2001 Max 3.0L A/T Cold start and dies immediately

[rber]

Hello to all

I have a new problem with my daughter's 01 maxima. It stalls after first firing up. Tach goes up to about 1500 rpm and then drops to 0. You can get it to catch and run if you feather the throttle when cranking. Once it catches, it goes through a normal warm up flawlessly and then drives flawlessly. There are no other problems with the car. Everything else is as it should be. The following is the diagnostics and part replacement I have done:

The problem manifested itself as a "cold start only" problem initially. It now does it on cold starts and intermittently on hot start. I will explain below. Also wants to die if engine is idling and you rev the engine at or above 2500 rpm (engine cold/hot; worse when cold). On the way down it stalls (cold), almost stalls (hot; then recovers to a normal idle).

Because the problem was initially on cold start only I first suspected lack of fuel as checked all cylinders for proper spark (ok) and IACV seems to be operating normally (opens when key shut off and goes to start position when key on). Throttle body is clean and pcv valve has been replaced. Checked fuel pump pressure - good. Swapped fuel regulator and damper with another set - no change. When I depressurized the fuel system by pulling the fuel pump fuse and cranked the engine to relieve the pressure I was surprised when the engine started right up normally and ran properly until it ran out of fuel. Tried this several times. Same result every time. At this point I got thinking too much fuel; possible leaking injector(s). Pulled intake and injectors/rail. Hooked up all injectors and fuel supply/damper and primed system by reinstalling fuse and ign on several times. No leaks. Tested each injector while connected to rail with seperate 12v source. All injectors spray. Removed and cleaned all injectors. Put everything back together. No change except that it would now intermittently exhibit the start problem when engine warm too . So I can get the engine to start correctly if I:
1. turn ign on (fuel pump starts and stops)
2. pull fuel pump fuse
3. crank engine over (it starts and idles up fine)
4. put fuse back in before engine dies (will continue to idle normally with no other problems)

Confused - yes! There are no codes being spit out or indications of any other problems.
Because the engine starts properly when the fuel pump fuse is pulled it seems to suggest that there is too much fuel on initial start up. After doing the injector test with no luck I though that perhaps the coolant sensor may be sending a bad signal to the ecu causing it to pulse the injectors open too long but it does it when warm now too (intermittently). I thought I would confirm that the coolant temp. sensor was within spec just to eliminate that from the back of my mind. I unplugged it first and tried starting it. It started. I tried plugging it back in. It fired up and died like it has been. Went back and forth several times with the same results. I measured the resistance across the sensor. It read 2400 ohms which, based on the approx. temp. of the coolant was low. I got a sensor from another car that I felt gave a more realistic resistance, plugged it in and attempted a start. It fired up and died. Unplugged it and it started right up. Another roadblock...not sure where we go from here.
I am at a loss as to why it does this and have run out of possibilities that would cause this condition. Any ideas/similar experiences out there?

[rber]

Thinking about the coolant sensor, by unplugging it I think the ecm sees it is not working and is making an adjustment (less fuel) at start up. This is circumventing (or masking) too much fuel signal being caused by another device which I can't identify. That is the real problem

[loystock]

You've done a great diagnostic! Problem may be with MAF sensor. A marginal MAF sensor seldom gives a trouble code. Try unplugging it and start the car. The car will be in 'limp mode' without the MAF sensor (injectors-plugs firing simultaneously.

[rber]

Thanks for your post loystock. I will try that. Haven't really looked at the MAF yet as nothing leads there. Furthur to what I have written above, I completed tests on the coolant temp circuit with everything checking out. Good voltage signal from the ecm, good grounds at ecm and tcm, no shorts in hot or ground circuits and sensor operting properly. This proves there is no actual problem with this circuit or the coolant sensor. Just when I plug it in the engine won't start! Makes perfect sense, no? Off to check the MAF. Will post here when checks are complete.

[rber]

So I tried unplugging the MAF sensor (with coolant sensor plugged in) and result is the same...starts then stalls.

[loystock]

You have a good grasp of electrical circuits. Per your diagnostic the sensor and wiring are good, the ECU provides power and ground and no short circuit. Since you have isolated the problem to the coolant sensor only when plugged in, it could be in the internal circuitry of the ECU.

[rber]

Yes i am inclinded to agree with you. There is likely an issue in the ecm which I do not intend to pursue as all else works flawlessly. I just got back from the boneyard with a nissan momentary dash switch (traction cntl) which I am going to wire in series in the fuel pump control circuit. Pressing the switch will temporarily cut power to the fuel pump with the ign on/cranking. Once the engine starts up and goes to idle letting go of the switch will restore the fuel pump power. Not perfect but a cheap and dirty solution to an otherwise very expensive problem to fix. Thanks for your comments.

[maxiiiboy]

rber, before doing all this special work - and before applying an ugly wart rather than a proper fix - I would first check all&any PENDING codes. There must be some, as the car is stalling/flooding. You need an ODBC II scanner to do that; you can either buy an inexpensive on at Amazon (~ $40), or go to Autozone and they will read it for you.

The code(s) you retrieve should give you a good indication of what the problem area is. Oh yes, and be aware that many MAF failures don't throw a code.

Since the engine is flooding, there is either not enough air (MAF) or too much fuel (Fuel injector control). So, I would try:: a) The MAF first, then look at b) The sensors whose input the ECU uses to compute the length of the fuel injection pulse. The FSM will tell you what these sensors are; there are quite a few, and the coolant temperature one is just one of many ,,,,,

BTW, when did you clean or replace the MAF ?

[rber]

Maxiii, with all due respect, if you read my 1st post I state that there are no codes being thrown. I do have an odb code reader and used it throughout the troubleshooting process. The only problem I am having is the start issue. Everything else operates normally. As you would have read above, I pulled the MAF connector and started. No difference. There are no codes, which, by the way demonstrates the lack of smarts the nissan ecu has. I have spent numerous hours working on this cars ec system and it is clear to me the system is very poorly designed. It does not have a self check diagnostic which would tell you if the ecu had an internal problem. It does not recognize sensors which are operating out of specification and send fault codes for such. It only sees open or shorted sensors. Nothing in between. The internal ecu circuits which use mosfets (power transistor arrays) to drive IACV, injectors etc have a huge flaw...no fusing or other protection on the intput (ground side switches in ecu) to protect the ecu in the event of a high current short of one of these devices being driven. I have already replaced the ecu once in this car for the infamous failed IACV due to coolant leaking into it, shorting the coils and backing up into the ecu, burning out the driving circuitry complete with having to get keys reprogramed to match too it (that's $100 alone, everytime you do it!). I am not going to replace another. This one issue alone has caused so many owners so much maxima pain and suffering (not to mention the cost of repairs). Just look around on the various nissan forums for yourself. Unbelievable! Many of these problems are drivablility issues too and as such should have resulted in recalls of these cars. When I bought this car for my daughter I thought we had a good car for her. Wrong. This car has been a complete disaster and its no wonder you don't see too many newer ones around today. I wouldn't buy one either. Oh and once your warranty is done nissan washes there hands of there product and takes no further responsibility for it, no exceptions. I have a 2011 Frontier too. It will likely be my last nissan I am sorry to say.

[maxiiiboy]

OK, no pending codes - I wanted to be sure.

You did not answer my question about the MAF but in your 4/10 post you said you haven't looked at it yet. You said you unplugged it, but .... that's not a good test, the car will idle very poorly without the MAF.

Clean it, and if that does not work, replace it wit Nissan/OEM MAF (http://www.courtesyparts.com/22680-mass ... cPath=1956& , $77.69).

Your problem has all the symptoms of a typical MAF failure! (bad idle, no codes,dying when shifting into neutral, OK once driving). I had the same problem few years back and my mechanic did all kinds of things (replaced fuel pump, etc.) until I suggested he replaces the MAF. When he did, all my problems went away.

Just do it, you'll be happy with the result!

[rber]

Maxiii
When i pulled the MAF plug. Nothing changed. I think it is reasonable to conclude that the problem isn't the MAF based on this as the voltage signal that was being sent by the MAF that could be a cause of the problem is removed by doing so. I do however have another MAF I ordered some time ago that I will try (nothing to lose here, for sure). I did also clean the one that is in there right now a couple years back when I was doing another troubleshooting session. I will give it a shot and report back later.

[maxiiiboy]

ok. Btw, cleaning does not always work and neither do aftermarket MAFs. Replace with Nissan/OEM MAF.

[rber]

Well I cleaned the old MAF and plugged it back in...no difference. Put the other MAF in...no difference (not a Nissan unit but the fact it made absolutely no difference in good enough for me).

[NutriaforBreakfast]

Have you tested the throttle position sensor? You can check it
pretty easilty with a multimeter