Engine does idle with accelerator pedal down to the floor...

[LeoMurano]

Hi guys,

My Murano has died with alternator failed. It has been replaced and now I have another problem. At any time driving it can quit accelerating, so I have to stop and it does not react to accelerator at all, just sits at idle. ABS and break lights come up. It could last for minutes and then suddenly can start working again. Usually switching off and starting up helps, but not for a long time - maybe few minutes everything is fine, then it dies again.

I search for a forum and could not find solution, has someone had similar problem? And what it could be, please help!

PS Murano 2004 SL

[nitely]

Check the TPS ( throttle positioning sensor ). Does your idle sound good at start up when on park?

[LeoMurano]

I don't think failed TPS would trigger ABS and break And how do I check TPS?

Actually idle sounds very good and shows ~650RPM when parked, also car runs good when it runs. It's just that stupid condition when it ignores accelerator pedal.

Originally Posted by nitely

Check the TPS ( throttle positioning sensor ). Does your idle sound good at start up when on park?

[LeoMurano]

More info:

Looks like after about 5 minutes (more likely when all is warmed up to normal temperature) car drives without any problem.
On cold start ABS and break (I don't have AWD) lights are on and could stay on or sometimes they off but depressing accelerator causes them to on again. Power roof does not operate during this condition WTF!!!! Everything else looks fine. I am starting to think about disconnecting roof controller and see what will happen. Or is it bad grounds problems? Is there instruction how to check bad grounds? Do I have to disassemble whole dashboard?

I cleaned up with Sea Foam and checked throttle body, looks good. But nothing changed after that.

[JayS]

Check your battery. Good chance that when the alternator went and the car drained the battery down to nothing the battery never recovered. Modern cars, with all their computer driven systems and sensors, do not like low voltage conditions.

[njjoe]

LM-

Is the SES light illuminated? If so, have you checked for codes?

-njjoe

[LeoMurano]

Originally Posted by JayS

Check your battery. Good chance that when the alternator went and the car drained the battery down to nothing the battery never recovered. Modern cars, with all their computer driven systems and sensors, do not like low voltage conditions.

I installed a new battery after old one has drained.

[LeoMurano]

Originally Posted by njjoe

LM-

Is the SES light illuminated? If so, have you checked for codes?

-njjoe

No SES light and no codes. There was one P1720 - Vehicle Speed Meter Circuit Malfunction (but no SES light) however I believe it maybe the consequence from alternator failure. I erased it and since that there were no codes.

What are chances that I have bad CVT? I really don't think it's CVT because it happens when car is parked too... Basically does not matter if it's moving or not.

[Warhammer]

Maybe the pedal sensor is dead. I'd suggest swapping that one out first. If you're electronically inclined, do the signal tests for the accelerator pedal position sensor and throttle position sensors. My bet is the gas pedal.

[zebelkhan]

You maybe reading into it too much. Why would you want to disconnect the roof controllers? There is no reason for CVT to be at fault here. There has to be a good reason for pedal sensor to go bad and I don't see it. The more you mess around with things that logically seem to be unrelated, the more issues you will create. So think simple first.

Clearly, the ECM and TCM are getting data that is either in error and gets interrupted. As the result your MO is placed on limp mode because computer wants to protect the components. It seems to me the issues you are experiencing has to do with or around the alternator replacement or things that you touched during that process. Even though your battery is new, I would disconnect it for 15 minutes and re-install it. Then carefully check the output of your new alternator, both amps and volts to make sure nothing is off. Then check around and disconnect and reconnect any connectors that you have touched. You maybe pleasantly surprised.

[JayS]

^ Yep, this really feels voltage related. Loose or dirty battery connection maybe. Chance who ever swapped the alternator left something unplugged. Go back to the basics, cold start battery voltage reading, running voltage reading, running voltage reading once warmed up and not running battery voltage reading once warmed up.

[LeoMurano]

Thank you everyone, Murano is back at shop, mechanic will be looking into it. I used to trust him, he has been taking care of my cars for 10 years.

As I drove it to him SES light came on and there were 3 codes two of them transmission related: speed sensor (P1720 I think) and another one I did not remember.

Update: he just called me and said it's a bad alternator which gives over-voltage. We will see how it goes. To change the alternator is a hell of work on Murano.

[JayS]

^ Like we said... voltage related.

Sometimes the reliance on the modern OBDII system can really lead you down the wrong path. Mechanics need to take a step back and remember the days of basic troubleshooting without the computer's guidance sometimes.

[LeoMurano]

Yes. I think now it's clear to me what happened. After I picked up the car from shop, I was able to drive to home, because battery was charging and the voltage was normal, once battery was charged completely, the generator started to output ~18 volts = computer goes to safe mode. If car stopped and restarted battery got discharged slightly and it was able to drive normally until the battery charged fully again.

Will be picking up the car today, looks like everything is resolved, apparently there was some wiring issue on top of new bad alternator, so I have to chip in some money for wiring fix, but that's it.

Originally Posted by JayS

^ Like we said... voltage related.

Sometimes the reliance on the modern OBDII system can really lead you down the wrong path. Mechanics need to take a step back and remember the days of basic troubleshooting without the computer's guidance sometimes.

[zebelkhan]

I agree with JayS. Sometimes it is best to take a step back and rather than relying on a computer code think about what maybe logical.

Glad issue has been resolved.