's a fueling issue?


The exhaust smells like it should (like a new car) until it warms up and the idle drops to normal run idle.
 

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I've got a 98 Vulcan pwrd Wagon with 170k and it runs pretty well. I notice a very very slight miss at idle (very slight) and a little less power than my sedan had, but other than that no real performance issues.

How do I know if the rotten eggs is the cats or if it's a fueling issue?


The exhaust smells like it should (like a new car) until it warms up and the idle drops to normal run idle.
put in new motorcraft platinum plugs and spark wires if you have not done so recently. Check all vacuum hoses closely for cracks and replace as needed. change air filter. change fuel filter. after all normal maintenance, get a live OBD2 scanner and see what its doing real time if its still not up to snuff. both of my Vulcan will occasionally miss-fire at idle.
 

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Discussion Starter · #3 ·
Forgot to mention it's got new plugs and wires. It only misses slightly after it's warmed up. That's what makes me thing fuel. And the miss is VERY slight. Barely noticeable.

But it's the rotten eggs smell after it's warm that I'm most bothered by.
 

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The cats have no moving parts, they are a catalyst. Catalyst by nature causes other chemical reactions to happen more smoothly and effectively at lower pressures and temperatures, but without the catalyst being altered or affected in the process. The catalytic converter is designed to last the life of the vehicle.

If you have a mis, fix it. The catalytic converter is not meant to handle unburned raw fuel, and if you get a misfire, that will overheat and damage the converter. The rotten egg smell is ultimately caused by your misfire, but will be most noticeable if your converter has been damaged.

Regardless of whether your cat is bad or not, if you don't fix the other issues that caused it to fail in the first place, you will just end up replacing it again.

Replace all the spark plugs with Motorcraft or Autolite double platinum plugs, if needed replace the wires with Motorcraft. Check the Long Term Fuel Trims with a scan tool. Whatever you do, don't ignore the warning signs. If the converter fails, you will likely be forced to do something, and it will likely cost a lot more than a tune up.
 

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Forgot to mention it's got new plugs and wires. It only misses slightly after it's warmed up. That's what makes me thing fuel. And the miss is VERY slight. Barely noticeable.

But it's the rotten eggs smell after it's warm that I'm most bothered by.
well, is it only missing at idle, or is it missing under load? If its only occasionally misfiring at idle and you have done the rest of the maintenance, i would just leave it at that. Like i said, both of mine occasionally misfire at idle, at load, there OK. If you really concerned, get a live scanning OBD2 scanner and see what the fuel trims and such are real time. If the plugs have been in awhile, you might pull them and inspect for any plug that looks different from the others that would indicate a problem in that cylinder. You might also run a few bottles of injection cleaner through it or maybe seafoam too. Bottom line, when you get a car pushing 200K, its not going to be perfect. Do what you economically can to it, and drive it until it dies. If your really ambitious, take off the intake, clean it out with the IAC, and put new gaskets on it. That might take some gasket leaks out of the equation (if there are any) Keep in mind too, a head gasket that's starting to go can cause some misfire symptoms as it leaks occasionally. If you losing coolant, you might consider that possibility. My old 93 was misfiring pretty good and would clear up after it was run. I am pretty sure that was head gasket issues, but i drove it to the Upull under its own power.
 

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Discussion Starter · #6 ·
I've never heard it miss under load. The plugs were toast when I bought the car. I used Autolite Double Plats and Napa wires. Seemed to help.

Also to Kahn, I'm not sure the cat cannot cause a miss. I know if they plug they're very power/performance robbing. Also, I know that with no exhaust the engine won't run right once it warms up. I'm guessing that's O2 sensor/control related. I know that from experience. When I replaced the intake gasket and timing gasket on this car I ran it for a few minutes with no exhaust just to see if there was a major restriction somewhere.

There was LOTs of timing chain stretch. I really should have replaced the timing set while I was in there but money was tight and this is a 170k car so I left it.
 

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I've never heard it miss under load. The plugs were toast when I bought the car. I used Autolite Double Plats and Napa wires. Seemed to help.

Also to Kahn, I'm not sure the cat cannot cause a miss. I know if they plug they're very power/performance robbing. Also, I know that with no exhaust the engine won't run right once it warms up. I'm guessing that's O2 sensor/control related. I know that from experience. When I replaced the intake gasket and timing gasket on this car I ran it for a few minutes with no exhaust just to see if there was a major restriction somewhere.

There was LOTs of timing chain stretch. I really should have replaced the timing set while I was in there but money was tight and this is a 170k car so I left it.
If your concerned about the O2's and such, get a real time OBD2 scanner and look at the fuel trims and O2 sensor graphs real time. I got one at harbor freight for about $100 on sale with coupon. Get on the harbor mailing list and they send you 20% off coupons from time to time. I think if your cats were really plugged, it would bog way down under load. I am kind of curious about the stretched timing chain comment. I wonder how many higher mileage Vulcans suffer from this and what the result on engine operation is? Up to now, i have never changed one on a Vulcan. Had to do one on My S10.
 

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Discussion Starter · #8 ·
If your concerned about the O2's and such, get a real time OBD2 scanner and look at the fuel trims and O2 sensor graphs real time. I got one at harbor freight for about $100 on sale with coupon. Get on the harbor mailing list and they send you 20% off coupons from time to time. I think if your cats were really plugged, it would bog way down under load. I am kind of curious about the stretched timing chain comment. I wonder how many higher mileage Vulcans suffer from this and what the result on engine operation is? Up to now, i have never changed one on a Vulcan. Had to do one on My S10.
There's a guy on here who posted a picture of an old stretched on on the gears compared to a new tight chain and there was a big difference. Mine was just like his old one (really stretched).

I would think that'd effect fuel economy since valve timing will be a few degrees retarded with the stretched chain. I think ignition timing might be retarded too since the cam is retarded and it depends on the cam sensor for it's timing cue if I'm not mistaken.
 
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