2000 Maxima problem continues

[ERUOTANEN]

Problem: I previously had a topic here about what I thought was an ECM problem and/or possibly NATS key programming issue. Trying to shorten a long story, I tried a private garage, and finally the dealer who could not determine what is causing the car to cut out. Current situation after ECM was rebuilt and re-checked, new crankshaft sensor, new fuel pump, extensive diagnostics by the dealer who concluded it could be a broken wire somewhere that when it gets hot it opens up, but trouble code checks do not reveal that. Gave up on everyone else and I cleaned the MFS and throttle body myself after some other advice, and the car ran better than it ever has. I took it on a test ride and it did not miss a beat, going from idle to 60 mph and everything in between, including stopping and restarting. Just when I was feeling cocky after about 20 minutes of driving, the engine suddenly quit. And it would not re-start. I tried letting it cool down for 5- 10 minutes and still would not re-start. Got AAA to tow me home, and then the car started and ran great backing it off of the tow truck. Now it starts and seems to run great, no missing, etc, but I know that it will shut down again after 15-20 minutes of driving so I am leaving it parked for now and looking for ideas. Someone suggested vapor lock, and that is the first time anyone suggested that. I may replace the MAF, but I my suspicion is that it is OK because it ran so well until it shut down. My other experience with a bad MAF was that it would run rough, but still run, and this sympton is total engine shutdown. All other sensors that input the ECM have been checked or replaced. Any ideas out there or similar experiences would be appreciated.

[loystock]

The ECM s still questionable. Check the ECM connector and grounding. Apply dielectric grease on the connectors. When the car 'dies' try to wiggle the main engine harness near the pax side tower and see if you could re-star the car.

How is the battery and alternator charging voltage? Check and re-secure your ground wires.

Is the Security LED working normally?

[ERUOTANEN]

Security light is working normally and I think that situation is fine. I will try the ECM as you advised. Funny you should bring up the alternator though. Last nite I ran the car in my yard (to save AAA another free tow job), and again it ran well, so I tried a few things. First I stopped it and disconnected the MAF. Sure enough, it restarted for a few seconds and stopped kind of how it did on the road, so I turned the key off, reconnected teh MAF, and it started and ran fine. Then I did an electrical load test: I turned on the A/C with fan on high, the rear defroster, and the radio. Car ran fine until the cooling fan kicked in and it shut down a few seconds after that. I shut off the electrical accessories, checked the battery voltage, which was 12.4v, and re-started the car. It ran OK, and the voltage was now 13.8v so it looked like tjhe alternator was doing it's job. Turned on the accessories again, cooling fan came on, and car shut down and would not re-start. Battery still read 12.4 volts. Could not re-check alternator since it would not run. may try this again tonite with the voltmeter where I can watch it when the cooling fan kicks in. It all may be coincidence but I would like to see if the voltage drops below any threshold if it cuts off again when the cooling fan kicks in. Wierd because everything was bright and the voltage checks look good. Thoughts?

[loystock]

At 12.4VDC, your battery is weak or the alternator is not charging it properly. A good battery should read 12.6 VDC or higher (each cell in the 6-cell lead-acid battery, in good condition, has 2.1 VDC or higher). A good alternator should provide >13.8VDC charging voltage (spec is 14.1-14.7 VDC) and must be steady (no spikes, indicative of failing diode or regulator). Crazy things do happen when the alternator is on the way out.

You can take you battery and alternator to Autozone and the likes for free testing.

[ERUOTANEN]

Thanks-Good advice. That is my next step. I bought the battery 2 years ago at an Autozone that I am hopeful that I can get to before the car dies. If it is alternator/battery issue, I will leave everything off that I can while driving there. Could it be that all the "experts" at the dealership missed the obvious? I hope this is it. Not knowing what to fix is the frustrating part.

[ERUOTANEN]

I did try to take it to Autozone but car would not get there. So I got it back home and ran my own tests to check alternator and battery. Both of those are fine.
Up to this point, I have had the ECM rebuilt ( and re-checked), new plugs, new MAF, new crankshaft and camshaft sensors, diagnostics run on it by dealership who gave up on it. They checked the trouble codes which they said all checked out OK. My symptoms now are: Once the car gets warmed up and runs for 10 to 20 minutes, it simply quits running, either at idle or at speed. It may "cough" once or twice and then just quit. SES (CEL) comes on and it may or may not go out. Sometimes the car will restart and run for a little while longer until it quits all together. Usually after a 30 minute wait, it will restart and run again for another 10 -20 minutes before it stops again.
My latest thoughts from other people with simiar problems is that the catalytic converter could be stopping up when after it heats up, and opens up enough to run after it cools down some- for a while before the cycle starts again.
When I tested alternator and battery with the hood up and meters, I noticed that the car ran much longer (30 minutes +) than usual. I am thinking that the heat under the hood could be the trigger because with hood down, it seems to die in more like 10 minutes.
But I am open to any other suggestions.

[NutriaforBreakfast]

At this point I would take Loystocks advice first. Maybe your alternator is not working after it gets hot but works when it is cool. If that didnt work I would move to a fuel delivery test.

Even though you got a new fuel pump I would start testing for a fuel delivery issue
* Check pressure of gas at and after fuel filter
* Make sure fuel pump fuse is not loose (it might be #16 in fusebox inside car?)
* Test fuel regulator

Doesnt sound like cat converter problem

[ERUOTANEN]

Thanks-my original mechanic who put in the new fuel pump is also suspecting that as he wanted to monitor fuel pressure with the car running. I might take him up on that.

[loystock]

What code are you getting when the CEL is ON? Did you ever get a fault code for Coolant Temp Sensor? Did you replace both camshaft sensors? Did you ever get a fault code for front O2 sensor? Double-check the condition of the alternator since the previous charging voltage is marginal (13.8 VDC). It's possible that due to marginal alternator (one of the power diodes could be bad), when the cooling fan kicks in, the alternator voltage abruptly goes down, causing the ECU to shut down the engine.

[ERUOTANEN]

Good points. When I ran the car thru all the cycles of the fan operations, the charging system was a steady 13.8 volts, with just a slight dip when the temp switch brought the fan to high speed, then back to 13.8. It did die one time during this 30 minute test, and I wastched the voltmeter when it died, and it just went back to the 12.5 volts or so of the battery. No real dips when it died.
I do need to see the codes immediatly after the next time is stalls and SEL comes on. I don't have that diagnostic device. Do I need one or can I read a code otherwise?
Also, Autozone and my other mechanic said there is only one camshaft sensor, the one that is easy to get to on the belt side high of the engine. This is confusing because others have said there is a 2nd one and it makes sense as this is a DOHC.
thanks for the advice-I will try to follow up in the next few weeks. tag on this runs out in Nov, so it must be resolved one way or another by then.

[loystock]

The charging system and related wiring is still suspect.

As for the Camshaft sensor, I think you are right - VQ30 has 2 Crankshaft sensors and 1 Camshaft sensor while VQ35 has the opposite, 1 Crankshaft sensor and 2 Camshaft sensors.

Below is the link to the Engine Control System. You can look into the various fault codes.

http://www.nicoclub.com/FSM/maxima/2000/ec.pdf

There are lots of useful info in the forum 'sticky'

nissan-maxima-how-to-s-read-first-t219453.html

[ERUOTANEN]

thanks for the advice: The link to the engine trouble codes was very helpful. The codes from the dealership indicated previous NATS programming issues as well as cam and crankshaft sensor problems. Both those sensors were replaced and the NATS key programming has been resolved. I contacted another dealership who supposidly has better techs than the one I went to first who could not solve the problem. The service manager sounded confident they could fix it, so I am going to try them and see what happens.

[ERUOTANEN]

Update- my 2000 Max is at a different dealership for diagnosis. The original dealer's diagnosis had one suggestion as a stretched timing chain, and it would cost another $200+ to check that out, so I passed on it. When I talked to one of the maintenance techs at the other dealership where it is now, he indicated that he had seen that condition in several other Nissans, including a Pathfinder with the same engine as my Max as well as a Sentra. So I am waiting on them to call with an update, but all the SES codes indicate Crank or Cam sensor inputs are wrong. With both of those having been replaced, it kind of makes sense that a timing chain with a stretched or bad section would pick up signals which the computer would read as faulty. Has anyone out there with a Nissan ever seen or heard of this condition, a faulty (stretched) timing chain?

[ERUOTANEN]

Took the car to another dealer who finally accurately diagnosed the problem as a bad fuel pressure regulator which also messed up the new fuel pump. Also, in the final corrections and with test drives, the dealer determined the ECU still had a problem. This is the same ECU I had sent to the ECM Depot, who had it TWICE and it still was not right, so I bit the bullet and the dealer put one in for his price ($650 vs $950). Also, there is some additional programming required that the ECM Depot was wrong about. They said simply plug in the rebuilt one and it should work-WRONG! The original ECU may not even have been bad had the problem been correctly diagnosed in the first place which neither my (non-dealer) mechanics or one dealer could not diagnose properly. Total cost of this fiasco is in the $3500 range but car is now running fine and still has less than 100K miles so hopefully I am good for another 100K. If I had taken it to the second dealer right away, I think my total bill would have been in the $1000 range or less as much was done and replaced that did not have to be.
Lessons learned:
NO. 1- If it isn't a straightforward or easily diagnosed problem, take it to a dealer who has a good service staff.
NO. 2 - Do not even try to send a ECU/ECM off to a 3rd party for rebuild unless you know how to do any re-programming, which is typically dealer-only anyway. (I will try to negotiate with ECM Depot to get my money back, but since I turned the rebuilt one in on a core charge, I doubt they will do anything. Worth a try though.)
NO. 3 - If you have a NATS key and your car won't start, try all the NATS keys you have for that car before you try anything else.
NO. 4 - As much as I enjoy the power and ride of the car, I will not buy another Maxima, and I may even be done with NISSANs after this mess.
thanks for listnin'