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STRONG Exhaust smell

245 Views 11 Replies 4 Participants Last post by  BoltspeedMen
Hey guys, I picked up a 03 RCSB Silverado a while ago. It was originally a v6 truck but the person I bought it from did a 5.3 gen 4 swap along with a 4L8e swap. He replaced the heads to 706 heads that are lightly ported. He did a Btr stage3 cam kit, DOD delete & used 6.0 truck intake and injectors. He put a new magna flow muffler on it as well.
So far I have replaced the mass air flow sensor on it with a new OEM one. I put a new 02 sensor on it as well. There were codes being thrown for these replaced parts.

But ever since I bought the truck it has a strong odor of exhaust. There are no leaks in the exhaust. It sounds really good with the magna flow muffler but the exhaust smell is enough to knock you out when standing by the tail pipe. It smells at idle and will fill up the garage instantly. Outside you dont smell it in the cab with the windows closed but you will smell it at idle with the windows down if the wind blows your way.

I do have a EVAP large leak that is intermittent and kicking the CEL at times. Im currently trying to find that leak.

Can anyone share some advice on what I can check to cure the strong smell? Is it possible it's the magna flow muffler itself?
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probably not the muffler. I would look at the engine fuel trims, to see how the ecm is running the engine, perhaps something is making the ecm put too much fuel into the engine. There might also be codes (yes, you can get them even if the cel is off).
 

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Sorry, I didn't process the first part of your post. I would guess the tune for the truck needs to be done/redone. You don't mention if the guy had it tuned, but all those parts will require it, and if it was tuned, it probably wasn't done right.
 

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Discussion Starter · #5 ·
Sorry, I didn't process the first part of your post. I would guess the tune for the truck needs to be done/redone. You don't mention if the guy had it tuned, but all those parts will require it, and if it was tuned, it probably wasn't done right.
I honestly can't say if there is a tune on it or not as I never thought to ask the seller nor did he offer the information either. He caught covid and I was in a bit of a hurry when I purchased the truck as I needed one and didnt want to really stay around him since I didnt catch covid at the time. lol!
Anyway, over the months of owning this I've been reading from others posting stuff about what theyve done to their truck & that they needed a tune once you change up to these types of parts.

I will definitely agree with you about it not being done right as I have found a few things he claimed where done or new and weren't. My fault there. But in my defense the seller bragged about being a performance shop yet the truck wouldnt pass inspection where I took it once the sticker ran out. The front suspension needed to be replaced according to my shop. Im kinda bitter about that yet but oh well part of it is my fault too. It drove well with a bit of wooble/play or loose feel from the lower ball joints. I made the choice to just replace everything since it looked aged.

Can you give me some hints on what to ask some shops to be able to tell if theyre worthy of doing a tune?
I have some mechanic shops around here but absolutely none I know personally or know if they know what theyre doing especially when it comes to tuning a truck. I live in a rural area & hate to trust some garage that doesnt know much about this type of set up and have it come out worse than what it goes in. lol!
Or is there anything I can do to it? I have a zurich z13s code reader that I believe is capable of reading live data. I was going to scout around on youtube to see if there was anything I may be able to try to seek some knowledge on how to do it. I know you have to watch with youtube videos but I have common sense not to touch or mess with something if I dont know what Im doing. I dont want to pay double for messing it up worse myself. lol!

Today I noticed the rpms at idle are at 1100. I'm not sure if that around be the range it should be at with a btr stage 3 cam or not though? Or if that has any effect on it for that matter? Would greatly appreciate any insight on that if you could.

Any help or info is greatly appreciated.
 

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Sorry, IDK much about tuning. I know your code reader isn't going to do anything, you'd know, if it could, because it would be a lot more expensive than other code readers and have "You can do tuning with this" all over the packaging.

The main problem for you is that you have a frankenstein truck, that you don't know exactly what's been done to it.

From what little I know about it, you need to start with figuring out what computer systems are in there running the engine and transmission, as it's my understanding you either need to use a different computer from what's normally used in gmt800's to run the engine because the reluctor wheel in the gen iv engine is different from gen iii's, or he took apart the engine and changed the reluctor wheel to what is used by gen iii's (and probably need to change other bits as well).

You might also verify:
-injector p/n's (either directly with an inspection camera or pull one to verify it) to see what's in there
-check casting numbers and/or labels on the head to verify what they are
-possibly pull a valve cover and use a dial indicator to check how much intake/exhaust valve lift you are getting, to see what cam is in it
-maybe use live data and examine the downstream o2 sensors to see if the cat's are still in working order (some people will punch them out, and then put spacers on the sensors so they don't read correctly, or put dohickeys on the connector to act as fake sensors

Once you've figured that stuff out, then perhaps contact someone like blackbearperformance.com, they seem to have a good reputation (this is not a recommendation of them, just a name I've heard over the years that other people are happy with, there are other good tuners as well, I just can't come up with any other names at the moment), and see what they say about what kind of tune you need and how to get it into your computer.
 

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Are cats gutted? If the truck runs good then that may be your issue. I get the feeling that it is tuned but has gutted cats. Who does all that work and then just leaves stock exhaust lol
 

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Discussion Starter · #9 ·
Sorry, IDK much about tuning. I know your code reader isn't going to do anything, you'd know, if it could, because it would be a lot more expensive than other code readers and have "You can do tuning with this" all over the packaging.

The main problem for you is that you have a frankenstein truck, that you don't know exactly what's been done to it.

From what little I know about it, you need to start with figuring out what computer systems are in there running the engine and transmission, as it's my understanding you either need to use a different computer from what's normally used in gmt800's to run the engine because the reluctor wheel in the gen iv engine is different from gen iii's, or he took apart the engine and changed the reluctor wheel to what is used by gen iii's (and probably need to change other bits as well).

You might also verify:
-injector p/n's (either directly with an inspection camera or pull one to verify it) to see what's in there
-check casting numbers and/or labels on the head to verify what they are
-possibly pull a valve cover and use a dial indicator to check how much intake/exhaust valve lift you are getting, to see what cam is in it
-maybe use live data and examine the downstream o2 sensors to see if the cat's are still in working order (some people will punch them out, and then put spacers on the sensors so they don't read correctly, or put dohickeys on the connector to act as fake sensors

Once you've figured that stuff out, then perhaps contact someone like blackbearperformance.com, they seem to have a good reputation (this is not a recommendation of them, just a name I've heard over the years that other people are happy with, there are other good tuners as well, I just can't come up with any other names at the moment), and see what they say about what kind of tune you need and how to get it into your computer.
i greatly appreciate your information, knowledge, & tips you shared. I still have an EVAP large leak code to correct on the truck and still doing some cosmetics to it plus the a/c system. They never recharged the a/c after the install. It looked thrown together honestly. I had the a/c system checked out and was the shop told me what it needed. Still in the process of getting those parts for it. I did replace the drivers side o2 sensor before the cat. That was one code that came up on it. Currently still seeking someone local around here that does tunes but its a rural area and not many shops that I know of do it. I kinda figured Im on my own with it. I was thinking on getting in touch with the seller and seeing if he knows anyone in his area that does it but Im not sure if I want to do that. He may not respond or ???? who knows.


Are cats gutted? If the truck runs good then that may be your issue. I get the feeling that it is tuned but has gutted cats. Who does all that work and then just leaves stock exhaust lol
You bring up a great point on this. Its one that I havent thought of so a big thank you for mentioning it. The last time I was under there it has the original cats on it but I never thought it might be possible the insides were knocked out.
Is there a way I can tell with the code reader if the cats are working and still there? Thats a very good point and Im really glad ya mentioned it.
I agree on the exhaust but again in my opinion they threw this truck together rather quickly. When I bought it the inspection sticker had a month left only. The seller was struck with covid and I really needed a truck badly at the time. It was a decent looking truck and exactly what I wanted. I liked it alot but once I got to know the truck more I started to really see some things that I didnt notice when I went to look at it. Granted I saw some stuff but still didnt see everything. I asked the seller to get it inspected but the whole covid thing landed him in the hospital so we had to wait for his recovery & it had me scared of catching it upon visiting. lol! Anyway long story short when I took it to an inspection station, they said it needed lower ball joints and wouldnt pass it. So I just replaced the uca and lca arms with new joints, sway bar bushings and stabilizer bushings as well.They all looked to have seen better days.
I love the truck but just have limit knowledge on it all plus searching on how to find out what to do with it. As davester mentioned its frankensteined which is making it harder for me to figure it all out. But man it gives me a smile from ear to ear when I drive it.
 

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For the cat's, I wrote above:
-maybe use live data and examine the physical downstream o2 sensors to see if the cat's are still in working order (some people will punch them out, and then put spacers on the sensors so they don't read correctly, or put dohickeys on the connector to act as fake sensors
 

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1100rpm idle is alot for a big cam. BTR truck stage 3 is a very friendly camshaft. They idle and run smooth with very minor adjustments at 650rpms.
 

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Eyes almost water when your around the tailpipe?
 
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