Thread: problem came back

The only thing you haven't mentioned changing is the Throttle position sensor.
If the reading is out of range the car may be slow to drop to idle revs and the stepper slow to react. Ask me how I know. for the last year I have been chasing a variable idle and coincidentally took off my inlet to find a broken TPS signal wire. the car runs almost normally because the O2 sensors and MAF control the mixture,but the ECU recognises < 0.49 volts as idle.

BTW cars with o2 sensors should have the MAF at 1.8 volts as I speculate that it is easier for the sensors to take out fuel than add it.

I take it you are not in Australia as AFAIK 97 here did not have O2 sensors.

I would also replace the correct tune resistor.
Regards Philip A

o.k, i have checked the TPS, it was 0.4V and i changed it to 0.3V.
the RPM respond better but still go up and down.
have changed the alternator and distributor, but still the problem is there.
i have to say hat every change was checked for two days because the computer need time to adjust.
another idea about the stalling?
another problem is that shifting into "D" the rev go dawn and then fix the revs to the correct one. any idea?
thanks for any idea.
Sharon
disco 96 3.9

i have to say hat every change was checked for two days because the computer
need time to adjust.
another idea about the stalling?

The 14CUX is a dumb ECU which does not learn, so there is no point checking changes for two days. All you do is turn off, wait a minute and switch back on.
You should also replace all your spark plugs and plug leads/wires. It could be a missing cylinder or more causing the problem.
Regards Philip A

Originally Posted by PhilipA

The 14CUX is a dumb ECU which does not learn, so there is no point checking changes for two days. All you do is turn off, wait a minute and switch back on.
You should also replace all your spark plugs and plug leads/wires. It could be a missing cylinder or more causing the problem.
Regards Philip A

i did the plugs at the beginning, when the problem has started, so i believe it's not the plugs.
the wires, i don't remember, so i'll change them and let you know.
is there a prefer wires?
what you mean "leads" ?
we talk about an electrical problem, but could it be a mechanical one, one that influence the electrical devices? let say i have a crack in the block, could it be notice in that way?

You haven't mentioned the Fuel Pressure Regulator, check to see if it is leaking fuel back into the plenum via the stepper motor vacuum hose, check whether it maintains fuel pressure, or just replace it and see what happens, Regards Frank.

the wires, i don't remember, so i'll change them and let you know.

For some reason in English we call the wires from the distributor to the sparkplugs "leads" That is why I added wires in case you were a non native English speaker.

By changing to a Yellow tune resistor you have disabled your O2 sensors, which I do not think is advisable. With a yellow tune resistor the ECU will not look for an O2 sensor signal. in this case your MAF sensor reading of 1.2 volts is correct , but you should reinstate the white tune resistor and set the MAF at 1.8 volts.

Lucas 14CUX Fuel Injection System

There is a diagnostic in the workshop manual which you should do to approach your problem in a systematic way, seeing you have not been successful by replacing parts in an Adhoc way.

With the white resistor the fuel consumption was bad, with the yellow one it was
at first batter but after two weeks it became worse.

It sounds like your ECU is going into "limp home " which happens when a sensor is out of specification.

Originally Posted by PhilipA

For some reason in English we call the wires from the distributor to the sparkplugs "leads" That is why I added wires in case you were a non native English speaker.

By changing to a Yellow tune resistor you have disabled your O2 sensors, which I do not think is advisable. With a yellow tune resistor the ECU will not look for an O2 sensor signal. in this case your MAF sensor reading of 1.2 volts is correct , but you should reinstate the white tune resistor and set the MAF at 1.8 volts.

Lucas 14CUX Fuel Injection System

There is a diagnostic in the workshop manual which you should do to approach your problem in a systematic way, seeing you have not been successful by replacing parts in an Adhoc way.


It sounds like your ECU is going into "limp home " which happens when a sensor is out of specification.

tank - i will check the Fuel Pressure Regulator
philip - i working with the white resistor and with the MAF on 1.88
the yellow resistor was for a month or so in order of see the deference and i think to see if the problem, is the O2 by passing them.
i'll check the workshop and do what is need.
does the ECU going out of limp by himself or i should help him?

does the ECU going out of limp by himself or i should help him?

The ECU will go into "limp home" if a sensor is out of the expected range and stay in "limp home" even if the sensor returns to the expected range while the engine is still running.

If the sensor is replaced , the ECU will recognise the correct signal the next time the engine is started after the engine has been turned off long enough for the ECU to lose all power, usually about 1 minute, or you can disconnect the 40 pin plug , wait 10 seconds at least then reconnect it.
Regards Philip A