Strange stalling problem

[poll250 0]

Hi,

 

This is a bit of weird one, but has happened a few times over the last 3 months, and seems different to the usual ISV related issue.

 

When I dip the clutch coming to a roundabout, junction or traffic sometimes the car stalls. Normally when this happens, you can let the clutch out and the car bump starts itself, but I've had it a few times now when letting up the clutch doesn't do anything at all.

 

This happened on Tuesday when I was leaving the M40, so doing about 70 and the battery should have been charged. I eventually stopped on the slip road, turned the key, heard the fuel pump prime, but it just wouldn't start. I waited about 5 mins, tried again and it was fine for the rest of the journey.

 

Does anyone have an idea what could cause this? I've got a late CP ecu with the Immob deleted, could this be playing up?

[Critical_Mass 10]

This is strange by no means uncommon, ive currently got this issue. BUT hasnt done it for a while. Not sure if people have ever got to the bottom of it.

[wy906 0]

Happens to me too though not often! One of those VR6 mysteries!

[Supercharged 2]

Could be the MAF but the fact that it would not start could be an ECU relay fault - when was this last changed?

[Storm Guy 0]

Happend on my Blackberry VR6 many years ago, cant recall what we did back then. More recently though (2006) my Storm also did the same thing. Is frustarting and can be dangerous to say the least. VW diagnostic resulted in replacement of damper part # 021133429A, appx £20 odd at the time. Never stalled or missed a beat since. Worth a shot for small money.

[dannyboy 0]

I swore i remember seeing something about a loose wire for the immobiliser was causing engine to turn off. Could be one of the wires loose somewhere

[Critical_Mass 10]

Yeah tell me about it, when it last happened to me id just pulled onto the roundabout and it stalled. Luckily its started first time every time.

 

Im ruling out the damper pot. At least for me as mine new, only been on the car 6 months.

[RW1 0]

If you have disconnected the battery at some point (or don’t know from the previous owner) and not done “Basic Settings” on the Throttle, then the ECU does not know where exactly the Throttle position is, essential near idle will be critical to stop the stall ........ (That’s why in the Wiki, the ECU reset has to be performed in full after the Engine ECU has lost 12 volt power at any time.)

 

BTW, Not advisable to bump start a VR6 Engine at speed (or due to flat battery/no starter) cos the Chain Tensioners could have gone slack and therefore before the oil pressure can re-pressurise the tensioners, the chains can jump a cog on the Camshaft Drive Sprockets with terminal consequences to valves and piston crowns.

 

1) Get hold of VCDS and do Basic Settings on the engine ECU on Group 000 or 001 as per the wiki "ECU Reset", ie. which ECU is fitted by part number governs which Group Number to use. No need to the first part of disconnecting the battery and 10 minute drive, this is not about lambda setting.

 

You can do Basic Settings on the engine ECU anytime - harmonises the Throttle Potentiometer Sender.

 

This is providing the mechanical throttle stop hasn't been adjusted! (There is a paint mark over the stop screw which should be intact if its not been adjusted.) And the Throttle Potentiometer Sender is sound by checking with a very slow sweep (Accelerator Pedal press) of the full sweep and observing the reading in VCDS Measuring Blocks is progressive and not jumpy. Not 100% check but good enough.

 

Throttle Checks: ....

 

2)

- Run the engine at idle when warmed up and generally idling at 680rpm.

- VCDS to 01 Engine ECU Measuring Block Group 003, field 3.

- At idle the Throttle Body Angle should be between 9º - 19º, ideally 13º/14º. It can be done with out running the Engine, just Ignition ON but as this area is the problem, better to look at the dynamic reading with air flow. It should the same with and without the Engine runing.

 

- Exit VCDS (to prevent lock up of software).

 

3)

- Stop the Engine & turn the Ignition back ON.

- VCDS to Engine ECU Measuring block Group 003, field 3 again.

- Floor the accelerator pedal and hold.

- The reading should be between 94º and 101º, ideally 97º/98º with the Accelerator Pedal held fully down.

- Exit VCDS & turn off the Ignition.

 

Nothing changed due to Basic Settings or Throttle angle readings have been found to be OK? Then, this is not the problem.

 

Would then look at the Throttle Damper replacement first and Throttle Potentiometer Sender having a poor sliding contact track around the idle position. Change of parts unfortunately with risk it won't fix it.

 

----------------------------------------------

 

Throttle Mechanics:

 

If VCDS Throttle Angles measurements not within the to the above VCDS Throttle Angle readings tolerances above: .........

(Best with the coil pack end, rear & top engine covers removed to perform these adjustments.)

(The checks can be done without removing the rear cover but access is slightly limited.)

 

* Adjust the Throttle Damper position for Throttle Idle position.

 

- Engine stopped.

- At the Damper Stop Plunger, make sure it is just contacting the small roller on the throttle valve arm. (This needs to be held by hand, the throttle is not hard onto the Throttle Stop )

- Now measure the gap with a feeler gauge (or 3mm drill bit) between the stop adjuster screw next just ahead of the Throttle Damper and on the rearside of the Throttle Spindle with Spring and its Throttle stop. It should be a 2.5mm - 3.5mm gap, ideally 3mm.

-If not in this range, adjust the Throttle Damper ( not the Throttle Stop Screw) with the 3mm feeler or 3mm drill bit jammed in between Throttle Stop and Throttle Adjuster Screw.

- Set the Damper Stop Plunger just touches the roller without force present and no more. The roller should just be able to rotate by finger with hardly any friction. Do this using the Damper's lock nut and the threaded rod on the rear of the Damper.

 

Now recheck the Throttle idle position with VCDS as above at 2).

 

 

* Adjust the Throttle Cable Tension for full throttle.

 

- Engine stopped.

- Push the Accelerator Pedal fully down while a 2nd person observes the throttle in the engine bay. The Throttle should stop moving as the Accelerator Pedal fully floors and Throttle cannot be opened further at the Throttle Body. It should not however put the Throttle Cable under strain by reaching Throttle Body fully open position while the Accelerator Pedal can be pressed further.

- Adjustment is performed by locating the C clip on the plastic body of the Throttle Cable where it attaches to the Throttle Body (located under the rear engine cover). Move the C clip to a new position until the Accelerator Pedal fully depressed also achieves full throttle open position at the Throttle Body. This avoids straining the cable.

 

Now recheck the Full Throttle position with VCDS as above at 3).

 

If adjustments are made, it will be necessary to perform “Basic Settings” again as detailed at 1).

 

.