Lumpy idle when cold

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mikexgough
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Re: Lumpy idle when cold

Post by mikexgough » Sun Aug 03, 2014 9:56 pm

I'd start with a set of glowies..... cheap fix really....and to be honest the most common issue for poor/lumpy starting......
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Re: Lumpy idle when cold

Post by Snail921 » Fri Aug 15, 2014 4:45 pm

Just got it back after service and MOT. Failed on back diff leaking onto brakes. That sorted plus had the cam belt done but still starting weirdly. Mechanic reports glowplugs and relays all OK but he suspects a faulty solenoid hence too much fuel when cold. Does this ring any bells?
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Re: Lumpy idle when cold

Post by Northern Bongolow » Fri Aug 15, 2014 7:28 pm

no-------------.


do a search on here for cold and start and solenoids, and have a read. the AND aids the search to find the individual words.
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Re: Lumpy idle when cold

Post by Snail921 » Sat Aug 16, 2014 2:06 pm

the AND aids the search to find the individual words.
So it does, wonderful what a bit of Boolean logic will do. Thanks for that. I'll have a look at the engine this weekend and see if I can identify the solenoids (as I understand it from what I've read there are two of them) and also run a test on each.
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Brian.
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Re: Lumpy idle when cold

Post by Snail921 » Sun Sep 07, 2014 2:30 pm

Finally got round to changing the glowplugs, the delay being mostly caused by me being daft enough to order the wrong ones. At first glance this seems to have fixed it. I'll know more when starting from fully cold in the morning.
Just got back from a 650 mile run to Luton and back, ran like a dream
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Re: Lumpy idle when cold

Post by Snail921 » Mon Oct 20, 2014 1:48 pm

Been laid up for a bit but can now report that the new glowplugs weren't the answer, still very lumpy when cold. The manual says that the two solenoids just above the inlet manifold should both be energized when the engine is cold, number 1 should close when it warms up a bit with number 2 closing just before normal working temp. Instructions to open / close being given by the PCM. I find that number 2 functions as it should but number 1 is closed no matter what the temp. Changing the circuits over will cause it to open so it's not a duff solenoid. All of which leads me to think it's not getting the right message from the PCM. So the question is, where do I find the PCM? Have looked under drivers side but am none the wiser
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Brian.
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Re: Lumpy idle when cold

Post by rita » Mon Oct 20, 2014 3:58 pm

Snail921 wrote:Been laid up for a bit but can now report that the new glowplugs weren't the answer, still very lumpy when cold. The manual says that the two solenoids just above the inlet manifold should both be energized when the engine is cold, number 1 should close when it warms up a bit with number 2 closing just before normal working temp. Instructions to open / close being given by the PCM. I find that number 2 functions as it should but number 1 is closed no matter what the temp. Changing the circuits over will cause it to open so it's not a duff solenoid. All of which leads me to think it's not getting the right message from the PCM. So the question is, where do I find the PCM? Have looked under drivers side but am none the wiser
Regards,
Brian.

Test it with the AC on and the engine at tick over speed.
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Re: Lumpy idle when cold

Post by Snail921 » Mon Oct 20, 2014 5:28 pm

Thanks, Rita, have done but that's number 2 according to the manual. That does as it should, it raises the idle from 750 to about 1100. It's the other one that's problematical. What I can't understand is why I'm getting a live 12v to the solenoid and a working earth when tested with an avometer but it won't open. Put the other connector in, with the same readout from the meter, and it works fine.
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Brian.
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Re: Lumpy idle when cold

Post by Northern Bongolow » Mon Oct 20, 2014 6:15 pm

your understanding and testing of the 2 solenoids is correct, the first works as a low temp (full choke) to pick up the revs when really cold, then turns off when the coolant temp is about 10 deg c, this turns on the second solenoid to give (half choke revs) this remains on until about 50 deg c, then they are all off. unless the ac is on then the second remains on to control the revs for the ac load.

it does sound odd that it doesnt work when the engine is cold.

they are interchangable so you could try this.

the switching temp is got from the coolant temp switch on the side of the head on the passy side, just above the starter motor if its a diesel.
check the connections, and that the sensor is good. a damaged sensor can (wobble) where it goes from steel to plastic, this can affect the resistance (trigger point) of the sensor. this sensor also controls the glow plug temp switching and the egr trigger point.
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Re: Lumpy idle when cold

Post by Snail921 » Mon Oct 20, 2014 6:39 pm

thanks for that. Have changed them over, works fine if sited as number 2, and the replaced number 1 still won't work which means it has to be the instruction coming from the PCM. I take it the PCM takes its readings from the coolant temp switch? Will check that tomorrow, weather permitting
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Brian
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Re: Lumpy idle when cold

Post by rita » Mon Oct 20, 2014 8:13 pm

Northern Bongolow wrote:your understanding and testing of the 2 solenoids is correct, the first works as a low temp (full choke) to pick up the revs when really cold, then turns off when the coolant temp is about 10 deg c, this turns on the second solenoid to give (half choke revs) this remains on until about 50 deg c, then they are all off. unless the ac is on then the second remains on to control the revs for the ac load.

it does sound odd that it doesnt work when the engine is cold.

they are interchangable so you could try this.

the switching temp is got from the coolant temp switch on the side of the head on the passy side, just above the starter motor if its a diesel.
check the connections, and that the sensor is good. a damaged sensor can (wobble) where it goes from steel to plastic, this can affect the resistance (trigger point) of the sensor. this sensor also controls the glow plug temp switching and the egr trigger point.

That sound very interesting can you elaborate a wee bit on the function of the Choke please.
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Re: Lumpy idle when cold

Post by g8dhe » Mon Oct 20, 2014 9:35 pm

Is the vacum getting to the solenoid, given that e very think else seems OK?
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Re: Lumpy idle when cold

Post by Snail921 » Tue Oct 21, 2014 11:31 am

Yes, there's vacuum to both, and both parts of the FICD respond to vacuum, but the solenoid won't open using its own electrical connection. If I take number two connection and put it into number 1 it opens as it should but then, of course, it won't close until the engine is at nearly working temp rather than at 10 deg.
I'll check the temp sender once the wind goes down enough that I can stand up outside:-)
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Brian.
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Re: Lumpy idle when cold

Post by Northern Bongolow » Tue Oct 21, 2014 12:29 pm

if the sensor probe is covered in crud as is usual then the sensor may not be responsive enough at its lower range to send the signal, this can happen when the sensor has been boiled also.
if you take off the wires to the sensor you can measure the resistance readings that should be present at a known temp.

this is taken from the manual.
remove sensor and put end in water

water temp 20 resistance 2.3-2.6 k ohms
water temp 80 res 0.29-0.34 k ohms.

if resistance is outside this, replace it.
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Re: Lumpy idle when cold

Post by rita » Tue Oct 21, 2014 5:31 pm

Is the AC working properly.
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