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Vs V8 base ignition timing question

myvscalais

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Had my VS Calais V8 rebuilt about 2 months ago and it was slightly surging when sitting on about 95kmh, only when coasting not under acceleration etc and I told the bloke that rebuilt it.(wife's sisters husband, aka family mechanic, by trade)
He came over and checked the timing which was out about 5 deg, he said he couldn't check it properly after he first got it going because his timing light was stuffed, but I think he retarded it on purpose until I ran it in properly :)
He set up the timing again and all was fine for about 3 weeks, (and boy does she go) until yesterday.
Driving at 100kmh engine died and would not restart. Got it tray trucked home and done some checking was found to have no spark from the coil. The bloke that rebuilt it changed the coil because it died on him when he first took it for a drive, it had cracks in it etc. I had doubts it would be the coil again as it was only 2 months old but I had a spare at home so decided to try that first even though he said it would be the ignition module. What would he know he's only a mechanic lol.. (replacing v8 coil = prick of a job) Still the same.
Rang around for prices of an ignition module, god damn expensive found a changeover for $188 from Bursons. Put that in no worries, started and running no problems, BUT the surging is back probably worse than before. Again only while coasting up around 100kmh.

Because I replaced the coil and the ignition module do you think I should check the base ignition timing again, or does it sound like a dodgy plug or lead (which are all new) There is no miss at idle and coasting at low speeds is ok.
The slightest touch of the accelerator the surging disappears it's only there when holding one speed between 90 - 110kmh.
I might have disturbed one of the leads on the dizzy when I changed the coil but wouldn't it be rough on idle if a lead or plug is dodgy or could it be breaking down on higher speeds?
The base timing should be set at 10 btdc with diagnostic pins bridged but is this set at idle speeds? It seemed to go away after he set the base timing last time. It's got a slightly larger cam in it now from standard, does the timing stay the same?
Got me puzzled everything is new, fuel filter, air filter, plugs, leads, coil, ignition module, injectors professionally cleaned and tested.
No fault codes being generated only #12 continuously.
Apart from this surging the car is running perfect but it is annoying the **** out of me. I don't want to ask him to come and check it as he lives a couple hundred K from me and I can get hold of a timing light myself but just need to know if the timing is set on idle or should I be looking somewhere else for the problem. After I changed the ignition module and first started the car it was idling like a pig for about a minute then settled down and came good.
Any thoughts, ideas or suggestions welcome.
Thanks everyone.
 

immortality

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checking thebase timing definitly won't hurt. you will need to put the car into diagnostic mode and follow the tuning label on the passanger strut tower. it should give you a reference idle speed + base timing setting which should be something like 850 rpm +/- 50rpm, 10degrees btdc. if you run premium fuel, giving an extra degree or 2 of base timing shoudn't hurt the car either
 

myvscalais

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Thanks immortality for your feedback didn't know about the premium fuel either.
Ok just checked the base timing and was retarded about 6 deg from where it should be at 10 d btdc at 750rpm in diagnostic mode. Set it back to 10 deg and took it for a run, seems to run a lot better on lower speeds already but when I go to work today on the freeway I'll be able to see if it still hesitates when on 100.
Also found 1 spark plug lead slightly loose in the dizzy cap fix this up also.
Will report back here if it has solved this problem. (I hope so)
 

myvscalais

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So far, so good, ran ok yesterday seems that was the issue.
 

greenfoam

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Set it to 13 or 14 degrees and run 98 octane, you will be a happy chappy :)
 

Stato Jay

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On the topic of failing ignition modules, I've had this happen to me twice.

I carry a spare around in the boot.

But, I've found that if you're handy with a soldering iron, there's a good chance you can repair these quite easily (and inexpensively).

The power transistor on the case of the module gets dry solder joints (on the circuit board), as do some of the pins on the socket. I've repaired a couple of these now for myself and others with 30 odd minutes of my time being the total cost just by looking over the circuit for dry solder joints.

I've found these units fail a short period after pressure cleaning the engine bay. I figure there is a weather proof varnish on the modules from teh factory, which burns off after a few good years of use. The case of the power transistor is at a potential other than 0v, I'm not sure what voltage is developed here but ever leant on the igntion module while the engine is running? ZAP! OUCH!

The water on the module (after cleaning) conducts between the case of the transistor and the case of the module and makes the transistor (and the entire module) work a lot harder than it was ever designed to.

This "cause" is all just a theory based on previous observations. Criticisms and corrections are welcome.

I now wrap the module in plastic before cleaning the engine bay and I've had no problems so far.


p.s. If you're shitty with a soldering iron (ie: Your solder job looks like silver bird sh!t dropped from on high), get someone else to do the job. A TV repair guy would probably do it for a few bucks and probably quite a few bucks less than an exchange module would cost you.

Bad soldering makes me sad, don't do it.
 

immortality

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On the topic of failing ignition modules, I've had this happen to me twice.

I carry a spare around in the boot.

But, I've found that if you're handy with a soldering iron, there's a good chance you can repair these quite easily (and inexpensively).

The power transistor on the case of the module gets dry solder joints (on the circuit board), as do some of the pins on the socket. I've repaired a couple of these now for myself and others with 30 odd minutes of my time being the total cost just by looking over the circuit for dry solder joints.

I've found these units fail a short period after pressure cleaning the engine bay. I figure there is a weather proof varnish on the modules from teh factory, which burns off after a few good years of use. The case of the power transistor is at a potential other than 0v, I'm not sure what voltage is developed here but ever leant on the igntion module while the engine is running? ZAP! OUCH!

The water on the module (after cleaning) conducts between the case of the transistor and the case of the module and makes the transistor (and the entire module) work a lot harder than it was ever designed to.

This "cause" is all just a theory based on previous observations. Criticisms and corrections are welcome.

I now wrap the module in plastic before cleaning the engine bay and I've had no problems so far.


p.s. If you're shitty with a soldering iron (ie: Your solder job looks like silver bird sh!t dropped from on high), get someone else to do the job. A TV repair guy would probably do it for a few bucks and probably quite a few bucks less than an exchange module would cost you.

Bad soldering makes me sad, don't do it.
nice, maybe post this in it's own thread so others will see it, maybe the mods should move this to the "how-to" section:thumbsup:
 
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