I did some snooping around before I decided to make this thread. My 2004 Acura TL Base just went under the knife and received stage 4 exhaust treatment. I love it in every way, especially the rasp and rice that it's added. I will eventually create a custom exhaust so I'm not driving a ricer. But for the time being, I embrace it.

To the subject at hand, I am having a hard/extended cold starts as well as when the engine is up to temperature, however the hard/extended warm starts are intermittent. I only ever noticed this after I had stage 4 exhaust completed.

So here is my question. Can the absence of the mid muffler and resonator create back pressure issues? I'm not by any means an expert, but to my knowledge a naturally aspirated engine does need a certain amount of back pressure to run correctly.

I know diagnosing issues like this are very subjective when considering mileage, maintenance history, ambient temperature, etcetera. I'm just trying to figure out if what I'm experiencing is a trend, or if was a coincidence.

I'm planing on having a mechanic at work run a Moch fuel injection service kit through my fuel injection system. It's a three stage fuel injection service where one bottle is dumped into the tank, one bottle you cut off the fuel supply and run the engine on the cleaner, and the third is ingested into the vacuum system like Seafoam. I'm starting out with this because now that I am nearing 200k, I haven't had a fuel injection service done to my car in the almost 20'000 miles I have put onto my car.

My second plan of attack was to have my EGR system inspected for the beginning of any clogs. I don't have a check engine lights or any other drivability issues. My car still makes incredible power for the mileage, and gets good fuel economy. I guess my only other complaint is that cold starts consistently return a rough idle. Very occasionally I will be surprised with a cold start idle that is much smoother than usual.

Thanks for your feedback!

 

Well. One question to start with. Do you run premium fuel?

 

Happenstance, that's all.