Exhaust issues

maestrolx · Aug 21st, 2007, 11:09 AM

I'm sure this has been discussed before but I have a 94 pathfinder. When I first got it, it would tick and glug glug when i would start up. Then it would go away after driving for awhile. But then it got to where it had no power and would glug glug constantly.Okay, I found out that was the exhaust manifold problem from the forums. I went to change them and of course a stud was broken in the head. I take the head to the shop and he says that the exhaust manifold would not cause lack of power. He said it must be something else. Is that so? Thanks for any help.

smj999smj · Aug 21st, 2007, 02:41 PM

For the most part, yes, unless the exhaust leak compromised the reading of the front O2 sensor...probably not the case.

You usually don't need to replace the exhaust manifolds on VG30 engines. Unlike the manifolds on the later VG33E engines, the manifolds usually don't crack. Here's what happened: VG30 engines used 8mm exhaust studs that, as you found out, had a tendancy to break and cause manifold leaks. Nissan later addressed the issue with a TSB and made countermeasure studs that were harder than the originals. When they released the VG33E engine, they tackled the issue by using larger 10MM exhaust studs which almost never break, but made the casting of the manifold too thin and then had issues with the manifolds cracking, especially on the right side. They then came out with a countermeasure manifold and heat shield to correct this issue.

So, unless your manifold is cracked or warped, I would recommend you re-use it. I would recommend you get the countermeasure studs from Nissan and, at least, replace the two end studs and the center,lower stud along with any that have broken.

As far as the lack of power, that's a whole 'nother issue. Might not be a bad idea to have an exhaust backpressure test performed once you get the system airtight. Could be any of a lot of things, really,including due for a tune-up, low fuel pressure, jumped timing belt, or something else.

maestrolx · Aug 22nd, 2007, 09:43 AM

Thanks for the reply. I didn't think about this when I was trying to find TDC with the crankshaft. The markings on the timing belt and the camshaft sprocket did not line up. So it's possible that it jumped timing. That would explain the lack of power. When the belt jumps time, is it time to replace it and does this happen often? It seems to be in good shape. No missing teeth.

**88pathoffroad** · Aug 25th, 2007, 09:16 PM

If the belt slips too many teeth, it will eat valves and you will need a rebuild. I'd change the belt.

Toolman5523 · Aug 25th, 2007, 09:56 PM

your marks on the belt will not line up on every revolution, but rather every couple of hundred or so (can't remember the exact number). when they get too far out they don't run worth a popcorn fart.

maestrolx · Aug 25th, 2007, 11:27 PM

Just found out something new. The reason it went off time is because the woodruff key on the crankshaft started moving from its keyhole and damaging the crankshaft. I bought a new woodruff key and it fit in, but I don't know if the key will hold. It seems to hold under hand pressure. I am starting to put it back together to see but I can't find the timing mark for the crank sprocket. Any suggestions?

smj999smj · Aug 26th, 2007, 01:29 AM

The timing mark on the crank sprocket should be approx. in the 5 o'clock position; it should align with a mark on the oil pump. More important is matching the marks on the belt with the marks on the gears, because the marks on the rear timing cover are a bit "off" from where the cam marks should be. If the marks have worn off the timing belt, I would recommend a new belt. Make sure you get the timing belt correct for your gears...there were "round-toothed" gears (105000 mile belt) and "square toothed" gears (60000 mile belt).

**88pathoffroad** · Aug 26th, 2007, 02:47 PM

A slipped woodruff key will only slip further and then take out your crank later. I've seen it happen several times. That's not something you want to hokey back together and hope it'll stay running. The best fix is to remove the crank, have it welded or filled, reground and re-slotted.

There IS no mark on the oil pump. The only oil pump timing alignment marks I've ever heard of were on JDM import engines. None of the US imports OR produced V6's have a mark. All the books say they do but I've never seen one or heard of anyone having one. You have to make your own mark.

smj999smj · Aug 26th, 2007, 05:51 PM

Quote:

Originally Posted by 88pathoffroad

A slipped woodruff key will only slip further and then take out your crank later. I've seen it happen several times. That's not something you want to hokey back together and hope it'll stay running. The best fix is to remove the crank, have it welded or filled, reground and re-slotted.

There IS no mark on the oil pump. The only oil pump timing alignment marks I've ever heard of were on JDM import engines. None of the US imports OR produced V6's have a mark. All the books say they do but I've never seen one or heard of anyone having one. You have to make your own mark.

I know I've seen it on some, but can't speak for all...it's basically just a tiny slot on the protruding lip of the pump. Since the lines are on the timing belt, it's a non-issue. I wish they would put the lines on all timing belts rather than rely on timing mark marks on the engine.

quiksilver_kj · Aug 29th, 2007, 02:12 PM

Hello. New to this board because I needed answers to basically the same issue. Bought my 94 Pathy a couple months ago, had it inspected and everything EXCEPT the exhaust, was perfect. The whole system is rusted to shit and they said it may need to be replaced soon.
I find on rainy days if it sits outside while im working, when i go to start it up, it sounds rough and idles low. It will continue to run low driving home. I recently went through some little mud puddles (nothing big whatsoever) and then driving home it started to shake and was really loud when I accelerated. I also had hardly any power to accel, even in 3rd gear. Its idleing low and sounds like it wants to stall out. I let it sit and dry out a bit and the shakes are gone, but is still pretty loud, have a little more power, but not as much. Can ANYONE help me??

**88pathoffroad** · Sep 2nd, 2007, 03:38 PM

Have you gotten underneath to have a look yet? First rule: eyeball the source of the problem instead of asking people that live thousands of miles away how to fix a problem they can't see...

smj999smj · Sep 3rd, 2007, 04:00 AM

Quote:

Originally Posted by quiksilver_kj

Hello. New to this board because I needed answers to basically the same issue. Bought my 94 Pathy a couple months ago, had it inspected and everything EXCEPT the exhaust, was perfect. The whole system is rusted to shit and they said it may need to be replaced soon.
I find on rainy days if it sits outside while im working, when i go to start it up, it sounds rough and idles low. It will continue to run low driving home. I recently went through some little mud puddles (nothing big whatsoever) and then driving home it started to shake and was really loud when I accelerated. I also had hardly any power to accel, even in 3rd gear. Its idleing low and sounds like it wants to stall out. I let it sit and dry out a bit and the shakes are gone, but is still pretty loud, have a little more power, but not as much. Can ANYONE help me??

If you are experiencing driveability concerns in wet weather, you should check your secondary ignition system (cap and wires, especially). The misfire could be the cause of your exhaust sounding "rougher."