EGR and Limp Mode - MAF Sensor Problems
12-18-2007, 08:00 PM
#1
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EGR and Limp Mode - MAF Sensor Problems
I just want to apologize in advance that my knowledge of cars isn't that great, so I'm sorry if something I say doesn't make any sense. I've tried searching for not only this forums but others, and haven't really found any solid answers.
The Background
I have a 2000 Nissan Maxima SE that was purchased new in June of 2000. For the most part I haven't had too many problems with it, aside from the fact that it turned out to be a lemon, from what I gather. Unfortunately I wasn't really aware of the lemon laws in Florida at the time, but that's over and done with and there's nothing I can do about it now.
I'll cut to the chase. In 2001, I had a check engine light come on. Not only that, but when it did, the car would go into a 'safe' or 'limp' mode where the car would not accelerate past ~2,500rpm. Brought it to Nissan, and turned out to be error code p0403, EGR Volume Control Valve Circuit. Nissan ended up replacing the EGR assembly and everything seemed to be working correctly. Unfortunately, about 6 months later, the exact same thing happened again. I brought it back to Nissan, and again they replaced the EGR part and things worked again. To make a long story short, I had this exact same problem 4 times within 2.5 years of owning the car, and each time they replace the same part (or what I think was the same part - EGR assembly vs. EGR solenoid) and the problems would go away. Unfortunately, it happened again about a year later. At this point the car was no longer under warranty and neither was the part they replaced last. Nissan said they'd look at it, but that they wanted my car for a week and I just didn't have the time. It turns out that I never got the problem looked at again, however it still shows the problems to this day. The check engine light is constantly on, and is the same error code p0403...I've checked. I start the car and after about 20 seconds of driving the car it happens and the car's in limp mode. I actually figured out a 'hack' to get it working. Whenever it would happen, if I turned off the car and started it up right away it would be fine (it only ever came back on a handful of times in the years that I did this). Most of the time I wouldn't bother since I was just driving around the city and so not being able to accelerate wasn't a big deal.
Last Week
I finally decided that enough was enough and so I brought the car to a local shop that was recommended to me. The guy supposedly only works on Japanese cars and when I spoke with him on the phone, he mentioned that he's seen lots of EGR problems and that he should be able to figure mine out no problem. I brought it to him last Thursday and told him everything I've just told you. After about two days, he came to the conclusion that the EGR valve was working correctly, but that the motor that operates it was malfunctioning. He said he replaced the motor and the light didn't come back on but that the car was still going into limp mode. A day later he came to the conclusion that the MAF needed to be replaced and I gave him the go-ahead. He did this and told me to come pick up the car on Friday. Unfortunately, the car wasn't ready on Friday. He said that when replacing the ECU you have to reflash the ECU and that they weren't able to download it from Nissan for whatever reason. He said that the car was drivable, but that it was idling rough. He said to come back on Monday and he'd have it sorted out by then.
I drove the car some over the weekend, and I immediately noticed a few things:
1. The check engine light wasn't on nor was it coming on anymore.
2. The car wasn't going into limp mode. Acceleration seemed fairly normal.
3. The car had a hard time starting up most of the time.
4. The car was idling extremely roughly. At every stop the car is bouncing around and sometimes the tach jumps and the car tries to go forward. Sometimes the engine just dies and it shuts off.
5. The brakes were acting really weird. If I just slowly depress on the brakes, they seem fine. If I have to press somewhat hard on them, they lock up and become extremely stiff and won't press in. I almost crashed into the back of another car the first time this happened. When this happens there is almost zero braking power.
6. Once driving the car drives fairly normal and I can't really notice anything weird except for the braking issues and the idling issue.
He mentioned most of this to me before I picked up the car, except for the brake issue. Supposedly the reflashing of the ECU would take care of the problems.
Today
He finally got things sorted on his side and told me to bring by the car for him to 'reflash' the ECU. I show up hoping that everything fine, but of course it isn't. He tells me that the car is still idling roughly, but that he thinks driving it for a few days will 'break it in' and the problems should go away. Like a dumbass I didn't mention the brake problem to him, mostly because I was so frustrated that what he originally said was a 'simple' problem turned into a week of me bumming rides off people. I drive the car away, and immediately the brake problem is still there. I wanted to immediately turn around, but I figured I'd give it a chance to see if the problems would correct themselves. I really don't see that happening though.
Everytime that Nissan replaced the EGR assembly, the car ran fine afterwards. Of course the part would end up braking again, so I'm sure that's not the root of the issue. Right now I want to drive the car around town overnight and see if I can put it through what I'd normally do in a week, that way I can tell him that I gave it a chance and can bring it back to him first thing in the morning. There won't be as many cold starts as there would be in a week, so not sure if that would be a big problem or not.
So, does anyone have any ideas as to what might be causing these problems?
I tried doing some searching via google about the rough idle problem, and some people mention to remove the MAF while it's idling and see if the problem goes away. I might try that later this evening.
I didn't find as much information about the brake issue. Part of me thinks that the braking is probably controlled by the ECU, but the other part thinks that it's gotta be mostly hydraulics based and so a problem with the ECU wouldn't cause the brake issue. The brake fluid level is fine (it's the only thing brake related I know how to check). It could be that there's some separate issue that cropped up at the exact same time, but that'd be a pretty big coincidence, especially considering that I've never had brake problems before.
Again, thanks in advance for any insight you can offer. This has been driving me nuts for years, and I'd almost rather that I just left it how it was...at least then I didn't feel like I was on an amusement park ride while sitting at stop lights.
The Background
I have a 2000 Nissan Maxima SE that was purchased new in June of 2000. For the most part I haven't had too many problems with it, aside from the fact that it turned out to be a lemon, from what I gather. Unfortunately I wasn't really aware of the lemon laws in Florida at the time, but that's over and done with and there's nothing I can do about it now.
I'll cut to the chase. In 2001, I had a check engine light come on. Not only that, but when it did, the car would go into a 'safe' or 'limp' mode where the car would not accelerate past ~2,500rpm. Brought it to Nissan, and turned out to be error code p0403, EGR Volume Control Valve Circuit. Nissan ended up replacing the EGR assembly and everything seemed to be working correctly. Unfortunately, about 6 months later, the exact same thing happened again. I brought it back to Nissan, and again they replaced the EGR part and things worked again. To make a long story short, I had this exact same problem 4 times within 2.5 years of owning the car, and each time they replace the same part (or what I think was the same part - EGR assembly vs. EGR solenoid) and the problems would go away. Unfortunately, it happened again about a year later. At this point the car was no longer under warranty and neither was the part they replaced last. Nissan said they'd look at it, but that they wanted my car for a week and I just didn't have the time. It turns out that I never got the problem looked at again, however it still shows the problems to this day. The check engine light is constantly on, and is the same error code p0403...I've checked. I start the car and after about 20 seconds of driving the car it happens and the car's in limp mode. I actually figured out a 'hack' to get it working. Whenever it would happen, if I turned off the car and started it up right away it would be fine (it only ever came back on a handful of times in the years that I did this). Most of the time I wouldn't bother since I was just driving around the city and so not being able to accelerate wasn't a big deal.
Last Week
I finally decided that enough was enough and so I brought the car to a local shop that was recommended to me. The guy supposedly only works on Japanese cars and when I spoke with him on the phone, he mentioned that he's seen lots of EGR problems and that he should be able to figure mine out no problem. I brought it to him last Thursday and told him everything I've just told you. After about two days, he came to the conclusion that the EGR valve was working correctly, but that the motor that operates it was malfunctioning. He said he replaced the motor and the light didn't come back on but that the car was still going into limp mode. A day later he came to the conclusion that the MAF needed to be replaced and I gave him the go-ahead. He did this and told me to come pick up the car on Friday. Unfortunately, the car wasn't ready on Friday. He said that when replacing the ECU you have to reflash the ECU and that they weren't able to download it from Nissan for whatever reason. He said that the car was drivable, but that it was idling rough. He said to come back on Monday and he'd have it sorted out by then.
I drove the car some over the weekend, and I immediately noticed a few things:
1. The check engine light wasn't on nor was it coming on anymore.
2. The car wasn't going into limp mode. Acceleration seemed fairly normal.
3. The car had a hard time starting up most of the time.
4. The car was idling extremely roughly. At every stop the car is bouncing around and sometimes the tach jumps and the car tries to go forward. Sometimes the engine just dies and it shuts off.
5. The brakes were acting really weird. If I just slowly depress on the brakes, they seem fine. If I have to press somewhat hard on them, they lock up and become extremely stiff and won't press in. I almost crashed into the back of another car the first time this happened. When this happens there is almost zero braking power.
6. Once driving the car drives fairly normal and I can't really notice anything weird except for the braking issues and the idling issue.
He mentioned most of this to me before I picked up the car, except for the brake issue. Supposedly the reflashing of the ECU would take care of the problems.
Today
He finally got things sorted on his side and told me to bring by the car for him to 'reflash' the ECU. I show up hoping that everything fine, but of course it isn't. He tells me that the car is still idling roughly, but that he thinks driving it for a few days will 'break it in' and the problems should go away. Like a dumbass I didn't mention the brake problem to him, mostly because I was so frustrated that what he originally said was a 'simple' problem turned into a week of me bumming rides off people. I drive the car away, and immediately the brake problem is still there. I wanted to immediately turn around, but I figured I'd give it a chance to see if the problems would correct themselves. I really don't see that happening though.
Everytime that Nissan replaced the EGR assembly, the car ran fine afterwards. Of course the part would end up braking again, so I'm sure that's not the root of the issue. Right now I want to drive the car around town overnight and see if I can put it through what I'd normally do in a week, that way I can tell him that I gave it a chance and can bring it back to him first thing in the morning. There won't be as many cold starts as there would be in a week, so not sure if that would be a big problem or not.
So, does anyone have any ideas as to what might be causing these problems?
I tried doing some searching via google about the rough idle problem, and some people mention to remove the MAF while it's idling and see if the problem goes away. I might try that later this evening.
I didn't find as much information about the brake issue. Part of me thinks that the braking is probably controlled by the ECU, but the other part thinks that it's gotta be mostly hydraulics based and so a problem with the ECU wouldn't cause the brake issue. The brake fluid level is fine (it's the only thing brake related I know how to check). It could be that there's some separate issue that cropped up at the exact same time, but that'd be a pretty big coincidence, especially considering that I've never had brake problems before.
Again, thanks in advance for any insight you can offer. This has been driving me nuts for years, and I'd almost rather that I just left it how it was...at least then I didn't feel like I was on an amusement park ride while sitting at stop lights.
12-18-2007, 08:09 PM
#2
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My EGR was un-plugged for nearly two years and I never had a problem with my car... Only a CEL, no limp mode.
This is more than your EGR, possible it was a bad MAF that he put in... How did he reach your EGR? Pull the intake or go from under the car?
Another option is a coil-pack, but you should get a CEL if one is that bad or un-plugged because it will cause a misfire.
This is more than your EGR, possible it was a bad MAF that he put in... How did he reach your EGR? Pull the intake or go from under the car?
Another option is a coil-pack, but you should get a CEL if one is that bad or un-plugged because it will cause a misfire.
12-18-2007, 09:54 PM
#3
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Join Date: May 2004
Location: Vancouver, BC
Posts: 933
It sounds like you've pretty much lost the power brakes, and because this issue appears to have started right after the shop having done work on your car, I suspect that they've damaged or pinched the vacuum line/hose from the intake manifold to the brake booster. They would have been working in that area when dealing with the EGR valve. I would have the car towed back to the shop, because it basically isn't safe to drive any distance. The brake booster hose may be leaking vacuum which may also explain the rough idle. Can you hear any air "hissing" at idle? The repeat "failure" of the EGR valve motor or circuit (the code 0403) is not normal for these cars. As you've alluded to, there is probably another root cause, like a harness or connector issue for example. The Nissan dealer should have picked up on this after the second repeat failure when it was still under warranty. Plain incompetence or just not wanting to take the time to troubleshoot? This latest shop has just replaced the ECU or the MAF as well as the EGR valve motor?
12-18-2007, 10:10 PM
#4
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Join Date: Dec 2000
Posts: 85
It sounds like you've pretty much lost the power brakes, and because this issue appears to have started right after the shop having done work on your car, I suspect that they've damaged or pinched the vacuum line/hose from the intake manifold to the brake booster. They would have been working in that area when dealing with the EGR valve. I would have the car towed back to the shop, because it basically isn't safe to drive any distance. The brake booster hose may be leaking vacuum which may also explain the rough idle. Can you hear any air "hissing" at idle? The repeat "failure" of the EGR valve motor or circuit (the code 0403) is not normal for these cars. As you've alluded to, there is probably another root cause, like a harness or connector issue for example. The Nissan dealer should have picked up on this after the second repeat failure when it was still under warranty. Plain incompetence or just not wanting to take the time to troubleshoot? This latest shop has just replaced the ECU or the MAF as well as the EGR valve motor?
Also, I'm fairly certain I'm going to bring it back to him in the morning. The braking issue (pedal firmness/lack of braking power) usually happens at lower speed/lower rpm). I haven't heard any hissing from inside the car, but I'll pop the hood in the morning and take a listen.
And yes, it's extremely disappointing that Nissan never took the time to fix the root of this problem. They fixed the EXACT same problem four times while it was under warranty. I'm probably going to end up writing them a letter just on principle.
Again, thanks for any help or potential insight that anyone can offer.
12-18-2007, 10:12 PM
#5
i had this same problem when i had my 2000, and i was also going into limp mode, but i was able to solve the prblem by simply cleaning out the egr tube that goes from under the throttle body with a wire a hanger and carb cleaner it might be plugged up.
12-18-2007, 10:13 PM
#6
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Posts: 85
My EGR was un-plugged for nearly two years and I never had a problem with my car... Only a CEL, no limp mode.
This is more than your EGR, possible it was a bad MAF that he put in... How did he reach your EGR? Pull the intake or go from under the car?
Another option is a coil-pack, but you should get a CEL if one is that bad or un-plugged because it will cause a misfire.
This is more than your EGR, possible it was a bad MAF that he put in... How did he reach your EGR? Pull the intake or go from under the car?
Another option is a coil-pack, but you should get a CEL if one is that bad or un-plugged because it will cause a misfire.
Also, I've had a coil go bad in the past, and had the same rough idling, but like you said, I got a CEL and right now I'm not getting anything.
12-18-2007, 10:27 PM
#7
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Posts: 85
I had read that this is a potential problem, and from what the mechanic told me, the tube wasn't clogged, it was fine. When I first brought it in I was hoping that this was the problem as it's a simple fix.
12-18-2007, 10:56 PM
#8
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Location: Vancouver, BC
Posts: 933
Re the brake issue..........engine off, step hard on the brake pedal and start the engine........the pedal should drop a little and you should feel a "change" if the power brake booster is working. Just to clarify.......the ECU has just been changed, or just the MAF? Replacing the ECU may cause this shop headaches because of NATS (the immobilizer) just for starters. The reflash I don't get. The MAF replacement MAY technically require an ECM update.
Last edited by P. Samson; 12-18-2007 at 11:05 PM.
12-18-2007, 10:58 PM
#9
My EGR was un-plugged for nearly two years and I never had a problem with my car... Only a CEL, no limp mode.
This is more than your EGR, possible it was a bad MAF that he put in... How did he reach your EGR? Pull the intake or go from under the car?
Another option is a coil-pack, but you should get a CEL if one is that bad or un-plugged because it will cause a misfire.
This is more than your EGR, possible it was a bad MAF that he put in... How did he reach your EGR? Pull the intake or go from under the car?
Another option is a coil-pack, but you should get a CEL if one is that bad or un-plugged because it will cause a misfire.
12-18-2007, 11:27 PM
#10
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Join Date: Dec 2000
Posts: 85
Re the brake issue..........engine off, step hard on the brake pedal and start the engine........the pedal should drop a little and you should feel a "change" if the power brake booster is working. Just to clarify.......the ECU has just been changed, or just the MAF? Replacing the ECU may cause this shop headaches because of NATS (the immobilizer) just for starters. The reflash I don't get. The MAF replacement MAY technically require an ECM update.
The braking issue is really tough to explain. 75% of the time the braking appears normal. It's only after the initial slowdown when I go to depress the brake more that it sort of 'solidifies' and the braking power is dramatically reduced, whereas normally it should be stopping much quicker. It also happens if I slam on the brakes hard.
To the best of my knowledge, they replaced:
1. EGR Motor
2. Air Mass Meter
I don't think the ECU was physically changed. Basically he said that he had to download something from Nissan to 'reflash' or 'reprogram' the ECU after replacing the MAF.
12-18-2007, 11:40 PM
#11
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I recall that the brake pedal should react (drop) immediately when the engine starts. I'd check mine right now, but it's a couple of blocks away at the moment. Either way, something isn't right with your brakes by the sound of it, and if it wasn't an issue before you took your car to the shop, then it seems like they've done "something" haywire. The MAF only being replaced makes sense now. The ECM is also big bucks!
12-18-2007, 11:58 PM
#12
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I'm definitely going to call up the mechanic tomorrow and tell him that he needs to take another look at it. I had planned on leaving town for the holidays on the 22nd, but I can't do that if my brakes aren't working correctly. I really do believe that the brake issue and the rough idling are connected somehow...I just wish I knew more about how all this works so that I could know what all the possible problems that could cause those two symptoms.
I read somewhere to try starting up the car with the MAF unplugged. I just tried that, and the idling is even rougher and the car shut off after a few seconds. Does this mean the MAF isn't at the root of my current problems?
I read somewhere to try starting up the car with the MAF unplugged. I just tried that, and the idling is even rougher and the car shut off after a few seconds. Does this mean the MAF isn't at the root of my current problems?
12-19-2007, 07:07 AM
#13
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I am going with unplugged Vacuum lines on the intake manifold like P. Samson mentioned...
It has to be... There are like 4 million Vacuum lines that come off of the IM and it's easy to miss one or two or even put them on the wrong spot.
I was not sure before because I did not know if he took off the IM manifold to get at the EGR, but it's most likely what happened since you have to take off every single Vacuum line from the IM to take it off.
As far as a re-flash for the new MAF, it's not really needed and would not cause all of this.
It has to be... There are like 4 million Vacuum lines that come off of the IM and it's easy to miss one or two or even put them on the wrong spot.
I was not sure before because I did not know if he took off the IM manifold to get at the EGR, but it's most likely what happened since you have to take off every single Vacuum line from the IM to take it off.
As far as a re-flash for the new MAF, it's not really needed and would not cause all of this.
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