ECU failure - 156 GTA

Citroënbender · January 30, 2018, 08:52:58 AM

Without any diagnostic screenshots, it's hard to suggest anything. All would be conjecture. Most ECUs of this vintage will start and idle with nearly all sensors disconnected save for crank and cam.

bazzbazz · January 30, 2018, 02:23:42 PM

Crankshaft sensor is on its way out would be my bet.

When they heat up car wont start, when they cool down car starts again.

And when is the most likely time the car is hooked up to diagnostics, when its in the workshop and engine cold, that's also why it may not show up as an error.

Citroënbender · January 30, 2018, 02:44:15 PM

A failing crank sensor often shows up by the tachometer not reading right... You'd spot that in a jiffy, being trained in avionics.

amrus1 · January 30, 2018, 06:22:18 PM

Interesting. Still though, it only started after everything was disconnected and reconnected. Car had been cold for a number of days prior to this so I wonder if this means it could be something other than the crank sensor?

Car had been idling rough for a month before, little blips downward in revs, slowly increasing in frequency.

It's a weird one. I guess the frustrating thing is not knowing if it'll happen again given we never figured out the cause.. $:-\$

Citroënbender · January 30, 2018, 06:47:13 PM

Another one which can trap people is a dishonest fuel gauge.

bazzbazz · January 30, 2018, 07:15:33 PM

Quote from: amrus1 on January 30, 2018, 06:22:18 PM
Interesting. Still though, it only started after everything was disconnected and reconnected. Car had been cold for a number of days prior to this so I wonder if this means it could be something other than the crank sensor?

Car had been idling rough for a month before, little blips downward in revs, slowly increasing in frequency.

It's a weird one. I guess the frustrating thing is not knowing if it'll happen again given we never figured out the cause.. $:-\$

Well the problem simply could have been just that, a faulty connection somewhere. 99% of all electrical problems are bad connections.

pasey25 · January 30, 2018, 09:46:14 PM

Could it be wiring connectors. Reseating it could have improved a previously dodgy connection

bonno · January 31, 2018, 01:43:52 AM

Quote from: amrus1 on January 30, 2018, 02:25:12 AM

BUT

When he re-connected everything and turned the key the engine started! As if nothing had ever been wrong....

So that leaves another problem, that is, what was the original problem to begin with?

My laymans instinct reckons it's something to do with the sheer amount of heat the GTA engine bay generates. I recently learned that this heat actually gets worse after the car is turned off and that explains, why in the past, attempting to start again after a drive has sometimes been difficult. Once it cools down it would start first time.

Does that give any clues?

One way to test your theory is to simulate the condition at the earliest possible opportunity.

amrus1 · January 31, 2018, 10:48:32 AM

Good call. Picking it up today, will do this.

Thinking of doing the CF2 manifold mod to try to reduce engine bay temp also.

amrus1 · February 02, 2018, 06:25:52 PM

****UPDATE****

The issue happened again! Disconnected the throttle body and sure enough, it started. I turned it off again, reconnected the throttle body and still the car started.

So I guess this means the ECU is on the way out.

Thank you to all who helped along the way.

Now the question is:
1. What are the options with a failing ECU?
2. Is there a way to mount a repaired/secondhand/new ECU which is not right on the heat of the throttle body?

Autolusso quoted $4000 AUD for a new virginized ECU. Not ideal.....

Citroënbender · February 02, 2018, 06:43:29 PM

1. Have it professionally repaired, including something like the flowable silicone protectant over the top. Ask Bazz for a price.
2. It's vibration, not heat, that does it. Keep the motor mounts and suspension in good shape to minimise repair frequency - once every fifteen or so years, is not too bad.

My personal experience with Autolusso involved paying a good amount of money in advance for new items they only partially delivered, then being fobbed off with excuses and a used part so bad it went in the bin. I will never go near them again. I have some good contacts and cordial arrangements with people in the UK, however Autolusso won't ever make that list.

bonno · February 02, 2018, 07:24:30 PM

Based on your location being in Melbourne and the UNCERTAINTY of ECU failure, I would take it to a local ECU repairer for a check and possible quote & repair (search the net in Melbourne). It would be a shame to arrange the repair of ECU thru Baz and find out it was a waste of time and money because it was some other fault, as identified above (faulty crankhaft sensor).

bazzbazz · February 02, 2018, 08:53:01 PM

Thanks for the vote of confidence guys but before blaming the poor ECU I would find a spare throttle body from some where, wreckers even, and swap it with your current one & test drive for a period of time.

The fact that all he does is unplug the Throttle body and plug it back in and she's off again points more to the throttle body module than the ECU. Either that or the actual plug that connects to the throttle body. I would get a Auto Electrician to check the Throttle body plug & socket first, then try a spare Throttle body from someone.

I could be wrong, but it's a lot cheaper to try a different Throttle body first, than to send an innocent ECU for repair.

I am sure someone in Melb would have a spare on hand that they would be happy to loan you.

Just a thought.

amrus1 · February 04, 2018, 01:03:50 PM

Will put that to my mechanic Bazz, cheers

Also, regarding ECUs on the GTA, was it not a problem to mount them on the engine from a heat point of view?
If it turns out to be an ECU problem, is it possible to mount it elsewhere once repaired to ensure there's no repeat (whether it be a heat or vibration issue as Citroënbender mentioned)?

Quote from: bazzbazz on February 02, 2018, 08:53:01 PM
Thanks for the vote of confidence guys but before blaming the poor ECU I would find a spare throttle body from some where, wreckers even, and swap it with your current one & test drive for a period of time.

The fact that all he does is unplug the Throttle body and plug it back in and she's off again points more to the throttle body module than the ECU. Either that or the actual plug that connects to the throttle body. I would get a Auto Electrician to check the Throttle body plug & socket first, then try a spare Throttle body from someone.

I could be wrong, but it's a lot cheaper to try a different Throttle body first, than to send an innocent ECU for repair.

I am sure someone in Melb would have a spare on hand that they would be happy to loan you.

Just a thought.

bazzbazz · February 04, 2018, 01:15:31 PM

Quote from: amrus1 on February 04, 2018, 01:03:50 PM

Also, regarding ECUs on the GTA, was it not a problem to mount them on the engine from a heat point of view?
If it turns out to be an ECU problem, is it possible to mount it elsewhere once repaired to ensure there's no repeat (whether it be a heat or vibration issue as Citroënbender mentioned)?

No, the ECU Cables won't reach if you move it.

ECU failure - 156 GTA

bonno

bonno