Too lean

[wettrackday]

Hi there, can anyone help me ? I have a 1991 cosworth sapphire which has sat in my garage for many years now, it used to be my daily drive. It has always ran a little lumpy because it runs so weak 0.12% to be exact. I know it has been chipped some time in its life, fuel pressure is 3.5 bar with vac disconnected which is correct. I have tried turning the screw on the ecu to richen up but don't make any difference. Any ideas anyone ? Help ????

[stevieturbo]

So the car has sat in the garage and not been run for several years ?

There could be a load of problems.

You may need to inspect the inside of the fuel tank, fill with fresh fuel if it's still clean, have the injectors cleaned and tested.

And then take the car to a competent tuner to make sure it is safe to boost.

Mark at MADevelopments wouldnt be a million miles away from you. Or ask over on PassionFord to see if there is anyone closer

[wettrackday]

Sorry forgot to say I did drain fuel and fill with fresh. I am thinking along the lines of the ecu being the issue as its what controls the fuel mixture etc.

[stevieturbo]

wettrackday said:

Sorry forgot to say I did drain fuel and fill with fresh. I am thinking along the lines of the ecu being the issue as its what controls the fuel mixture etc.

I would say the least likely thing to have a problem is the ecu.

Exactly how long was it sitting for ?

[davepoth]

My bet would be the "chip". If it's sufficiently old school, it'll have been done with a piggyback tuning box, which takes the sensor inputs and doctors them so the ECU gives a different response to the various systems.

The obvious thing is to unplug that and revert to standard tune.

[wettrackday]

The car is only used once a year to drive to mot station. Can the chip in the ecu just be unplugged then ? Surely it would have to have the standard reinstalled ? It does have the piggy back system as far as I can tell with the small board and chip on top of the main one inside the ecu. I have always been suspicious of this as its always ran weak. This chip is what controls the fuelling isn't it ?

[stevieturbo]

Rather that starting to suspect the least likely option which you have no real way of testing itself, ie the chip

Try some basic diagnostics

ie, check fuel pressure, check mixture, inspect the plugs.

If the car has sat for a long time, it isnt uncommon for the fuel tank to rust and this rust in turn blocks the fuel pickup.
And it isnt also uncommon for injectors to have problems if left unused for very long periods.

[wettrackday]

I have tried a set of 803 s which I had (brand new) and also as said previously tested fuel pressure and is ia 3.5 bar on idle with vac disconnected i am thinking chip. Any other thoughts appreciated !!!!

[stevieturbo]

The screw should make a difference as far as I am aware.

Although if it has always run weak. Who initially installed the chip and set it up ?
Or was there no proper setup ever done ?

Or is this a new problem of running even worse than previous ?

Also, ask over on PassionFord, there will be more people familiar with that stuff there.

[wettrackday]

I don't know who installed it as it was done before I bought it. I will have a chat with the bloke I bought it from to see if I can find out anymore info. I will also check out the fuel tank theory, many thanks .

[stevieturbo]

wettrackday said:

I don't know who installed it as it was done before I bought it. I will have a chat with the bloke I bought it from to see if I can find out anymore info. I will also check out the fuel tank theory, many thanks .

If fuel pressure is fine, then it's less likely the fuel tank is a problem.

What are the plugs like ?

[wettrackday]

Yes I think I might still have a look though, have had the plugs out and put a new set of standard ones in. Exactly the same. If I wind the fuel pressure up it runs well but only when it approaches 9 bar, obviously that's not a solution.

[stevieturbo]

wettrackday said:

Yes I think I might still have a look though, have had the plugs out and put a new set of standard ones in. Exactly the same. If I wind the fuel pressure up it runs well but only when it approaches 9 bar, obviously that's not a solution.

It could be any number of things. Obviously is is lean. But you need to establish why.

It would be better to take it to someone who can interrogate the ecu to read all sensors etc
You could maybe go around testing them manually, but it would be very slow and you'd need to know what values to look for.

Or do those old ecu's give out flash codes of any kind ?

[wettrackday]

I have done a scan on it after finding my old mt2500 scanner and there is no codes present. I have tested all sensors in the past did have a problem with the throttle position sensor so replaced that a couple of years ago. Might run through them all again though. Will keep posted on progress.

[stevieturbo]

Didnt think the likes of that would even communicate with such an old vehicle.

If it does, does it not offer live data ? Really that's what would be most useful

[neiljohnson]

Is this a green top engine??

[wettrackday]

Hi, no it's the non catalyst red top engine.

[neiljohnson]

wettrackday said:

Hi, no it's the non catalyst red top engine.

That blows my theory then

[wettrackday]

Lol !