Heres the story . About a 1 1/2 weeks ago my car started randomly stalling out so then I removed the SC to see if it made any difference, of course it made no difference and the car felt even worse. So I then put some Bosch paltinum plugs in and the car seemed all better. But infact the problem is still here but far less noticably. The only time the car acts up now is after I have been driving about 20 minutes in stop and go traffic, the problem begins to show up a little and then sometimes goes away and then comes back stronger then ever, at that point I can't put my car in nuetral or the car will stall, or all most stall. Heres what happens, it first seems to show up by making the car a little shaky at idle and then the needle bounces a little bit between 600-800 RPM's. Then out of nowhere it will dive down to 200-300 RPM'S, and sometimes the car goes down to a indacated 000-rpms and emmiadatly jumps back up to about 800 rpms and then dives back down to .2-.3K rmps. I noticed a strange smell comming from what seems to be under the hood, it smells like something burning and/or roten eggs{sulfer}. Another thing I should mention is when I accelerate away after it has a "eppisode" the car has a bit less pic up and is a little noisier.


I did replace one o2 sensor but there seems to be no difference, I also did the AC? valve test buy running my AC and the idle was fine.

I have a few suspesions now, could it be a engine coolant sensor malfuntioning? How about a bad PCV valve? maybe a week o2 sensor? Maybe the Bosch plugs? I plan on replacing all the stuff I said above unless someone can tell me that it is not related to my problem. BTW there is no check engine light. Well thats all I can think of right now so if you have any info on this problem then please help me. Also thanks a LOT for reading this huge post.

I think it would be better if you brought it in to a shop to have it inspected. It seems like you are just throwing parts at it and hoping it'll fix the problem. The parts you mentioned costs over a hundred dollars and may not be the problem. Most shops can do the diagnosis for under that. The rotten egg smell is coolant burning or running too rich. I forgot which one.

It will probably cost a lot more then a $100 to bring it to a shop and then they will say they relaced such and such and the problem will still be there. I hate having other people work on my car because they always mess things up. I will try a few ideas out and if thet does not work I will just make my car completly stock and have infiniti fix it under warranty. It will be a huge pain in the butt to make my car stock though.

The rotten egg odor is a sign of an over-rich mixture. This could be caused by ...
- bad Engine Coolant Temperature Sensor
- bad Fuel Pressure Regulator
- obstructed fuel return line
- sticking fuel injectors

If one of these was the problem whould that explain my cars stalling problem? Also is there a way a DIY Mechanic can test any or all of these parts? Thank you so much Daniel.

The fuel injected engine has an Engine Coolant Temperature Sensor. This sensor sends a signal to the Engine Control Module (the computer). When the ECTS sends a "cold engine" signal the ECM responds by instructing the fuel injectors to deliver a rich mixture. The rich mixture helps a cold engine to start run smoothly during the warm-up period. This is similar to the operation of the choke on a carbureted engine.

On the 4th Generation Maxima engine the Engine Coolant Temperature Sensor is located in the water outlet tube close to the engine end of the upper radiator hose. There are two sensors in that vicinity. The one nearest the hose is for the dashboard temperature gauge. The ECTS, the one you're interested in, is adjacent to the the gauge sending unit. There is a good picture of these sensors in the Haynes repair manual on page 3-7.

With the engine cold, disconnect the ECTS measure its resistance. Reconnect the ECTS, start the engine, run it until fully warmed up. Stop the engine, repeat the resistance measurement. The "warm" reading should be a much lower value than the "cold" reading. These are the specs:
Engine coolant temperature 68F, ECTS resistance 2.1 - 2.9 Kohms
Engine coolant temperature 194F, ECTS resistance 0.24 - 0.26 Kohms
(Roughly a factor of ten difference.)

The ECTS is a relatively inexpensive sensor something the home mechanic can replace without special tools.

I think the sensor will test out fine because my cars problem only happens for short periods of time after a lot of stop and go traffic. It's so darn confusing becuase it only happens under those circumstances, other wise the car runs 100%. I will probably buy the sensor tommarow, do you think Parts America will have a ECTS? Thanks again! Ohh BTW whould a bad PCV effect my cars idle at all?

fuel pump?
fuel filter?
throttle position?

I am preatty sure it is electrical because how it comes and goes, I meen if it was a clogged fuel filter my car should always run like crap, same goes for a defective fuel pump. I know it is definatly not a throttle position issue becasue that would be very noticable and whould not work 99% of the time. Thanks for help Cheston. I am lost in a giant maze here, whens it gonna stop!

The diagnosis should cost under 100. The repair is another story. If it is a computer control problem, they shouldn't mess around with anything. They just need to plug in the scanner, and they can see most of the major sensor's reading.

Test the ect when the car stalls. That should tell you if it is the problem. Fuel filter, pump, pcv valve shouldn't cause a rich mixture. When you replaced your spark plugs, did one look different than the others or did they look the same? If they were the same, you can eliminate items that only affect one cylinder like fuel injector and ignition coil.

Fuel pressure regulator and return line can be checked with a fuel pressure gauge. Hook up the gauge and disconnect the vacuum line to the regualtor and look at the pressure. Then pump the regulator with a vacuum pump and the pressure should go down. Not sure how accurate this test is though. Just an idea.

Tps can be the problem. If it sends a wot signal to the ecm intermitenly? at idle, it will cause it to dump more gas and to ignore the o2 sensor.

It only acts up after you run it for a few minutes? Could it be the catalytic converter? Do you still have the original cat on your car?

Thanks a lot for the info. When I changed my plugs all the plugs were real black{Carbon build up} and it seemed to be evenly distrubuted on each plug. The reason the plugs were black is becuase when I had my SC on my car was running WAY to rich. BTW I did a diagnostic on my ECM and no trouble codes came out. I wish I got a trouble code then I would know what to fix. Do you think if Infiniti does a diagnostic on my ECM they would get a code that I can not/did not get? Thanks again.


Rutnick, thanks for your particapation but a Catalytic converter is strictly for emmision and has nothing to do with a car's idle or drivability, unless of course it was clogged, which it is not.

may be a long shot, but check the cables from the distributor cap for any burns on them. it can happen if oil gets on them. maybe its the cap/wires itself.

Thanks, but if that was the case I think the problem would always be there and not intermitent. I will check out right now though, just incase.

A technician can see a lot by hooking up a scanner. Some problems must be detected 2 or 3 times in a row before the ecm will turn on the mil and set a dtc. But pending codes which only a scanner can read, needs to see the problem only once. The scanner can also see the sensor's reading. Like the tps, o2, maf, ect can be seen without touching the actual sensor.

Thanks maybe I will bring it to infiniti then

Thats weird about the rotten egg smell.. Cause when I was running my venom I had that nasty smell.. I guess thats what it was then.. Good to know... I disabled it and it went away..hmmm...

Hmm...Ethan, could this be the aftermath of your little accident? (misshift on the freeway)

The misshift was on a little street{not freeway}. I don't see how it can be related to the misshift. I believe the problem is a result of my car running so rich with my SC, most likely "some"?} sensor has a carbon build up on it or something? I am going to go with my gut feeling on Monday and buy a bunch of new sensors and NGK plugs, if the car is still messed up I guess I will have to bring it to a mechanic.



On another note, Dan B. or other, do you think the sensors at parts america are anygood? The brand is something?/arnold? They are only $65. One other question, could a Intake air sensor cause the problems I have been experiencing? I ask becuase I had to modify it a little when I installed my SC and when I took the SC off I never got it back in the intake thingy correctly and it is kinda sticking out. Thanks for your time.

This is unlikely because the 4Gen Maxima engine does not have a distributor. No distributor, no cap, no wires.

Yes. A Postive Crankcase Ventilation valve can stick open or closed. The symptoms of failure are ...
- stuck open = bad idle and possibly stalling due to the overly lean mixture.
- stuck closed = oil leaks because the engine blowby will find some way out.

You report a rich mixture so the PCV valve is probably not the guilty party. Furthermore, these valves rarely fail which makes me think owners who replace them on a routine basis are wasting their money.

Interesting because I do have a oil leak. I will replace the valve just in case. Thanks again.

Intermittent problems are always difficult to troubleshoot.

The specs for the Engine Coolant Temperature Sensor are ...
Engine coolant temperature 68F, ECTS resistance 2.1 - 2.9 Kohms
Engine coolant temperature 194F, ECTS resistance 0.24 - 0.26 Kohms

Notice that higher resistance corresponds to a cold engine, and a cold engine signal prompts the Engine Control Module to make the fuel mixture rich. Now think about a loose or corroded electrical connection between the ECTS and the ECM. If it suddenly goes from 0.25 Kohms to 2.5 Kohms the ECM will respond with a rich mixture. You could test the ECTS and still see 0.25 Kohms because the sensor is not at fault, the connection is!

probably not the problem, but my car had similar problems but not the same and it was a vaccuum hose that had come off.

I think I may have found the problem!!! I just removed my PCV Valve and it seems to be frozen in place. I shook it back and fourth and all and it was not making a clanking sound. I banged it on my pomb{S?} a few times and now it makes a little bit of clanking sound but not nearly as much as it should. I have found traces of oil in throttle body and my trannsmission leaks when the car is running. I will by a new valve tomarrow and see if it was the culprit. Thansk again for the great advice.


Justin, thanks for your input buy I think if it was a vacume leak the problem word be there all the time rather then just under my circumstances. BTW I have checked all my vacume lines and they are all on nice and snug.

i had a problem with my altimas idle dropping below 500. the ecu code said i had a bad egr valve. does the max have a egr valve?

It was worth a try. I had the exact same problem a few years ago with a car and it was the cat.

Yes.

could it be the egr valve thats causing the car to stall?

Perhaps. If the Exhaust Gas Recirculation valve fails, it usually fails by sticking in one position rather than opening and closing normally. The principal symptoms are ...
- stuck closed = engine pinging, failing inspection because of excessive NOx concentration
- stuck open = rough idle and (maybe) stalling

An O2 sensor won't make your car stall. It sounds like you have an intermitant problem in the fuel pump circuit. Before you go buying sensors, check the basics first. I would hook up a fuel pressure gauge and take it for a ride. Observe the pressure when the car acts up. Check all your filters. It's probably a mechanical part failing if you not setting any codes. Maybe a fuel pump, or bad injector(s).I am a diagnostic tech for Lexus and I have seen this before.

I agree.

The fuel pump relay is mounted behind the plastic kick panel to the left of the driver's feet. It is a Type 1M relay in a blue plastic case. All blue relays are alike, so you may exchange the fuel pump relay with any blue relay found in the passenger cabin fuse block or the two relay boxes in the engine compartment.

The fuel pressure test is a good idea. This is a standard diagnostic test. You will find instructions and a diagram or picture in the Chilton repair manual (page 5-3) and the Haynes repair manual (page 4-3,4).

Bleed the fuel rail pressure by pulling the fuel pump fuse and making several attempts to start the engine (it won't start). Install a T-fitting with a pressure gauge in the flexible rubber fuel line just downstream of the fuel filter. Install the fuel pump fuse. Start the engine. You should see the pressure maintain a stable 34 psi. After turning the engine off the fuel system should hold pressure for many hours. If the residual pressure bleeds off in only one hour that is a sign of a problem... bad fuel pump check valve, injectors with an internal leak, bad fuel pressure regulator, or an external fuel leak.

Isn't the car running too rich? Don't you look at the fuel pump and wirings when it doesn't get enough fuel?

This engine may be suffering from more than one malady.

Intermittant drivability issues can be very difficult to pinpoint. If you don't have the equipment and resources to properly diagnose the problem you may want to pay a visit to the dealer. Many times a problem that seems very strange to you may be somthing the dealer sees very often. The next step after checking and repairing or replacing servicable parts (ie. plugs, fliters) is to check engine managment circuits which cannot be accomplished without the use of a scan tool. A scan tool allows you to look at all the input/output data going to and coming from the ECM. Studying this data at the when the car is running badly is the most acurate way to determine the true problem.

Thanks, I am going to take one more stab at it today and see if I can fix it. In a minute I am going to get a PCV Valve{mines busted}, NGK plugs,Fuel relay and maybe a Engine Coolant sensor. I sure hope I fix this damn thing because it is driving me nuts.

I agree with everything you say ... but ... fuel pressure is not monitored by the Maxima/Infiniti Engine Control Module. A few posts back you recommended a fuel pressure test and that is a good idea. Emax95 seems too eager to swap parts and too reluctant to do the basic diagnostic work. A correct diagnosis is the first step toward a successful repair. There is no shortcut.

Yep, as little as I have of each, I always have more time than $$$$......

Emax95, have u found out what is causing the car to stall. I have a 95max and recently experienced similar stalling problem with my car. It first started with hesitation on a couple of occasions where I would floor the gas and it would just sit there(rpm did not go up) for a few seconds. Then today I had run the car for about 10 miles then parked it around 15 minutes and started the car again. This time it just flat stalled out when I hit the gas even though the engine was already warmed up. Started it back up and it ran fine again. I'm worried that this might happen at an unexpected time such as when crossing traffic!!! Does anyone have any idea?

no solutions here? im lookin at the same symptoms here