MPi stalling

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Charless
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MPi stalling

Post by Charless » Wed Jul 22, 2015 11:43 pm

Does anyone have experience of an MPi running well hot and cold, but occasionally nearly stalling out when ticking over cold and actually doing so when idling slower, fully warmed up. It started having a momentary loss of power while driving within a couple of miles of home tonight and then it would not tick over for more than ten seconds once I got home. It restarts perfectly happily and ticks over at the right speed for most of the time but then suddenly slows and sometimes dies.
I have replaced the rotor arm as the (3000 mile) 'old' one had an internal resistance of nearly 1100 ohms as opposed to 880ohms new - but it makes little difference to the symptoms. It had a 60k mile service (cambelt w'pump etc) 3000 miles ago
Any ideas?

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Re: MPi stalling

Post by talkingcars » Thu Jul 23, 2015 8:20 pm

My first guess is the throttle position sensor is failing.
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Re: MPi stalling

Post by scruffygit » Thu Jul 23, 2015 10:09 pm

May be worth considering the fuel pump relay that's in the big multi relay unit that's located behind the Ecu. It suffers from dry solder joints and will cause intermittent problems like that. Eventually it packs up and the fuel pump itself stops working so then the car won't start at all. I had a similar problem. Its possible to open up the mfru and resolder all the joints where the relays are mounted on the circuit board.

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Re: MPi stalling

Post by Charless » Fri Jul 24, 2015 1:11 pm

Thanks chaps; so far I know it isn't plugs, distributor cap or rotor arm. Next I was leaning toward fuel pump, leads or coil. I'll check out the relay soldering.
Any others?.....

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Re: MPi stalling

Post by willyphixitt » Fri Jul 24, 2015 4:13 pm

Hi Charles,

My thoughts are towards the fuel delivery also. Is it possible to wire your pump up (temporarily) directly to a 12 volt source. If your problem goes then, as suggested, there may be a solder joint problem somewhere. Solder joints are not as reliable as crimped or wire wrapped joints.

Good luck with your quest.

Regards.

willyphixitt

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Re: MPi stalling

Post by Charless » Mon Jul 27, 2015 10:57 pm

I substituted out the multirelay unit and the coil without a change in symptoms; so maybe the shaft encoder...

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Re: MPi stalling

Post by RobboMC » Tue Jul 28, 2015 4:07 am

I see you have written MPi and has a distributor so I assume it's MEMS 1.9.

I would remove and replace all the plugs to the injection system and throttle body as well as the
crank sensor ( this is a bugger to get at under the inlet manifold)

Sometimes removing and replacing can highlight the issue.

And maybe also do the same for the exhaust sensor, there's a join in the wiring under the distributor.

Check all the simple things first, it will most likely be a connector or a wire that is failing.
Hopefully it won't break completely before you find it.

Could it be the plug leads?

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Re: MPi stalling

Post by willyphixitt » Tue Jul 28, 2015 8:31 am

Hi Charles,

As RobboMC has mentioned, my next thought would be a low output from the crankshaft sensor. The nature of the beast would mean enough signal strength as the revs are increased. The engine might lose syncronisation because of low output at tickover. There's a threshold voltage where pulses will be detected as good. Do you have anything that can measure the pulse strength at the input to the MEMS? That would save you a lot of hassle getting at the sensor itself.

willyphixitt

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Re: MPi stalling

Post by Charless » Tue Jul 28, 2015 1:45 pm

I have a handheld scope - but I also have a local source of reasonably priced used parts too - busy evening by the sound of it. Thanks for all your inputs,
Charles

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Re: MPi stalling

Post by Charless » Wed Aug 05, 2015 1:29 pm

OK so it isn't: plugs, leads, distributor cap, rotor arm, coil, crankshaft sensor and multi-relay behind ECU as these have all been replaced. The lambda is producing good readings and the MAP sensor is within the ECU on MEMS1.9 so would mean a new ECU. The symptoms remain that it starts instantly, drives well but for occasional flat spots, accelerates as strongly as ever and will sometimes tick over faultlessly. At seemingly random intervals it just stops or nearly-stops-and-recovers to a steady tickover. The moment it has stopped the engine can be restarted immediately as if nothing had happened.
Could the aircon pump or alternator bearings be causing this without making a noise of belt slip?
If I were a teenager it would be 'doing my head in'; but those years are so distant that I am a 'bit miffed' instead. Any more affordable ideas?

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Re: MPi stalling

Post by scruffygit » Wed Aug 05, 2015 1:50 pm

Fuel pump itself? Rather than it's electrics.

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Re: MPi stalling

Post by Rob Bell » Wed Aug 05, 2015 2:14 pm

Hi Charles - I now see your frustration that the pscan does not yet read early MEMS 1.9 live data... Any fault codes stored? I presume not as you've not mentioned any.

You haven't mentioned the IACV? Is it opening as it should? Also check the air pipes are clear of oily gunk - might be restricting the idle air flow, allowing the engine to stall at idle.

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Re: MPi stalling

Post by talkingcars » Wed Aug 05, 2015 9:01 pm

talkingcars wrote:My first guess is the throttle position sensor is failing.
I'm still for checking this.
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Re: MPi stalling

Post by Charless » Thu Aug 06, 2015 10:15 am

I have another TPS, but took the old one off for a clean and like the IACV, it looks good - however:
When we put the car on a modern diagnostic tuner it came up with 2 faults stored:- injector rails 1/4 and 2/3.

Sadly, as yet, these were invisible to pscan, but hopefully in the future.... :o)

So if it is a temporary loss of the injector rails, I wonder if the error code is triggered by the loss of the supplied common 12v(also feeding the coil amongst other things), or something about the paired rail switched negatives driven by the ECU?
Does anyone know if it is sensible/safe(eg tamper switch) to open the sealed ECU to check solder joints? The common 12v is linked straight through the engine management main relay unit.
Typically, in the nature of an intermittent fault, it completed a 10 mile mixed traffic journey without a single interruption yesterday!

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Re: MPi stalling

Post by Rob Bell » Thu Aug 06, 2015 4:03 pm

May not be the ECU - could be a faulty ignition or fuel pump relay?

Interesting that pscan didn't find those fault codes: have you let Philip know? This have him furiously looking into data packets now! :lol:

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Re: MPi stalling

Post by talkingcars » Thu Aug 06, 2015 6:41 pm

Charless wrote:I have another TPS, but took the old one off for a clean and like the IACV, it looks good - however:
When we put the car on a modern diagnostic tuner it came up with 2 faults stored:- injector rails 1/4 and 2/3.

Sadly, as yet, these were invisible to pscan, but hopefully in the future...............
When my TPS failed it still looked good.

Did you do a pscan at the same time as the "modern diagnostics tuner"?
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Re: MPi stalling

Post by technozen » Thu Aug 06, 2015 10:15 pm

The ECU would be the last item on my list of suspects, they are well built and don't suffer from poor soldering or dry joints.

You can open the case, the aluminium cover is sealed in placed with a bead of mastic so the cover will end up like a sardine tin
lid by the time you have finished!

The board is covered with a rubberised coating, absolute sod to remove.

I have never seen injector fault codes on a MEMS1.9 ecu, I would tend to believe the pscan results rather than the other diagnostic tool.

Is the engine wiring loom ok where it passes over the metal coolant rail?

Is the tubing to the MAP sensor in good condition, leaks would affect the signal and the idle, plus there would be no fault codes
stored.

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Re: MPi stalling

Post by Charless » Thu Aug 06, 2015 11:42 pm

James - OK I will change the TPS! Yes I did pscan it and was not getting any error codes after an initial MAP fault which stayed cleared - possibly historical. I have checked the vacuum tubes to the MAP sensor for leaks and will try a different tube direct if I can find a suitable pipe in the garage!
Rob - I have swapped out the fuel pump relay with no change in symptoms. I haven't hardwired the fuel pump yet as Bill suggested. It could be the ignition switch - rather difficult to check - this may come later. I did let Philip know - and testbook must be able to make some sense of 1.9 data if all else fails.
Paul - thanks very much for the ECU info. It seemed well put together and I didn't want to just wade in without a good reason (but no tamper switch if I do decide to have a go)! It sounds as if the pcb is conformally coated - test engineer's nightmare for rework - so I'll be leaving that alone for now! I felt that the paired injector code was a bit contrived - a sort of default assignment. The loom going around the back of the engine appears well protected with a black corrugated plastic outer going under the coolant elbow, it seems intact.

While the cutting out at idle was one easily tested symptom it has also suffered a complete loss of power while driving at speed - up to five seconds at a time sometimes in groups which is why it feels electrical to me. It then clears and frustratingly works as perfectly as usual.
Thanks to all for your input, I will feed back updates,
Charles

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Re: MPi stalling

Post by scruffygit » Fri Aug 07, 2015 8:29 am

There is another relay associated with the fuel pump and it's located in the fuse box area, drivers side under the dash. It's a small red one, may be worth checking.
Is it also possible the multi function relay unit, containing the other fuel pump relay that you fitted may have a similar problem? The only reason I ask is that when I opened my original, a number of the relays in there had dry joints, or the beginnings of dry joints. I suspect as these cars get older the MFRU will be rersponsible for a number of intermittent problems.
It may be worth opening up your original and checking for bad joints, resoldering and then re-fitting it.
The MFRU is a bit fiddly to open but once opened simple to resolder and make good. I think there are 4 relays in there from what I remember.

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Re: MPi stalling

Post by Rob Bell » Fri Aug 07, 2015 10:14 am

Charless wrote:While the cutting out at idle was one easily tested symptom it has also suffered a complete loss of power while driving at speed - up to five seconds at a time sometimes in groups which is why it feels electrical to me. It then clears and frustratingly works as perfectly as usual.
This strongly sounds like an ignition switch fault to me Charles, if I am understanding what you mean by power as being loss of electrical function?

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