2.0 MP9 surging / jerking - Help please

MacMan
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2.0 MP9 surging / jerking - Help please

Post by MacMan »

Hi guys.

I hope someone will be able to help me with this problem because I have been battling with it for ages and I haven't managed to fix it.

What happens is on part-throttle the car jerks / surges quite a bit. I suspected the water temp sender and sure enough when I connected the VAG-COM up there was an Engine Coolant Sensor - Short to Ground Intermittent error. So I cleared the error, replaced the sensor with a new one from VW, but the problem is still there, so it is not the sensor.

What I then did was drive with the VAG-COM connected so I could keep an eye on the water temp while driving and I noticed something interesting. The water temp increases uniformly as it should, but every now and then it will shoot up by 20 or 30 degrees and then drop back down again. The car jerks / surges when this sharp increase in the water temp reading occurs.

I assume there is a short somewhere, but when I do resistance tests with the ECU unplugged, everything measures correctly according to the fault finding manual.

Any ideas what could be causing it? Faulty ECU perhaps?
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Re: 2.0 MP9 surging / jerking - Help please

Post by joggiep »

What the wire like ? any possibility that there might be a break in the wire that could cause the resistance in the wire to suddenlt go up or down. What's the earth like ..

These things are a bugger to try and find.. I have a couple of grenlins hiding in the jetta's wiring and it's a mission to try and fig. it out.
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UDC
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Re: 2.0 MP9 surging / jerking - Help please

Post by UDC »

so most probably theres a short in the 4wires that go between the 4pin switch and ecu, maybe run direct wires to the ecu from the 4pin switch and then check
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Re: 2.0 MP9 surging / jerking - Help please

Post by MacMan »

Thats the thing, if I measure the continuity of both wires for the ECU (one is ground and one is signal to the ECU) between the sender plug and the ECU plug I get a closed circuit, which means the wires are fine.

If I measure the resistance between the ground wire and the signal wire I get an open circuit which means the wiring is not shorting either.
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'99 Citi Golf 2.0i

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Re: 2.0 MP9 surging / jerking - Help please

Post by nasti »

Mac man stop the car an tell the jerk to get out . Lol ! Friend of mine had similar problem on his velo and it was due to fuel pressure . Hope u sort the problem out good luck .
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Re: 2.0 MP9 surging / jerking - Help please

Post by UDC »

but all these test's are being done when the car is parked, most probably when the vehicle is moving theres a weak contact or short occuring due to the vehicle movement
have you tried another ecu?
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Re: 2.0 MP9 surging / jerking - Help please

Post by maranou »

start rhe car and pull up handbrake and release and depress clutch like rocking the car to get the same movement when driving and see if the wire then gives problems and check some engine mounts then and if motor doesn't flex too mutch or pull too hard on wires then?
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Re: 2.0 MP9 surging / jerking - Help please

Post by MacMan »

UDC wrote:but all these test's are being done when the car is parked, most probably when the vehicle is moving theres a weak contact or short occuring due to the vehicle movement
have you tried another ecu?
Are you volunteering to sit in my engine bay and hold the one multi-meter lead while I drive? :lol: But yeah I get what you are saying.

I have tried another ECU and it seemed better, but the water temp still jumped around. Weird.
'20 SEAT Tarraco XC 1.5 TSi
'12 VW Up! 1.0 MPi

Ex:
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'04 Golf MKIV GTi.:R
'99 Citi Golf 2.0i

Patience is the ability to idle your motor when you feel like stripping your gears.
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Re: 2.0 MP9 surging / jerking - Help please

Post by UDC »

MacMan wrote:
UDC wrote:but all these test's are being done when the car is parked, most probably when the vehicle is moving theres a weak contact or short occuring due to the vehicle movement
have you tried another ecu?
Are you volunteering to sit in my engine bay and hold the one multi-meter lead while I drive? :lol: But yeah I get what you are saying.

I have tried another ECU and it seemed better, but the water temp still jumped around. Weird.
ya sure anytime, as long as we remove the windscreen and bonnet :lol:
hope you get sorted out but wiring gremilns are the worst :cry:
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Re: 2.0 MP9 surging / jerking - Help please

Post by sixteen10 »

first time i've ever seen you stumped mac, hope you get it sorted :cry:
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Re: 2.0 MP9 surging / jerking - Help please

Post by JVR »

Hi Guys, my 1.8 Polo is giving the same kak http://www.vwclub.co.za/phpbb3/viewtopi ... =3&t=72150 except mine only does it when the car is used when the outside temp exceeds 40'C - in Upington, e v e r y DAY!!!
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Re: 2.0 MP9 surging / jerking - Help please

Post by Ted »

hey shaun

after you changed the sensor, do you still get the short error on the VAG?

get a loose plug just to test and wire it up loose, one lead goes to ECU(pin 42) , ground the two brown wires, and the yellow and red goes to cluster temp so just leave that out for the test?


if it still does that its defnitly not a wiring problem
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Re: 2.0 MP9 surging / jerking - Help please

Post by MacMan »

Ted wrote:hey shaun

after you changed the sensor, do you still get the short error on the VAG?

get a loose plug just to test and wire it up loose, one lead goes to ECU(pin 42) , ground the two brown wires, and the yellow and red goes to cluster temp so just leave that out for the test?


if it still does that its defnitly not a wiring problem
Thanks for the reply Ted.

Yip after I changed the sensor the error still came up in the VAG-COM.

I will give that a try. If I am still getting the problem then what else could it be? ECU?
'20 SEAT Tarraco XC 1.5 TSi
'12 VW Up! 1.0 MPi

Ex:
'06 Golf MKV GTi
'04 Golf MKIV GTi.:R
'99 Citi Golf 2.0i

Patience is the ability to idle your motor when you feel like stripping your gears.
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Re: 2.0 MP9 surging / jerking - Help please

Post by JVR »

Hi Guys,

Got back home on Friday and started driving around town to see i can drive the Polo to destruction, did quite well as it now no longer idles, or revs, it sounds like its got a 282 cam in while idling, and top RPM no load is at 3000. Took the car to VW in the condition that its in, the oke there says he has got no idea... But i must take it in this week to see whats up, will keep you posted if i can sort this out.
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Re: 2.0 MP9 surging / jerking - Help please

Post by UDC »

JVRDesign wrote:Hi Guys,

Got back home on Friday and started driving around town to see i can drive the Polo to destruction, did quite well as it now no longer idles, or revs, it sounds like its got a 282 cam in while idling, and top RPM no load is at 3000. Took the car to VW in the condition that its in, the oke there says he has got no idea... But i must take it in this week to see whats up, will keep you posted if i can sort this out.
sounds like you map sensor is stuffed
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Re: 2.0 MP9 surging / jerking - Help please

Post by Dman97 »

Hey guys, really old thread I see and I'm not quite sure how to start my own.
However, I have a similar issue to what JVR is talking about however, mine only seems to happen when the car is hot.
I have a 2.0 mp9 CLi that runs perfect usually, but recently I got an intermittent jerk under low revs and acceleration once the car is hot. Anyways, last time it happened, the plug going into the coil from the center of the dizzy was out and this caused the rev counter to also jump up and down upon idle. After plugging it in tightly again, car was fine. Now, the jerking is back but the plug lead to the coil is in tightly as well. My initial thoughts are fuel and the water temp sensor but I just replaced the sensor a few months ago. Now I'm not sure if this is fuel or spark related, anyone had a similar issue? And found the fault? Please guys, appreciate any help.
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Re: 2.0 MP9 surging / jerking - Help please

Post by UDC »

Intermittent issues are the worst, could be a faulty plug lead or maybe a lead arcing against something, put the lights off and check when its dark, maybe would see the spark jumping and arcing
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Re: 2.0 MP9 surging / jerking - Help please

Post by Dman97 »

@UDC I also just replaced the plug leads with the bremi ones from goldwagen about 4 months ago or so and I don't drive much. But will plug the old leads back in as nothing was wrong with them and see what's happening.....problem is, there's no misfire. It intermittently jerks when car is warm. 2 weeks ago when the smothering/jerking occurred first time, it was fine after I unplugged the plug lead running from coil to dizzy and pushed it in again. Could something maybe be wrong with the coil? Because usually right before it does the jerking, the revs tend to intermittently shoot up when I clutch is engaged. This is frustrating, because one day it's a pleasure to drive this car, and then bam this happens.
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Re: 2.0 MP9 surging / jerking - Help please

Post by UDC »

Could be coil is cracked and expanding when hot...also check that your clutch cable is not pushing against the plug leads or coil
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Re: 2.0 MP9 surging / jerking - Help please

Post by Dman97 »

@udc, I scratched around on the car today, everything looks fine in terms of leads, dizzy etc. Before i run off to buy a new coil which isn't the damn cheapest thing to blind buy, there is a crack in the thick cable that runs to the knock sensor. Could this cause my symptoms I described above?
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Re: 2.0 MP9 surging / jerking - Help please

Post by UDC »

knock sensor will not cause a miss, will just make the car abit sluggish if it throws a knock sensor error but it will drive fine...just not as responsive
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Re: 2.0 MP9 surging / jerking - Help please

Post by ICE King »

Considering you've replaced most things that the ignition side , could be the fuel pump or perhaps something small like a partially clogged fuel filter?
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Re: 2.0 MP9 surging / jerking - Help please

Post by Dman97 »

So, car is fine for 3 day sthem the **** happens again. It's a very quick jerk that happens when the car is at temperature. Very intermittent and not all the time. It's low down in the revs when accelerating, but seems to be fine when the car is at a steady speed. Car idles fine too. It doesn't feel fuel related because I dealt with an issue where the car smothers from lack of fuel, it's almost as if someone is holding onto the car when you accelerate, this isn't the same. It's quick, like when a learner driver first pulls away. Also, just before the jerking starts, let's say I slow down and engage the clutch, it's as if the revs surge, then when I give petrol to accelerate, the jerking starts. It's very quick, then the car moves off again. Could a faulty coil cause this? I have relatively new spark plugs, new plug leads(bremi), rotar replaced last year October. Getting annoyed now that I can't figure eout what it is and replace it. Don't want to dive into a money pit and replace a bunch of stuff that has nothing wrong with it.
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Re: 2.0 MP9 surging / jerking - Help please

Post by Dman97 »

Also, might I add, the thing that's making me doubt the coil is that the car starts on first swing. No starting issues. But could it be faulty in the manner described above? Maybe by delivering a weak spark or something. If so, then it's defs a first for me
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Re: 2.0 MP9 surging / jerking - Help please

Post by Dman97 »

Anyone with any suggestion? Drove the car now down the road to shop, 100% fine. Seems this issue is only there when it's hot.
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