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Dry joint or loose connection ?


GARTHV896

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PROBLEM:

My V8 was running perfectly until about 4 weeks ago when it started to missfire on cylinders 5 & 8. After checking the plugs the leads and replacing one of the ignition coil packs it transpired that the problem was iether with the ECM or the connector block that plugs on to it.

SYMPTOMS:

The car will growl along running beautifully for a while and then suddenly begin to cough and splutter.

QUICK FIX:

With the engine still running I just wiggle the connector block and the car runs smoothly again, somtimes for a week, somtimes for a day, and somtimes only for a few minutes.

OSERVATIONS:

I have removed and inspected the ECM; the connector blades (male connectors) are clean and sound. I have also removed the lid and base of the ECM and can see no obvious defects on the PCB or connection pins. Lastly I have inspected the connector block in wich the female conectors are housed and that seems fine too!!. However the "QUICK FIX" above would suggest a dry joint or loose connection somewhere between or within the ECM or the connector block.

It was a chat with one of the guys at lotusbits.com that promted me to post this query. Has anyone else suffered similar problems and if so how did you resolve them?

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Hi Garth,

I had a dry joint after having my ECU upgraded to the Red Code software. Fortunately, I knew what had been worked on (soldered on) so suspected the Eproms. Very quickly it was obvious after tapping the Eproms where the problem was. hence a relatively easy fix.

In your case it will be a bit trickier, as you have several possible culprits. I guess that what you could do is meter the resistance between the varies relevant connectors and eliminate them one step at a time. As you seem to have an intermittent problem, you will probably need to simulate the vibrations of the running car by moving the cables around whilst measuring the resistance, hence you will probably need a meter with clip-able probes.

I hope you find it quickly.

Regards,

Peter.

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I'd check all the connectors on the wiring harness (the female side) are all griping the male connectors on the ECU and none have become loose as this is could well be the problem, if you can find something in similar size to the blades on the ECU plug you can gently pull it in and out of each connector and see if any are not griping tightly. If the problem is not on the wiring harness side then the only option is to inspect the ECU pcb along where the connector is soldered preferably under a magnifier, look for any obvious cracks, dry joints and "doughnut rings" arround the connector pins.

If you do dissmantle the ECU please be careful of static which might damage the components in the ECU, keep away from carpets etc and preferably touch something grounded before handling the PCB.

Good Luck

Martyn :)

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Hi Gareth,

I've had a dry joint on my ECU recently. This caused me all sorts of problems. I have a guy I know that can fix them if you get stuck. PM and we can discuss.

Regards,

David Walters

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Since the ECU has not been tampered with, there's a good chance that it a contact problem in the connector. There is some almost magic stuff called "stabilant 22" it's a electronic contact enchancer created for use in small cameras. go to www.stabilant.com and read the review by motor magizine. The stuff does work, but it's not cheap.

Wayne

The Older I get the Faster I was

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Having carried out a closer inspection it appears that female connector 52 is damaged causing an intermittent connection. Connectors 29, 32, and 49 (the remaining connectors for the ignition coils) seem fine.

Does anyone know where the female connectors can be purchased? I have checked the web under spade connectors but can find nothing that looks remotely similar. Perhaps somebody out there knows of an alternative means of repair.

Again many thanks for your previous assistance I'm not sure I would have found the problem without it.

Garth

p.s. Steve at SJSC can get the quick release fuel lines that connect the secondary injectors to the plenum for about

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If you can't find the right spade connector and are completely stuck then I have spare engine loom.

Any ECU or loom repair companies will want you to send them your loom BTW.

Only way to fix on car is DIY.

David Walters

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