I took my truck in to get checked for an exhaust leak, and come to find out the driver side pre-cat is completely destroyed inside. so the guy is going to cut both out and replace with a single cat, not a high flow though...

anyways he noticed a weird gurgling sound coming from the CAI. I have a K&N '77 series on my 2001 4.2. has anyone ever heard of something like this? could is have been caused by the damaged cat? or is it a totally different problem, not dealing with the CAI?....

i really dont want to take off my K&N, so do you guys have any thoughts?? Please....

 

if it gurgles as he is trying to rev the motor then its just because of the cat not allowing the air to flow through. so your motor is taking in more air than its letting out. that is if the cat is clogged. i dont think it would be anything wrong with the intake except maybe a dirty filter.

 

filter has been cleaned in the past month. i talked to the guy and he took the 1st cat off and said it looks alittle contaminated, but still cant really tell if its plugged, or destroyed really....i will find out all the details tomorrow.

 

I am not sure what this has to do with the EGR system, but the K&N intake is not likely doing anything for you unless your motor is highly modified.....ie stroked, forced induction etc. So getting rid of it in favor of a factory air intake system would not hurt anything as long as you maintain a clean filter.

As far as the clogged exhaust causing noises at the intake........never heard of that one.

 

i have never heard of a cat being contaminated. ive only heard of them melting, plugging up, breaking apart. please explain what they mean when you find out.

 

I agree it has nothing to do with EGR, and if you take 2 cats out and put a single one in, that will help performance as less back pressure allowing the truck to fart easier, assuming this doesnt mess with the 02 sensors. (I dunno how many are on a v6).

Also, your K&N is probably fine I wouldnt mess with it. It will increase power despite what benmon says. You may not feel it but it actually does. Its hard to feel a power increase when a truck weighs between 5-6000lbs.

A clogged exhaust can make a noise if it was EXTREMELY clogged. If cats get melted close they truck will have to much exhaust build up and and will cause the engine to run horribly as it cannot take in any air because it cannot fart any out. Thus it could possibly go back out through the intake, however your truck would be near undriveable for that to happen.

 

See if you can understand this analogy:

Stock air intake flows up to 950cfm
The K&N flows up to 1600cfm
The stock motor flows 750cfm

(numbers for demonstration only)

Sure the K&N flows more air, but does that matter? Not really unless you increase the displacement or the volumetric efficiency somehow.

If there is blockage in the exhuast, more HP gets used up on the exhaust stroke to get the exhaust gases through the said blockage and out the tail pipe. If the blockage gets too severe or if there too many other demands on the motor (the weight of the vehicle, other parasitic load etc.) in addition to the load caused by the blockage, the motor will stall.

Exhaust coming out the intake???? Explain that one...

 

im not exactly sure what he meant by "contaminated". the only thing i would think of is he's saying that something is inside that isnt supposed to be.
as far as the egr goes, the only thing i can come up with id the inside of the cat is restricing airflow out, therefore causing more pressure to the EGR....but hes not sure what exactly the noise is. the did a simple vacuum test last time i took it in....hooked a hand pump gun up to the intake and pumped a few times, and it didnt do it...so i dont know. like i said, i was just wondering what you guys might think. i will know more tomorrow.

 

Havent seen it on a ford, but on a few buicks where they have the 3.x motors that have a two into one pipe which then goes into 1 cat. Ive actually seen a few in which needed towed in due to the cats melting completely shut. The car will run fine until the exhaust cannot hold any more exhaust causing the car to stall, but so far a few times Ive seen them almost "burp" in which exhaust will back its way out just as the car stalls. Its real hard to describe. Could just be buicks but Ive seen it before.

I also understand ur anology about CFM of the motor and air filter. However I still cannot believe that companys dyno (any make model and air intake) and show improvements. I honestly dont know enough about it to go into further details, but Unless all the companies and independent people doing it themselves all lie, I really believe a intake will improve HP/TQ on a vehicle.

I mean you could say that about exhaust too, same thing if a motor only expells so much, doing a cat back or header back on a stock motor wouldnt gain much of anything, but it seems the opposite too.

Now this is all given some companys have more restricted intake/exhaust set ups. But I still believe both would help his truck. If he already purchased it, he might as well keep it on there too.