Hi all, today I finally decided to the people of my neighborhood a favor by installing a new muffler. However, with the muffler on the damn car won’t start. 90% sure the cylinders are getting too much gas because the exhaust stinks of it (the car was running a little rich even with the muffler off). The PO had a tuner chip installed and it ran fine with the old Flowmaster. I don’t know how much more restrictive my new Dynomax is (if at all), and I’m thinking reverting to the stock tune fix may help remedy my problem, but I want to know if there anything else that could be causing my no start condition?

 

Replacing a muffler would not cause that. Something else is wrong...

 

There's fuel pump wiring in the general area you were working on. Check fuel pressure, if you have that check for spark.

 

Was the muffler welded on?

 

I really do not have much to go on, based on the description....

So... Maybe a clogged Catalytic-Converter

 

The muffler was not welded on, and the car runs fine without it on, so spark and fuel pressure are a non-issue. As for the cats, I’m pretty sure they’re blown out as opposed to clogged…

 

What does the computer think engine temp is?

 

if it runs fine without the muffler, then the muffler is clogged.

 

I just took the muffler off, it isn’t clogged or anything it just doesn’t flow well enough. The car starts right up with it off. The muffler I want to have on is a Dynomax super turbo, which flows quite a bit better than stock, but it don’t work on my car. I’m still thinking it’s the tuner that the PO installed that’s causing my problems, but I’m open to you guys’ thoughts on what it could be

 

It's a little difficult to grasp the possibility of the restriction of a "standard" muffler preventing an engine from starting, considering backpressure should be almost non-existent at cranking speeds. My dumb-guy guess is that something is going on within or with installation of the muffler.

 

I also can't see the possibility of a new muffler being restrictive enough to choke out a car, there's something else going on here. does it run at all with the new muffler? Verify your fuel pump is running, you have pressure at the rail, and spark going to your plugs.

regardless of this issue, I would ditch that worthless chip and go back to stock prom if the engine is stock, intake and exhaust doesn't count.

 

Maybe the new muff was manufactured wrong? Baffles in the wrong place or some other similar manufacturing derp

 

Thats what i was thinking, maybe a baffle or something slamming shut once the car is starting up...…. there is just no other explanation going by what the OP said. car runs fine without the muffler, and wont run with the muffler installed.
i have had a very clogged catalytic converter before and the car still ran with that even.

 

Mouse nest inside the muffler?

 

I have seen the Cats Fail and end up stuck inside the Mufflers, clogging the exhaust system many times...

 

Yah I'm with the others, if it runs after removing the muffler then maybe it's defective/clogged inside. Is it a used, new to you or a brand New out the sealed box muffler? Got a part number?

Otherwise like also mentioned the cat is clogged and with the muffler on, makes it too restrictive.

 

Howdy all, to answer your questions the muffler is brand new. Still have the box for it. (It’s a Dynomax 17739 by the way) I visually inspected it, it isn’t clogged, and I pushed some air thru it with my shop vac just to verify. I also verified that it wasn’t installed incorrectly.

The engine itself is mostly stock. Only mods are to the ECM (as mentioned) and a 3 inch intermediate.

At this point, what the hell could be causing my issue? Maybe the muffler really is defective, I dunno

 

Just curious; what was the result in terms of how the engines ran under those bad CAT/clogged muffler conditions?...

 

Any of the following individually, or any combination there of:

-Hard to get to start and run... sometimes stalling-out over and over.

-Poor idle quality, and difficult to rev/ increase Engine speed/ RPM.

-Fowl exhaust odor and/ or abnormal exhaust sound quality.

-Engine temperature climbs easily.

-Vehicle struggles to accelerate/ struggles under a load.