Rough Idle?
 

I've noticed I've received a rough idle after the Corsa exhaust install.
It's more like a constant vibrating idle. Not all that bad with A/C off, but it gets very anoying when the A/C is on.
Everything in the truck will vibrate from the rough engine idle.
It's been like this for a little over a month now.
What could be the problem? Would the idle need to be raised 50-100 rpms?
I've noticed I can manually raise the idle with the gas pedal and it will almost eliminate the rough idle.
What do you guys think and why?

Jim

Is the exhaust rubbing somewhere? Maybe it's not completely in one of the hangers? You may be experiencing engine harmonics vibrating through the cab.

I tend to agree with with your call about it being likely that the exhaust is touching somewhere. I know that my Corsa is a three peice unit (where my MagnaFlow was a 2-piece) and it was much harder to get it to all go together and get everything turned so everything was lined up well. Some times the more adjustment there is in a system the easier it is to get some misalignment. I'd get under the truck and look the whole thing over. Make sure you have at least 3/10-4/10 of an inch clearance between a pipe and the frame everywhere. Also check all the clamps and the hangers to make sure they are properly installed. On my Corsa I had to get under the truck and put my fert on the diff to get leverage to shove the muffler a little more forward to make it all line up nice. You might have to pry something to make it all good.

No guys, you don't understand. It's not that type of vibration. It touches nothing. It is definately the motor. 100% its the motor not a harmonic vibration from the exhaust touching the frame or underside of truck.
Like I said, if you idle it up between 50-100 rpm's manually the motor will QUIT vibrating or running rough (whatever you want to call it).
Another solution please.

Jim

My Corsa system fit perfect. No grunting, forcing, or prying needed.
I have all the required spacing needed from my frame or bed. All of the exhaust hardware is tight.
The exhaust install being the problem will just need to be eliminated from being the problem.

Jim

Maybe your tune needs to be tweaked a little to compensate for the added load of the ac? Or is it possible that the PCM needs to relearn and adjust to the added exhaust flow? Vacuum leak, air intake leak? I'm trying to figure out how adding a cat back would cause the condition you're describing...no exhaust leaks?

PCM had over 4,000 mi already to learn. No vacuum or exhaust leaks found.
I guess I will just have to have my tune upped 50-100 rpm's on the idle.
I couldn't understand it myself. :confused:

Jim

Check This Out
 

Hey friend, don't feel bad, I fought the same problem for about 4 months until I took it to my buddy's house (who happens to work at a dealership). He listened to it and got under the hood and sure enough.....my crankshaft pulley was making that sound at idle.....because it was too close to the engine. A GM factory oversight. He took it off and re-installed it, pulled it about 1/4 inch foreward and now......no annoying rattle/vibration. Good as new....try it.

I don't think that is the problem. I have 14,000 mi on my truck. The exhaust has been on for 3,500 mi already. It only started after the exhaust install.
I don't see how the crank pulley would cause that. It is torque on at or over 300 ft lbs and it is designed to be seated as far on as it will go.
I assume if he pulled it out a 1/4 in, he would have placed shims behind it as well?? If not.......I don't see that as the right way to do it if he didn't shim it.

Jim

The crank pull doesn tjust slide easily on the crank. The damn torwue to yield bolts suck. The crank pulley problem should not be discounted it could have moved on the crank cause the bolt is not as tight as it should be. The factory torque spec on the crank bolt is 240 ft-lbs. Most of the time I havent been able to get that much on there. I would look under the hood next time it is making that noise and just look at the pulley and see how close it is to the front cover you may be surprised dont discount anybodies suggestion right now Ihave had some annoying problems like that, that were simple solutions. For instance did you know that an engine coolant temp sensor that is going bad can make your truck buck like a damn bull. I didnt and it was something so simple. Check it out it may be worth your time. Other than that man i dont know, you shouldn thave to get your idle raised to make that go away something has to be amiss with your engine. I would take your belt off and check all your pulleys to make sure there is nothing wrong with any of them. It sounds like to me that you have some sort of harmonics going on so IMO that wouldnt be caused by the engine tuning, raising the idle would just cover up the problem.