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Author Topic: 2.5 v6 loss of power/engine stops  (Read 2642 times)

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El_Swervo

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2.5 v6 loss of power/engine stops
« on: 12 October 2010, 21:21:38 »

Hello All,

I have an intermitant fault with my '96 V6 2.5 petrol.
It has in the past,(some 5 or 6 weeks ago), lost power for a short time and went into a kind of limp mode. This cleared after a minute or so and was ok for a couple of weeks. Then it did it again for a few seconds when my wife was driving, the engine light,(the engine shape with lightning flash), came on and is also intermitant. I was driving it today when the car stalled/cut-out, on a busy roundabout. I coasted to a halt and after a few tries, the car started again and seemed to be fine. I wouldn't like this to happen to my wife with the kids in the car though, and its her that uses the car everyday.
I have been out to the car and done the excellent paperclip test and found faults; 49:Batt voltage high, and 73: Mass air flow sensor voltage low, as well as the usual 31 as the car was not running.

I am assuming its not the 49 code, as 5/6 weeks  or so ago, I had to get a jump start after running my lights for too long putting up a tent. The battery seems to be ok since with no subsequent problems, however come to think of it, the first time the car had the fault was the journey home from the camping weekend.Not sure if the problems are linked or co-insidence

Any ideas? havn't as yet checked the battery voltage, I will be doing as soon as I get home tomorrow, but as we have not had any issues with it, I am,(rightly or wrongly), assuming its ok?

Thank you for reading!
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Kevin Wood

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Re: 2.5 v6 loss of power/engine stops
« Reply #1 on: 12 October 2010, 21:46:05 »

I would check the battery voltage isn't getting excessive at a fast idle. That code doesn't normally pop up spuriously IME. The acid test would be to see if other systems (ABS, Autobox, etc) have also reported a high supply voltage.

I wonder about the crank sensor, although normally I would expect a 19 in the list of codes. :-/

Was it losing power under load or just stalling when coming down to idle? I wonder if the ICV and / or EGR valves could do with a clean? Either of these sticking could cause idling problems but not serious loss of power when you've got your foot down.

Mass Air Flow sensor codes often pop up spuriously when the car has another fault but it could just be the MAF, I guess. Worth checking the connector is secure. If it gets to the point that it's seriously playing up, try disconnecting the MAF and see if it'll start and run. It'll be a bit ropey as it'll be in limp-home but it might prove a point.

Couple of things to check, anyway. :y

Kevin
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El_Swervo

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Re: 2.5 v6 loss of power/engine stops
« Reply #2 on: 13 October 2010, 18:08:55 »

Hello Kevin,

I was driving at around 60-65 mph the first time it happened, straight road just driving along as I remember.
Yesterday, I was probably gently accellerating, as I was pulling round the roundabout, definitely not going down to idle.

I have just remembered also, when starting up and driving along for the first 100 meters or so,( I only notice this in the dark), the lights are bright then dim,  bright then dim etc, It seems to clear after a while, I will check this out later. It does seem to be a voltage thing? The car still runs and drives ok but for these problems now and again. I have only noticed the lights flickering last week as I used the car for work, leaving in the dark.

How do I check voltage on the car apart from sticking a meter across the battery? I am a bit dim when it comes to these new-fangled machines, I am used to 50s & 60s tech!

Thanks Kevin, Dave

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aaronjb

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Re: 2.5 v6 loss of power/engine stops
« Reply #3 on: 13 October 2010, 18:11:55 »

Don't worry, those of us used to 90's and 00's tech still just stick a meter across the battery  ;) :y
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El_Swervo

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Re: 2.5 v6 loss of power/engine stops
« Reply #4 on: 13 October 2010, 19:55:46 »

I will do just that then! ::)
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cem_devecioglu

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Re: 2.5 v6 loss of power/engine stops
« Reply #5 on: 13 October 2010, 20:12:59 »

Quote
Hello Kevin,

I was driving at around 60-65 mph the first time it happened, straight road just driving along as I remember.
Yesterday, I was probably gently accellerating, as I was pulling round the roundabout, definitely not going down to idle.

I have just remembered also, when starting up and driving along for the first 100 meters or so,( I only notice this in the dark), the lights are bright then dim,  bright then dim etc, It seems to clear after a while, I will check this out later. It does seem to be a voltage thing? The car still runs and drives ok but for these problems now and again. I have only noticed the lights flickering last week as I used the car for work, leaving in the dark.

How do I check voltage on the car apart from sticking a meter across the battery? I am a bit dim when it comes to these new-fangled machines, I am used to 50s & 60s tech!

Thanks Kevin, Dave


you have problem with alternator or some connections are loose.. you need to sort that first..
or your battery will surprise you in the near future  :-/
« Last Edit: 13 October 2010, 20:13:55 by cem_devecioglu »
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El_Swervo

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Re: 2.5 v6 loss of power/engine stops
« Reply #6 on: 13 October 2010, 20:38:18 »

Will do, does sound like I need to check the battery as soon as, as this may solve a few problems anyway.
Will post results Thursday afternoon, as my central heating has packed up and that according to the family is more important!
Could be an expensive week!
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RobG

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Re: 2.5 v6 loss of power/engine stops
« Reply #7 on: 13 October 2010, 20:41:49 »

Quote
Quote
Hello Kevin,

I was driving at around 60-65 mph the first time it happened, straight road just driving along as I remember.
Yesterday, I was probably gently accellerating, as I was pulling round the roundabout, definitely not going down to idle.

I have just remembered also, when starting up and driving along for the first 100 meters or so,( I only notice this in the dark), the lights are bright then dim,  bright then dim etc, It seems to clear after a while, I will check this out later. It does seem to be a voltage thing? The car still runs and drives ok but for these problems now and again. I have only noticed the lights flickering last week as I used the car for work, leaving in the dark.

How do I check voltage on the car apart from sticking a meter across the battery? I am a bit dim when it comes to these new-fangled machines, I am used to 50s & 60s tech!

Thanks Kevin, Dave


you have problem with alternator or some connections are loose.. you need to sort that first..
or your battery will surprise you in the near future  :-/
If it`s only on initial start-up and for a very short distance could possibly be faulty SAI pump making lights pulsate.
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cem_devecioglu

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Re: 2.5 v6 loss of power/engine stops
« Reply #8 on: 13 October 2010, 20:59:53 »

Quote
Quote
Quote
Hello Kevin,

I was driving at around 60-65 mph the first time it happened, straight road just driving along as I remember.
Yesterday, I was probably gently accellerating, as I was pulling round the roundabout, definitely not going down to idle.

I have just remembered also, when starting up and driving along for the first 100 meters or so,( I only notice this in the dark), the lights are bright then dim,  bright then dim etc, It seems to clear after a while, I will check this out later. It does seem to be a voltage thing? The car still runs and drives ok but for these problems now and again. I have only noticed the lights flickering last week as I used the car for work, leaving in the dark.

How do I check voltage on the car apart from sticking a meter across the battery? I am a bit dim when it comes to these new-fangled machines, I am used to 50s & 60s tech!

Thanks Kevin, Dave


you have problem with alternator or some connections are loose.. you need to sort that first..
or your battery will surprise you in the near future  :-/
If it`s only on initial start-up and for a very short distance could possibly be faulty SAI pump making lights pulsate.

not sure.. but can be eliminated by disconnecting..
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El_Swervo

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Re: 2.5 v6 loss of power/engine stops
« Reply #9 on: 14 October 2010, 18:52:12 »

Thanks for all the relpys so far, I have been out to the car and made a note of exactly what it does.

Before starting the voltage at the battery is aprox 12volts. When I start it the voltage goes up to 14+ volts. I assume that means both battery and alternator seem to be functioning as they should?

The RPM does change, and the voltage goes with it, ranging from 11 to 14 volts. The rpm goes up and down say in around 5-10 second intervals. Rev the car to get it off choke as it were and it starts to smooth out. Then there is a click(?) from the intake duct area, possibly from the switchover valve? It then stops changing around and settles to 14 ish volts.
Sometimes though,(quite often), the engine seems to hunt/change rpm when idling at a junction or traffic lights.

Some specific questions,
is the Mass airflow sensor referred to as intake air temperature sensor in the Haynes manual,(page 4A.7).
What is the SAI pump?
Would cleaning varios sensors and valves cure this problem perhaps as kevin has said. I know the egr valve Kevin, but what is the ICV?

I am not overly concerned with the RPM issue, just the stalling, power failure thing unless of course they are linked?

thanks again guys,

ps, central heating is fixed, Family(girls) happy!
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Kevin Wood

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Re: 2.5 v6 loss of power/engine stops
« Reply #10 on: 15 October 2010, 01:35:53 »

I would say we can probably rule out the EGR or ICV for now if it's cutting out under load.

Sounds like something's odd in the electrical supply side for the lights to be varying in brightness, unless this is just down to the idle dipping low enough for the voltage from the alternator to drop.

Does the battery positive terminal get hot when it's running? The crimp of the cable into the terminal often fails.

Kevin
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bigdods

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Re: 2.5 v6 loss of power/engine stops
« Reply #11 on: 15 October 2010, 13:20:43 »

I've had exactly these symptoms. The rev up/down and voltage change when first started is due to the SAI pump. Its an air injection pump that runs for 30 seconds after the car is started to reduce emissions. It is not needed and was not included on later models. If it is faulty it will cause the lights to dim every few seconds and the revs to drop to stall level. Unplug the SAI fuse - IIRC its the big red one under the bonnet among the fuses near the battery.

The second problem sounds like it wont idle cleanly. Does it improve if you have the aircon in AUTO and get worse in ECO mode ? Mine wouldnt idle cleanly at all in ECO , kept trying to stall. Had Daz round a few weeks back to fit a new cam belt , now its fine so either something wasnt connected properly or the timing was knackered and now sorted. When was your cam belt and kit last changed ?
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pscocoa

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Re: 2.5 v6 loss of power/engine stops
« Reply #12 on: 15 October 2010, 14:11:33 »

sorry guys - I am going for the crank sensor again - all the symptoms

El Swervo - just noticed your other cars - are you down near the Squirrel pub in Farnborough?
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El_Swervo

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Re: 2.5 v6 loss of power/engine stops
« Reply #13 on: 16 October 2010, 12:29:13 »

Hello All,
thanks for all the ideas, I am going out now to check some of it out.
I will see if the Batt terminal gets hot, unplug the SAI fuze, 30 seconds is about how long it does it for, and I will try the eco thing.
Kevin helped me change the Cambelt last year or so with only a few thousand miles since.

Still more concerned with the car cutting out, hopefully sorting out the idle/lights may sort this too.
Will post results later.
 

...And I do live near the Squirrel, but the place nearly next door to the pub is a mates garage, North American motors.

Cheers Guys,

Keep watching
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El_Swervo

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Re: 2.5 v6 loss of power/engine stops
« Reply #14 on: 16 October 2010, 16:27:26 »

Well, I have removed A fuze from the auxillery fuze box adjacent to the Battery, I hope it was the right one. There is only one red fuze in there and its 50amp.
Anyway, the engine no longer hunts or changes RPM from start, in fact it purrs like a kitten now. I am going to go out there after dark and see if the lights flicker. I dont think they will now,so thanks for that! :y

I have run the car and checked the Battery pos. terminal to see if it gets hot but it does not, even after a spell at idle. The next time I go out in it for a drive, I will see if it gets hot then.

So any ideas on the cutting out loss of power issue. Could it be the Mass airflow sensor,(because of the fault code?), or the crankshaft sensor or something else?  Or could it just be the SAI pump issue we may have cured? Looks as if the crank sensor could be a bit of a mare. I may be able to get access to a ramp to do this. Where is the best place to get the parts if needed?

Sorry, questions, questions! :question
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