Changing the engine ECU on a mark 1 TT
Discussion
Feeling very satisfied about having changed the brake-pedal, brake-lights switch on my TT this weekend for the £15 price of a new switch. (local garage wasn't able to do it until Wednesday, took bloody ages to get the bottom of the dash back in place, but only 2 screws left over so counts as a result in my book), I've been considering swopping the engine ECU for one that might actually work properly.
Here I need some advice.
First the symptoms that make me think the ECU is on the blink:
With a cold engine the idle sometimes hunts for a stable speed, perhaps by +/- 100 rpm
Twice in the last couple of months the car hasn't fired. First time I did the old trick of jabbing the throttle a bit to prime the carburetors and then starting up at 1/4 throttle (I know it doesn't have carburetors, but it's a nostalgic thing). Weirdly this worked and the engine fire into life, but the ECU light was on. Next time I started the normal way with no problems and no ECU light.
Second time it didn't fire up an AA get-you-home repair was required. I wasn't in the car but my wife reports the AA man got it running and then told her not to switch it off for an hour.
Possibly related is that the traction control and airbag warning lights have been on for a while (2 to 3 years to be honest)
Now the potential solutions:
a) Audi, which will probably cost a grand
b) Pre-used ECU for the same year, engine and gearbox combination from a parts dealer for £108, an hour or two to fit it, and probably a couple more left over screws. There's bound to be a long part-model-spec number on my ecu so as long it matches the replacement (reasonably well?) it should work.
Option b sounds appealing, but is it really that simple or will I run into problems with the key and ECU not knowing each other and the immobiliser giving me hassle. And if so, can I immobilise the immobiliser in a simple way?
What's the thoughts, worth a £108 gamble to save a grand?
Here I need some advice.
First the symptoms that make me think the ECU is on the blink:
With a cold engine the idle sometimes hunts for a stable speed, perhaps by +/- 100 rpm
Twice in the last couple of months the car hasn't fired. First time I did the old trick of jabbing the throttle a bit to prime the carburetors and then starting up at 1/4 throttle (I know it doesn't have carburetors, but it's a nostalgic thing). Weirdly this worked and the engine fire into life, but the ECU light was on. Next time I started the normal way with no problems and no ECU light.
Second time it didn't fire up an AA get-you-home repair was required. I wasn't in the car but my wife reports the AA man got it running and then told her not to switch it off for an hour.
Possibly related is that the traction control and airbag warning lights have been on for a while (2 to 3 years to be honest)
Now the potential solutions:
a) Audi, which will probably cost a grand
b) Pre-used ECU for the same year, engine and gearbox combination from a parts dealer for £108, an hour or two to fit it, and probably a couple more left over screws. There's bound to be a long part-model-spec number on my ecu so as long it matches the replacement (reasonably well?) it should work.
Option b sounds appealing, but is it really that simple or will I run into problems with the key and ECU not knowing each other and the immobiliser giving me hassle. And if so, can I immobilise the immobiliser in a simple way?
What's the thoughts, worth a £108 gamble to save a grand?
First thing to do would be to get the car scanned with VCDS to see what is actually causing the issues.
The first problem (hunting) may be down to a dirty throttle body, carb cleaner, toothbrush and reset would be the first thing to try.The rest could just be a dodgy sensor or even a failing battery.
How has it passed an MOT with the warning lights on for the past 2 or 3 years?
The first problem (hunting) may be down to a dirty throttle body, carb cleaner, toothbrush and reset would be the first thing to try.The rest could just be a dodgy sensor or even a failing battery.
How has it passed an MOT with the warning lights on for the past 2 or 3 years?
Lorne said:
I've been considering swopping the engine ECU for one that might actually work properly.
the ECU light was on.
Very, very rare for the ECU to be the root cause on almost anything.the ECU light was on.
ECU Light - The check engine light?
http://www.diagnostic-world.com/_familyCustom/0/ar...
Must have been the one that says EPC, although for some reason I thought it said ECU.
edit: I don't think an orange light is a reason to fail an mot, just an advisory.
VCDS looks like buying a cable and downloading some free software. Is this the case or is it something I need to go to a local garage to have done?
edit: I don't think an orange light is a reason to fail an mot, just an advisory.
VCDS looks like buying a cable and downloading some free software. Is this the case or is it something I need to go to a local garage to have done?
Edited by Lorne on Wednesday 5th July 10:56
VCDS Licenses are keyed to the cable from Ross Tech, the software is free to download and will work with some cheap cables but are limited in functionality.
If you don't want to spend the £200 odd quid to get your self a cable there are plenty of people who will scan the car for you for a 6 pack of beers. Where are you based? The TT forums will have a list of people with VCDS who will help you out.
If you don't want to spend the £200 odd quid to get your self a cable there are plenty of people who will scan the car for you for a 6 pack of beers. Where are you based? The TT forums will have a list of people with VCDS who will help you out.
Mr-captain said:
VCDS Licenses are keyed to the cable from Ross Tech, the software is free to download and will work with some cheap cables but are limited in functionality.
If you don't want to spend the £200 odd quid to get your self a cable there are plenty of people who will scan the car for you for a 6 pack of beers. Where are you based? The TT forums will have a list of people with VCDS who will help you out.
Brentford, which is the London borough of Hounslow. Or to give it the official title, 'Democratic Peoples Socialist Republic of Hounslow, don't dare park your car for 1 minute longer than you paid for'If you don't want to spend the £200 odd quid to get your self a cable there are plenty of people who will scan the car for you for a 6 pack of beers. Where are you based? The TT forums will have a list of people with VCDS who will help you out.
Anyone with a cable and computer nearby??
edit: traction control (orange) light for a few yrs, airbag (red) since about a week after the last mot. will get the red light fixed before next mot. : - )
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