Unnerving ticking noise under load, may be getting worse

Fastback86 · Post by **Fastback86** » Mon Nov 24, 2008 9:43 pm

My car seems to have developed a ticking noise that's got me worried. The engine is a pushrod 3.4L V6 with some custom parts on it (Truleo and such). Within the last few weeks, it's developed this noise. I only hear it under load, and usually only if I've giving it a decent amount of throttle. It started out as a ticking noise, but it sounds worse today.

My highly calibrated ear doesn't think its pinging, as it sounds more like ticking, not popcorn. I don't think its the beginning of a spun bearing, but I'm not sure there either. My best guess at the moment is an exhaust leak, though I haven't found it yet. I ported my stock exhaust manifolds years ago, though I thought I was carefully to only remove the lip and not grind into the welds. I also installed a weatherstrip to keep water off the front manifold, but it could still have cracked anyway.

I'm concerned now because it started to sound worse today. It's gotten a bit louder and more pronounced, to the point where the car is starting to sound like an old truck almost. Under decel in first gear (I was in LA city traffic) it did some popping as well that it hasn't done before. Not full on backfires, but definitely a new noise.

Any thoughts? I was going to drive home for Thanksgiving in two days (~350 miles each way) and I'd rather not end up stranded somewhere. There's no indication of trouble on the gauges and only an intermittent Code 32 that's been off and on forever. Only work done recently was an oil and filter change, as well as a fuel filter change. It was making the noise before that. The engine has about 80,000 miles on it.

Aaron · Post by **Aaron** » Mon Nov 24, 2008 10:04 pm

Sounds exactly like an exhaust leak to me.

Shaun41178(2) · Post by **Shaun41178(2)** » Mon Nov 24, 2008 10:12 pm

I think its an exhaust leak too. Might need to pull out the rubber hose(stethoscope)

Fastback86 · Post by **Fastback86** » Mon Nov 24, 2008 10:18 pm

I think its an exhaust leak too, but I haven't found it. I'll just have to keep looking. In the event that it is an exhaust leak, should I be concerned? If its upstream of the O2 sensor, I could see it messing with the engine management (stock). Should I not be driving it until its fixed, or is it not really going to hurt anything? I'm reaching the end of my patience with this car, so I don't care all that much about fixing it unless it's necessary to keep it running until a suitable replacement can be found.

Aaron · Post by **Aaron** » Mon Nov 24, 2008 10:20 pm

It won't hurt anything to drive it.

It is probably at the cylinder head though, that's where most leaks occur (That or the manifolds).

Shaun41178(2) · Post by **Shaun41178(2)** » Mon Nov 24, 2008 10:34 pm

it won't hurt anything. Might see a change in mileage but thats it.

Double check your oil pressure. what weight oil are you using?

Fastback86 · Post by **Fastback86** » Mon Nov 24, 2008 10:37 pm

5W-30 Mobile 1 Fully Synthetic. I'll have to borrow a manual gauge, but the dash gauge doesn't drop below 40, so I doubt its low enough to be a problem.

Emc209i · Post by **Emc209i** » Mon Nov 24, 2008 10:40 pm

Exhaust manifold gasket?

CincinnatiFiero · Post by **CincinnatiFiero** » Mon Dec 01, 2008 9:45 pm

I saw my mixture richen up with an exhaust leak and craptastic gas mileage but you're not really hurting anything.

Aaron · Post by **Aaron** » Mon Dec 01, 2008 9:53 pm

CincinnatiFiero wrote:I saw my mixture richen up with an exhaust leak and craptastic gas mileage but you're not really hurting anything.

It will not change your a/f ratio, or your gas mileage. The only way it could happen is on cold start, where it runs rich, and it will take it longer to get into closed loop. But you'll still be in closed loop by 10 minutes after startup, easily.

The Dark Side of Will · Mon Dec 01, 2008 10:42 pm

An exhaust leak CAN screw up your gas mileage. The exhaust system can actually pull air in between pulses. The O2 reads lean and the ECM compensated by richening the mixture, which causes the backfiring. Closed loop control only works when the whole loop is known.

Do you still have the stock V6 exhaust? Backfiring in the old exhaust can pop the muffler apart.

Fastback86 · Post by **Fastback86** » Mon Dec 01, 2008 11:09 pm

SpinTech Muffler, 1-year-old Cat, Ported Manifolds, otherwise stock. Will, what you said about air being pulled into the system and screwing with the O2 sensor is what I'm worried about. However, my gas mileage has been unaffected.

CincinnatiFiero · Post by **CincinnatiFiero** » Tue Dec 02, 2008 9:39 am

A lot was wrong with my car but my impression was I pulling in pure air in the crack which made the ecm see a really lean condition, and compensate like will said.

Mach10 · Post by **Mach10** » Thu Dec 04, 2008 11:04 am

Broken piston skirt would do it, too...

Dunno if you have 'em locally, but Acklands Grainger parts/supply has a borescope (sorta) for $149... Oil-proof and submersible.

I'm trying to bully my boss to get one for me