RHarvey

Hi guys. I’ve just bought a 4x4 cosworth which came to me running terribly rough, but it did run! It was apparent that the issue was on cylinder 3. We renewed plugs, leads, cap, rotor etc, and checked timing, still ran rough. It turned out that the fuel pressure regulator was to blame, it was allowing fuel to run down the vacuum pipe and into the intake manifold opposite cylinder 3, and therefore over fuelling cylinder 3, (and cylinder 2 but to a lesser extent). So I removed the vacuum pipe and blocked the vacuum port on the regulator with my thumb while a friend started the car, it ran perfectly! Then cut out after a few seconds.
I have just fitted a new (aftermarket) fuel pressure regulator (the ones that look pretty similar to original but without the adjuster) which is a set to standard (3.5bar) pressure. The car fires, but cuts out after a few seconds. We’ve tried taking the plug off the coolant temperature sensor but this makes no difference. The car is standard in every way.
Any help will be gratefully received!!

RHarvey

I should also add that any attempt to give it some throttle once it starts, also kills the engine.
We can hear the pump working. It’s as if it’s getting enough fuel to start, but not enough to keep it going more than a few seconds…

stevieturbo

http://www.bigturbo.co.uk/

Obviously a large problem here, is you bought this as a non runner ? So really you've no idea if it even should run ?

Get back to basics and check everything, and find out if the ecu itself ( ie chip inside ) is suitable for any other parts fitted like injectors/map sensor.

Test to see what sort of injector pulse width you're getting during starting and if there is still a signal when it starts to stall.
Likewise confirm spark.

GVK.

Not sure if its on a 2wd or 4wd thing but on some Cosworths the ICV plug is the same as an injector and its easy to fit the icv plug into one of the injectors...not sure if its all been apart before or whatever

RHarvey

Thanks guys. Once I’d fitted the fuel pressure regulator, I had the return pipe fed into a fuel can rather than onto the pipe back to the tank to check it was functioning, after fitted it so it fed back to the tank it started running fine, but it now idles at 2000-2500 rpm, then drops to 1600 rpm once it’s up to temperature. If I disconnect the plug on the idle control valve, the revs drop to a satisfactory 900 rpm, but once connected again the revs shoot back up to 1600 rpm. I’ve had the idle control valve out and cleaned/lubed it along with checking spring length so I’d like to think I can eliminate that, Does this indicate now a TPS sensor fault?

stevieturbo

No. It means the engine is getting too much air.

So establish why.

RHarvey

Thanks Steve. So even though the revs drop down to 900rpm with the iscv unplugged, this would still indicate the engine is getting too much air?

stevieturbo

The engine is not designed to be running with that unplugged.

The website I linked gives some basic testing info

Or buy a Haynes manual that will also gvie some info so you can at least ensure things are set up correctly.


But obviously if the idle is too high, the engine is getting too much air. There's no point unplugging things then saying that's better when those things should not be unplugged in normal operation

RHarvey

Thanks Steve. I understand it’s not designed to be ran with things unplugged, but am I right in thinking that if I unplug the iscv and the revs drop down to 900rpm from 2000rpm, this means there is no air leak on the intake anywhere, as surely it would still be idling high with the plug connected or not if there was an air leak. Does it also mean the iscv is working if the revs drop once unplugged?
So I’m thinking that something is telling the iscv to open too much….?

stevieturbo

No, it just means the ISCV has closed when you unplugged it.

I did not say there was an air leak. I said the engine is getting too much air.

that could be an actual leak, it could be the idle valve, it could be the throttle incorrectly opened etc.

I have already given you two references where you can find out how things work and to test. Use them.

ray barker

hello there i had very similar problem on my saff. as said before there is a proper procedure for setting the icv which starts with the base idle and tps values and adjustment. download a workshop manual theres a few links kicking around here, you dont know what others haven't done