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Symptoms of clogged precats???

G

getsum111

Yes I am a Pirate, 200 years too late.
Joined
Apr 5, 2005
Messages
4,188
Location
Pillaging in Freedom, PA.
Was drivin' home having my usual issues, hesitation from idle to about 3500 rpm's. Then, it sounded/acted like the motor was louder, but the increased noise didn't increase speed. Then, I got a kinda buzzing sound that seemed to come from two spots. One source seemed to be under/around the EGR valve. The other sounded like it came from under the car. Can't be more specific as it was snowing/raining pretty good.
Left car at the mall parking lot, as I was barely able to get it there from about 1/2 mile away. The car will idle, but when i give it throttle, the motor feels like it's chocking. I've never heard a colapsed/bad precat, but this is kinda what I imagine one would act/sound like.
I did do the "el-cheapo duratec exhaust test" from the FAQ's about two weeks ago. Loosening the O2 sensors didn't improve the hesitation i've been dealing with for a long time. See post titled "hesitation/bucking is back" for full rundown. Anyone have experience with a clogged precat? What did it act like. ALso, no CEL.
 
The symptoms of a plugged exhaust are very similar to poor fuel dilivery (weak fuel pump or clogged fuel filter). That is a severe loss of power that gets worse as the revs climb.

One of the most noticable differences is the restriced sound from the tailpipe, giving a wheezing type of sound. Stand at the back of the car and have someone rev the engine. The difference in noise usually isn't subtle.

Also there is a tool for measuring exhaust backpressure. It is similar to a tire gauge. To use it, a small hole is drilled before the suspected restriction and a reading taken with the engine reved up at a steady speed, then another reading after the suspected restriction. A restriced cat would show a significantly higher reading before the cat. I never needed such a tool. I was always able to identify exhaust restriction by other means.

Other than the early 95 models for which there was a recall, the V6 Contour has not had much of a problem with plugged exhaust. The 4 cylinder has had more of a problem though. A plugged exhaust plays havoc on the EGR system, melting and blowing out the hoses to the DPFE.
 
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Happened to me twice-once on my 95 and again on my 96. 95 covered by warranty, 96 not. Distinct smell of rotten eggs. Car got louder as honeycomb material was blown out of rr precat. Ruined the main cat. Headers now-no worries!
 
Maybe, but another symptom of the cats being plugged up is engine running hotter. I would also think the O2 sensor after the precats would throw a CEL, since they could not be working to well. Based on your description your EGR may be stuck open.
 
Kevin, yes, I think it is now, but there is definately a restriction in my exhaust. You can hear the air being held up. I'm afraid I messed up either my EGR or DPFE. I'll have to check them out when I do the header install. :shrug:
 
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