Posted: 7/24/2005 7:37:50 PM EDT
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First, the car: 1993 Lumina Z34 3.4L V6 97k miles The problem: One block from my apt, while slowing from 25 to about 15 for a right turn, car very suddenly starts stumbling and not running very well. Exhaust appears a LOT louder. Large smell of exhaust all around car. RPMs all over the low end of the dial (I'm guessing the ECU went a little nuts trying to keep it running). Edit to add: Upon starting, while in park or neutral it idles roughly, but (for the most part) keeps running. When put in gear (drive or reverse) it mostly wants to die. Adding gas causes more-or-less sudden death. What could have caused this? My first thought was water in the tank, since its been very hot and humid out with fairly heavy dew overnight from the temperature drop, and the tank was pretty low (needle at about 1/8th tank -- after getting gas card from apt I was going to run to the gas station). I don't think that would explain the increase in exhaust smell or noise. Then I got to thinking maybe the EGR valve or the exhaust manifold gasket failed, which might mess with compression and therefore cause the stumbling, while at the same time causing the increase in exhaust smell and noise. Suggestions please! Update! Doing the "jumper the aldl connector to make the Service Engine Soon light blink out ECU error codes" routine yeilds a code 32 (three blinks, pause 2 blinks) which a google search says is "EGR Error". Not sure if that actually means the EGR has failed, or if it means something else is making the EGR valve act up. |
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Timing Belt , and if its like the 100 other ones I've done . It will be the rear exhaust cam that’s jumped time . Luckily 93 is a freewheeler , but it isn’t a job for the faint of heart since the cam sprockets do not have marks you can rely on and the tensioner can be a little tricky . |
Would the timing being off cause the exhaust to be significantly louder, and also cause the strong exhaust odor? I can definitly see it causing the car to run rough, but the noise and smell have me a little confused. |
The screwed up valve timing effects engine vacuum and throws off both the air fuel calculation and the feedback system . ( The Smell ) The exhaust note change is most likely the result of the valves now opening while compression is still high in the combustion chamber . ( The Noise ) ETA Just read your update , An EGR stuck open can cause similar symptoms since it's basically doing the same thing by introducing exhaust gasses back into the intake , killing vacuum . But the exhaust note shouldn't change much . It will just run like crap from the inert gas not supporting combustion . 93 may or may not have a linier EGR valve which are notorious for being held open by a chunk of carbon . TOMCO makes a screened EGR gasket if that turns out to be your problem . |
Ah, ok. Assuming that's the problem....what can I expect to pay to have it fixed? (ballpark-ish figure) |
See my ETA above , but if it is the belt . Which is due at 97K anyway . Expect $500 -700 for a good job with belts , seals and possibly a new tensoiner . |
Ok, thanks for all the help. My plan for tomorrow (and or tuesday, depending on when I can get a ride to the parts store) is to put the car up on the jackstands and look at the exhaust piping from the engine back to the catalytic converter (it was mentioned a couple times that a hole there could be the problem) Then I'm going to pull the EGR valve and check for carbon. Or maybe just replace it with a new one and the screen, just in case. Hopefully that will fix it, if not, I'll most likely be sending it to the shop, since I'm not comfortable enough with engines to mess with the timing. Just curious, if it ends up being the belt, and not the EGR valve, will starting and running the car for a couple of brief (1-2 minutes) periods (ie, seeing if replacing the EGR valve fixed it) hurt things? Of course I wouldn't be trying to drive anywhere, just starting the engine to see if it behaves itself. |
The DOHC 3.4 in your Z-34 is a freewheeler up to 97 , which means that the valves and the pistons don't touch if things get out of time . BUT I have seen valve damage when the belt lets go at high RPM's . So as long as you don’t get above 4000 rpms you should be fine . As far as the EGR valve goes , if you do have the linier valve Which can be identified by multi wire connector sticking Out of the top of the valve and no vacuum line . The valve itself isn’t cheap and responds well to just taking a Pick and removing the carbon chunk ( easy to see once the valve is off ) And then using the screened gasket . |
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