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Alright, updates, since I still have the thing and am actually working on it (slowly…).
I did test “knocking” on the cat when I was first trying to figure this out. I don’t recall it making any rattling noises – sounded solid but hollow.
The muffler is actually disconnected from the rest of the exhaust line at the moment – the shaking from the misfires caused the weld to break, so the exhaust effectively exits the system just prior to the muffler now. So I think I can rule that out as being clogged. Besides that, the front side of the muffler is caked with black crap, so it’s clearly “upstream.”
I bought a 2001 Accord 3.0L V6 at the beginning of May, and have since bought/moved into a house (which needed project time also), so haven’t really done much on the Altima until recently. However, in order to drive it the 4 miles to the new house, I tried to fix it again at the old apartment. All I did was take the heat shield off of the front of the engine block, and attempt to get the exhaust manifold off (there is a hairline crack in the front of that as well), as replacing that piece is relatively inexpensive via Amazon and I suspected that the clog might be in the “pre-cat” (I seem to have a so-called California model).
During this process, I removed the front O2 sensor that is seated in the exhaust manifold, and had a look at the “pre-cat” guts. It appeared clean/fine – the latticework was not melted, and I didn’t notice any soot or anything, with what little I could see with a flashlight and peering around.
So I put the thing back together…and it ran “fine”, albeit loudly, for a while. I drove it to the new house and started it up every 3 weeks or so to keep the old battery charged (it was slowly losing charge). The battery has since failed (2011 when I bought that), but I’ve got the Accord handy if I want to jump it. When I started it up the last time, about 3 weeks ago, it was back to misfiring and running rough.
Also, while it was sitting for 6 weeks at the apartment, the fickle left front brake caliper seized up and I have to fix that too :whistle:
Last weekend it was rather warm, so I went out with the goal of getting to the EGR passageways to see if they are completely clogged up for one or more cylinders. Thus far, I’ve removed the EGR valve assembly and some of the other stuff at the top of the engine there, taking pictures as I go so I can be sure to get it put back together exactly the same. I have yet to take the fuel rail off, but that’s next. I have some more learning to do. The thing isn’t really worth much in the condition that it’s in, even with car prices around the DC area, so my plan is to slowly work on it. I’ll replace the caliper for sure, but am starting with the engine troubles.
Paying for registration/insurance on the extra car is only costing me about $15-20/mo in total. If I can resolve the engine issues, then I am fairly certain that the car will pass the state inspection once I also fix the caliper and have the muffler welded back onto the exhaust, and I would be able to sell for $900 – 1100 ($1100 being the KBB “fair” price). If I can’t resolve the engine issues, I could junk the car for about $250 or maybe fix the caliper and then try to sell to someone who could repair/replace the engine for hopefully $400-500. I’d love to fix it and sell it (or even hang onto it, as I’m somewhat sentimental about it), it’s just a matter of finding the time to learn and then do. I might be able to get out into the driveway tonight, after I work on our bedroom closet first B).
Amusingly, the Honda had a clogged EGR when I bought it, but I knew that on the first day that I saw it and did my research that night. Bought it the next day and cleaned it out, no issues with the EGR in it since then, although I am having general “old car” problems with it now.
[quote=”Fmxvxx” post=132586]Read through as best I could One thing I would of done is blanked the EGR off yes this would introduce a fault code in the system but you would be able to see if there was any difference in the running of the vehicle that will give you a good indication of how the EGR is functioning if you are unable/unsure how to test it properly.
One thing that caught my eye is the MAF sensor and installing a new one causing a no start condition that is something I might investigate further.
precats can collapse internally causing a build up of back pressure which will stall the engine
Honestly looking the time and energy you’ve put into this car I’d of sold it a long time ago[/quote]
Thanks. Judging from how badly clogged my EGR valve was and all that, I think that while the EGR valve wasn’t my original problem it definitely needed to be replaced.
I will be hooking it up to the vacuum gauge tonight, assuming I can get the front O2 sensor out to check the back pressure. I’m 99% sure I’m going to see a pretty high back pressure reading… but the O2 sensor has a 22mm or 23mm nut, and I only have a 19mm wrench as my biggest. The manifold’s heat shield is in the way to get a pair of grips on it, so that will have to wait until I get home from work.
Unfortunately, the problems began and continued through a period of time when I had to use all extra cash to pay off emergency trips (deaths in the family) and medical bills, so I just couldn’t get together the couple thousand bucks for a new car – especially since it would only be a couple hundred bucks to fix it. Even harder to sell instead of fix when it would be cutting into the price I could get for this car, which is cash I’d need to pay for the replacement. Being poor with an old car really sucks.
That said, I’ve learned a ton throughout all of this and given that I’m 28, assuming that I can put the knowledge to future use… I judge it worth it, even though it’s painful right now. I just want to get the thing fixed.
I then bought an IR thermometer (along with a vacuum gauge) and this also seems to be inconclusive when I look at the catalytic converter, however I noticed that my car seems to have the California emissions system – and so it has a “pre-cat” up under the exhaust manifold. After some googling, it seems to be a common problem that these things overheat and fall apart, causing exhaust restrictions/misfires/engine damage.
I am still getting an error code almost every time I commute now. P0301 misfire. Looking in my repair manual, I see this:
When the code comes on for the first time, about 50% of the time, it blinks 5 times before staying on. Other times, it simply comes on and doesn’t blink. It took forever to find this in the manual, and I just found it by browsing. Looking up by code doesn’t mention the “three way catalyst” at all for codes P0300-P0304, and of course I can’t search the text of the manual as it is all hyperlinked.
So my thoughts are this: I should take the so-called “pre-cat” off of my engine, bang it around and get all the melted bits out, and then put it back on. Since I’m not in California, I don’t need it. However, since there’s so much black crap getting spat out onto the front side of the muffler, maybe I need to also replace the actual catalytic converter? Given the length of time I have been experiencing this problem (basically because no shop I went to could properly diagnose it, much less fix it), I think the entire exhaust system was basically FUBARed.
TL;DR –
1) Replaced EGR and BPT valves. EGR and multiple misfire codes fixed.
2) Bought IR thermometer, measured in front of and behind catalytic converter. Temperature is right around 350-370 degrees F at both ends…
3) Excessive rough running made my muffler disconnect from the rest of the exhaust.OK, I have some updates. I have more documentation on my phone (pictures/video), but I think I have nailed down the problem. I’d like to think out loud here, and maybe somebody can tell me if I’m off base? All I know is what I’ve “learned” on the internet, and my education could be incorrect…
I went ahead and replaced my EGR valve with an OEM I ordered on Amazon. The car immediately performed differently. In some respects, it was better – smoother idle, sometimes, however it still stalled out about 30 seconds after the second time I started it. I drove it later that night to get my girlfriend from the Metro station, and the CE Light came on. Maybe strange to some folks, but I was actually really excited that I finally got an error code so I could continue troubleshooting. Once again, it was the EGR system code. So I put in the EGR-BPT valve (at least that’s what Nissan calls it – in universal terms, I think it’s the solenoid/valve that controls the EGR valve), another OEM part I had ordered on Amazon as that’s the only place I could find it.
Again, the car ran differently. The EGR code (P0400) is gone and hasn’t come back, so I know that was part of my problem. However, I was still stalling out and I couldn’t figure out exactly what was going on. The O2 sensor readings didn’t seem conclusive, at least from the previous videos I’d watched on the catalytic converter diagnosis. About a week went by before the car started running very roughly, intermittently, just like before – however it caused the muffler to disconnect from the exhaust system. (Awesome :unsure:) So now I rattle and rumble down the street. Pic attached… am I correct in assuming that I can take that anywhere and they’ll be able to weld it back together? It’s worth noting that there is a TON of black stuff immediately following this breach. You can see it in the pic.
Another update. I’d already watched this ETCG video last week, since my friend had been telling me of catalytic converter symptoms (http://youtu.be/9VZ5K8n5jj0)
I got my scanner on Tuesday – an Autel MS509. On Tuesday while I was driving home, I hooked it up and loaded up several custom data sets including ETC temp, O2 sensor 1, O2 sensor 2, RPM, MAF sensor flow (I actually don’t know what the “g / s” unit is…), and Load %. Unfortunately, the data print outs from the scanner aren’t that useful as they update slower than the data itself updates while driving the car, but here is what I found:
My operating temperature is in the mid-80s Celsius. (Is that hot? Seems like it is, but it’s been running at these same temps for 2 years)
While driving at operating temperature, and while experiencing the sputtering/poor performance, I noticed that the O2 sensor 2 jumps around a bit (from 0.4V to 0.8V, but not as rapidly as in Eric’s video) while the O2 sensor 1 doesn’t change a whole lot. It starts around 0.6V when I first start the engine, and gets up to 0.8V – 0.9V at operating temperature. It pretty much hovers around the same value the entire time.
Does this test tell me anything? The O2 sensor 1 should be showing rich/lean changes, correct? But it is not, so does this point to a problem prior to this point in the exhaust system, basically confirming that my problem is in the EGR system?
I still have the P0400 code and no others. I made a few videos on Monday evening, however need to load them onto the computer and edit together, all that jazz. Now that I have the scanner, I can show what I see with the scanner also.
Update: EGR Valve test
OK, as an update… while I was making a few short videos of what’s going on, from inside the cab and under the hood, I was able to properly test the EGR valve. I held 2 fingers under the valve to feel the plunger while I revved using the throttle cables. I had previously tested with a coworker, and she must not have revved the engine high enough.
As I revved using the cables, I could feel the plunger depress on its own, so the valve is working. Also, it got really, really hot!
Thanks for the response! My issue with just buying an EGR valve and hoping it solves the problem is that the manual says I should replace if the plunger doesn’t move. However, if I move the plunger on my own, as soon as I make it start moving the engine begins running worse. This makes me think that it may not actually be the problem? Am I understanding incorrectly here? Here is my understanding:
When “at rest”, EGR valve is closed (plunger is not depressed). When it receives a vacuum signal from the solenoid valve (my EGR is 100% mechanical, not electric at all), it should open the valve – meaning the plunger will depress. I guess I’m not understanding how if I simulate by hand the functioning of the EGR, and it makes the idle worse, that means the EGR isn’t functioning properly?
