Shortest version possible here: A month ago, I hydrolocked my motor. I was able to get all the water out, changed oil twice since, changed plugs, and it ran better than ever for about 2 weeks. Someone told me that I might have actually cleaned out some carbon deposits, and this could be the reason. I had it checked out just in case, and verified nothing was broken/bent, and that all sensors were doing AOK. Then just about a week ago, my car began to sputter for a second every time I started it up, I lost all kinds of torque (it hardly wants to move without stalling in any gear below 3k RPMs), and it smelled like exhaust when I was moving forward slowly. I took off the headsheild (stock exhaust, 99 GS), and noticed that my stock exhaust manifold was cracked, in the same place I’ve heard a lot of 2GNTers complain about. For grins, I’ve ordered the Greddy 4:1 header and PS cat-back exhaust (since my muffler has lots of tiny holes in it, anyways), but I somehow doubt this will fix anything when it arrives. Sometimes, when I’m trying to get going in first, it’ll even pop (sounds like a backfire?) if I’m taking off without giving it tons more throttle than I’m used to. Even though I'm conscious of this problem and nursing it now, I'll still occaisionally almost stall it now trying to get going. It seems to run decent though any time in any gear as long as I'm above 3k RPMs or so. The gas mileage is also taking a major turn for the worse. I used to get ~ 330 mi to a tank whereas now I’m lucky to get 220. I’ve changed plugs again, and all seems fine with the old ones. It idles OK, but when I'm sitting in neutral and I give it just a bit of gas, it sputters before it revs again. I checked out the spark wells, and there is no oil leakage (new valve cover gasket and rings just about 6 months ago. I have no idea what could be causing this, but it almost seems to be worsening. My only thought after everything I’ve checked is that perhaps the crack on the exhaust manifold is causing a bad reading to the O2 sensor @ the down pipe, and this is perhaps sending bad data to the ECU causing it to run like crap. But I kinda doubt this as it's just a small crack, and have heard several guys tell me they've had this before with no performance differences noticed. Can anyone tell me why I’m experiencing this huge loss in torque and general crappy performance? Thanks always for all your help.

maybe need a new fuel filter, maybe new plug wires, maybe have a bad fuel pump or fuel pump relay, maybe a bad coil pack, maybe an o2 sensor going bad, maybe a clogged cat, maybe need to regap your plugs to make sure that's right, maybe some clogged injectors, maybe a blown headgasket...

How big of a crack are we talking about?

Fuel filter is 4 months old, plug wires are nice ones, about 8 months old. Plugs are gapped OK, but I'll check into the rest though. Thanks!

The crack is a hairline crack, about .5" long right in the middle where the pipes come together. I had to water test it to make sure it was really a crack. Thanks guys, and let me know if you think of anything else I should check.

Anything I can do to narrow it down before I go spend $$$$?

My header was cracked when I bought the car and the O2 was reading lean, so the ECU added fuel. It cut down on my performance and gas mileage.

I had the header welded at the flange and changed the O2 and the car ran a shit load better, better gas mileage, too.

Well, hopefully my new header and new O2 will fix it right up. The only reason I'm pessimistic though is because I know that hairline crack has been there for a while, and I really doubt it's to blame for the sudden decline in performance. We'll see though.

Anybody else have any ideas? I'm thinking maybe I DID damage something when I hydrolocked it, it's just not showing itself until now... (???)

Another thing to note is that this hesitation/sputtering problem is at it's worse when I first start the car, then seems to get a little better after it's ran for a while. Just when I left work today to head home, I almost got in an accident because I took off right out of the parking lot, but the damn thing wouldn't hardly get going (with traffic coming) until right at the last moment. Ya, I got the finger... :S

I'll have the new header, O2 sensor, and catback exhaust on by end of day Friday. I'll let you guys know if this helped. Thanks again for all your help!

Edit: I took a look at the crack yesterday, and it IS getting bigger. My parts get here today, but I won't have time to work until Friday...

still no luck. i replaced my upstream O2 with Bosch pt no 13399... no CEL, but car is still running like crap... no torque, stuttering, backfires, and no power < 3k RPMs... this blows. i'm going to mess with plug wires, coil pak next.

so far i've done O2, fuel filter, plugs.

1999 GS: Custom CAI w/ extra large filter, Front strut tower brace, Rear sway bar, Brembo xDrilled & slotted rotors, Performance Friction pads, Greddy 4:1 header, Greddy SP cat back exhaust, Bridgestone Potenza RE950’s, VIS carbon fiber Hood & pins, Optima Red Top battery, Custom taillights and rear end mod

wheres the new header?

under my hood... :D

anyone ever fix this problem? there was that long long thread (http://forums.2gnt.com/dcboard.php?az=show_topic&forum=5&topic_id=49984&mesg_id=49984&page=) that talked about probs just like mine, but no one ever seemed to resolve it. :( one of life's great mysteries i guess. we'll see what the plug wires and coil pak do for me. thanks guys.

Custom CAI w/ extra large filter, Front strut tower brace, Rear sway bar, Brembo xDrilled & slotted rotors, Performance Friction pads, Greddy 4:1 header, Greddy SP cat back exhaust, Bridgestone Potenza RE950’s, VIS carbon fiber Hood & pins, Optima Red Top battery, Custom taillights and rear end mod

K, changed my plugs, got 8.5mm wires, and new MSD coil pack. Car runs better than it ever had. Think I had a bad plug wire. I'm so glad I finally fixed this crap!


1999 GS OZ Edition (her name's Janet)

~~Custom CAI w/ extra large filter, Front strut tower brace, Rear sway bar, Brembo xDrilled & slotted rotors, Performance Friction pads, Greddy 4:1 header, Greddy SP cat back exhaust, Bridgestone Potenza RE950’s, VIS carbon fiber Hood & pins, Optima Red Top battery, MSD Blaster Coil and 8.5mm wires, Custom taillights and rear end mod~~