Transmission drain/fill causes problem?

It could be that the new fluid is washing off crud that has accumulated on seals and in passages.

Drive it a couple times like you stole it and shift it through the gears a few times. Then see how it acts.

Trans slipping usually occurs ALL the time, especially under higher loads. So if the tach normally reads say 1500 at 55 mph with a normal trans a slipping trans may read 1800 to go the same speed.

On your 99 slipping should also set a code, if it is actually occurring.

Would it be safe to do a flush at the dealer now that the cruds are out? Would another drain/fill help?

Would it be safe to drive like this for a while? or do I need to fix this to prevent this to become a bigger problem?

Raymond

Hard to say if another flush would help. Maybe take it to an actual transmission shop and see what they say. Without seeing it myself I can't give you a guaranteed answer. However if you beat on it a bit and it doesn't change or get worse then I would drive it.

Or if it worries you, Rent a nice new vehicle.

Are you sure its not the ABS initializing? If it never makes the noise except the first time it moves in the morning, it could be that.

A little clunk (ping) when changing the direction of axle rotation could also be an indication of a tired U-joint in one of the drive axles.

Keep checking the fill level, paying careful attention to how hot the fluid is when you check it. For the fluid to be at the full-hot mark, it should be painful to touch. If the fluid is cool to pleasantly warm, it should be closer to the full-cold mark. Look for frothing on the dipstick as a signal that it is overfilled. Nissans really hate being overfilled. As long as it's above the min mark, don't add any.

It's not. My maxima unfortunately does not have ABS break.

Now that I've driven a bit more, the sympton can be described as a slight hesitation when starting from a stop.

- press gas paddle

- car moves slowly for a very brief time

- then perhaps the transmission shifts into gear, and I feel a slight 'thung' and it moves normally. The 'thung' is felt as a motion of the car, rather than sound.

After the car has warmed up, it doesn't seem to happen. It's very reproducable early in the morning when the car is cold.

Today on my way to work, I seem to notice the hestitation during gear shift while I am driving. It's difficult to descirbe, just a subtle hestitation. flooring the gas seems fine, the car accelerates well.

Ah, I did add a little bit after thinking that a lack of fluid level would cause it to slip. Didn't add much, perhaps 1/5 quart.

Hope the transmission is not on its way out. Man I should've skipped the 2nd drain/fill. Could a dirty transmission filter cause this? dirty fuel injector? bad gas?

Raymond

Did a test drove again just now for about 20 minutes and can't reproduce the problem. The car's been parked for more than 4 hours. On my final leg of commute this morning to work I did follow the advice of theo ther poster and floored it a few times. Maybe the new oil needs a little break-in time? Let's see how it goes tomorrow morning.

It has gotten a little cold recently, so perhaps, just perhaps it's not related to the transmission and something else due to the temperature.

Raymond

I disconnected the battery to reset the ECU last night. This morning after about 15 minutes of drive the "service engine soon" light came on! I went home and took out the reader, here are the codes:

P0325: knock sensor circuit malfunction, bank 1 P0172: system too rich (bank 1) P0172:

So perhaps it is totally unrelated to the transmission fluid change and the thing I felt was the knock sensor failing. If it's indeed an engine problem might explain why the sympton goes away once the car warms up.

Could it be due to the gas being used? How serious is this code?

Called my local Nissan dealer and they want $214 for the sensor parts. Damn.

Raymond

God damn, this could be caused by the KN filter which I slapped on a few days ago. Could the oil from the filter have messed up the MAF sensor? The damn thing is $600 to replace.

Raymond

K&N filters are renown for their ability to f*ck up a MAF.

They filter poorly and precipitate oil into the intake airstream, giving you a "double whammy" of an oil contaminated MAF and more dirt/grit to stick to that oil in your intake/throttle body/MAF sensor.

K&N air filters = Trouble or at least sub par filtration. You do get more "sporty noise" tho. Al

Ah damn. So after work today, I drove to my local pepboys and picked up 2 non oil regular filters. The car seems fine, other than the "service engine soon" light. The hesitation doesn't even seem to be there anymore.

Afraid that the K&N filter will mess up my MAF, I swapped out the K&N with the regular filter at the pep boy's parking lot.

Boy did the trouble start. The car idles roughly, and the front shakes slightly. I was able to drive home OK but the engine doesn't seem to be normal.

Thinking that my ECU reset last night might have caused the car to adapt to the new K&N filter and is having trouble with the restricted airflow of the new regular filter, I removed the negative battery terminal. After About 2 hours, I reconnected it and start the car. No change, it idles rough.

Did I completely reset the ECU by 2 hours of disconnect? The engine code was still there so it might have been running on the old (K&N) parameter?

I am going to leave the battery disconnected over night to see if it resets. It really troubles me that a filter will make that big of a difference. With the KN filter the car runs almost normal. Now with the regular filter it runs like shit. If I have to take it to a shop I'll probably have to put in the K&N filter and then drive it there.

Is the MAF toast? Can I use MAF cleaner? (pep boy didn't have it, they do have some electronics cleaning stuff..) The code says knock sensor (the shop says i can ignore it claiming it's the default code..) and "System too rich", whatever that means.

Raymond

The K&N filter isn't your problem. The things DO give lousy filtration and in the long run they are going to result in a lot of crap in your engine that you don't want there, but that's not your immediate problem.

The ECU doesn't care about the filter. The ECU gets information from the MAF about how much air is coming in the intake. It doesn't matter how restricted the intake is (within reasonable limits) because the MAF compensates for it.

(This is why the only benefit you'll get from a high-flow filter is at full throttle.)

No. You have something wrong that is causing rough idling. It's not related to the filter at all. It might be related to a screwed up MAF, but if that is the case the codes on the computer will tell you precisely that. You should be able to diagnose a bad MAF with an ohmmeter and your fingers, too.

But there are plenty of other sensors that can cause similar problems, including the oxygen sensor. And for that matter, you could have an ignition issue.

Almost certainly unrelated. I bet if you put the K&N filter back in right now it won't run very well either.

SYSTEM TOO RICH! There is your answer. Your oxygen sensor is out of range.... the ECU cannot lean the engine down enough to get it into the correct level.

Now... walk behind the car and smell as it's running. You should be able to smell whether it's too rich or too lean. If it's too lean, I'd look at the O2 sensor first. If it's too rich, I'd look at the MAF.

Don't just swap things out randomly. Get out the ohmmeter and measure the value... move the vane on the MAF and make sure the resistance moves smoothly as you do so. If the vane hangs up or the meter jumps, either clean the resistive element with CaiLube or replace the whole thing.

--scott

If I were you, I'd a) clean the MAF sensor, and b) look for an air leak, wiring problem, or other issue related to the MAF sensor. Just swapping in a paper air filter in the parking lot should NOT cause an immediate change in behavior. However, a leaky hose or something that got disturbed during the air filter change certainly could do so.

Swapping in the air filter in the parking lot causes the immediate change in behaviour because the system is running open loop! The computer has an incorrect notion of how much air is flowing through the intake and so it's squirting the wrong amount of fuel.

If changing anything on the intake side makes a change in the running, it's a sign the system is not running with a properly closed feedback loop.

One good reason for the feedback to be malfunctioning is if the MAF sensor is squirrely. Or if there is a leaky hose (it takes only a tiny crack in the hose between the MAF sensor and the intake to cause big trouble).

--scott

Ah crap. I can't remove the damn MAF sensor unit. I losen the retaining clamp, removed the 4 screw connecting the MAF to the upper half of the filter hosing, even removed the upper half of the filter housing. But for the life of me I can't remove the MAF sensor unit. This is with 2 people, one trying to twist the MAF in a clock or counter clock wise motion and the other holding the part where the MAF is connecting...

Well I guess repair shop is the only answer now. They are not going to clean it, just replace the parts I think... What do they do to remove the damn thing? Special tools? Stronger guys?

Raymond

Ah, the fun continues.

By the time I drove to the repair shop, which took about 15 minutes on the highway, the car seems to have fixed itself. It idles fine and there are no hestitation during acceleration.

They tested it out, and said the fuel injection system, and oxygen sensor is fine, so the likely culprit for the "system too rich" code is the MAF. They said they put in a different MAF that they know is working, and got "different results" than the one I have.

The "system too rich" code was thrown:

- KN filter

- battery disconnect over night

- after 5 minutes on the highway

At the time, car drives fine. There's a sutble hesitation on acceleration from a stop but that's it. Idles ok.

once I remove the KN filter and put back a regular filter, car idles eradically and the front shakes up/down slowly. I disconnected the battery overnight (hoping to clear the ECU operating parameter for the K&N), was the same. still idles rough.

But after a drive on the highway (to the repair shop), the sympton seems to have completely disappeared. The idle is quite normal now, and acceleration, and engine sound seems to have returned to normal. (it sounded different with the K&N)

Perhaps the engine have 'unlearned' the K&N filter parameter (a disconnect over night wasn't enough?) and now back to normal operating parameter? Should I still take out the MAF and clean it? I never got a code indicating the MAF was faulty.

My best conclusion, if the car did fix itself, is the K&N filter pushed some sensor or component over the operating limit, as the car is adjusting its self to work with the increased air flow. Perhaps on a new car this would be fine, but on my 10 year old car with 130k on it, it's just too much.

If they did remove the MAF and tried a different one, then I should be able to remove it now. Should I try clean it with a CRC electronic cleaner? Or just leave it?

Raymond

Right, because either you shook the MAF so much that whatever gunk was making it stick was loosened, or you closed up the vacuum leak in the big hose to the throttle body.

What are those "different results" and did they test the MAF with an ohmmeter? The ohmmeter tells you what you want to know.

Right, none of these things matter. They are unrelated to the problem and they did no good and no harm.

Right. The MAF is bad, the system is running open loop. So changing the filter changes the way the car runs. But it still doesn't run well no matter WHAT you do because the computer still isn't getting proper feedback about the airflow.

No, after you spent time trying to get the MAF off, and shook it around and wiggled all the hoses, the symptom has disappeared.

There is no learning taking place here. Your MAF is pretty clearly bad.

The car NORMALLY adjusts itself to operate with any air flow. That is what the MAF does. If the MAF is not working, the computer cannot adjust things properly and it will run too rich or too lean, and changing the air flow restriction will change the way the car runs.

Right now you can get some duct tape, block off half your air filter, and you won't notice any difference in the way the car runs at low speeds, because the computer is using the MAF data to get the mixture set right. Go on, try it.

They removed it, they put a different one in and got "different results" and they didn't replace it? I'd definitely clean it immediately and I would carefuly inspect all the hoses since you have pretty firmly established where the problem is.

--scott

I don't bother cleaning them any more. It's usually a waste of time. UNLESS I know they ran an oiled filter, then I'll give it a quick cleaning and see if it is any different. One nice thing about having a good scan tool is that I can watch what the computer actually sees. That can make a BIG difference.

Ok. Problem solved. It IS the damn KN filter that's causing all the trouble on the car.

With the KN filter on, after a day or two, I got the initial sympton of hesitation from stop when car is cold (which I initially thought was related to the transmission oil change), and the check engine light came on with "system too rich code" after a while.

Removed the KN filter, the engine was a bit rough on idle, probably due to the system tuned to the increased air flow of the KN, and have trouble with the decreased air flow of a regular filter. It ran OK on street level driving. I never tested highway, and thought the MAF was messed up by the KN.

After a bit of street AND highway driving, the system learned the new air flow, and now its running very smoothly. The hestitation problem is gone, the rough idle problem is gone. Everything is back to normal. Maybe the Maxima takes a bit of driving of 'full range', from city level to highway level, to adapt. I really didn't drive much after i slapped on the regular filter. About 5 minutes of street driving.

I bought the KN not for the performance ga> Right, because either you shook the MAF so much that whatever gunk was

No. I took extreme care not to shook it while trying to get it off, as I've read it's very fragile. 2 people, one holding the thing it was attached to, the other trying to rotate the MAF housing.

The car was still idling rough when I started the car to drive to the shop. So it's probably not due to I accidentially closed an opening or shook the MAF to get something out. After a bit of highway driving, all the problem went away. So it appears the car needs a wide speed range to perperly adjust to the air flow.

I could be proven wrong again tomorrow morning. But to me it's the car unable to fully adapt to the KN filter's air flow. It did try to adapt, which is why it was idling rough when I slapped on a regular filter.

Could be. But it's now running very smooth just like it did before I put on the KN filter where all the shit started to happen slowly.

Perhaps the MAF is not working too well, so the car took longer to adjust? When I slapped on the KN, it took a bit of driving before I realized the change in engine sound. So perhaps the adjustment is not instantious.

Interesting idea. It's working fine, and if it continues to work fine for Thu/Friday, then I will assume the problem has been fixed. I am not going to *&(*& with it any more before the trip. ;)

I did try to remove it after I come back. Still can't. I put all the screw back and drove to Pepboys and promptly returned the 2 damned K&N filter. The car was fine the whole way. I even let it idle from cold to warm and it was fine.

Let's hope it continues to work as well tomorrow . ;)

Well, another theory of mine is the MAF's aged, its sensitivity is not that good anymore. On low input level, it just can't measure accurately. On high input level, it still works. Probably the highway drive correctly set the 'high point' in the operating parameter, and as a result fixed the low point also. On a brand new MAF, the low point would've been measured instantly and corrected immediately.

Raymond

I thought of another reason why the KN filter might have caused the problem on my car. Basically with increased air flow, the car's air flow system has to work with a reduced set of range from min to max to set the correct air flow.

The MAF senses the air flow, but something in the car has to adjust for the proper air flow. Not being a car person, whether this is the fan speed, a valve, I don't know. But for the purpose of discussion, it doesn't matter. It's a physical device that sets the proper air flow rate based on sensor data.

Let's say this physical device has absolute input range 0 - 100. Let's say with a normal air filter that the car was designed for, the level at idle to 80mph is from 20 - 80. It's probably not linear from 20-80 with respect to speed, but the range is 20-80. The key point is, the 'working range' covers a large portion of the physical range.

Now with a high flow air filter such as the KN, much lower setting is needed to bring the correct amount of air flow. Let's say this is actually 10 - 40. This is a much reduced set of range. The response of the system from 10 - 40 may not track as well as it does from 20 - 80. This is just like the volume control on a stereo. If you get to play with the full range, you can get a much precise level calibration. But if you are only restricted to 40% of the dial, you don't be able to dial in as precisely.

With the car's air regulation system's physical range reduced to a subset of the normal designed working range, it may not be possible to accurately set the level at low input levels, such as the case of idling. If the level is not accurate, either too high or too low, then trouble starts.

Now in an ideal car, this won't matter. You should be able to correctly set the air flow rate whether you are 20 - 80, 10 - 40, or even 30 - 40. But if your car isn't designed for the reduced dynamic range, then the response won't be correct and you'll have problem.

This is likely the cause of the hesitation on acceleration from stop that I experienced with the KN filter, and the P0172 "system too rich" code on highway speed, and the rough shifting. With a reduced range, the system just can't work as accurately as it could if it had a larger range. (Imagine a cheap car stereo where 10% volume is barely audible, but 20% volume is painful already. Each 'click' of volume change between 10% and 20% produces too big of a volume change to allow one to set the volume precisely).

Moral of the story? Don't do MODs that the car is not designed for.

Raymond