feelnlo

iTrader: (2)

Whatup. Got my first Fbody, 98 camaro z28 and I love it!

I'm a complete noob to the Fbody/LS1.

I've heard a small backfire in the exhaust when accelerating hard a couple times... and also when revving high and upon deceleration it backfired.

I'm wondering why? Too much fuel?

The only mods on the car are Pacesetter LT, ORY (no rear o2s), no cats, and MagnaFlow muffler-currently no pipes/tips on the "outs."

I do have a CEL on. I think it's due to the removal of the rear o2s since the ORY has no sensor bungs. Are there supposed to be two rear 02s?

The car runs strong but like I said this is my first Fbody so I'm pretty clueless.

Car came with a HyperTech Power Programmer but I haven't had the time to play with it. I also know NOTHING about this at all.

I'm pretty good with engines, generally speaking about repair and maint. I have always done my own repairs when practical, and also rebuilt an older carbed 4 cylinder.

I have ZERO experience with EFI tuning tho.

Anyone have any suggestions for me about this backfire?

Too much fuel resulting from the missing rear o2s?

Any input would be great! Sorry for the noob-ness.

Thanks

406malibu

rear o2's wont change anything about how the car drives. hook up your handheld tuner and there should be an option to turn off that code. when you hook up your programer it should tell you why the check engine light is on.

as far as backfire, it could be due to a couple things. do you still have the air pump connected to the headers, or did you get race headers? does it only backfire when its cold, or always? does your car skip at all? if it has stock wires, it likely is skipping (not enough to hear, but when hooked up to a proper scanner you will see the misses). That was my problem, once I added MSD wires, it no longer backfired.

SSickLS1

iTrader: (2)

if it is backfireing under acceleration (engine load) id say its either a dirty mass air sensor or old front o2's goin bad.

spray the mass air sensor w/some berrymans B-12 chemtool and hook it up to ur code scanner if u still have problems - likely a o2 sensor code will show or misfire - is there loss of power?? Make sure all your filters and plugs are relatively new before u spend alot of $.

SSickLS1

iTrader: (2)

P.S. with that exhaust setup itll always have a lil growl and pop after u get out of it.

ur back o2's may cause the light, but not the mis/backfire, like mentioned before they have nothing to do with how the engine performs

un17real

+1
Yeah its normal with your set up to hear backfiring under acclearation (load)

SSickLS1

iTrader: (2)

not so much under acceleration but after u get outa the throttle after WOT you will likely have some moderate backfire with a low back pressure setup. The engine will dump raw fuel into the exhaust for a fraction of a sec and at night youll even see a back fire flame w/a straight thru setup. If its more than what should be normal w/even a low back pressure setup i say its a sensor/plug/wire issue. Somethin simple. Itsa 98 i bet it has an old *** fuel filter, they never get changed.

Just read ur an M6 so yea between shifts itll do that. Esp if not tuned properly.

feelnlo

iTrader: (2)

I believe it still has the air pump. The headers were on the car when I bought it. I've only had the car for one day. Well I've only had the privilege of driving it for one day. I got the car and have been out of town since the day after...

I noticed that it backfired mildly maybe 3 times on deceleration and a couple times on-throttle load. The car was warm at operating temp (bout 175-180 F, running 160 thermo). I NEVER get into it before its up to temp.

There wasn't any noticeable miss that I recall, but I wasn't giving her all she's got. Runs strong. I'll have to investigate it some more.

Pretty sure its got stock wires. I'm a fan of MSD products so maybe I'll pick some up

feelnlo

iTrader: (2)

Well, it had a mild backfire a couple times under load. It didn't seem to "cut out" tho...Runs strong. I need to spend some more time driving her and figure out exactly how she is reacting to my right foot.

I'll pick up some B-12 (i swear by their fuel treatment).

Car only has 24,000 miles on it. All original. 98 z28/m6

And yeah, always start with the simple stuff first. It couldnt hurt to change the fuel filter... any certain part # i should go with?

feelnlo

iTrader: (2)

BTW it does sound mean

And thanks for the help guys, too bad I'm not with the car right now

fxgs

iTrader: (2)

It happens on deaccerleration as a result of being catless........

feelnlo

iTrader: (2)

Yeah, I had a minitruck as a teenager with no cat and I remember it doing that between shifts. Its just kind of annoying tho

SSickLS1

iTrader: (2)

B-12 is some badass stuff - too bad their not a LS1tech sponsor - we fight over it at work.

a 98 w/ 25k tells me its been sittin. Just get the most expensive filter that your local auto store has for the 98 - 02 f-bod ($16). Its in-line near the drivers side rear tire. It only takes 2 crescent wrenches (i cant remember the exact size) to do it, and be ready to get gas on you. The line will drain and drip out for 2 or 3 min. Do that and get a full tank of good premium gas with some SeaFoam or B-12. Get a can of the spray and blast the mass air sensor with it - i use like a 1/4 can and mines not even dirty. It only takes 30 min to detach the throttle body, clean it w/the rest of the B-12 and reinstall. Not a bad idea when you already have the intake tract detatched (3bolts). Read the sticky in the GM&R sect on SeaFoam if your not already familar with its amazing restorative powers!!!

SSickLS1

iTrader: (2)

P.S. U can turn off the air pump by simply removing the BOSCH relay in the lower fuse box that is labeled AIR PUMP. It wont hurt anything. U can also have a pro tune it out. If your "backfire" still reappears u know it wasnt that!

feelnlo

iTrader: (2)

Thanks bro. I'll check into that when I get back home. I was really surprised (and happy) to find this 98 with only 24000 miles, I think all she really needs is a little attention-- from my right foot! Just need to take her out and play a little bit, have some fun, and blow out the cobwebs!

I wanna make sure everything is straight before I accidentally tear something up tho. Gotta take care of my new baby