Any Ideas?

[markNtennessee]

My Expy is a 2001 EB 4X4 5.4l 3.55LSD and i have put a drop in K&N filter and opened the breather box up ( mod i seen on some forum). It not the gotts mod, Also i have a SI/SO flowmaster 40 series and rear 2 cats removed.

I'm having issues now with no low end power, i have plenty top end power when passing on the interstate, but no take off at all. I have read on several other forums that it could be due to the flowmaster, and to get my low end performance back i should look at a magnaflow muffler to replace it with.

The truck isnt miss firing or running bad now, it just just lacks power.

What do you think is the culprit robbing my low end torque?

 

[panda24619]

that happened to me while wheeling this past friday. but mine was cause of a dirt filter, which i still havent replaced, and my gf had the air on. other then that idk what it could be. clean the maf sensor with some maf fluid. and clean the filter. that should help. if not then it could be too much back pressure from the flowmaster. oo and check that elbow in the back along the firewall. i had no low end torque when mine went out.

 

[Racenut]

I still have my two rear cats for now, but I removed the factory Y and replaced with a DI/SO Flowmaster and also removed the rear resonator and I picked up power across the board ( low end and high end) not to mention about 100 miles per tank (if I can keep my foot out of it ) I would recomend checking what panda said, and how many miles are on it? o2 Sensors? Now on days where the outside temp was around 95 - 100+ and I was driving in the city, I was loosing some low end but found it was due to heat soak on the CIA, wrapped it with a product by Thermo Tec and it took care of the problem. ( see last pic )

 

[markNtennessee]

the truck has right at 160000 miles on it, and as far as i know its all factory components on it. I have changed the plugs about 6 months ago and they were not that bad, so i suspect they have been changed in the past. I have cleaned the air filter and the MAF, but that didnt seem to help. I just got some deep creep and i think im going to take the TB off tomorrow and clean it and the IAC real good and see if that helps. After all i have read on the internest, I really think that its the flowmaster causing the power loss. you can stand next to my exhaust when it idling and when you rev the engine and there isnt much coming out at all, compared to my wifes 4 banger. Also my brother has an older model chevrolet truck and it has alot more flow coming out the exhaust than i do. I have had my cats checked and the shop that checked them said they were fine.

I have checked the elbow on the back of my intake, and its not cracked and leaking.

I might need to look at that heat wrap, cause i did notice that if my truck sits at idle for a while and its hot outside then it does seem to be more sluggish versus when i start it up and drive it when its cold and cool outside.

 

[Racenut]

the truck has right at 160000 miles on it, and as far as i know its all factory components on it. I have changed the plugs about 6 months ago and they were not that bad, so i suspect they have been changed in the past. I have cleaned the air filter and the MAF, but that didnt seem to help. I just got some deep creep and i think im going to take the TB off tomorrow and clean it and the IAC real good and see if that helps. After all i have read on the internest, I really think that its the flowmaster causing the power loss. you can stand next to my exhaust when it idling and when you rev the engine and there isnt much coming out at all, compared to my wifes 4 banger. Also my brother has an older model chevrolet truck and it has alot more flow coming out the exhaust than i do. I have had my cats checked and the shop that checked them said they were fine.

I have checked the elbow on the back of my intake, and its not cracked and leaking.

I might need to look at that heat wrap, cause i did notice that if my truck sits at idle for a while and its hot outside then it does seem to be more sluggish versus when i start it up and drive it when its cold and cool outside.

You should be able to feel the exhaust coming out. The Flowmaster is actually a free flowing design and will let more thru than a stock muffler that is why they are so much better than the stock mufflers that use a "packing" to make them quite. The Flowmasters do NOT use any kind of packing in them, they actually just use baffles to redirect the exhaust and that is why they flow more. In all reality the only time the Flowmaster would make it worse is if you are running a stock motor and go to say 3" exhaust pipe all the way back with no cats at all, because then you get rid of close to all the backpressure and the motors do require some. When I put the Flowmaster on mine I can feel almost double what used to come out at idle and I put on the big three chamber 70 series it is 26" in overall length. To me it sounds like your problem is some where else, does your exhaust ever smell like rotten eggs? If so your cats could be plugging up, there really is no way to tell if a cat is GOOD OR BAD without pulling it off but the symptoms you have definatly point in that direction (ie; cats start to plug, flow decreases and backpressure increases this will make the motor take longer to get up into the higher RPMs because it is fighting the back pressure, but once the RPMs are up their it is not as noticable) one thing that you can do is start the truck in your drive way and once it warms up bring the rpms up to 1500 or so and hold it there for a couple of min. then get out and look undernieth at the cats if they are almost completly plugged some times you will see them glowing red.

If it where me I would start by replacing the cats with some aftermarket cats, and also changing out the o2 sensors ( when the o2 sensors get old and dirty the vehicle starts to run on the rich side, meaning you burn more fuel and get worse mpg not to mention the extra work the cats have to do to BURN off the extra fuel leading up to the cat pluging) Just my .02 but with that many miles and what you have described that is what I would do.

You may also want to try and use some Sea Foam to clean out the inside of the motor from carbon deposits, just fallow the directions and on the expy's use the vaccum line that goes to the brake booster ( it will feed all 8 evenly). Hope this helps and keep us posted.

 

[markNtennessee]

I have seafoamed my engine a couple times since i have owned it. Now the muffler shop that i had check the cats said that the 2 i have left on the truck were working fine and they claim that i had plenty of exhaust coming out of the truck. the truck dont struggle to build up rpms, it dont go when the rpms build up at low speed, almost like the parking brake is not fully released. it doesnt do this all the time. now after reading one of your posts on this thread, it got me to think about my intake, Now my breather box is completely modified and my K&N filter is completely open to breathe, but its breathing from inside the engine compartment, so I suspect that at lower speeds and at idle, its breathing hot air from the engine, and maybe thats killing my power. Cause i mentioned before about its more sluggish after i sit at idle for a while. what do you think?

I dont see how a Flowmaster is a Free flowing muffler, cause of the baffles? it seems that the baffles would restrict the exhaust and create more back pressure versus having a muffler that is more of a straight through design. But i dont know, i have never been much of an exhaust guru.

 

[panda24619]

hmm... i would say its lack of air but obviously your not haveing the air come from the fender. idk what it could be. and the baffling to create some back pressure. cause engine do need it. what you can check is take the muffler off and have it straight piped for a day and see if you still have the lack of power. nvr mind the sound will be louder but if that is it the baffling could be causing too much back pressure for the engine. then just get a free flowing muffler.

 

[Racenut]

It does sound like you could be getting to much hot air, I had to order the hot air sheild from Airaid for my CIA and also like I stated before wrap the intake tube, but the reason I had to wrap it is because mine is aluminum. If you are running the plastic one those don't absorb as much heat but you definatly need to duct it to the fender or some where it can get cooler air. I am still looking at cutting the hole in the fender a bit bigger so I can duct it down behind the headlight area to make sure I can get the coolest possible air. I live in southern NM and during the hot days 95 + and I am in town I still have issues, but if it is around 85 - 90 the truck runs like a ***** ape and in the winter months even better.

As for the Flowmaster the "baffles" are actually just <<< depending on the series you get will contribute to how many < there are. These "Deltas" as they call them basically make the sound waves cancel eachother instead of absorbing them, which alows the gasses to freely flow thru Where as a standard muffler usually has multiple preferated cores that have been wrapped with many layers of a fiberglass and steel padding to absorb the sound, they go thru one and then the gases turn to go thru another and sometimes turn again and go thru another. These preferated cores actually slow down the gasses as they are directed thru the cores and into the abosorbing material but they are quite unlike the Flowmaster or another high end muffler where they have the rumble becasue they are less restricted and more of a straight thru design.

With all of that said, it sounds like you are on the right track now let me know how it turns out if you can get some cooler air into that beast. I am even playing with the idea of a fiberglass cobra style ram air hood for mine, but that will have to wait with the price of $1000+

 

[markNtennessee]

tomorrow, i going to call a few salvage yards and see if i can locate a breather box and if i can, i will install it and do the gotts mod on it and see if the hot air is hurting my performance and if its not, I guess im going to be on here again asking more questions. I'm definately going to change the muffler out though, i'm really not satisfied with the sound or performance with the flowmaster.

 

[Racenut]

If you are going to change out the flowmaster you should look at doing the 2 into 1 setup, getting rid of that factory y really helped mine alot. I hope everthing works out keep me posted.

 

[markNtennessee]

ok, bought another breather box for my truck, and now my low end power has greatly improved.. But now when i have been idling for a few minutes, like my wife ran into the store for about 5 minutes and when i put it in reverse and start to move the RPM's go way down like its wanting to die and then they jump back up.. it had done this twice since i put the breather box on.. I'm going to clean the IAC and the MAF along with the TB to see if that cures it..

 

[panda24619]

mine dose that if i start my truck shift into drive and turn the truck really fast it goes down to like 400 or 500 rpm. dont remember then it jumps right up. its always done that. so not a big deal at least for me.

 

[Racenut]

Just checkin to see if cleaning the MAF and the Throttle body made a difference? After you mentioned that I got to thinkin and could not remember the last time I had done the same so I went and bought the electrical cleaner for the MAF and some throttle body cleaner and holy S**T ! I can not belive the difference it made.