oilstain

2001 Camaro ss. 99k miles. M6. Have LT headers with true duals, no cats and dynomax bullet mufflers.

As the title states, the passenger side exhaust pipe backfires after I kick it in neutral when I'm about 3k rpm on the highway. And if I rev the engine to about 4500 rpm it shoots black-ish/blue smoke out of the passenger side pipe after I back off. The car HAD a mail order street tune from Frost, but I had the battery unhooked for 6 months when I was deployed so I think that may have thrown off a few things. I'm getting a cam installed soon so I need the car in top shape. What kind of problem do I have on my hands?? Thanks!!!

TyCZ28

is it black or is it blue... it really does matter... but sounds like an issue i had with my car, try cleaning the MAF checking the coil packs.. go ahead and pull all the plugs... black and burnt is ok if theres any wet ones then your not firing on all cylinders...


if its blue smoke then either you lost a ring or your valve seals are toast

mr.beachcomber

TyCZ28 pretty much said it all. Just for clarification on the color of the smoke you're seeing...backing off the throttle at 3,000 RPM creates a sudden high vacuum that can pull oil past the marginal rings/seals into the combustion chamber yielding blue-gray smoke at the tailpipe. If the issue is excessive fuel (either ECM doesn't react fast enough to staunch the flow of fuel or one or more of the ignition coils is weak and not firing the mixture, the smoke is jet black plus you may hear some popping as the excess fuel detonates in the headers/exhaust pipes.

One other item you may want to check is a vacuum leak around the mating surface of the intake manifold and head. The extra air flowing into the combustion chamber may not be apparent at 3,000 RPM as your fuel map may be rich enough to cover the extra air, but backing off the throttle allows the high vacuum to draw in enough air to lean out the mixture to the point it won't fire. Just a thought!

Good luck correcting the problem.

Wrench7777

When u have no muffler and only an slp loud mouth can the motor eat oil" my car eats oil like crazy

oilstain

Upon further investigation, the smoke is black. Not real excited about pulling all the plugs and checking them but gotta do what needs to be done. The engine doesn't miss at all and it idles, starts and runs great. Just the backfiring and smoke worries me!!

TyCZ28

ok so pull the pulgs and check the color to see if theres a random missfire thats not showing up in the comp... an ls1 will idle and run just fine down a cylinder or 2. ive seen mine run on just the driver side cylinders hahaha

beachcomber kinda said it pretty well on check for vacuum leak. easy way to test for that is get a can of carb cleaner and spray all around the intake when the car is at idle and see if the idle jumps up any. if it does then the area you sprayed is were the leak is...


i would say the backfire is normal and more of a rasp pop from the exhaust but there being black smoke runs that theory.. has it been tuned for the longtubes and such? if not get someone to throw HPtuners on it while you drive around and check out the other random possible issues... O2's freaking out when the idle drops, the TPS sending a strange signal, IAT or idle air control issues could also cause this.. but im leaning towards there being a plug or plug wire issue.

oilstain

Thanks folks you have been great!

oilstain

Ill check the plugs and such. I'm getting a cam install plus a full tune from Cunningham MS. So I'm sure he will be able to spot the problem. I had a mail order tune done after the LT's but had the battery unhooked for 6 months so it may have messed up the tune some.