75ZT Community

Hi guys.

Me again.

Oil and water issue seems to have been resolved, all clear on that front.

Now suffering a misfire on all cylinders on front bank.

A massive thanks to David who travelled down to diagnose on his T4 (Testbook version 4.Computer Diagnostic System) .

Earths on front and rear bank connectors checked.

Runs fine for about a minute regardless of engine temperture, then runs like a bag of nails.

Showing fault codes P0172 and P0300, also brought up open circuit fault, but don't know where?

Steve ( Devlish ) suggested symptoms of a transistor failure, but have no idea where to look next apart from ECU (Engine Control Unit).

Any other suggestions greatly appreciated.

We also checked the connectors on 1 3 5 coil packs and injectors for corrosion. All fine. Continuity checked from ground through connectors on the coil packs and ground connections, all good. The only one looking a bit flakey due to lots of bending was the front bank earth, so to elimintate it completely I cut the spade connector off and made the connection good to the block.

A phone call to Russ also suggested the ground points but they were fully checked, unless there is one we couldn't find.

If you have had an open circuit on the LT sides of the coils then the ECU may well be damaged. 50% chance from what I have seen in the past. The drivers in the ECU do not like being OC on their outputs.
We knew about that kind of problem 40 years ago and designed around it but, alas, designers think themselves to be so clever that they do not need to look at the past.

Disconnected front lamdar sensor on advice, and seems at least initially to be the culprit.

Will replace in the week and keep my fingers crossed it's not a damaged ECU. A huge thanks to David for travelling down, T4'ing and eliminating faults in very cold weather, and to his patient other half.

Also to Russ and Brian for the advice.

i do hope you get this sorted Ben, one problem after another, fingers crossed

Am hoping the Lambda sensor is your culprit and you can enjoy your ZT as it was meant to be enjoyed.

It appears no such luck. Finally replaced sensor today, ran ok for 20 miles or so, then started all over again!

Car went to Austingarages on Friday. Nick spent a large part of the day, tracing small airleaks etc, waiting for each one to solve the intermitant misfire. At about 6pm, he found the engine loom had water ingress, and had managed to track up to the ecu. ECU it's self was bone dry, with no sign of any water near it, and front lamda sensor plug also bone dry with no sign of contamination. Lost as to how this amount of moisture has gotten in to the engine loom.

At least your mind's at rest now eh I have to say it was running silky smooth yesterday

Engine loom goosed.

Cleaned and dried the ECU plug several times, but it is now turquoise. Coolant sensor link harness shows coolant at both ends. Not happy.

Just want to say a big thanks to Duncan, who has helped out a lot with tracing connectors etc.

Thanks!