My Focus RS is not holding full boost and misfires between 3500-4000rpm its only since i was driving it home straight after buying it the temperature light came on and i descovered a water leak which is now sorted!

HELP FOLKS

 

MK1 RS (Zetec Turbo) or MK2 (2.5 Turbo) mate?

 

If mk1 leads or coil pack.

 

pull plug leads out and see if they are wet, its quite common for the two core plugs next to the plug holes to leak coolant wetting the plugs and leads which causes missfires under load

 

its a mk1 focus rs i did check all the plugs

 

im thinking its maybe boiled the engine and the heads warped is this a possibility?

 

Plug leads and coil pack..... My first one did this years ago when a lead was breaking down.

 

Can be the map lots of people complain about this on rsoc, there are many threads relating to the first OE map and the later AE map which apparently got rid of this issue.

 

Other way round, early AE map had cold start issues, later revised AF map had a 4K "cough". It's only a brief missfire, some cars do it some don't.

First things to check are plugs & leads, check the plug gap and gap as necccessary. I run at 0.7 gap, any more than that gives a missfire on boost. There's lots of debate on what plugs should be used, some tuners recommend using std Ford plugs, some prefer Denso Iridiums. I tried the Iridiums in mine and had no probs but there were a few people who had problems with them dropping the centre electrode, probably caused by ham-fisted gapping technique more than a fault with the plug, I switched back to std Ford plugs and have had no problems running 300+.

Also, as you don't know the history, I would check how much boost you're running, connect up a temporary boost guage if necessary.

 

Known as the 4k cough,

What maps it running?

Also if the high temp light has come on im sorry to say you need to get the hg done,

As std they run about 112 degress,
The high temp light dont come on until 118 degs

 

Its totally standard and iv tried holding the foot down, its back in the garage as it has warranty so they are going to try a few things

 

Is there an easy way of checking what map an RS is running?