Rotten egg smell under slight accel

mavmavv · Feb 20, 2008

So, what do you guys think it is? I just smogged the car, its really clean under cruise and slight acceleration. Im thinking it could be coolant, but its a very strange smell. Maybe the rust in the cooling system or something? I dunno, do you guys have any ideas?

jd-hart · Feb 20, 2008

A clogged converter?

mavmavv · Feb 20, 2008

Thats what the smog guy said it might be, how do I check?

mavmavv · Feb 20, 2008

wait, what converter? Torque converter or Cats?

Edit: I just thought about what I asked, A TC cant really clog. My cats are brand new magnaflow.

giddyup306 · Feb 20, 2008

A rotten egg smell is typically a good indication of a plugged cat con. Their are several ways you can test it. You can take out the 02 sensors and put a pressure gauge in and rev the car to 1500 RPM. I made a tool with a bad 02 snapping off the end and hooking up a low pressure fuel gauge to it. I think the Ford spec is 3 PSI (anyone know for sure what it is?). You can also monitor the inlet and outlet temp with a heat gun, use a 3/5 gas analyzer, or with OBD II vehicles you can monitor the post cat o2s but the first method is usually the easiest. But you can have a bad cat and not have any excessive backpressure. I ran into that once.

mavmavv · Feb 20, 2008

Damn, Im gonna have to contact magnaflow if its bad, I really dont want to ship that thing back.

giddyup306 · Feb 20, 2008

mavmavv said:
Damn, Im gonna have to contact magnaflow if its bad, I really dont want to ship that thing back.

It is very probable that you have a bad cat. Things like an overly rich mixture, oil, and just plain abuse (mustang owners never mash down the throttle) kill a cat.

mavmavv · Feb 20, 2008

giddyup306 said:
It is very probable that you have a bad cat. Things like an overly rich mixture, oil, and just plain abuse (mustang owners never mash down the throttle) kill a cat.

The thing is that the cats are only a month old and I havent really noticed a drop in power. My friend here at work says the cat may just be "working", or breaking in. On a certain road I always get the smell, Its a slight uphill and the speed limit is about 50, once I get to the top I can almost always smell it. Under regular city driving its not there at all.

giddyup306 · Feb 20, 2008

mavmavv said:
The thing is that the cats are only a month old and I havent really noticed a drop in power. My friend here at work says the cat may just be "working", or breaking in. On a certain road I always get the smell, Its a slight uphill and the speed limit is about 50, once I get to the top I can almost always smell it. Under regular city driving its not there at all.

Do you live in a state that has emissions standards by chance? You could have the vehicle tested and see for sure if they are bad. This would be a lot cheaper than having a shop diagnose it for you. I generally stay away from exhaust work but I don't remember having any "break in" period for a cat con. Like I said you can have a bad cat w/o it being plugged. You could wait and see if it clears up but I doubt it will.

mavmavv · Feb 20, 2008

giddyup306 said:
Do you live in a state that has emissions standards by chance?

Yeah, I wish I could toss the cats, but im in CA. Gotta have it all.

Bolt on 5.0 · Feb 20, 2008

Try running different or better fuel. Sometime a bad tank of fuel can cause a egg like smell.

Bolt on 5.0 · Feb 20, 2008

also are you running the air pump to the cats?

mavmavv · Feb 20, 2008

Yep, all emissions equipment is set up and running properly. Ill have to wait it out and see, everything is functioning properly and power is ok (Its got 2.73's so its still slow as a dog) it just stinks sometimes.

facemelter71 · Feb 21, 2008

Your car is running rich.If you smell rotten egg's that means your cats are working properly.For the cats to clean up unburnt fuel it goes through a chemical and heat process,one of its effects is the rotton egg smell.If you smell it,your junk is workin,and workin hard.Your car is running overly rich and the cats are workin overtime to clean it up.I highly doubt that magnaflows cats are gonna clog.Any one who says that the rotton egg smell means they are bad,has to take another look at it.

mavmavv · Feb 21, 2008

Ok, thanks for that knowledge! The last time I got the smell was before I went through the wiring and got rid of my CEL. It was running very rich at the time. My car has been running much better lately and I haven't gotten the smell.

As always, I appreciate the help guys!

redneck15431 · Feb 21, 2008

I would also check to see if your cats are glowing when you notice the smell. Another indicator that your car is running rich. I had a bad spark plug last year when I was first done doing my H/C/I swap, and it was arcing off the head and letting unburnt fuel get into the exhaust. Looked underneath my car and seen the cat on the passenger side glowing cherry red. Put in new plugs; problem solved.

giddyup306 · Feb 21, 2008

facemelter71 said:
Any one who says that the rotton egg smell means they are bad,has to take another look at it.

Even if that wasn't the original problem unburnt HCs will kill a cat fast and their is a very good chance that it is now bad. I've had several cars come in with a missfire and a week later it comes back with catalyst inefficient code in memory.

FWIW in my previous posts I was also assuming that the engine was running correctly.

facemelter71 · Feb 22, 2008

He also said he didnt have any running issues.Lead me to assume that the cat is not clogged as performance would suffer almost immediatly.

mustangmike6996 · Feb 22, 2008

have you tries switching grades of fuel... or switching brands???? i know this sounds dumb but i work for lexus and there is a TSB for this exact complaint (yes i understand we dont drive lexus).... just thought id let you know... get the little things out of the way first.

jrichker · Feb 22, 2008

Dump the codes and see what the computer says is wrong…Codes may be present in the computer even if the Check Engine light isn’t on.

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great. You watch the flashing test lamp or Check Engine Light and count the flashes.

See http://www.troublecodes.net/Ford/

If your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see http://www.midwayautosupply.com/pc-7208-90-equus-digital-ford-code-reader-3145.aspx – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.

Look for code 41/91 (O2 sensor problems) or code 42/92 overly rich fuel mixture (leaky injectors, high fuel pressure, bad spark plugs)

Rotten egg smell under slight accel

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