Idle valve blew a step driver?????

[smurfinator]

this morning was not good.  The car is back on the road after a year and was behaving very well until now.

stone cold startup and it fired up fine as normal.  It ran for maybe 8 seconds, then the laptop computer beeped and all went dead.  Car would not restart and computer would not see the VEMS.

Turns out the VEMS main 5 amp fuse was blown.  I replaced that and the car started but died after 3-5 seconds.

Much fiddling confirmed that the idle valve was no longer working.  The idle valve is on a switched 12v+ circuit with the fule pump but has it's own 5 amp fuse on the power line after the relay bus.  This fuse did not blow... the VEMS fuse did. 

The engine is a 1998 north american Audi ABZ V8 using the stock idle valve.  Andy Hills has the same setup and I copied his numbers. on S259 i3.

SO, QUESTIONS:  Should I find a 3 amp fuse (could not find one at 2 stores when I looked) before I try to hook up the idle valve to another stepper output?  What might have caused the blowout?

Why does VEMS hate me?  Jorgen pronounced my ground wiring to be "textbook".

[GintsK]

Did you get back VEMS to comunicate?

Bosch 2-pin idle valve? I don't think this is good idea run it from stepper output. Current is close to maximum and there can be heat problems from flyback (external diode for IACV?). No any IGBT chanell free?

Gints

[smurfinator]

Did you get back VEMS to comunicate?

Bosch 2-pin idle valve? I don't think this is good idea run it from stepper output. Current is close to maximum and there can be heat problems from flyback (external diode for IACV?). No any IGBT chanell free?

Gints

8 cylinder with direct ignition, so nothing free.  HIlly is using this setup and didn't mention any flyback or diodes needed.  Could I have an earlier hardware version that is lacking something?

[PeepPaadam]

Funny, I've used stepper output to drive Audi s6 4.2 V8 idle valve and it's been working for almost two years now wihtout any problem.

Reason is because all of the ign and inj outputs are in use.

I remember Jörgen once mentioned that the idle valve can be driven through stepper output as current would be maximum when valve is fully opened, but on normal use it wouldn't be any problem.

[rob@vems.co.uk]

You need to limit the current that the stepper chip is driving, they can only handle 1A IIRC so the resistance of the coil shouldn't be less than 14 to 15 Ohms...

[PeepPaadam]

IIRC the resistance of the valve was 16ohms.

[smurfinator]

I just measured the 2 pin bosch idle valve at 9 ohms.  So.. that is bad?

Should I throw in a large 8 ohm resistor?

Since Stepper A appears to be smoked, would other stepper channels be smoked as well or can I just use another one when I get a resistor?

Thanks!

[smurfinator]

arrgh!  I moved the idle signal to Stepper C and the found a 13v signal coming so I assume the stepper chip is OK - HOWEVER, the car does not respond when I change the idle speed under 'basic idle settings'.

It does not seem like the valve is doing anything, as when I blip the throttle, the speed falls way down to 500rpm before bouncing back.  I have changed no settings since it was working perfectly yesterday.


Any ideas what could be going on there?  The engine is warm so I can't be 100% sure what is happening, but pretty sure the idle valve is not doing anything.  Still measures 9 ohms so it can't be broken, right?  Or can it?


I found a 20 ohm resistor but that is probably too high, right?

Bugger this, I should lease a new Toyota.

[smurfinator]

F****K!!!! guys HELP!

When I connect the idle valve, the engine now slows down and dies!

I have not changed anything!

Yesterday it worked perfectly and today it is totally fvcked!  It won't even start now - it floods every time and I have to pull out the injector fuses to clear it.

What could have happened? I am ready to kill somebody here.

[lugnuts]

I'm not sure what idle valve you have. If you have the two wire external, they have a strange setup to them.

Unpowered, (or at 0% duty) the valve is slightly open - to allow the engine to idle.
As the duty % increases, the valve first Closes, then eventually Opens back up and then up to 100%.

I use an IN4007 diode on these type valves and have a pretty good control of them.

It sounds like when you plug the valve in, it is closing and causing the engine to die?

Try holding the throttle blade slightly open, hold the engine at ~1500 rpm or so, then connect the ISV and see if it stays running. If not, then something may be electrically wrong.


Also, there are two spare "injector" outputs in the VEMS, one of which is used for the Wideband O2.
Is it possible to use the other one for the ISV on the V8 cars?

[smurfinator]

I'm not sure what idle valve you have. If you have the two wire external, they have a strange setup to them.

Unpowered, (or at 0% duty) the valve is slightly open - to allow the engine to idle.
As the duty % increases, the valve first Closes, then eventually Opens back up and then up to 100%.

I use an IN4007 diode on these type valves and have a pretty good control of them.

It sounds like when you plug the valve in, it is closing and causing the engine to die?

Try holding the throttle blade slightly open, hold the engine at ~1500 rpm or so, then connect the ISV and see if it stays running. If not, then something may be electrically wrong.


Also, there are two spare "injector" outputs in the VEMS, one of which is used for the Wideband O2.
Is it possible to use the other one for the ISV on the V8 cars?

Yes, to wire, external-ish... integrated into the throttle body but the round can us external.  Anyway, it's weird because it worked fine up until this morning and now it's kerflooey.  Jorgen said I had no extra 7A outputs on my board, but I got a hardware build version since he said that.

[smurfinator]

I just tested the valve itself with a 1A 12v supply and it opens just fine.  The VEMS is supplying 13v at the plug through a 3amp fuse (formerly 5 amp) and the numbers in the Basic idle settings have not changed.

What the hell is going on?  Anyone?

[GintsK]

arrgh!  I moved the idle signal to Stepper C and the found a 13v signal coming so I assume the stepper chip is OK ......

Unclear statement! Normally your non-ecu side of IACV must be connected to Ubatt. If chip didn't do anything (e.g. fried or misconfigurated), you have Ubatt on this ecu pin.

Also take a look here regarding diode:
http://www.vems.hu/wiki/index.php?page=MembersPage%2FPeterJensen%2FAudiSidle

Diode give better control and in addition unload driver.

Gints

[smurfinator]

arrgh!  I moved the idle signal to Stepper C and the found a 13v signal coming so I assume the stepper chip is OK ......

Unclear statement! Normally your non-ecu side of IACV must be connected to Ubatt. If chip didn't do anything (e.g. fried or misconfigurated), you have Ubatt on this ecu pin.

Also take a look here regarding diode:
http://www.vems.hu/wiki/index.php?page=MembersPage%2FPeterJensen%2FAudiSidle

Diode give better control and in addition unload driver.

Gints

NOWwww, they tell me... 

I was running the valve without a diode, one pole to a stepper chip output (inverse) and one to relayed 12v+ with a 5 amp fuse.

I just took the case apart and the stepper chip is smoked and cracked, overpowering the delightful aroma of my morning tea with it's powerful carcinogenic stench.

My v3.3 does not have #5 digital 7A output so I've ordered some bits from the vems shop (including diodes) and will sit here fuming until they arrive.

BUGGER FLAMING ARSE LIPS SODOMY!!!!! I'm going to go look at Toyotas today.

Thanks for the help, especially Andy, who answered my email poste haste with pictures and everything!

[lugnuts]

Sorry for the basic question, but I was un-aware the Stepper outputs could even pull a ground?

I thought when you invert the output, it changed OFF to ON, and vise versa??? Am I nutty?