Hi, have an annoying misfire when engine had warmed up, 40 -50mph particularly bad. I changed the injectors, WUR, AAV, plugs, fuel filter, fuel pump. I'm at a loss as what to do next. Starts fine, idles fine. Any help is appreciated. Cheers

 

Checked the RSi ignition AND injection wiring diagrams.

Although the K-Jetronic is basically the same as in the XR3is, it works a little bit different because of the unique RSi iginition ECU.


First of all it sounds like a fueling problem, so let's start with this:

CO is set correctly? 0,6 +/- 0,2 @ 950 RPM

Forget the AAV. This will just let a small amount of air pass by the throttle body, especially when the engine is cold. So you'd have your engine cutting out when cold or running at about 1200-1400 rpm when warm.

Warm-up regulator sounds better. Have you changed it for a new one? Used ones might have the same problems. So the first thing to check is the K-Jetronic control pressure. This should be at about 0,6-1,1 bar when the engine is cold (10° C) / 1,1-1,5 bar (20° C) and it should be at about 3,4-3,8 bar when then engine is fully warmed up.

Pressure not ok?
Find out why. As the warm-up regulator is both operated by voltage AND coolant it's usually reliable as long as the bimetal strip inside is still working. When the engine is running, you should have 12V at the connector and when the engine is warmed up the mounting plate (which is connected with hoses to the thermostate housing on one side and the heater matrix on the other side) should be as warm as the coolant is. With 12V at the plug AND a hot mounting plate and the control pressure still too low... get a working warm-up regulator.
-> Pressure not ok and no voltage? Check for the wiring, both auxilary air device and the warm-up regulator are connected to pin 87 at the engine pump relay. (red/black cable)
Pressure ok?
Not it gets trickier. There COULD be a problem with the the thermal time control switch. This controls the cold start valve. It's only operated when the engine temp is below ~55° C and only for a few seconds after the engine was started. If it's stuck, it might let the cold start valve inject additional fuel to the inlet all the time making the engine run too rich when warmed up. The cold start valve itself could be broken and being open all the time. Check both things.

other fueling issues?
I don't think there's a major problem with the fuel distributor/metering head as the engine is running fine when cold. With broken gaskets/seals inside the distributor I'd expect your engine to have the same issues warm and cold.


Ignition issues / problems with the ECU
The RS1600i has two coolant temp sensors. Both sit in the flange between the cylinder head and the inlet manifold. The thermal control switch is mounted horizontal while the ECU's temp sensor is screwed in from the underside on the opposite side of the coolant hose connector. Check the voltage cold/warm.
With the values from the temp sensor the ECU controls the ignition map and the fuel cut-off.
Forget the ignition maps. There are only two maps for full throttle and nearly full throttle @ above 105°C to prevent engine damage at high temperatures, the ignition is retarded for a few degrees at high revs.
Deceleration fuel shut-off might be an issue. It works when the engine is warm (no clue when for the RSi, but usually above at least 50-60°C), revs are above ~1200-1500 rpm AND the trottle body is closed. There could be an issue with the throttle switch, the wiring, the shut-off valve or the ECU itself. Just disconnect the cut-off valve from the air duct, blank the opening or the hose and try again. Now you just have to find out if it's the switch, the wiring, the valve or the ECU.

These are the most common problems with a warm engine, provided that the engine runs fine when cold. Does it? You don't have to push it too far, but going flat out up to 4k and more is fine???

There might be other issues that can cause an engine to run bad when getting warm. Electric resistance might cause some problems. When cables get warm, resistance rises. This might result in sensor readings getting wrong, ignition is not working as it should etc. But first try to check the obvious things I mentioned above.


IMPORTANT: You're using the correct spark plugs? Ford AGPR 902C or at least NGK BCPR9ES-11? Gap is 0,75 mm. Ignition coils/leads/plugs are fine and nothing is loose?