Erratic Idle.. Bouncing revs

[TT Tim]

Morning All,

I've been doing a fair amount of work on my son's new '05 E85 2.5.

All was going well, PCV changed, DISA valve upgraded, Throttle boot replaced, water-pump, rocker cover gasket, pulleys, tensioners, belts, plugs etc etc, the list goes on on this much neglected car.

All was going well, engine running sweet as a nut after all the fettling. Until the revs randomly started bouncing between 1100 and 1200, rather than a steady idle. This started as the car was idling very normally.

I have tried to reset the error. 002796: DME: Throttle: adaption values incorrect.

It has reset and the car has run smoothly, but once you turn it off and restart the problems has returned.

It also seem that I now have a Can-bus error.

005E18: ABS-DSC: CAN data fault from DME/DDE

I was capturing input to the DME through MS45QuickFlash, when the error started again.

https://docs.google.com/spreadsheet...oDLO_WVZStz/pubhtml?gid=566847064&single=true

You can see from the red line, when the problem kicked in.

I was concerned that the IGN retardation stopped, but that seemed to be about all. The throttle position seems to be static at 18% but I have checked that was another OBD reader and it does seem to be moving when the pedal is applied.

So, my question is: What are the main potential causes?

I have: DME, Throttle Body, Crank/Cam position sensors.

What are your thought?

Thanks, in advance

https://imagekit.io/tools/asset-pub...Dje2b6HK1KyHtsVQW7bIBVYRJijHiYJNB2TXGgiDA__"}

 

[colb]

Take the idle control valve out and wash it out with carb cleaner until it rattles when you shake it in you hand. Refit and see if idle improves, they do get gummed up and can be a side of what you are experiencing.

 

[TT Tim]

Update:

I've done a fair bit of Googling, this problem seems to crop up a number of times, I even have one person contact me to say they've had this problem for 1.5 years and still haven't sorted it! That sounds very depressing to me!

What I changed yesterday to try and eliminate potential causes:

New DME
Throttle body
ICV
DISA
MAF

Yesterday I changed over the DME and the car ran beautifully, on 2 cycles of the ignition, then the problem returned!

Next I'm looking at:

Crankshaft sensor.
ABS ECU <-- one person said that was a cause.

Can I please have any other suggestions.

Could it simply be a break down in the CAN-BUS wiring?

All help most gratefully received.

Thanks

 

[FunkyGBrown]

Idle control valve, give it a clean and it'll likely sort the issue.

 

[TT Tim]

Idle control valve, give it a clean and it'll likely sort the issue.

It’s had a brand new ICV. That didn’t fix it.