4.2 engine set up help needed
Discussion
i've just spent all day trying to get my 97 4.2 to run correctly, i've just been soaked & am pissed right off.
Fitted new plugs, new magnecors today, & fitted 2 new throttle pots 2 weeks ago, but the car still runs like crap. It was not too bad ( major stuttering from 1900-2500 rpm ) until today after fitting the new plugs etc.
I have the cerb software but still cannot get the engine to run as it should.
I'm setting it up as follows:
1) idle screw fully wound in.
2) Link rod removed
3) pots set at 15.0
4) adjust idle to 1000 rpm ( using idle screw)
5) adjust passenger side bank (using link rod) until pot reads 18.4/7
6) adjust drivers side pot ( by adjusting pot itself) to 18.4/7
when the engine is started it will fire then stall.
if i then adjust link rod or idle screw the engine speed goes up to 2000+ rpm, & listening to the exhaust the motor is clearly not running right.
The setup software is showing no faults & adaptives have been reset each time.
If anyone can help me with the setup, you'll save the life of this great car ( if i go through the same tomorrow it's curtains!) & possibly my marrige(?)
I know the ideal situation is to take it to an expert/dealer but i'm in Guernsey & we have no experts/dealers so i'm left to my own devices.
Thanks in advance for any help at all.
Darren.
Fitted new plugs, new magnecors today, & fitted 2 new throttle pots 2 weeks ago, but the car still runs like crap. It was not too bad ( major stuttering from 1900-2500 rpm ) until today after fitting the new plugs etc.
I have the cerb software but still cannot get the engine to run as it should.
I'm setting it up as follows:
1) idle screw fully wound in.
2) Link rod removed
3) pots set at 15.0
4) adjust idle to 1000 rpm ( using idle screw)
5) adjust passenger side bank (using link rod) until pot reads 18.4/7
6) adjust drivers side pot ( by adjusting pot itself) to 18.4/7
when the engine is started it will fire then stall.
if i then adjust link rod or idle screw the engine speed goes up to 2000+ rpm, & listening to the exhaust the motor is clearly not running right.
The setup software is showing no faults & adaptives have been reset each time.
If anyone can help me with the setup, you'll save the life of this great car ( if i go through the same tomorrow it's curtains!) & possibly my marrige(?)
I know the ideal situation is to take it to an expert/dealer but i'm in Guernsey & we have no experts/dealers so i'm left to my own devices.
Thanks in advance for any help at all.
Darren.
Hi Darren, sorry to hear about the problems, hopefully this will be of some help. In addition to the TVR ecu diagnostic software you will need a synchrometer. TVR use a Weber carburetor's unit which can be obtained from Demon Tweeks for about £50. It has has the appearance of a stubby retro-style hairdrier and is used to measure the airflow at each of the throttle bodies. In order to set the engine up really well, you need to know what effect each of your adjustments is having on the overall setup.
The ecu has an excellent adaptive mapping facility which attempts to manitain the correct stoichiometric ratio (fuel/air mixture) and idle speed at all times. The trouble is that it is very quick to adapt, and can mask a running problem. Resetting the adaptive maps after each adjustment will help to prevent this, and starting from a zero baseline will also make things easier. This is a general guide and should be carried out with the airboxes removed and the fuel purge pipe carefully clamped upstream of the junction (fuel tank side). It also assumes that the engine and it's sensors are all healthy and within range.
1. Remove the throttle pushrod at one end and undo the idle stop screw so that both throttle banks are completely closed.
2. Very carefully move the throttle pots until they both read 15% (number 1 is on the left bank).
3. Re-connect the throttle pushrod and adjust so that both banks remain fully closed and at 15%.
4. Adjust the idle stop screw to open the throttles until both throttle pots read approx 19%.
5. Reset the adaptive maps and then start the engine and run until up to temperature.
6. At this point the engine should be idling at around 950 rpm with the ignition timing at about 17 degrees. Engine idle speed is adjusted by the ecu retarding (less rpm) and advancing (more rpm) the ignition timing. Moving the timing also has the effect of changing the mixture (retard=richer) and this should be kept in mind.
7. Use the synchrometer to measure the airflow into each throttle body and write down the results. The reading should be between 4 and 5 and be equal on all 8 inlets. If one bank is higher than the other, adjust the throttle pushrod carefully to open or close the affected bank until the airflow is equal.
8. Reset the adaptive maps and move the throttle pot on the adjusted side to read 19% again
9. Re check the airflows and repeat the procedure until equal.
10. If everything is running well the adaptive figures should be below 10 and fairly equal between each bank. If they are above 20 then the ecu is having to move too far away from the original base maps, indicating that the engine is still not in tune.
The ecu has an excellent adaptive mapping facility which attempts to manitain the correct stoichiometric ratio (fuel/air mixture) and idle speed at all times. The trouble is that it is very quick to adapt, and can mask a running problem. Resetting the adaptive maps after each adjustment will help to prevent this, and starting from a zero baseline will also make things easier. This is a general guide and should be carried out with the airboxes removed and the fuel purge pipe carefully clamped upstream of the junction (fuel tank side). It also assumes that the engine and it's sensors are all healthy and within range.
1. Remove the throttle pushrod at one end and undo the idle stop screw so that both throttle banks are completely closed.
2. Very carefully move the throttle pots until they both read 15% (number 1 is on the left bank).
3. Re-connect the throttle pushrod and adjust so that both banks remain fully closed and at 15%.
4. Adjust the idle stop screw to open the throttles until both throttle pots read approx 19%.
5. Reset the adaptive maps and then start the engine and run until up to temperature.
6. At this point the engine should be idling at around 950 rpm with the ignition timing at about 17 degrees. Engine idle speed is adjusted by the ecu retarding (less rpm) and advancing (more rpm) the ignition timing. Moving the timing also has the effect of changing the mixture (retard=richer) and this should be kept in mind.
7. Use the synchrometer to measure the airflow into each throttle body and write down the results. The reading should be between 4 and 5 and be equal on all 8 inlets. If one bank is higher than the other, adjust the throttle pushrod carefully to open or close the affected bank until the airflow is equal.
8. Reset the adaptive maps and move the throttle pot on the adjusted side to read 19% again
9. Re check the airflows and repeat the procedure until equal.
10. If everything is running well the adaptive figures should be below 10 and fairly equal between each bank. If they are above 20 then the ecu is having to move too far away from the original base maps, indicating that the engine is still not in tune.
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