VZ U2100 code - Rough Idle

[craigfo]

Hi. I have a 2005 VZ V6 LEO and the issue I have is that it will start and run smooth but after a couple minutes it will drop revs to around 725 RPM and shake like it’s about to stall. Once warmed up there are no issues. The scanner came up with code U2100 and it’s got me a bit stumped. I’ve cleaned the MAF sensor with no luck and not sure where to go from here. Has anyone got any clues to what the problem is? Thanks

 

[Fu Manchu]

Make sure it’s not a KnN air filter. Just use paper.

Is it a genuine MAF sensor?
Is the plug at the MAF in good condition? Is the wiring in good condition?

Vacuum leaks. A smoker will find them. It will find them all. Vacuum leaks can happen when cold until heat gets into things, they expand a bit and seal up enough. Or hoses can soften a bit with heat and seal up.

Are all the hoses soft? Are they tight? Can they be twisted easily on the barb? Intake plenum gasket, is it paper or metal with a seal? Was the intake torqued down to 23-25Nm?

Is the PCV blocked?

 

[Fu Manchu]

Disconnect the negative terminal.

Go through all harness earths. There are quite a few in the engine bay. Two on the right hand head. One on the left hand head. Undo them. Check for corrosion. Clean the threads. Clean the contact surfaces. Retighten up.

There is a little 7mm bolt that earths the ECM. Clean that one.

Theres a major earth point behind the battery on the inner guard. Clean it up as well.

Make sure the plugs for the ECM are clean. Undo them, spray CO Contact cleaner in. Let it dry. Carefully reconnect them. Make sure the lever is down and the plug is snug.

Clean the main Earth terminal. Make sure the Earth is tight when reconnecting.

 

[Fu Manchu]

Has the battery been out recently?

Is there a background story we should know about?

 

[lout]

U2100
what is not original in the way of computers/instrument cluster

 

[craigfo]

U2100
what is not original in the way of computers/instrument cluster

Replacement ECU from P.E.C a couple months ago but had no issues until recently. No vacuum leaks, replaced O2 sensors, cleaned MAF and PCV… I’d sell the POS if it didn’t owe me so much money.