Advice On Resetting Mk4 Efi Ecu

[Guest jonathanjead]

Welcome some advice. My MK4 Cab is in the garage, before putting it away for the winter it had some issues with cold engine tickover, however the more I read and the more I think about it the more I suspect the problem is down to me. It was OK when I got the car but got the problem started when I was cleaning under the bonnet. I now remember that I disconnected the battery for quite some time but never went through a ECU reset procedure when I connected it back up.

 

Anyway, when I start it up in a couple of weeks I'd like to do it properly. Car battery is currently disconnected. Before I charge and reconnect I will be putting on 2 new sensors (inlet manifold sensors) and a new TPS. What is your advice on the procedure I should go through in reconnecting and starting the car up to ensure the ECU settings are correct?

 

 

Any advice appreciated - I have the info in a Haynes manual but have a history of finding the HAynes isn't always the right or best way o doing things.

[ianxr3i]

Try this mate

 

ECU will have been reset if thebattery has been disconnected for more than 1 hour however, it then has to bedriven for a minimum of 5 miles during which time full throttle operation mustbe used a number of times (2nd or 3rd gear is best) but there is no need totake it to the red line...just have your foot planted up to 4 or 5,000 rpm eachtime and then change gear. Also need to cruise at half throttle a number oftimes for as long as the road will allow...again 3rd gear is best at around3,000 rpm.......and then accelerate flat out and change gear. Lastly, need tocome a full stop a number of times and let the engine settle at idle. Thiscovers a reset and re-learn of the ECU

To set the base idle: get engine to operatingtemperature and while at idle, disconnect the ISCV. Engine should still idlebut around 650 to 700 rpm. If it does, re-connect ISCV, allow engine to settleat idle without revving and then turn off ignition.

 

If engine does not tickover with ISCVdisconnected, locate idle adjust screw (found at 9 o'clock in the recess in theface of the throttle body where the air inlet pipe joins the throttle body) andturn it clockwise until it lightly seats and then back it out 3 complete turns.Re-connect ISCV and then restart engine. Allow to settle at idle and thendisconnect ISCV again. If engine does not idle, turn idle screw 1 turn anticlockwise and re-connect ISCV. Restart engine and repeat process as necessaryuntil such time the engine will idle at 650 to 700 rpm with the ISCVdisconnected. Once this base idle is achieved, re-connect ISCV while engine isstill running. Idle may surge initially.............allow to settle on its own.Do not rev. Once idle has settled, turn off engine.

 

After the base idle has been set, the CO will needto be checked and set using a CO meter. Set at around 1.5% with the fanrunning. After CO has been set, do base idle check again following the aboveprocedure and adjust as necessary

 

If base idle and CO are correct, when the engineis revved to around 3,000 rpm and the throttle let go, the rev counter needleshould drop straight away to 1800 rpm, pause ever so slightly then drop to 1300rpm and then slowly drop to idle of 950 rpm. If the needle "hangs" at3,000 rpm when throttle is released then base idle is set too high. If revcounter needle drops like a stone to below idle and then creeps back up toidle, the base idle is set too low.

 

Edited January 9, 2011 by ianxr3i

[Guest AstonB]

Some good stuff there. I unplugged battery while fitting new manifold and exhaust system so it could 're-learn' with the new bits fitted, i must say it seemed to make a very noticeable difference!

 

Still get a strange vibration around the 5k mark when it's warmer though, just before it gets to running temperature the vibration is hardly noticeable and much quieter :S

[Guest dave29]

so if the your car is say for eg......... garaged up for the winter with the battery disconnected......its gunna run like shite when you put the battery back on it?