Advice Needed

[Lukek286]

I have a 2011 450 St-X navara and sometimes when i come to a stop at an intersection or slow down in traffic my truck starts making a pulsing noise the revs do not change but my electrics all pulse and and the car jolts forwards if i ease off the break this only happens intermittently and as soon as i start driving again its like it never existed and the car runs perfectly fine i have had the car in and out of the garage trying to fix this problem but it never seems to happen when they have it and i have asked them to inspect the fuel and electrical system to which they have said there is no issue really confused as to what it might be any advice would be great thanks

 

[Old.Tony]

Intermittent problems are like cheap vacuum cleaners - they suck really badly.

I wonder if you could somehow monitor the battery voltage to see if there's a problem with the alternator feed? I am wondering if there's a belt or pulley slipping that's causing a large voltage fluctuation at idle, and perhaps this combined with a not-so-new electrical connection (even the battery terminals!) is causing the issue.

For a really cheap (as in zero cost) attempt to fix the problem, try cleaning the battery terminals AND this means the other connections on the positive terminal as well. See if you can prod the fusible links any in case one of them is cracked and the vibration at idle is making it make/break connections in time with the motor.

You could try removing the belt that runs the alternator. I've had my pulley come loose on the shaft and caused odd things to happen.

 

[Lukek286]

Cheers Tony will definitely give that ago this weekend

 

[Lukek286]

Hey Tony i have checked the fusible links which seemed to be fine and was able to monitor the voltage change on my in car 12v port during the surge and my voltage would fluctuate from 12v all the way to 14.8v but never lower than 12 after i was able to pull over i got out and checked my battery voltage and the surging had stopped but my battery’s voltage while idling was only 12v wondering if i need an entirely new alternator or battery or if anything else could be the issue revs never seemed to change during all this

 

[Old.Tony]

It sounds like the alternator is underperforming. Even on mine - after leaving my car sitting for a week and the battery voltage drops to around 12.2V - as soon as the engine starts the voltage rises to 14.5V (usually, sometimes 14.6). It stays at that voltage even at idle.

How's the fan belt? Tight? Is it possible that the pulley is slipping on the alternator?

 

[Phunk]

I have a 2011 450 St-X navara and sometimes when i come to a stop at an intersection or slow down in traffic my truck starts making a pulsing noise the revs do not change but my electrics all pulse and and the car jolts forwards if i ease off the break this only happens intermittently and as soon as i start driving again its like it never existed and the car runs perfectly fine i have had the car in and out of the garage trying to fix this problem but it never seems to happen when they have it and i have asked them to inspect the fuel and electrical system to which they have said there is no issue really confused as to what it might be any advice would be great thanks

Mine does the same, I thought it was the battery - Nope, I checked the alternator - all fine, belts? only 5000k's old.

When I stop at lights, the dash lights all surge and pulse with the revs.

@Old.Tony - is this classic SCV?

 

[tweak'e]

i would be checking alternator pulley.
also check any dual battery setup.

 

[Old.Tony]

@Old.Tony - is this classic SCV?

If the engine itself was hunting (and not the brightness of the lights) - absolutely.

 

[Phunk]

If the engine itself was hunting (and not the brightness of the lights) - absolutely.

The engine is definitely hunting. On idle it revs up and down like a constant surge, this is when the lights are also surging on the dash at the same time.

Now I need to figure out if the 13 model VSK has the short or the long SCV as always there are different types!

 

[tweak'e]

The engine is definitely hunting. On idle it revs up and down like a constant surge, this is when the lights are also surging on the dash at the same time.

thats most likely caused by an electrical problem. if the battery/alternator is not supplying enough power you will have engine issues. those injectors take a fair bit of power to run.

 

[Phunk]

thats most likely caused by an electrical problem. if the battery/alternator is not supplying enough power you will have engine issues. those injectors take a fair bit of power to run.

That's what's throwing me off, Alt checking out fine, battery is 6 months old (did it with the old batt as well) and changed the belts in the last few months as well.

Like I was saying, it definitely does the surge of revs when it happens, it's not all the time, happens sporadically

 

[Old.Tony]

If the dash lights are surging with the engine then there's an electrical problem - possibly as well as the SCV. But a voltage problem could also affect engine operation.

I had a mob do a discharge test on my battery and it passed - it passed so well that it made their machine start to smoke. My battery was still stuffed.

What kind of voltage is present when the car is idling? Mine usually produces 14.5V at idle.

Checking the belts and the pulley is a good move.

 

[Phunk]

If the dash lights are surging with the engine then there's an electrical problem - possibly as well as the SCV. But a voltage problem could also affect engine operation.

I had a mob do a discharge test on my battery and it passed - it passed so well that it made their machine start to smoke. My battery was still stuffed.

What kind of voltage is present when the car is idling? Mine usually produces 14.5V at idle.

Checking the belts and the pulley is a good move.

hmm 14.5 you say, I'll need to check again since the belt change, prior I was sitting at 14.1 / 14.2

 

[Old.Tony]

hmm 14.5 you say, I'll need to check again since the belt change, prior I was sitting at 14.1 / 14.2

I don't have a standard alternator though - I have a 150A Trump unit (not the Donald variety, mine's not orange and it doesn't rely on cocaine).

Still, small variations aren't a huge deal.

 

[Billy54]

My engine was hunting before it went into limp mode, the mechanic replaced the scv and i add fuel doctor to every tank. no problems since.

 

[Phunk]

For what it's worth I'll change the SCV and re-tighten the belt.

Alternator was changed by the previous owner at 207k and it's now at 253k, this was changed by Nissan as well, not aftermarket.

As for fuel doctor, been a big fan of that stuff for 65+ years. use it on every 2nd tank for both cars.

 

[Billy54]

I even add a tiny drop in the unleaded fuel for the lawnmower, runs smooth and cuts the grass better.

 

[Phunk]

I even add a tiny drop in the unleaded fuel for the lawnmower, runs smooth and cuts the grass better.

Might be a bit hard to do it on my 82v' machine

In all honesty, I'm 100% converted, I don't think I'll go back to a petrol mower any time soon.

I had a Honda powered mower and the Electric one doesn't bog down anywhere near as bad as any of the petrol's I've used. (Then again, I'm not comparing to an 18V Ozito mower)