Hi aol as you know iv turbo the 1242 8v engine using MF2

Still having a few running issues...now when the engine warms up it cuts out...it'll slowly develop a misfire only a slight one then just stall...but I realised if I unplug the MAP sensor wire it looks perfect son as MAP sensor is plugged back in same problem??...id of thought that the car wouldnt run without the MAP sensor tbh but it runs perfect

This is off boost in tickover problem it revs abd rubs fine just when warm it will not tick over...any ideas?? Btw iv changed MAP sensor it made a difference before it would cut out when cold bow when warm lol

Update...it's literally just the map signal wire causing the problem.l

It runs for around 2 mins them starts to try and stall then does an instant stall like someone turning the key off??

If I leave the sensor plugged in and cut the MAP signal wire it runs perfect and drives perfect...the sensor wire itself is giving 1.40-1.50v on tickover and even when it's about to stall still the same voltage...iv changed MAP sensor again now

Iv stripped the wiring back no damage ti it the signal is coming from the sensor I tryed to hook the signal to a 3bar cosworth sensor at 0.90v on tickover but it stalled straight away soon as I turned key it turned back off

It's. Not running on boost it's on tickover so I can't get my head round why it won't work...it worked in the old engine all iv done is swap engines no ECU or wiring?

I can't get why it runs fine without the signal wire on though...will it be ok to have it on rolling road set up without the signal wire connected??

The MAP sensor has a 5v reference voltage supplied to it (IIRC) - check that that is stable.

arc said:

The MAP sensor has a 5v reference voltage supplied to it (IIRC) - check that that is stable.

Click to expand...

The 3 bar cosworth sensor has a solid 5v reference voltage but the standard MAP sensor has a 4.75-5v reference...but it always did have even with me old engine and it worked fine on that

where does the reference voltage come anyway so i can check that?

or can i just bypass the wiring from my 3bar cosworth map and use that 5 volt reference for the standard one?

It comes from the ECU. I don't recall which pin. The same feed goes to the TPS as well though iirc.

arc said:

It comes from the ECU. I don't recall which pin. The same feed goes to the TPS as well though iirc.

Click to expand...

Cool I did take ecu off to check pins for corrosion but there fine...errm im goin give the reference wire a 5v supply see if that helps it

Probs from second maps sensor il checkTPS signal aswel make sure that's not playing up lol

From where

Be careful, you'll introduce ground loops and upset everything if you're using a different power source.

Is your ECU OBD2? Plug something in and look at what pressure the MAP is reading.

arc said:

From where

Be careful, you'll introduce ground loops and upset everything if you're using a different power source.

Is your ECU OBD2? Plug something in and look at what pressure the MAP is reading.

Click to expand...

42Kpa on tickover and when it stalls

Why is the reference voltage low ECU f*ked??

I was going to add the reference from the MF2 as that gives a reference to its own MAP sensor the cosworth one im mentioning

What's been done to the engine, is it low comp? It might be stalling because the ECU doesn't know what to do.

I take it you have checked your vaccum lines? To check reference voltage turn off ignition pull apart the MAP sensor 3 pin plug, put a volt meter accross terminal A B or 1&2, turn back on the ignition and you should have a steady 5v, if this checks out I would suspect your problem lies elsewhere and should pay particular attention to the closed loop sensor componetns i.e engine coolant temp sensor (ECT) and lambda sensor. Get the vehicle up to normal operating temp and disconnect the lambda, if the problem is not apparent while disconnected I would suspect the lamda sensor is not working or is tierd and not giving a fast enough voltage switch. For around £7.00 change the ECT to rule it out. You can test both these sensors but not realy worth the effort without a scope or a way of measuring temp such as a infer red temp reader. The poster above makes a valid point and check all the sensor connections are clean and in good order.

Another potential problem is the crank sensor, the clue is in the engine being hot. When the coil winding within the crank sensor is breaking down heat will cause it to lose its crank ref and stop fueling.

arc said:

What's been done to the engine, is it low comp? It might be stalling because the ECU doesn't know what to do.

Click to expand...

yh its lower compression ratio, ported head, lightened and balanced bottom end, P75 cam reshimmed and valves relapped...it shouldnt make that much difference to have the engine stall ONLY when warm aswel when temp gauge shows half

it should run of stock ecu with those changes tbh

spedo said:

I take it you have checked your vaccum lines? To check reference voltage turn off ignition pull apart the MAP sensor 3 pin plug, put a volt meter accross terminal A B or 1&2, turn back on the ignition and you should have a steady 5v, if this checks out I would suspect your problem lies elsewhere and should pay particular attention to the closed loop sensor componetns i.e engine coolant temp sensor (ECT) and lambda sensor. Get the vehicle up to normal operating temp and disconnect the lambda, if the problem is not apparent while disconnected I would suspect the lamda sensor is not working or is tierd and not giving a fast enough voltage switch. For around £7.00 change the ECT to rule it out. You can test both these sensors but not realy worth the effort without a scope or a way of measuring temp such as a infer red temp reader. The poster above makes a valid point and check all the sensor connections are clean and in good order.

Another potential problem is the crank sensor, the clue is in the engine being hot. When the coil winding within the crank sensor is breaking down heat will cause it to lose its crank ref and stop fueling.

Click to expand...

iv checked all vac pipes there is no vac leak, it ticks over perfectly, it still struggles to start though have to press throttle fully down to have it start otherwise itll just keep turning over and trying to start but not firing properly...the ECT sensor is brand new, i used the crank sensor of the new engine instead of swapping with my old on which i should of done as i knew the old crank sensor was fine

The lambda sensors should be working fine tbh but il have to check these

its just weird soon as i cut the MAP signal wire it runs perfect...if im not getting 5v reference voltage on ignition then whats the problem the ECU??

im sure i get 4.97v on ignition i tested...the map sensor and air temp sensor are one sensor on these cars 4 wire sensor

i too think its the crank sensor tbh...i dont know why the map wire is effecting it but i have a strong feeling its the crank sensor...although i changed the trigger wheel and crank sensor the other day they were spares i had laying around so wasnt sure if it was a good sensor or not

what about the cam position sensor can that cause a problem too??

All the ECU switching is through the earth connections so you will need to check all your earthings are good. Also check the crank sensor pin 2&3 should give 575-782ohms. Other things to check are the Intake Air Temp Sensor (IAT) the Idle Air Control Valve (IAC) and the Throttle Position (TP) Sensor. It could be so many things, if you can smell petrol it may be the EVAP Purge Valve or poor fuel pressure to faulty injectors. The worst case would be the ECU, check the harness for security and and clean connections.

spedo said:

All the ECU switching is through the earth connections so you will need to check all your earthings are good. Also check the crank sensor pin 2&3 should give 575-782ohms. Other things to check are the Intake Air Temp Sensor (IAT) the Idle Air Control Valve (IAC) and the Throttle Position (TP) Sensor. It could be so many things, if you can smell petrol it may be the EVAP Purge Valve or poor fuel pressure to faulty injectors. The worst case would be the ECU, check the harness for security and and clean connections.

Click to expand...

all them sensors were lifted off old engine fair enough i know they can go faulty...just odd to have only done so when changing over some are untouched like TPS and IAC and MAP

il try sort summat out...il try a new crank sensor first of all maybe cam sensor aswel there the only 2 i didnt use from old engine