catalytic converters smoking!

crazypete · 03-16-2003, 03:30 PM

So we were driving around yesterday and suddenly my friend goes "yo dude, your car's on fire!" and I looked and lo and behold, we were billowing smoke from midcar underneath. I further investigated today and reproduced the smoking after going around the block. The car seemed to have power cutouts and uneven acceleration, then suddenly I saw a LOT of smoke. I look underneath and see the cats and flange area (I have a pair of high flows mounted right on the other side of the muffler inlet flange) smoking wildly. This is the same amount of smoke as, lets say, I had smeared oil on them! I saw a bit of white smoke out the tailpipe earlier. The only thing I did was change the oil and top off the coolant. I dialed the idle screws in a bit cause my mixture guage was telling me it was rich. I hear a little doof doof popping coming from underneath.

I dont perticularly care, but I'm gonna try and have it inspected this week and I cant have the ole girl billowing smoke: they dont appreciate the comedy of this at mass inspection stations

Thanks guys!

oh yeah, and the car doesnt want to idle gracefully unless it is set rich on the idle circuit (68/70 jets/ 6.5 powervalve, silver sec spring). I have the air tube crossover, air tube feed in front of the cats and pcv nipple in the valve cover all hooked to dump tubes that exit behind the rear axle.

Technick · 03-16-2003, 04:19 PM

The A/F mixture screws would not affect the car driving down the road at all. That is why they are refered to as the idle screws. They affect idle A/F ratio only. If the rest of the carb is lean then the cat can get so hot it will melt undercoating off of the bottom of the car and drip on the hot cats. If the car is undercoated. I have also seen debris get in the carb and plug a primary jet and cause a lean condition. But that is counter to your gauge saying the carb is rich.

red82gt · 03-16-2003, 04:47 PM

Do you have an air pump hooked up? What's probably happening is that your car is either too rich or it needs the extra air from the air pump to burn the unburned fuel in the exhaust. The extra fuel in the exhaust is clogging your cats and the media in the cats is burning up.

crazypete · 03-16-2003, 05:10 PM

Yeah, the plugs did seem a bit crispy looking (white) and the A/F guage does one of two things: it's either up in the orange or red or blank (there is a very small window where it will bounce randomly up and down). Basically, theyre probably crap.

No, I'm not running an airpump. I'm using all the airtubes to suck exhaust out rather than put air in.

03-16-2003, 03:30 PM	#1
crazypete Registered Member Join Date: Sep 2002 Location: Boston Posts: 592	catalytic converters smoking! So we were driving around yesterday and suddenly my friend goes "yo dude, your car's on fire!" and I looked and lo and behold, we were billowing smoke from midcar underneath. I further investigated today and reproduced the smoking after going around the block. The car seemed to have power cutouts and uneven acceleration, then suddenly I saw a LOT of smoke. I look underneath and see the cats and flange area (I have a pair of high flows mounted right on the other side of the muffler inlet flange) smoking wildly. This is the same amount of smoke as, lets say, I had smeared oil on them! I saw a bit of white smoke out the tailpipe earlier. The only thing I did was change the oil and top off the coolant. I dialed the idle screws in a bit cause my mixture guage was telling me it was rich. I hear a little doof doof popping coming from underneath. I dont perticularly care, but I'm gonna try and have it inspected this week and I cant have the ole girl billowing smoke: they dont appreciate the comedy of this at mass inspection stations Thanks guys! oh yeah, and the car doesnt want to idle gracefully unless it is set rich on the idle circuit (68/70 jets/ 6.5 powervalve, silver sec spring). I have the air tube crossover, air tube feed in front of the cats and pcv nipple in the valve cover all hooked to dump tubes that exit behind the rear axle. __________________ 91 GT Carb conversion, holley 600 double pumper, edelbrock performer intake, FMS "C" drop springs, march 1000 underdrive pullies, crane 1.7 roller rockers, GT-40P headers, bassani x pipe, american thunder catback, FMS 4.56's, msd aL6, trunkmount battery, A/C eliminator kit, 3000 stall tci streetfighter, AOD with transgo kit, A+ servo, 300M hardened lockup shaft, kevlar bands and 28,000 gvw trans cooler, 3 core radiator, 300 lbs stripped with a full interior

03-16-2003, 04:19 PM	#2
Technick Registered Member Join Date: Feb 2003 Location: Seattle, Wa. Posts: 175	The A/F mixture screws would not affect the car driving down the road at all. That is why they are refered to as the idle screws. They affect idle A/F ratio only. If the rest of the carb is lean then the cat can get so hot it will melt undercoating off of the bottom of the car and drip on the hot cats. If the car is undercoated. I have also seen debris get in the carb and plug a primary jet and cause a lean condition. But that is counter to your gauge saying the carb is rich. __________________ No matter how much you spend, or how much you prepare, there is ALWAYS someone else faster or quicker than YOU!!!!!!!!!!

03-16-2003, 04:47 PM	#3
red82gt Sober voice of Reason Join Date: Nov 1998 Location: Kelowna, B.C., Canada Posts: 1,514	Do you have an air pump hooked up? What's probably happening is that your car is either too rich or it needs the extra air from the air pump to burn the unburned fuel in the exhaust. The extra fuel in the exhaust is clogging your cats and the media in the cats is burning up. __________________ 393W: AFR 205's, hydraulic roller, TKO600.

03-16-2003, 05:10 PM	#4
crazypete Registered Member Join Date: Sep 2002 Location: Boston Posts: 592	Yeah, the plugs did seem a bit crispy looking (white) and the A/F guage does one of two things: it's either up in the orange or red or blank (there is a very small window where it will bounce randomly up and down). Basically, theyre probably crap. No, I'm not running an airpump. I'm using all the airtubes to suck exhaust out rather than put air in. __________________ 91 GT Carb conversion, holley 600 double pumper, edelbrock performer intake, FMS "C" drop springs, march 1000 underdrive pullies, crane 1.7 roller rockers, GT-40P headers, bassani x pipe, american thunder catback, FMS 4.56's, msd aL6, trunkmount battery, A/C eliminator kit, 3000 stall tci streetfighter, AOD with transgo kit, A+ servo, 300M hardened lockup shaft, kevlar bands and 28,000 gvw trans cooler, 3 core radiator, 300 lbs stripped with a full interior

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