Running on less than 8 cylinders until warm

Hi all,

My Mondial T is confusing me even more now. When I start her up she has poor idle and I think less than 8 cylinders, although it sounds okay. I say less than 8 as I am pretty sure it is more than 4 as I doubt she would run much at all. Then after a period of time as she warms up to more than 70, she will suddenly pick up and run absolutely fine from then on. It is literally like a switch has flipped. It seems to be on Left hand bank. The left hand bank Idle Control Valve is new and does buzz with engine off and ignition on whilst the right hand does not…

I have already installed new spark plugs. It’s strange because it feels like something gets warm and overcomes resistance and then connects and all is well with the world once more and from then on until the next cold or less than 70 degree start.

My suspicions are:
Relays for fuel pump and injection - but I found a new spare and went through all of these with no change - although they had dirty connections which I cleaned.
Ignition coil or Control module - I have a new ICM coming
Ignition switch wires - but today I did a few starts whilst troubleshooting and had no difference.
Idle Control Valve - but then it feels like limp mode at all revs

Anyone else had this issue?

 

Thanks for responses, not getting any slow down lights (actually never seen them, must look to see if there are any bulbs in them).
The cam thing that is like a distributor I think feeds both banks, so would affect both.
I have thought about crank sensor, but those are newish.
I know the Ignition Control Module gets hot in normal operation, so perhaps that is failing and as it gets hot it overcomes resistance.

Thing is that it has been warm here and let her cool down on a hot dry day and the failure point will return even though there is no damp or humidity.

 

Well I fitted the Ignition Control Module today and no change. A new Bosch coil is arriving tomorrow, but I am beginning to think it is not reducing cylinders, just more like a limp mode kind of thing.

Today as she was warming up, I disconnected one MAF and no change so plugged it back in, then disconnected the other and she shut down. Then on restart she had cleared and was running good - may have been a coincidence that it cleared just as I unplugged the MAF, I will try that tomorrow. I will also do the ECU reset tomorrow too.

I tightened the alternator belt today too and noticed the idler pulley was not square with the belt. I think it is time for a new bearing as it is squeaking and there seems to also be no adjustment range on the belt either, it’s a newish belt, but I suspect it is too long (8pk… Dayco). I have to tighten the pulley to full to get some tension on the belt. The bracket has been repaired at some point and looks fine.

 

Well I thought I would get my phone, do a cold start and record each exhaust so I could put the audio in a editing software and see if I have a misfire or if it is some sort of slowdown limp mode thing or problem with reduced power. Anyway the Ferrari or the great simulation must have seen my plan and determination and thus she started up fine with no issues…
Anyway when the issue returns no doubt at a most annoying moment, at least I will have a better starting point.
One slight thing I just noticed, the balance throttle valve in the plenum between the two chambers was kind of stuck. I worked it with pliers gently and sprayed some WD40 on the linkage and now that is all free again.
In the meantime I am still getting air in the cooling system which may be a leak before water pump or my heater system valve preventing full bleeding of the system. I may bypass it for now.