Crimsonnaire

iTrader: (1)

Lately, I've been experiencing pretty loud pops from the exhaust when I start up. Kinda sounds like popping a balloon with a pin. I did have new AC Delco plugs intalled not too long ago, and one or more may be badly gapped. However, I only experience the pops at startup, not while I'm on the road... At least not yet. I've been driving about 3 weeks.

I've also had the rear main seal replaced at the same time, where the exhaust was cut and then welded afterwards.

Can someone tell me if what I'm experiencing sounds like backfiring? Apart from backfire, what else could cause a popping of the exhaust upon startup?

Any input would be greatly appreciated.

wssix99

iTrader: (5)

Mine has done that at start-up since it was delivered from the factory 9 years ago. It comes and goes. Never thought to much of it. I always chalked it up to being a backfire caused by some extra fuel in the system from when the engine was last shut down.

Crimsonnaire

iTrader: (1)

Yours did it since it was brand new?? Does it only happen at startup or does it also do it when you're driving? Does the sound come from the front or the rear? I would suggest you have a look at the spark plug gaps if they're stock.

I recently confirmed that having too large of a gap could cause exhaust backfires, and I just happen to have new plugs put in not too long ago at Meineke. I was told they come pre-gapped at .060", which is true. But the one I took home with me had a gap of over 2mm! So now I'm trying to get access to the remaining cylinders that I haven't verified yet.

I was told you could blow your catalytic converters with exhaust backfires.

wssix99

iTrader: (5)

It only happens at startup. Never really thought about it 'cause it doesn't bother me. The sound comes from the back of the car at the pipes only on startup when I am a little aggressive with the gas pedal. If I don't tear off out of my parking space, I don't have the issue.

I imagine one could damage a catalytic converter if the expolosion was in the exhaust manifold but that's definitely not my case.

cmc02

my car used to do that to but it stopped once i removed the air and egr system.

Crimsonnaire

iTrader: (1)

You mean you step on the gas pedal as you start up?

When it pops, is it when the engine is firing up, or a second after the engine is fired up?

How do you tell if it's coming from the exhaust manifold or not?

ae13291

iTrader: (8)

after i replaced my plugs with NGK tr55 IX gapped to .050 there is little pop sometimes! but on start up occatinally i get a loud pop sometimes, lik as sooon as it starts on a cold day. honestly i think i had more of a popping problem with the cats on! lol but now the cats are gutted

D-Webz

iTrader: (4)

Yep same with me, It would only happen right after start up. Took them off and there is no more pop.

clean99

mine does the same thing on a cold start when I get going around town untill its warmer, it may have something to do with the 02 sensor because I know mines out or throwing a code for it, or it may be the cat's

Crimsonnaire

iTrader: (1)

Are you guys saying that startup pops are normal for F-bodies?? All this time, I was thinking there's something wrong.

What's the air and egr system?

By the way, what does it mean if you see some black powder gathered on the plugs? If an O2 or coolant sensor is malfunctioning, you would get a code, right?

wssix99

iTrader: (5)

Yea, its sounding normal. I don't think the popping is a full-fledged backfire. I've heard cars really backfire, which causes people to hit the ground lest any bullets be flying around. This is more of a pop/gurgle.

It happens to me if I rev the engine at startup on a cold day and sometimes if I peel out after startup. If the engine is above 100 degrees, it never ever ever happens.

The note above regarding the EGR/AIR systems is interesting. I don't have an AIR sytem in my '99 but I could see that a "leaky" EGR might cause some issues? I understant that it is not supposed to be engaged at idle, but if some gases were recirculating, it might cause incomplete combustion in the cylinder. Either way, I'm not sure its worth getting one's hands dirty to tinker with.

GOR1LA

iTrader: (1)

i think its the o2 sensor. is your o2 sensor bad (service engine light on)? cause with mine it would "backfire" alittle bit and then be fine. I replaced the o2 sensor and she went away. So idk maybe its just mine, but i thought i'd throw that out there.

Crimsonnaire

iTrader: (1)

Hmm. I don't have a code for the O2 sensor, but I did find excessive carbon on my #3 plug. I'll be investigating for a leaky fuel injector, but if that's not the case, then a bad O2 sensor would seem to fit with the exhaust popping situation.

I honestly don't know if I have an air system on my car (don't even know what it is), but I am relieved to hear that startup pops are somewhat common. And I definitely don't want to get more cuts if it's not absolutely necessary. I already accessed all the driver's side plugs, which was unpleasant enough. So I guess I'll just look into the injectors and sensors first.

Is it difficult to install a new O2 sensor yourself? Is the O2 sensor one and the same as the coolant sensor? The coolant sensor was listed along the O2 one in the possibilities for carbon buildup.

Thank you guys very much for your time and input. I truly appreciate it.

Wdpballer46

i could have SWORN i have read on here that its the AIR system trying to heat up the cats, and when they are warm enough it stops... i'll see if i can find the thread.

sladekal

Mine pops/backfires all the time, definitely noticeable after my GMMG Exhaust install. I just got used to it, does it mostly when cold and down shifting with mid/high RPM's.