2000 Nissan Maxima

Tiny
MALLOSL
  • MEMBER
  • 2000 NISSAN MAXIMA
  • 6 CYL
  • FWD
  • MANUAL
  • 66,000 MILES
First I am not sure of my wheel drive type (64 yr old woman, sorry!) I will try to give you the facts in cronological order. I went for a long time with my sel on. Mnay factors going on in my liife at the time. Eventually I needed to have my alternator replaced. My neighbor (works at Muffler Man) replaced it for me. At this same time my car was barely running. Would only go about 10 mph. He also told me my cat was bad. Told me it was dangerous to drive it was glowing red. Scared I parked the car in my drive and tried to save money so I could fix it. On SS so it is hard to find extra $.I finally broke down and had it towed to a mechanic that several people recommended. He called me and said my cat was fine. He did some kind of test and it was getting enough backpressure? He replaced MAF sensor. Car runs great but. Now it stalls when I stop or slow way down to make a turn. Also I am getting an odor of gas outside car by gas tank area after I drive it and shut it off and park it.I bought a new gas cap. The one on car wasn't tightening. What do you think could be going on. Before I take it back to mechanic I want to be a little intelligent about what may be going on. How can 1 guy tell me cat is bad and the other say it is okay? Frightening!
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Monday, November 8th, 2010 AT 2:01 PM

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Tiny
CARADIODOC
  • EXPERT
Hi mallosl. Welcome to the forum. When the catalytic converter is glowing red it means WAY too much unburned fuel is getting into the exhaust system. Unburned hydrocarbons, (gas) are supposed to be burned there. The glowing red part means the converter is doing what it is supposed to do, ... Yet, but eventually the catalyst material will melt and plug the exhaust system. A plugged converter will restrict exhaust flow resulting in very low power from the engine. That's why the first guy said it was bad. He based his comment on the observation of low power and red-hot.

Further testing by the second mechanic revealed back pressure was low, (normal) so there was no restriction in the exhaust system and the catalytic converter wasn't ruined yet. The mass air flow sensor has the greatest affect on fuel delivery to the engine and has the greatest impact on how well the engine performs. The Engine Computer learns the characteristics of these sensors and keeps that in memory. If the battery was recently disconnected or run dead, that memory will be lost. Engine stalling is one common complaint until the relearn procedure is completed. I can only share with you the strategy Chrysler uses, but other car companies do similar things. On Chryslers, you must drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the brake or gas pedals. Doing that meets the conditions to trigger the computer to memorize sensor values when your foot is off the gas pedal. Once that is done, the computer will know when it must be in charge of idle speed. Until that is done, the engine will not stay running at idle unless you hold the gas pedal down about 1/8".

If you're still having the stalling problem after a few more days or many miles, contact the mechanic and ask about a relearn procedure. Normally they test drive the vehicle to force this procedure to occur before giving the vehicle back to you, but if they're busy, they could assume it will occur on its own.

They might also want to recheck their work. Any leak in the air intake system might result in "unmetered" air getting into the engine. That air does not get included in the computer's calculation of how much fuel to inject. Too little fuel can result in engine stalling.

Caradiodoc
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Monday, November 8th, 2010 AT 3:24 PM
Tiny
MALLOSL
  • MEMBER
I got an answer to my initial question. Well partly. There was no mention of the gas odor I am smelling outside car by gas tank area. This scares me it can't be good. If you read my previous question maybe some of what I explained (cat etc might help.) I am puzzled, before car stopped going above 10 mi an hr I never had a gas odor outside. .I hope you can pull up my previous question. I was hoping a Nissan expert tech would answer. I am a little disappoiinted he didn't address the fuel odor outside the car by the gas tank/rear drivers wheel. Could someone help me with that.I would like any suggestions, as I am taking the car back on
Friday to be looked at.(More money)! Could someone that deals with Nissans address these concerns.I do not have a lot of money, I am terminally ill and can't spend a lot. On SS and small pension. Please someone address my concerns
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Wednesday, November 10th, 2010 AT 6:44 PM
Tiny
CARADIODOC
  • EXPERT
A fuel odor means there's a leak but it does not have to result in a puddle seen on the ground. Start by looking under the car on the passenger side, between the front and rear wheels. Look for fuel dripping on the ground or wet spots along the bottom of the car. Also look between the two rear wheels. Check for wet spots on the ground after you move the car from where it was parked.

Rusted steel fuel lines and rotted rubber hoses are the most common sources of fuel leaks on cars that have not had the system worked on recently. Sitting for long periods of time on wet grass is very bad in this regard. For cars that have been recently worked on, mispositioned rubber gaskets on top of the gas tank can allow vapor to escape that you will smell, but liquid fuel will not drip onto the ground.

These things are common to all cars. For specific leaks, someone is going to have to actually look at it to see where the smell is coming from. No expert can determine that over a computer. You can find it yourself if it's coming from a loose or defective gas cap, but you will not smell those vapors from the other side of the car unless it is sitting in an enclosed garage.

If you can smell the fuel more in the engine area with the hood open, look around the top of the engine for wetness. There are rubber o-rings on each injector and there are rubber hoses that go from the steel fuel lines to the engine.

All of these potential leak sources should be inspected shortly after turning off the engine. Fuel pressure is supposed to remain in the system for weeks but a leak will let that pressure bleed down, sometimes in less than a minute. After that, any leaked fuel will evaporate.

Odor by the left rear wheel can also be caused by a loose / disconnected / rotted vapor line leading from the tank to the charcoal canister up front. Those vapors are the result of expanding fuel and are meant to be collected and stored. They are burned in the engine when it is running. A leak from this hose can be a simple as a rusted-off hose clamp.

One place to not overlook that is not pressurized is the gas tank. Most of them are plastic now. If yours is steel, ten years old is kind of soon for it to develop rust holes. Nevertheless, leakage on a steel tank will show up as wetness on the side when it is full, and staining if the fuel has evaporated. That staining is usually impossible to see on plastic tanks unless road dust has collected on the area. A light coating of mud in just one area of the tank is clue of where to look for that type of leak.

If you only smell this fuel when the engine is running and it is coming from the tail pipe, you may not even have a leak. Rather, that would be why the catalytic converter was getting red hot and why engine performance was poor. Here again, someone is going to have to look at many things to determine why too much fuel is entering the engine. Possible causes include a leaking injector, leaking fuel pressure regulator, defective spark plug or plug wire, defective mass air flow sensor, defective MAP sensor, even a defective Engine Computer in rare instances.

Has engine performance improved since the mass air flow sensor was replaced? How about the stalling issue? Did that take care of itself as I hoped it would?

Caradiodoc
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Wednesday, November 10th, 2010 AT 7:54 PM
Tiny
MALLOSL
  • MEMBER
Thankyou. Yes the engine performance since the MAFS was replaced is great. Its just I smell that "electrical burning" coming from unerhood close to the drivers side front window. I went out today and raised hood and if I bend down very close I smell this odor I am discribing. The car hasn't been used since yesterday when I took it for a thirty mile long drive. It didn't stall. But I got these terrible odors.I left windows open and didn;t turn anything on that would use power.I have made app't for Friday to take car in but I am skeptical because car didn't have this burning type odor under hood until MAFS was replaced. The gas odor I don't remember having at all even when car was barely running which I explained in first message to you.I am very worried about what they may tell me Friday and I have a hard time understanding why they didn't smell these odors/fumes before I picked car up after they made repair of MAFS. The owner of shop said he took it for a ride and it ran great. When he gave me ticket to sign the mechanics name was different than his.I need to ask him Friday who worked on car, and who took it for a drive when work was complete. This is why woman don't trust mechanics even if they come highly recommended. Any response would be appreciated. Thank you
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Wednesday, November 10th, 2010 AT 8:14 PM
Tiny
MALLOSL
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I am replying to your reply. Any suggestions?
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Wednesday, November 10th, 2010 AT 8:25 PM
Tiny
CARADIODOC
  • EXPERT
Please clear up my confusion. First you were talking about a gas odor by the left rear wheel. Now, for the first time you mentioned a burning smell while driving. A lot of things come to mind for a burning smell, but if we stick with the recent service, it is possible a wiring harness became mispositioned and is laying against something hot. That type of thing should be directed back to the shop that did the work so they have a chance to correct any mistakes they might have made. More on that later.

Not related to any recent service, some common causes of a burning smell are overheated and melted wires on the ignition switch, overheated wires or switch for the heater fan speeds, and a failing heater blower motor. Other wires can become overheated too in electrical connectors. All of those smells will subside shortly after turning off the offending circuit.

Even something as silly as the rubber strip along the back of the hood can allow normal engine smells into the fresh air intake if it is loose or mispositioned. Leaking heater cores will allow hot antifreeze to drip into a drain pan inside the car. That will cause an oily fogging on the windshield and a sweet smell, but some people describe it as a burning smell. There really isn't anything a mechanic could do to cause a leaking heater core. That occurs from the natural buildup of acids in the antifreeze over time. That acid eats away at metal parts and the heater core is usually the first thing to be affected. These acids are the reason we change antifreeze every two years.

If you do indeed have an electrical wire, connector, or switch contact overheating, the most common cause is from using the heater on the highest speeds a lot. The fan motor draws very high current which stresses the switch contacts and wiring. An overheated ignition switch is a very common cause of vehicle fires on Ford products. On other cars it mainly just makes an irritating smell and eventually some circuits will stop working. Most commonly the engine will stay running. The affected circuit is for the heater, radio, power windows, and possibly the dash gauges. If the heater fan switch is the culprit, the fan is the only thing that will stop working.

In general, if the smell stays the same whether you're moving down the road or standing still, it is probably coming from inside the car. If it gets more noticeable when standing still, it could be exhaust sneaking in from a leak in the system or it could be fumes from under the hood that normally blow under the car while it's moving.

There are a lot of reasons people, (not just women), don't trust mechanics, and most of them have valid explanations. There are disreputable mechanics just like there are disreputable tv repairmen, sales clerks, plumbers, etc. But it is unfair to hold an entire industry responsible for the actions of a few. Mechanics are actually held to much higher standards than doctors. When a doctor doesn't come up with the right diagnosis on the first try, we keep going back until he does. When a mechanic doesn't come up with the right answer the first time, we call him incompetent at the very least, or assume he is trying to rip us off. Doctors only have two models in varying sizes to learn. Only the cures keep improving. Mechanics in the 1960s could repair any system on any car in the world if they could memorize 5,000 pages of service manuals. Today they have to learn changes to hundreds of models with all kinds of variations to their systems sometimes twice per year. The insane addition of a computer to every part of a car makes things so complicated that it's almost impossible for anyone to keep up. Repair bills for these computers has driven repair costs through the roof and most manufacturers have their cars designed so you must go back to the dealer for these expensive repairs. Manufacturers profit handsomely from forcing you to buy their expensive replacement parts. Unfortunately, the mechanic is stuck in the middle being forced to sell you those expensive parts and services.

There is no longer such a thing as a mechanic who is an expert on even one brand of car. Young mechanics just starting their careers can do a little of everything, ... A little engine repair, a little suspension and alignment repair, a little electrical diagnosis, etc. But just as seasoned doctors specialize, so do mechanics. They are no longer a "Nissan specialist". Now they might be a "2004 - 2010 Nissan engine performance specialist" but know nothing about Nissan brakes or heater controls. For that reason, you might have a different mechanic work on your car at each visit to that shop.

I will never defend a disreputable mechanic or shop, but being a former mechanic and tv repairman, I've seen the best and worst of both worlds. Here are some of my observations that can lead to your mistrust. The person you spoke with at the shop was most likely not the mechanic who worked on your car. That is normal. Think of the mechanic as the doctor who pokes and prods you, and the service adviser as the person who schedules your next doctor's appointment. The doctor doesn't have time to do paperwork; he has to run to see his next waiting patient. Mechanics have very good diagnostic skills but they typically have rotten communication and customer skills. It's the service adviser who translates the mechanic's findings into terms you can understand, but most service advisers never were mechanics. A lot of them know little more about cars than you do so very technical things can get mixed up in translation. To add to the misery, two different mechanics will write their "story" on the repair order in different ways and two different service advisers will describe those findings in different ways. The two final versions might seem like they're describing two different cars but none of the people involved are lying or trying to mislead you.

Going back to your observation that the first mechanic said you had a bad catalytic converter and the second one said it was the mass air flow sensor, all that happened was the first guy stopped too soon. I can imagine hearing the second one say, "this car has a bad catalytic converter because it's glowing red, but let me check further. Hmm, there's no excessive back pressure so the converter is not damaged yet. I wonder what would be causing too much fuel to enter the engine". It that point, further testing would have also led the first mechanic to the sensor. He just jumped to the logical conclusion based on a quick observation and not enough diagnosis. Very often troubleshooting involves ruling out what is not causing the problem to narrow down the cause to what is causing it.

Some people will bounce from doctor to doctor looking for a diagnosis. To be sure nothing got overlooked, each new doctor will probably start from scratch and repeat what the previous ones did, so you can see how that is not the best way to approach the problem. Just like it's better to stick with one doctor you feel comfortable with, you will usually get better service when you stick with one repair shop that knows the history of your car. The service advisers at the very large dealership I used to work for knew most of their customers by name and their cars' service histories popped up automatically when the computer spit out the repair orders. While there are advantages with sticking with one shop, that becomes even more important when there's the possibility a new problem is related to their recent work. They should have the chance to correct their mistakes and apologize. That doesn't mean every new problem is their fault. Sometimes it's just coincidence that a number of things go wrong all at once.

Kind of related, most larger shops pay their mechanics on a system called "flat rate". That means every task can be looked up in a flat rate guide that lists the number of hours that job should take. He is paid his hourly wage for that job regardless of how long it actually takes him, and you will be charged for that many hours regardless of how long it takes or how many people work on your car. These guides let the shops provide you with a fairly accurate estimate that is in line with their competitors. It insures they will charge enough to cover their costs and they won't overcharge you.

As an example, I might pay my neighbor's kid ten bucks to mow my lawn. If he uses a scissors, it will take him all week! If he pushes a mower, it will take him all day. If he invests in a riding mower, it will take him an hour. Either way, it costs me ten bucks. The advantage of flat rate to the mechanic is if he invests in high-level training or expensive tools, or if he is very experienced and has done this same job many times before, he will get the job done faster. If he is being paid $10.00 per hour and does a one-hour job in half an hour, he still gets paid ten bucks for that job but he has extra time to get to the next job sooner. He is rewarded for sticking to business and working as quickly and efficiently as possible.

The checks and balances comes in when he makes a mistake due to his haste or he overlooks something. Under the flat rate system, he does not get paid again later to correct his mistake and you don't get charged again. That's another reason to stick with the same shop. Fortunately these mistakes don't happen often but when they do, that's what people remember and tell their friends about. They tend to forget all of the positive visits in the past.

A typical entry in a flat rate guide would look like:

Replace water pump
(4 cylinder): 3.4 hrs
(V-6 engine): 4.7 hrs
With air conditioning: add.6 hrs

That type of job is very specific and does not include the time it took to find it leaking or some other defect. The clock starts after the diagnosis has been done. Many shops do not charge for that diagnosis if it only takes a few minutes, but sometimes other related things get overlooked. For example, it is common for a worn water pump to ruin the drive belt. The cost of a new belt should be included in the repair estimate. Service advisers really hate it when the mechanic comes running up with a chewed up belt after the repair job is half done. Now they have to find you and tell you that more parts are needed than originally thought. The impression that leaves you with is "as long as you have your wallet out, I found something else to sell you". And if you agree to that part, they'll surely find something else later. You can see how that would make you mistrust them even though there was no intent to defraud you.

Sometimes the need for additional parts or services can't be foreseen until things are taken apart and inspected, but experienced service advisers will either warn you ahead of time or they might build those extra costs into the original estimate, then hope they can surprise you later with a bill that's lower than expected.

One last point. Now that I suggested you stick with one shop, if an estimate seems unusually high, there's nothing wrong with getting a second opinion. Doctors don't take offense at that and the only mechanics that would are those who are afraid they'll be found out for coming up with an incorrect diagnosis. The shop owner knows he might lose the job to a competitor but if that second diagnosis agrees with the first one, he knows there's a good chance you'll come back in the future.

Here's one thing to watch for with that second estimate, ... Well, actually both of them. There is nothing secretive about the flat rate guide. As long as the service adviser isn't busy with other customers, he should be willing to show you the labor times he is looking up. First of all, look at the book to be sure he is looking under "Nissan", not some other brand, and he is using the correct engine size and accessory information. GM cars are very involved and complicated. Their labor times will be much higher than for that same job on a Nissan so an unscrupulous service adviser might open the book to the GM section and show you that. Be aware too that there will often be two labor times listed. The shorter time is for vehicles still under warranty and are not practical. They assume no bolts are rusted tight or break off and the entire job goes smoothly. These times can rarely be met when you consider the time it takes to find the car, drive it in, get the parts, and test drive it after the repair. The mechanic does all of that for free. Usually there is only about a.2 hour difference between the standard and warranty labor times.

The last thing to look at is if there are multiple things being done to your car, do they each have separate labor times? As a steering, suspension, and alignment specialist, two jobs I did quite often were to replace the rack and pinion steering gear and replace the high pressure power steering hose on one particular model. Each job paid 3.4 hours so you would think I earned 6.8 hours pay for that car. In reality there was an entry in the flat rate guide that said the two jobs together only paid 3.7 hours. That's because all of the same things had to be taken apart to replace either part. According to my story for my students, that would be similar to paying for a five hour surgery for a lung transplant and another five hour surgery for a kidney transplant. If both were done at the same time, you might pay for six hours but not ten. Now, keep in mind that a brain transplant involves a whole different part of the body so while you might already be in the operating room, combining the two jobs might not always be practical when it comes to billing out labor times. Performing an alignment and replacing a muffler are two totally different things so there you COULD expect to be charged for both jobs.

For my water pump story, there will be an entry for replacing only the water pump belt, but that labor time is already included as part of replacing the water pump. It is not correct to add the belt replacement time to the bill. The belt, in that case, will be listed as included with the pump.

One final note, there are no labor times given for such things as smells, wind and water leaks, squeaks and rattles, or electrical problems. That's because there is no way of knowing what is causing the problem or how long it will take to diagnose it. Once the cause IS diagnosed, that's where the flat rate guide spells out how long it should take to replace something, but that will still potentially leave you with a separate diagnostic charge.

Hope I didn't bore you with too much information. Feel free to holler back with more questions.

Caradiodoc
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Wednesday, November 10th, 2010 AT 11:55 PM

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