Hello. I hope I'm on the right forum.
I'm English living in Spain with a 1999 F53 V10 motorhome on 65,000 miles.
It has always run perfectly, and been well maintained. It is dual fuel gasoline/LPG. Unfortunately, there's no-one here who knows about these motors, and I have to order parts from the USA, and get information from the internet.
A few weeks ago, when driving to southern Spain for the ferry to Morocco, I got a misfire and power loss, so came back home.
The problem was on both gas and gasoline.
Bought a scanner, which diagnosed Nº 1 misfire and excessive EGR flow. Fitted new plugs, boots, one coil, and fuel filter.
This cured the misfire and now I have no codes, but the engine runs very rough on idle when cold, although it is OK when hot and drives perfectly.
These comments apply to running on both gas and gasoline.
I assumed the excessive EGR code was due to something in that system. I have checked all of the EGR sytem components according to Alldata. All seems fine except that the EGR DPF sensor voltage increases from 1.05 volts key on to 1.35 volts engine on. Is this enough to cause the idle problem? The EGR pipe to the EGR valve gets only slightly warm on startup and idle.
I have also checked the IAC and cleaned the MAF sensor.
There is no water loss or oil in water or water in oil.
When it is rough idling cold, the tailpipe sounds as though it is missing on more than one cylinder and there is more steam than I think is normal.
I don't want to use it like this in case I am doing damage.
I presume someone will suggest head gasket or air leak but I can't find any evidence!
In desperation, I am about to order new EGR components!!!!!!
Please can anyone suggest why this poor cold idling motor turns into the smooth thing it should be when hot?

 

Just a couple of suggestions. Sounds like lean condition when engine cold.
-Check water temp sensor giving false signal engine is warm when it's still cold.
-O2 sensor running engine lean.
-EGR valve letting exhaust gas leak in while engine idling cold. The engine needs more volatile air/fuel mixture.

 

Wouldn't you still get a code if you have an EGR valve problem?

I would double check the IAC valve again. Clean it real good or replace if necessary.

 

Thankyou both for your replies and suggestions.
I have looked into them and rechecked everything else, but still the same. I agree that something is sending a wrong message when cold, but I can't find it!!!
Because I can't just go down to a local Autozone or similar, I have had to take a chance and order some possible suspects online from Rockauto.
Thanks again.
Peter