Curious engine behaviour

[Aus 0]

Hi, have a '94 VR6, 70K miles, serviced last month but about 6 months ago this all started ...

 

- on cold mornings, it starts immediately and then hunts between 400 and 1500 revs until warm

- when warm, always starts but turns over 10-12 times before starting (used to start immediately)

- when coasting to a stop, the engine often dies

- when it's warm it idles fine at about 650-700 revs

- pulling and running well otherwise

 

Have replaced the coil pack and leads, blue temp sensor, cleaned out the ISV (with brake cleaner and then lubed with PTFE oil), checked that the battery's OK.

 

Am now stuck - any ideas? Thanks

[dr_mat 0]

Any error codes?

[Kevin Bacon 5]

This cranking over 10-12 times..... I'll wager this is happening after an about an hour or 2 after stopping, but cranking it from cold or immediately after stopping it, it's fine?

 

That's a classic fuel pump sign....or relay 16 (IIRC), the fuel pump relay.

 

When you've ascertained a pattern for this, remove the pump relay and bypass it with a wire and two spades (RW1 will be along in a minute to advise which pins to bridge - or Vince at stealth can tell you - i can't remember) and if it fires up quickly....it's the relay....if it still takes ages, it's the pump.

[Taggart 0]

Sounds quite similar to what mine did, remove the ISV damper and check the bit of foam filter in there hasn't come loose and blocked the pipe. It's a worth trying first as it's free!

[chrishill 0]

I had simular problems, swapped the ECU relay and its fine now, changed the fuel pump relay first but it still stalled. Nothing to say both the ecu and fuel pump relay hadn't got problems i suppose.

[Aus 0]

Thanks all ... sorry, prob an idiot question but where would I find the ECU and fuel pump relays?

 

And I assume the ISV damper is the rubber 'box' by the ISV?

 

Thanks

[RW1 0]

remove the pump relay and bypass it with a wire and two spades

 

Bridge relay 12!! Marked "167", bottom row, right hand side corner. The pins are the 30 to 87 positions on the fuse / relay panel. It does mean the fuel pump is running all the time as this is bridging in the battery 12 volts not ignition 12 volts.

 

It would be better not to do this as fuel will be pumped all the time.

 

More difficult to do. Alternatively run a 12 volt ignition supply capable of at least 20amps load to the fuel pump relay connection pin marked 87 where the pushes into the relay fuse panel. That way at least you can turn the fuel off with the ignition key still and it will allow you to drive the car without flooding it.

 

The only source for this with current carrying capacity is a white plug on the back of the relay fuse panel, bottom row. The middle white one. Pin 4 should have a fairly thick Black wire which will take the electrical load. Check it with a meter for ignition +12 volts before tapping in.

 

Relays on fuse panel by drivers knee behind the removable small pocket shelf.

 

Yes the thing like a small hip flask.

 

.

[Aus 0]

Thanks - will go and investigate

[Supercharged 2]

I think Dinkus has a spare FP relay althoug they are not much from VW...

[Aus 0]

After some good advice (thanks guys) I replaced the ECU relay (cost £11) earlier this week and the signs are promising of the problems gone away ...

 

so thanks for the help and versus what the garage wanted to do, massively massively cheaper and a lot more rewarding!

[Supercharged 2]

Nice one, glad you've got it sorted!

[Aus 0]

not sure I want to be too confident yet but it's all looking good so far ... fingers crossed!