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PointedThree :  Vans, Trucks, SUVs and Other Forums : G-Class : Hesitation after slowing or stopping at junctions

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Hesitation after slowing or stopping at junctions
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Posted 4/14/2019 1:43 PM
darko
Member


Date registered: Mar 2012
Location: Isle of Man
Vehicle(s): 2003 G500
Posts: 43
25
Hesitation after slowing or stopping at junctions

Hi All

Hoping someone can help me with this problem..

When slowing or almost stopping at a junction (or turn) the engine dies / stumbles / hesitates to the extent that I am making sure I have no traffic approaching (if pulling out of a junction)

So far I have :

1) checked the HT plug leads & cleaned the coil pack electrical connectors
2) ran through two full premium grade tanks of fuel
3) ran with the MAF disconnected
4) replaced as many vacuum lines as I could get to (at the front of the engine most were quite bad)
5) given the engine some full throttle / high rpm runs

I "think" the vacuum line replacements made a slight improvement to the rough idle / misfire the engine has always had but made no change to the hesitation

My next steps are to start replacing parts like fuel filter etc, I was told to change the K40 relay but mine is a 2003 model which I believe does not have the K40 relay (?)

The car stood for about 3 months whilst I had some rust repairs done, replaced brakes etc but ran fine after that. I left the interior light on and flattened the battery and I think this is when the problem started. Could it be related to a flat battery ? After charging the battery up it has held a charge fine and starts up easily.

Has the throttle position sensor lost its setting after a flat battery situation ?

Could the fuel pump be dying ? If so I would have thought under load it would be playing up too ?

I have a basic OBD checker but the only code showing related to the charcoal evap system and I have always had that error for 12+ years, even Mercedes said to ignore it

The hesitation can be quite severe, almost like the engine is going to stall completely but then it just picks up and clears. In all other driving situations everything seems ok

Help !

Edited by darko 4/14/2019 1:45 PM
#240603
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Author
Posted 4/14/2019 6:58 PM
hipine



Date registered: Jul 2006
Location: US, CO, Bailey
Vehicle(s): 460 1980 280GE w. 617A
5000
RE: Hesitation after slowing or stopping at junctions

Your problem is a simple one and has a simple answer. Your vehicle has two-too-many wheels for driving on the island. Sorry, my endless lust to see the TT in person one day meant I couldn't resist.

But in the "trying to actually help" mode, I think it would be good to verify the voltage present in the primary wiring. The battery might not be as good as you think. I've had batteries that started the car 100% reliably but had ZERO reserve. I never knew it until it was too late. When I had similar conditions in my 460 back when it was a 2.8L petrol the issue was the ignition coil itself. My mechanic diagnosed and fixed it as I was completely baffled thinking a coil would play up under HIGH demand, not low. But in my case the coil wasn't functioning well when the car's voltage was a little lower at idle than it was when revs were higher.

So anyway, just some thoughts.

Good luck!

-Dave G.
#240605 - in reply to #240603
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Author
Posted 4/15/2019 4:14 AM
darko
Member


Date registered: Mar 2012
Location: Isle of Man
Vehicle(s): 2003 G500
Posts: 43
25
RE: Hesitation after slowing or stopping at junctions

Aha ! True, however I am abiding by Manx rules and have a motorbike in the garage too

I did a bunch of googling last night and found someone had a similar issue on a SL55 AMG - it turned out to be the EVAP / Charcoal canister so perhaps I should stop ignoring that issue now

The thread is here :

https://mbworld.org/forums/sl-class-r230/694073-help-sl55-amg-interm...

It turned out some kind of valve had gone bad near the charcoal canister and was allowing fuel to go into the EVAP system (not just fuel fumes) and replacing this valve cured the problem

Whilst we had the rear bumper off for painting and doing some wax oiling treatment I noticed a smell of fuel in the rear wheel arch, near the the fuel cap and charcoal canister. If it is flooded this could be the problem. I will check today once the whether improves.

I also notice someone having a similar issue in a post further down on their G500 :

http://www.pointedthree.com/disc/forums/showthread.asp?tid=24037&mi...
#240606 - in reply to #240603
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Author
Posted 4/15/2019 4:15 AM
darko
Member


Date registered: Mar 2012
Location: Isle of Man
Vehicle(s): 2003 G500
Posts: 43
25
RE: Hesitation after slowing or stopping at junctions

By the way Dave G you MUST come to the TT !!
#240607 - in reply to #240603
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Author
Posted 5/5/2019 4:10 PM
hipine



Date registered: Jul 2006
Location: US, CO, Bailey
Vehicle(s): 460 1980 280GE w. 617A
5000
RE: Hesitation after slowing or stopping at junctions

darko - 4/15/2019 2:14 AM

Aha ! True, however I am abiding by Manx rules and have a motorbike in the garage too

I did a bunch of googling last night and found someone had a similar issue on a SL55 AMG - it turned out to be the EVAP / Charcoal canister so perhaps I should stop ignoring that issue now...


Well? Did you fix it? Good job digging out that potential cause. I hope it's an easy fix.
-Dave G.
#240657 - in reply to #240606
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Author
Posted 9/15/2019 1:50 PM
darko
Member


Date registered: Mar 2012
Location: Isle of Man
Vehicle(s): 2003 G500
Posts: 43
25
Re: Hesitation after slowing or stopping at junctions

Hi, sorry for the lack of reply, its been a busy summer

so... I haven't got to the bottom of this fault sadly. I have an LPG conversion on the car and it runs fine on LPG so I suspect its a problem in the fuel system (fuel pump / fuel filter / fuel evap canister)

Should have some more time to look into it soon
#240992 - in reply to #240657
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Author
Posted 9/22/2019 11:54 AM
hipine



Date registered: Jul 2006
Location: US, CO, Bailey
Vehicle(s): 460 1980 280GE w. 617A
5000
Re: Hesitation after slowing or stopping at junctions

darko - 9/15/2019 11:50 AM
...I haven't got to the bottom of this fault sadly. I have an LPG conversion on the car and it runs fine on LPG so I suspect its a problem in the fuel system (fuel pump / fuel filter / fuel evap canister)...


Bummer. Are you able to check the injector signals at the injectors? Do some searching of this forum and others on injector wiring harness issues. I think vehicles in that timeframe might have had a problem with that portion of the harness, but could be mis-remembering. Your mention of running well on LPG is telling because that's probably a "fogging" sort of system near the throttle body, not relying at all on the petrol injectors, correct?

Best of luck!

-Dave G.
#241003 - in reply to #240992
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