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All About Exhaust Systems

142 messages,  Last post on Mar 06, 2012 at 1:09 PM

You are in the Maintenance & Repair Forum.

What is this discussion about? Exhaust, Diesel, Fuel Efficiency (MPG), Car Warranties, Coupe, Convertible, Hatchback, Truck, Sedan, Wagon, SUV, Van

Messages Page 14 of 15

#126 of 142 Re: hi [obyone] by turtlesdove3

Jun 27, 2010 (8:15 am)

Replying to: obyone (Mar 20, 2010 2:20 pm)
is this illegal though?

#127 of 142 Re: hi [turtlesdove3] by obyone

Jun 27, 2010 (10:37 pm)

Replying to: turtlesdove3 (Jun 27, 2010 8:15 am)
is this illegal though?
 
Yes it is. Does that stop someone who can't afford a new cat or looking to cheaply increase performance? Nope not in a state that doesn't have emissions testing.

#128 of 142 Cracked exhaust manifolds and defective catalytic converters by kartruck

Sep 14, 2010 (5:33 am)

New poster here with more of a statement than a question and looking for feedback.....
I run a fleet of 127 GMC and Chevy 3500 cutaway box trucks. The 2 issues that have cropped up consistently over the past few years are fuel pumps (inadequate design) and exhaust manifolds that crack before 100,000 miles. I researched every manifold repair I had done and noticed a pattern of prior O2 sensor failure of some sort in nearly every instance. Out of the 9 documented cases, 4 of the trucks also had to have new catalytic converters. My theory is this: Faulty O2 sensors or deteriorating cat converters are the culprits. I believe it's a domino effect starting with the sensor which in turn destroyed my converters and subsequently cracked the manifolds.
 
Thoughts?

#129 of 142 Re: Cracked exhaust manifolds and defective catalytic converters [kartruck] by srs_49

Sep 14, 2010 (6:17 am)

Replying to: kartruck (Sep 14, 2010 5:33 am)
IMO, I do not think a bad cat would damage an exhaust manifold.
 
One way to kill a cat is to have a overly rich fuel mixture , or misfire, which leads to high amounts of unburnt fuel in the exhaust, which in turn "burns" in the cat, overheating and destroying it.
 
So, maybe the crack in the manifold occurred first. This may have led the O2 sensor to think the engine was running too lean, so it caused the ECU to richen then air-fuel ratio, which results in high amounts of unburnt fuel in the exhaust stream.
 
Just a theory.

#130 of 142 Exhaust by bjpayton04

Dec 16, 2010 (6:50 am)

I am having problems with my car. I have been to 2 different Nissan Dealerships, dished out over a 1000 dollars and my car is still doing the same thing. When I crank my car(Nissan Altima 2007 4 cylinder) up it sounds like a loud truck. If I push the accelerator too hard or fast the rpm goes up to like 5 but im only going like 30 mph. If I drive more than 40 or 50 miles in distance the cars RPM goes up to like 5 and I am only going like 40. If I push the car too hard the speedometer needle will bottom out to 0 and if I have to come to a complete stop, like a red light or stop sign and try to accelerate it will only go like 5 mph with the accelerator pushed all the way to the floor and then after a while it will go back to normal. Idling is a huge factor because the car stalls when it idles. PLEASE PLEASE PLEASE HELP!!!!! I am so tired of paying people money and they have no clue what they are doing. What could be causing this problem? They said it could be my exhaust do you think so or is it a sensor?

#131 of 142 Re: Exhaust [bjpayton04] by obyone

Dec 16, 2010 (1:07 pm)

Replying to: bjpayton04 (Dec 16, 2010 6:50 am)
Sounds like a bad throttle position sensor.

#132 of 142 Exhaust smells only when passing(excellerating) by aggiedog

Aug 05, 2011 (9:43 am)

I have an issue that hopefully someone has seen with a solution. My vehicle (Lexus rx350) was rear ended. Prior to the collision, I had no issues with this vehicle at all, exhaust or otherwise. After all repairs including a new exhaust system (catalytic converter all the way to the muffler), I'm now experiencing an exhaust smell in the car typically when passing at higher speeds (45+ mph). They've (Lexus dealer) checked for leaks, they've done something called a "smoke test" but they can't find any leaks at all. I'm not a mechanic so I just read about the exhaust manifold this morning. Could the problem be coming from the manifold (which has not been replaced) or some where else? The smell starts up front and comes in from the floor on the passenger side. That's if the windows are up. if the windows are down, it also comes in thru the front windows too. Any assistance would be greatly appreciated.

Messages Page 14 of 15

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