Mk3 1.8 petrol
Still trying to clear the intermittent poor cold start and hesitation. TMAP and engine coolant sensor changed, plugs 6000 miles old. IACV and throttle valve cleaned. Cold starting has been good over the last couple of days, but it was a pig this morning (temperature a bit lower). The IACV works with a "thunk" if I wire it straight to the battery, there appeared to be an intermittent 12v supply at the connection to the IACV and the wiring to the connector plug looked dubious. Me, my trusty side cutters and my soldering iron improved the connection to achieve a consistent 12v, I won't know till tomorrow morning if the problem has been cleared, but the IACV still doesn't "thunk" when energised, suggesting a high resistance connection further back in the wiring.
However, this doesn't fully match the symptoms, the hot idle is always good, cold idle also good when it starts. So, if all the IACV does is control idle then it's working OK. But if it also controls cold start and transistion over low rpm then there it might be the cause of the problem. Is there anything else that alters the amount of air admitted to the engine during cold starts?
I've rechecked the fault codes, now shows none (thanks Paul Young).
At this rate, I'll be paying someone to look at the thing

Still trying to clear the intermittent poor cold start and hesitation. TMAP and engine coolant sensor changed, plugs 6000 miles old. IACV and throttle valve cleaned. Cold starting has been good over the last couple of days, but it was a pig this morning (temperature a bit lower). The IACV works with a "thunk" if I wire it straight to the battery, there appeared to be an intermittent 12v supply at the connection to the IACV and the wiring to the connector plug looked dubious. Me, my trusty side cutters and my soldering iron improved the connection to achieve a consistent 12v, I won't know till tomorrow morning if the problem has been cleared, but the IACV still doesn't "thunk" when energised, suggesting a high resistance connection further back in the wiring.
However, this doesn't fully match the symptoms, the hot idle is always good, cold idle also good when it starts. So, if all the IACV does is control idle then it's working OK. But if it also controls cold start and transistion over low rpm then there it might be the cause of the problem. Is there anything else that alters the amount of air admitted to the engine during cold starts?
I've rechecked the fault codes, now shows none (thanks Paul Young).
At this rate, I'll be paying someone to look at the thing