97 Lumina EGR Valve and O2 sensor Question?


gixxeracer87
02-24-2008, 03:10 PM
I have a 97 Lumina that is throwing 4 codes. I took it to AutoZone and they gave me this...

P0140 - The PCM has determined that there is insufficient activity from oxygen sensor 2 in bank 1.
P0141 - The PCM has determined that a malfunction exists in the heater circuit for oxygen sensor 2 in bank 1.
P0300 - The PCM has determined that multiple random misfires have occurred.
P0401 - The PCM has determined that there is insufficient flow in the exhaust gas recirculation system.

The employee quoted me a price for two O2 sensors, and said that that could be what was causing the random misfires. Reading the receipts it looks to me that only one of my O2 sensors is out. It seems to run fine except when I accelerate hard. Any thoughts / help is welcome. I'm wondering where O2 sensor 2 in bank 1 is, and if the EGR problem could be causing the problem with the O2 sensor? I'm pressed for money right now, and was wondering if I could get away with not replacing the EGR valve? Give me your thoughts please asap. Thank you!

jeffcoslacker
02-24-2008, 03:38 PM
Sensor 2 Bank 1 is the post-catalytic sensor, it looks at how the cat is working by comparing the reading to Sensor 1 (upstream, ahead of the cat)...there is only Bank 1 on this vehicle...bank 2 would be for ones that have two seperate sensor circuits on both sides of a V engine...

According to what Sensor 1 sees, it can command EGR to open when it requires oxygen to do it's thing if the o2 stage of the cat is depleted...

It sounds to me like the EGR is not working right, and the post-cat sensor is not seeing proper activity from the cat due to it...hopefully someone else can confirm...

If you are misfiring at heavy throttle, this is when the EGR opens the most, it could be causing the random miss...

I'd remove the EGR and see if the ports are clogged before doing anything...

jeffcoslacker
02-24-2008, 03:39 PM
Whoops.

gixxeracer87
02-24-2008, 04:06 PM
Thanks Jeff!!! Sounds to me like the guy at AutoZone didn't know what he was talking about. I'll try and take the EGR valve off tomorrow and inspect it.

Any other thoughts or comments?

jeffcoslacker
02-24-2008, 08:13 PM
It could just need a post-cat sensor, but once fully warmed up the heater circuit shouldn't cause a problem, and it would run normal...the heater grid is there to make the sensor begin to work sooner when the car is started cold...o2 sensors don't give meaningful data until fully heated...

The EGR code could be unrelated...I'd still take a look at the EGR ports...then take the post cat o2 sensor out and see if it's all hogged up or eroded...

gixxeracer87
02-24-2008, 09:04 PM
I took off the EGR valve today, it was full of yellow crap. I don't have any thing here to work with. I'll have to do it at work tomorrow. I'll take it off again and try to get it all cleaned up.

It misfires under hard acceleration, all the time. doesn't matter if the motor is cold or if I've been driving it for a while. I'll try to take off the O2 sensor tomorrow too. But I don't know what I'm doing really. I don't really know how to tell if they're bad. The EGR valve is $165, and the O2 sensor is $75. I'm broke, and I'd like to make sure I need something before I buy it. I guess I'll see what happens tomorrow...

jeffcoslacker
02-24-2008, 11:22 PM
The o2 sensor will have an outer shell on the tip with small "vents" that allow exhaust into the sensing elements without directly exposing them...if the vents are all hogged up with crud and closed off, or the outer shell is burned away, there's no doubt it's bad...

Were the passages coming and going from the EGR to the motor caked up and closed or really reduced in diameter at all?

I know those EGRs are really pricey...don't want to be wrong on that call...

So this is actually a misfire, with rough running or bucking, as opposed to just flattening out and refusing to accelerate?

jeffcoslacker
02-24-2008, 11:32 PM
Here is a heated GM o2 sensor...see the slits at the tip (well you can only see one in this pic)? Check to see that they are clear and the shell is intact....this one looks pretty good...

Yellow seems like an unusual color to find in EGR deposits...usually sooty black-brown. Have you been using some injector cleaner or something? That'll discolor plugs and EGR, etc...doesn't hurt anything, just looks weird...

http://www.chevythunder.com/myweb/heated%20_O2%20_sensor.jpg

gixxeracer87
02-25-2008, 12:20 AM
Thanks for all your help. Yeah it's misfiring. most of the time you can feel it lag back from accelerating, but some times it really runs rough. The passages in the EGR didn't seem to be "caked" up per say. I expected it to be dry, but it was wet. The Yellow stuff was puddled in the port to the motor, and was all in the EGR and in the port from the exhaust. I don't know if it was an oil mixture or what. I'm baffled. I hope there's not something seriously wrong with my car. I'll see if I can find my camera and take some pictures of it tomorrow...

gixxeracer87
02-25-2008, 11:59 AM
http://i16.photobucket.com/albums/b16/moto_master/PICT0006.jpg
http://i16.photobucket.com/albums/b16/moto_master/pict0001.jpg
Here are photos of the EGR ports. The creamy yellow stuff is oily. I cleaned out as much as I could. Does that mean I have a blown intake manifold gasket? Will that just ruin a new EGR? Is there a way of testing if the EGR works? or do I just have to go buy a new one? Do you still think the O2 sensor is ok? Any thoughts or comments wlecome...

jeffcoslacker
02-25-2008, 12:18 PM
Well...the EGR hasn't been operating at all, or it would look the same on both passages...that being said, that stuff is obviously not normal....I don't know if it's coolant residue or just the result of condensation, intake vapors (fuel and oil) and rust...but the consistancy and color are sure similar to what you get when you have oil and coolant mixing...

This is really puzzling, but it's a good thing you had a look before doing anything else...

Does your car have the red extended life coolant in it, or the conventional green antifreeze?

The green stuff will poison o2 sensors if it makes it into the exhaust, is why I ask...the red will not, as far as I know...but I'd think it would ruin the pre-cat first...

I'll keep thinking...

jeffcoslacker
02-25-2008, 12:26 PM
If you haven't been loosing coolant or seen evidence of mixing in the coolant or oil, I think it may just be residue from not operating...being a blind passage if not working, any vapors and moisture would collect there...you'll see the same kind of stuff in a clogged PCV system...

Have you priced an EGR from a salvage yard? Can the pintle in the valve be pushed open at all? I'd try to free that one up before giving up on it...I just can't remember if the electric ones can be manually opened...

gixxeracer87
02-25-2008, 01:20 PM
Yeah, while I was cleaning it I pushed the valve down. It moves freely. I cleaned as much of the pool of yellow stuff out, put it back together, and jumped on the highway and it accelerated just fine. Went a couple miles and then slowed down and accelerated again, but it choked that time. I wondered if it was the fluid that was clogging things up. I don't know how quickly condensation and vapors can build that puddle back up. The fluid is in the exhaust tube too, So I guess the EGR isn't completely broken. It's got the green antifreeze. I checked the oil dipstick and it was normal, no chocolate mixture in it. I'll look and see if I can find a used EGR somewhere.

jeffcoslacker
02-25-2008, 01:52 PM
It would take months to build up that kind of mess...

This gets stranger...keep waiting for someone to chime in and say they've seen it before and set us straight...

Hot exhaust through the EGR circuit should blow/burn out any contamination like that if the valve functions...I wonder if the exhaust tube is blocked somewhere farther down?

because normally, exhaust is coming all the way up to the valve, so the exhaust side should be dry if it flows all the way to the source...

you try starting it for a moment with the valve off, see if it bellows exhaust out of the pipe side (i've done this, believe me you'll hear it if it flows...)? If it will run like this, you could also pop the throttle hard a couple of times and see if the valve reacts (leave it plugged in so it operates)...it should open wide when the throttle is stabbed suddenly...be careful...if it's blocked it may forcefully eject a wad of crap suddenly...make sure nothing in the path of the flow gets burned if you let it run like that for any length of time...

jeffcoslacker
02-25-2008, 01:59 PM
What I'm wondering is if the pipe got carboned up enough to reduce flow to the point where the condensation and crud could build in there...then when you cleaned it you might have gotten a partial flow, that pushed more crap up from the exhaust side into the ports...and now it's blocked again...

I dunno...this is weird...but I do think we're on the right track...

gixxeracer87
02-25-2008, 02:44 PM
When I had it off earlier I did start the car up. I expected it to be loud with the exhaust being open, but it wasn't. I checked it and it was puffing so if it is blocked, it's not completely blocked. I didn't plug the EGR back in to see if it moved. I'll try that. I found a junk yard and bought another EGR for $45. The valve is freely moving on that one too. I'm going to go back up to my work and try and get all that fluid out, and try plugging in the EGRs to see if they move, and see what happens of that. I got a bunch of fluid out earlier today, but it just kept creaping out so I just kinda quit. I'll try to get it all out this time.

gixxeracer87
02-25-2008, 03:45 PM
Ok I'm at work now, and I took it off again, and the yellow stuff hasn't made it back into the EGR, so I'm guessing that it's not opening up... I plugged it in and started up the car and reved it up, and the valve didn't move. I plugged in the used one I just bought it it didn't move either. I'm going to go try and see if the wiring is ok. What do you think could be wrong?

gixxeracer87
02-25-2008, 04:05 PM
I don't know what I was thinking before. It is pretty loud with the EGR off. I looked at the wiring and I can't find any thing wrong. But I didn't take off all the conduit. If the valve is supposed to move when I rev the engine, than I don't know what could be wrong, unless the used EGR valve I just bought is bad also. I'm kind of at a loss on what to do.

j cAT
02-25-2008, 06:53 PM
I don't know what I was thinking before. It is pretty loud with the EGR off. I looked at the wiring and I can't find any thing wrong. But I didn't take off all the conduit. If the valve is supposed to move when I rev the engine, than I don't know what could be wrong, unless the used EGR valve I just bought is bad also. I'm kind of at a loss on what to do.

I just read all this info on your problem.. if you can start engine with EGR off and it will not stall the EGR port to intake manifold is plugged... but I also believe that coolant is getting into the combustion chambers causing the other codes also the exhaust will be very wet/water steam etc if this has coolant entering the combustion chamber as well as very white spark plug tips.....try to use coat hanger to clean out the intake egr port from blockage with this open engine should stall [a good thing] as this goes to engine vacuum....may have to remove throttle body to clean all this...green antifreeze will damage O2's..........so fix coolant problems before replacing O2.........intake manifold internal crack/leak very possible......

gixxeracer87
02-25-2008, 07:34 PM
Thanks j cAT.
I checked the resistance in my spark plug wires and they were too high so I changed them out and now it doesn't misfire any more (which was my main goal). I completely cleaned out the yellow gunk out of the intake and put the used EGR valve on and drove about 10 miles and took it off and checked it. there wasn't any thing in there. I'm going to drive it to work tomorrow and check it again. I'll try to clean it out with a coat hanger too to make sure it's not clogged. If it is leaking antifreeze could that just be the intake manifold gaskets? That's pretty easy to replace (I think), just more money. I'm going to try and clear all the codes and see what codes come back. I was told I just have to disconnect the battery for a minute to clear the codes, is that correct? Thanks for all your help guys!!!

j cAT
02-25-2008, 09:46 PM
Thanks j cAT.
I checked the resistance in my spark plug wires and they were too high so I changed them out and now it doesn't misfire any more (which was my main goal). I completely cleaned out the yellow gunk out of the intake and put the used EGR valve on and drove about 10 miles and took it off and checked it. there wasn't any thing in there. I'm going to drive it to work tomorrow and check it again. I'll try to clean it out with a coat hanger too to make sure it's not clogged. If it is leaking antifreeze could that just be the intake manifold gaskets? That's pretty easy to replace (I think), just more money. I'm going to try and clear all the codes and see what codes come back. I was told I just have to disconnect the battery for a minute to clear the codes, is that correct? Thanks for all your help guys!!!

that was good you check wire resistance and also check new wires as they also i found can be bad...the codes clear just remove negative battery lead for 5min... that should be long enoungh...if the egr ports are plugged the engine should start pinging when it gets to normal operating temp...and ecm may throw a code....

jeffcoslacker
02-26-2008, 07:50 AM
Holy carp! How did I forget that? I'm losing it.

If you take that EGR off again, check for vacuum on the intake port side...he's right, it shouldn't want to run with a wide open vacuum leak like that...if it does, that passage is blocked...I was getting to that when I said "if it will run like that", and then totally dropped the ball...sorry...

The engine may have to be fairly warm to see EGR move...I believe it is disabled until the ECM sees operating temperature...try letting the motor warm up real good and then remove it real quick and give it a go...the more load, the more EGR is needed, also try torquing it up in gear with throttle and seee if it moves...

Exhaust should blast outta the pipe side just as if it was a little exhaust pipe, no restriction...

gixxeracer87
02-26-2008, 02:55 PM
I took off the negative battery cable for about 30 minutes. While I was waiting I took off the EGR (again lol) and shoved a coat hanger in the intake as far as I could. Only got it maybe 3 inches because of all the bends. Pulled it out and it had some gunk on it, but I don't know if I just scraped that off the walls or if I hit the clog. When I had if off and running before it seemed to be running like normal, but I haven't noticed any pre-detonation. But then again it's only about 5 miles to my work, and it's rather cold out side. I may not be getting it to operation temperature. I didn't start it up with it off this time because I was trying to clear the codes... when I got it all back together the check engine light was still on, and I took it to AutoZone and it doesn't look like I got the codes cleared. The guy there said to completely remove the battery for 24 hours. (I read some where, it said to remove one cable for one minute and they would be cleared). He refused to clear them with his scanner because of liability issues. I can't really take it off for 24 hours because this is my only transportation at the moment. You guys have an idea? O and I think I forgot to mention earlier that I pulled the #6 spark plug and it was white...

jeffcoslacker
02-26-2008, 03:39 PM
You can't clear OBDII codes without the scanner.

jCAT was right, it should suck so much air through the manifold passage that it shouldn't be able to idle with it open...that was the point I meant to make, but got sidetracked originally. I'm glad he pointed that out.

So you are still clogged on the intake side...

You probably won't detonate without EGR, you have a knock sensor that retards the timing to kill that before it's audible...the old ones without it would ping with the EGR inop, true...

That's why I was asking if it was breaking up on acceleration, or just laying down...thought the timing might be being retarded and making it flatten out...

j cAT
02-26-2008, 06:05 PM
I think I forgot to mention earlier that I pulled the #6 spark plug and it was white...[/quote]


If all the plugs are normal color light brown and one is white this is the cylinder that is getting coolant in it.... probably head gasket but possible intake manifold.....

gixxeracer87
02-26-2008, 06:57 PM
I was in a hurry so I just pulled that one plug. I'm not looking forward to pulling the rear plugs. Any ways... You guys are Awesome!!! I found a clog in the intake manifold, and I think I got it cleared out. Had to rip off the air cleaner and all that jaz to get to it, but I think it's working now. I guess I got to go sweet talk a shop into clearing the codes for me. Do you think I still need to change the rear O2 sensor or do you think that clog was causing that too?

jeffcoslacker
02-26-2008, 07:14 PM
Like I said, the o2 bank of the cat may have been depleted and unable to get a supply of oxygen due to the clogged EGR...this makes the cat partly ineffective, and might account for the lack of activity seen from the rear o2 sensor...

The heater grid fault still bothers me though, but see what happens now....

j cAT
02-27-2008, 07:04 PM
I was in a hurry so I just pulled that one plug. I'm not looking forward to pulling the rear plugs. Any ways... You guys are Awesome!!! I found a clog in the intake manifold, and I think I got it cleared out. Had to rip off the air cleaner and all that jaz to get to it, but I think it's working now. I guess I got to go sweet talk a shop into clearing the codes for me. Do you think I still need to change the rear O2 sensor or do you think that clog was causing that too?


now that this intake clog is opened i would check to be sure by removing the egr....then go and disconnect battery for 5min and then go to auto zone for the codes and then report to us what the dtc's are....

jeffcoslacker
02-27-2008, 07:12 PM
now that this intake clog is opened i would check to be sure by removing the egr....then go and disconnect battery for 5min and then go to auto zone for the codes and then report to us what the dtc's are....

That won't clear OBDII codes...It will put the radio into security lockout, and he'll have to go through that headache...:banghead:

gixxeracer87
02-27-2008, 07:44 PM
That won't clear OBDII codes...It will put the radio into security lockout, and he'll have to go through that headache...:banghead:

Yeah, I tride disconecting the batery and then going to AutoZone, they were all still there. BTW, does O'reilly's check the codes for free too? I'm sure the people at AutoZone are getting tired of seeing me LOL.

I took the car by a shop, and they said that it would reset itself in time if nothing is wrong. I don't understand why it has to be so difficult...

Anywho, I'm a bit concerned because now the car doesn't start right up like it use to. I don't know if it's related to what I've been doing, but now sometimes it has to crank over a few times, and then when it does start, it kind of lags for a few seconds, like it's misfiring. I'm guessing I might aught to change the spark plugs? I just don't understand because it was running just fine except for the misfire at high RPMs.

I don't know much about O2 sensors, but I'm guessing that the rear one is bad because it's giving the P0141 code about the heater on it. I don't see how that could be related to the EGR. I guess I'll go ahead and replace it when I get some money. Thanks again for all your help guys!

jeffcoslacker
02-28-2008, 07:15 AM
Do you have the origianal EGR on it now, or the junkyard one? Make sure you haven't dislodged any vacuum lines during all this...might wanna see if the same contamination is in the IAC now...maybe it's not closing all the way when the motor is started....

Does it do it only on cold start, or any restart?

gixxeracer87
02-28-2008, 01:00 PM
I have the junk yard EGR on there right now. I did pop off a couple vacuum lines in the process, but I think I got them all back on. I'll go double check. I cleaned the throttle plate and stuff while I was in there. It's possible that I might have gotten something in the IAC. I guess I need to tear it apart again and check it out. It's not just cold start ups, it can happen on warm ones also, but it doesn't necessarily do it every time I start the car.

94Z28Conv.
03-18-2008, 07:23 PM
One of the two holes in the egr plate runs back into the intake, mine was really stopped up and throwing out o2 codes and egr codes, I cleaned the hole out with a peice of stiff but flexible cable in a cordless drill. I havent had any codes or idling problems since. Maybe check that out.

gixxeracer87
03-18-2008, 10:04 PM
Yeah the port was clogged, and I went in through the throttle plate and cleaned it out. The misfiring was due to spark plug wires. I changed the spark plugs, and the oil, and sold the car to a friend of mine. I got a guy at AutoZone to let me borrow his scanner so that I could clear the codes. My friend said the check engine light came back on again. She's suppose to go have it checked out, and then I'm going to continue fixing the car for her. Thank you guys for all your help!

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