I have a 1989 2wd sapphire cosworth and I still have a pretty bad flat spot when the engine is cold,it pretty well clears up after about 10 minutes of blipping the throttle.I`ve changed the injectors (new),map sensor,ignition module,temp sensor,air temp sensor,spark plugs,dizzy cap and rotor,fuel pump and filter,crank sensor,coil,adjusted the phase sensor gap,It`s got good fuel pressure.It`s running a brand new bayjoo stage 2 chip,rs 500 intercooler,md308 turbo.PLEASE HELP.Getting desperate (supposed to be competing in a hill climb this weekend.)

 

Almost defo a fuelling issue, or just a naff chip, badly written one, try richening the mix overall, or you may just have to put up with it not having a easily adjusted ecu/chip.
Have you rewired the fuel pump ?
tabetha

 

Thats a chip for a T34 on a 500bhp turbocharger mate!
Are you running 803s as well?

 

Stu,It ran perfectly well prior to me crashing the old car.It ran good figures on the dyno and air/fuel was spot on.I used it with this set up for the last 2 years.I know the turbo has the potential for 500hp but all i`ve done since the accident is put everything onto a new shell,same chip and engine harness etc.I haven`t re-wired the fuel pump circuit yet because I`ve got 12.6 volts at the pump.Could it be the engine harness ?If so which sensor wires could cause this ?

 

Is that 12.6 volts under load, or just idle!!
tabetha

 

That`s 12.6 volts at idle.I checked resistance values between ecu plug and various sensors today.All seemed ok and within the allowable range except for the ignition module which gave a reading of 11k ohm and the resistance between the coil low tension wires was 2k ohm.I changed the ignition module over to the one which read 26k ohm and the resistance went up to over 5k ohm at the coil lt wires.But it made no difference to the flat spot.I removed the air temp sensor plug and then started it.It ran rich for a moment and the flat spot disappeared for 2 or 3 blips of the throttle and then it returned.I then replaced the air temp plug and removed the coolant temp sensor plug and tried to start it,it fired once and wouldn`t start.Again ,once it reached normal operating temp (about 10 minutes) the flat spot went away.I put a stage 1 chip in just to try and no flat spot at all from cold,sound like a fuelling issue, what do you think ?

 

It defo sounds like a fuelling issue, but as eluded to by stu, if the chip is not for the parts you have fitted it will have fuelling issues, rather than being a duff chip it is the wrong one.
When you check the pump voltage it needs to be from the pump terminals themselves ideally UNDER load though, your apparent good voltage could drop drastically once hot, but I don't think it odes or you would have other issues.
tabetha

 

Problem solved,after trying 2 duff ecus and replacing all sensors,wiring,etc.tried another ecu,perfect.What are the chances of 2 ecus giving the same issue ?live and learn ,at great expense.The upside is that I`ve got plenty of spares now.Thanks to all who offered some great advice.