Are exhaust leaks dangerous

Solstice - Can an exhaust leak cause (really bad) hesitation?

My solstice says hello everyone. Keep going.

I've had some very difficult beginnings in the last month. I hadn't had time to really look at it until a few days ago when I noticed the downstream O2 sensor harness was cut. I'm assuming it is some kind of street garbage, although I'm not sure how.

Yesterday I swapped out the sensor and harness connector (which were melted while hanging freely next to the turbo / exhaust manifold) and lo and behold, my CEL is gone and the car starts much smoother, if not perfect.

The other (possibly related) problem is that under WOT, the car hesitates to the point where it feels like fueling degradation. It is intermittent but common.

While changing the sensor, I noticed that the gasket between the turbo and the exhaust manifold was burned out. There is a gap of about 2 mm between the turbo flange and the manifold at one corner, and a piece of the seal protrudes.

I ordered a new gasket and plan to install it this weekend.

The question

Can a large exhaust leak cause this type of hesitation? It hesitates, sways, sounds very bad and I have to lift and then gradually accelerate to get it to stop. No fun, a little dangerous the first time.

Cheers.

To update

It may not be worth anything that this only started a few days ago before I changed the O2 sensor. I think the car was running fat before (makes sense since the control unit couldn't read anything from the downstream sensor), possibly messing up the connectors. Too many things to check! The result is the service manual, diagnostics section. : /

Update the 2nd.

Pulling out the battery for half an hour regarding: @ Paulster2's suggestion seems to have (so far) fixed the gross startup problem, but the strange hesitation with WOT is still there. I haven't tried the tape yet. I did notice, however, that my AFR meter reads around 10.0-10.2 when it happens, which is typical of this tune (although it seems a bit over the top to me). That leaves air and sparks. I'll be checking the plugs as they seem the most likely culprit.

Pᴀᴜʟsᴛᴇʀ2 ♦

Hey David ... did you reset the control unit to the default settings after replacing the O2 sensor and the cable harness?

3Dave

@ Pᴀᴜʟsᴛᴇʀ2 Hello Paul! No, I haven't. Is that important? Is it enough to disconnect the battery or should I flash it again? (Reflashing is oddly cathartic.)

Pᴀᴜʟsᴛᴇʀ2 ♦

Don't flash it again ... just unplug it and let it sit for a good 30 minutes. This will pull out all of the long term fuel fairings and start over. It might help what's up, but it really is the best place to start. Let the computer go back to its basic setting and then from there it will figure out what happens for itself.

3Dave

@ Pᴀᴜʟsᴛᴇʀ2 Will be enough. Thanks for your help as always.

Pᴀᴜʟsᴛᴇʀ2 ♦

You realized what I meant by "camp" ... I'm sure your solstice was turbo tuned. Just reset it to the "default" fuel card of the new tune ... not the factory tune, lol. I don't want you to blow up your solstice, especially after all that work that involves putting in a good engine!

dlu

So this is not what is commonly meant by a "boost leak" - a boost leak is on the compressor side of the turbocharger. Compressed air that was supposed to get into the engine leaks out before it gets there. What you have is an exhaust leak in front of the turbocharger.

Even so, I don't think your exhaust leak would cause the behavior you described (but it should still be fixed immediately). The reason I think is because I would expect the leak to potentially limit, but not fluctuate, the boost that can be achieved. Depending on the volume of the leak, it may have no effect at all - especially with WOT. I think you could confirm (or reject) this with a quick and dirty test with some duct tape. It doesn't even have to be heat-resistant tape, I think you can spot it before the tape burns off. Just wrap the joint tightly with several layers of duct tape and take it for a ride. That would either rule out the leak as the cause of the problem or prove me wrong.

3Dave

Thanks, terminology corrected. I thought the low pressure leak wasn't that bad, it really "opens" at WOT. I'll put an HVAC tape in there and see what happens. I can plug in my HP tuners and log, but I'm not sure I have enough experience to interpret the data.

dlu

In the worst case, you would have some data that doesn't make sense to you and about which you can ask another question :-)

3Dave

Excellent point. :) Many Thanks! Any other ideas if the tape doesn't (temporarily) solve the problem?