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Model specific boards => Golf mk3 => Topic started by: bmouthboyo on 29 June 2011, 19:41

Title: Revs randomly dropping to 0 when driving?
Post by: bmouthboyo on 29 June 2011, 19:41: Hi Guys,

Recently when driving, especially when allowing the engine to naturally pull the revs (no accelerator) the engine revs drop down to 0 and usually back up a split second later. Seems to happen intermittently, say once or twice a short journey.

Occasionally when idling at lights it drops and stalls, oil light on when it does that. Can take a bit of cranking to start again and then seems to be fine with some revs.

I know I have a few breather hose cracks that I am meaning to sort, would this cause this? I thought for the engine revs to just drop and come back up would be fuel delivery related?

Any help or even shots in the dark much appreciated.
Title: Re: Revs randomly dropping to 0 when driving?
Post by: thai-wronghorse on 29 June 2011, 19:51: Check the cable to the crank speed sensor to see if it's perished. If that looks good then before shelling out £50 for a new one id be sticking it on Vagcom and possibly replacing both the fuel and ECU relays. Split breathers shouldnt be the main cause for you cutting out but wont be helping matters so get them sorted asap mate.
Title: Re: Revs randomly dropping to 0 when driving?
Post by: javalin on 30 June 2011, 09:06: >I know I have a few breather hose cracks that I am meaning to sort, would this cause this?
would sort this out first and see what change it makes to the car.

fix the problems you can see first IMHO.
Title: Re: Revs randomly dropping to 0 when driving?
Post by: bmouthboyo on 30 June 2011, 17:41: Thanks for advice so far guys, had a nightmare getting to work today. The problem is a lot more frequent now.

Today when it happened a lot I noticed a rapid clicking noise from the fuse / relay area. The revs just slam to 0 and back up and the engine is dying and cutting back in. Could it be fuel pump relay or something?
Title: Re: Revs randomly dropping to 0 when driving?
Post by: javalin on 30 June 2011, 17:43: yeah could be ECU relay (no.30) or fuel pump relay (no.167).

James
Title: Re: Revs randomly dropping to 0 when driving?
Post by: bmouthboyo on 30 June 2011, 18:39: Do these relays play up like this often? ECU relay sounds probable as when it plays up the revs cut to 0, even if the car is still doing say 40 with clutch fully engaged, so teh actual revs cant be 0 so suddenly.
Title: Re: Revs randomly dropping to 0 when driving?
Post by: thai-wronghorse on 30 June 2011, 19:51: Both of those relays are super common failure points on mk3 Golfs.
Title: Re: Revs randomly dropping to 0 when driving?
Post by: bmouthboyo on 02 July 2011, 13:09: OK so new relay 30 and having same issues. If i put hand on the relay i can feel and hear it clicking intimitently as the revs / engine cut.

What could cause this ECU relay to trip on and off?

Last time i used VAGCOM I had a lambda error with ABS. But worked fine for long time since then without these issues.

Also seems to be worse recently, and once it starts tripping it seems to do so frequently the rest of the journey. But until that first rev drop on a journey it runs fine.

I will test VAGCOM again on Sunday but just wondered if anyone can give a heads up to the kind of things that can cause relay 30 to switch on and off intermittently.

Thanks for help guys
Title: Re: Revs randomly dropping to 0 when driving?
Post by: Gti Gerbil on 02 July 2011, 13:42: I currently have the same problem.

I have already changed relay 30 last week and the problem continued although not as frequently.

Have purchesed a crank shaft sensor this morning, will let you know the results a little later once i get my lazy ass into gear.

When i connect up the vagcom i occasionally get a "engine speed sensor intermittant fault" but it is not there every day (sad i know but been monitoring it for a week to make sure i got the right bit) even though the fault is there on every trip
Title: Re: Revs randomly dropping to 0 when driving?
Post by: Gti Gerbil on 02 July 2011, 15:17: crank / enginine speed sensor changed .........

SORTED

the end of the sensor had a little crack in it and the insulation near the sensor had cracked up.

50 quid well spent at GSF
Title: Re: Revs randomly dropping to 0 when driving?
Post by: javalin on 02 July 2011, 15:21: yeah a few people have had this recently, and the GSF sensor seems to be a decent bit of kit. Got one in mine and its fine.

Good job.

James
Title: Re: Revs randomly dropping to 0 when driving?
Post by: bmouthboyo on 03 July 2011, 12:18: Does it take long to change? A quick read about and it mentions undoing engine mount bolts, gearbox supported with jack etc.

How does this compare to say head gasket job?

Cheers
Title: Re: Revs randomly dropping to 0 when driving?
Post by: javalin on 03 July 2011, 12:25: not long.

From memory you need to take the front engine mount off - so support gearbox with jack. Swap over sensor and re-fit mount.

Haynes manual if you are not sure.

>How does this compare to say head gasket job?
100% easier.

James
Title: Re: Revs randomly dropping to 0 when driving?
Post by: Gti Gerbil on 03 July 2011, 14:05: took me about 20 mins to do

put front on ramps

battery earth off

undid bolt from mounting bracket to mount/body

trolly jack under gearbox and lifted slightly (about an inch)

undid mounting bracket

got the allen key bolt out of sensor and levered gently with a large screwdriver

refitted in reverse

no special tools needed but the allen key bit / holder on the end of a short extension bar made undoing the retaining bolt on the sensor pretty easy, might be a little harder with standard "L" shaped allen keys due to fairly tight access unless you remove the oil filter too.
Title: Re: Revs randomly dropping to 0 when driving?
Post by: bmouthboyo on 23 July 2011, 11:51: OK so I finally got around to testing the car fully with VAGCOM. Here are the results:

Chassis Type: 1H - VW G/J/V Mk3
Scan: 01,02,03,08,15,25,56
-------------------------------------------------------------------------------
Address 01: Engine
Controller: 037 906 025 R
Component: SIMOS 4S 2104
Coding: 00000
Shop #: WSC 99999
1 Fault Found:
00513 - Engine Speed Sensor (G28)
16-10 - Signal Outside Specifications - Intermittent
Readiness: N/A
-------------------------------------------------------------------------------
Address 03: ABS Brakes
Controller: 3A0 907 379
Component: ABS ITTAE 20 GI V00
Coding: 03604
Shop #: WSC 00000
2 Faults Found:
00287 - ABS Wheel Speed Sensor: Rear Right (G44)
35-00 - -
00287 - ABS Wheel Speed Sensor: Rear Right (G44)
16-10 - Signal Outside Specifications - Intermittent
-------------------------------------------------------------------------------
Skipping Address 15-Airbags
-------------------------------------------------------------------------------
Address 25: Immobilizer
Controller: 1H0 953 257 B
Component: IMMO VWZ3Z0T1071555 V00
Coding: 09600
Shop #: WSC 00675
No fault code found.
End

Randomly I tried the scan again after a few times and it does not pick the 00513 - Engine Speed Sensor (G28) fault up? :undecided: I am also confused as the speedo is working fine, its just the engine revs drop, the ECU relay clicks rapidly and lose power. Sometimes it starts straight after, others not for a while.

So I assume it's the crank sensor? I have had a poke about and I think this is the sensor? and the wiring seems damaged. Would this cause the problems I outlined at the start of the post?

(http://i176.photobucket.com/albums/w182/bossman187uk/cranksensor.jpg)

(http://i176.photobucket.com/albums/w182/bossman187uk/DSC_0010.jpg)

(http://i176.photobucket.com/albums/w182/bossman187uk/DSC_0007.jpg)

Interestingly a fault I was getting about 8 months ago from VAGCOM about the Lambda sensor now does not show:

(http://i176.photobucket.com/albums/w182/bossman187uk/test.jpg)

Should I still replace the Lambda also?

Thanks :)
Title: Re: Revs randomly dropping to 0 when driving?
Post by: Gti Gerbil on 23 July 2011, 14:19: erm... hell yeah

thats the kiddie

changing that cured all my running problems
Title: Re: Revs randomly dropping to 0 when driving?
Post by: bmouthboyo on 23 July 2011, 15:28: Quote from: Gti Gerbil on 23 July 2011, 14:19
erm... hell yeah

thats the kiddie

changing that cured all my running problems

That sounds like good news. Not sure whether to repair the current wires or buy new?

I am not so confident removing engine mounts etc. Is it possible to remove and replace without doing this?
Title: Re: Revs randomly dropping to 0 when driving?
Post by: Gti Gerbil on 23 July 2011, 15:41: could try without taking mount out but it would be very difficult

as for repairing the wires, could try but while you got the sensor out may as well put a new one in as it could be the sensor its self and the wires are a secondary problem
Title: Re: Revs randomly dropping to 0 when driving?
Post by: Seanl on 23 July 2011, 20:02: Gonna be fitting a new lump on mine in the next couple of weeks, and the crank sensor on the old and new engine were split where you have shown, and by the sensor into the block itself. They were both very brittle on the insulation, and as soon as I disconnected them both, the flexing of the cable just made the wire start parting from the sensor causing the wires to short as both outer, and core insulation was fecked! IMHO I would replace it as it's most likely the same if still original.
Title: Re: Revs randomly dropping to 0 when driving?
Post by: bmouthboyo on 24 July 2011, 13:29: Yea good point, might as well replace it.

Is this the front engine mount? (sorry havnt played with mounts etc before)

(http://i176.photobucket.com/albums/w182/bossman187uk/frontenginemount.jpg)

Cheers
Title: Re: Revs randomly dropping to 0 when driving?
Post by: Seanl on 24 July 2011, 20:07: Yeah just take out the bolt at the top of the bracket. The rest is the whole subframe and not sure if you need to take that off, depends how much room you have.
Title: Re: Revs randomly dropping to 0 when driving?
Post by: RIPP3Y on 25 July 2011, 19:16: hi, i just fitted a new sensor too, to be honest i would have rathered it was done for me but decided to have a go, like yourself i wasnt confident. It sounds harder than it was, as long as you have a decent ratchet set, allan keys and a trolley jack you`l be fine. Change the oil and filter while your at it and you too will be beaming from ear to ear when youve finished. :wink:

instuctions are on my post, 2nd or 3rd page(horney blonde babe) something like that.
so much good advice on this forum,
i took the time to look through a load of pages yesterday and the same today
Cant fault it thanks guys
:wink: :wink: :wink:
Title: Re: Revs randomly dropping to 0 when driving?
Post by: bmouthboyo on 26 July 2011, 18:03: Quote from: RIPP3Y on 25 July 2011, 19:16
hi, i just fitted a new sensor too, to be honest i would have rathered it was done for me but decided to have a go, like yourself i wasnt confident. It sounds harder than it was, as long as you have a decent ratchet set, allan keys and a trolley jack you`l be fine. Change the oil and filter while your at it and you too will be beaming from ear to ear when youve finished. :wink:

instuctions are on my post, 2nd or 3rd page(horney blonde babe) something like that.
so much good advice on this forum,
i took the time to look through a load of pages yesterday and the same today
Cant fault it thanks guys
:wink: :wink: :wink:

That's great thanks, don't suppose you have a link to the forum post? Can't seem to find it.

I had a go today at repairing / soldering those wires in the pics I posted but still have same problems despite from what I can see under the car the rest of the wiring being OK to the sensor. It does now however consistently show the following issues on VAGCOM:

Address 01: Engine
Controller: 037 906 025 R
Component: SIMOS 4S 2104
Coding: 00000
Shop #: WSC 99999
1 Fault Found:
00515 - Camshaft Position (Hall) Sensor (G40)
16-10 - Signal Outside Specifications - Intermittent
Readiness: N/A

Do you think it is worth the £50 and replace the Crank sensor given this new Hall sender diagnosis?could this be a different underlying issue? The car does smell petroly and VAGCOM used to give a lambda warning but doesn't any more. Could the lambda have fully packed in and cause this? or unrelated?

Scratching my head as to what to tackle next.
Title: Re: Revs randomly dropping to 0 when driving?
Post by: javalin on 27 July 2011, 08:33: yeah, replace the crank sensor, clear the codes and see what happens next. Can't beat a new sensor really.
Title: Re: Revs randomly dropping to 0 when driving?
Post by: bmouthboyo on 04 August 2011, 18:18: Thanks guys.

Replaced the crank sensor today. Not the nicest of jobs but seems to have cured the problem (10 min drive), just need to hook to VAGCOM to confirm.

There is no way the sensor allen bolt can be accessed without removing the front mount. And even then there was a moment where I thought I have rounded the bolt :laugh: and I literally nearly peed my pants.

I found a whole wealth of other bits that need doing for MOT whilst I was under there :( so I am sure you will see more of me about lol

Thanks guys
Title: Re: Revs randomly dropping to 0 when driving?
Post by: Gti Gerbil on 04 August 2011, 22:11: Happyness is a freshly thrashed golf :evil: