V6 Engine Problem

[ukflyboy]

Hi folks,

As some of you may have seen, I joined the S ranks this weekend, picking up a PHer's S3 from Plymouth and having a beautiful smooth drive home to Oxfordshire. So tonight I go out to enjoy the sun and take it for it's first post-pickup run however all is not well... It starts ok but the engine completely cuts out whenever the revs hit 2500! The previous owner had bypassed the ISCV as it tended to settle on about 2000 rpm but with or without that plugged in the engine completely dies at the 2500 rpm mark.

Anyone able to offer any help? Hope it is something relatively easy to fix?!

[ukflyboy]

Haha, yes, definitely filled it up after my run and definitely with petrol and not diesel! I've seen somewhere else that it may be worth disconnecting the battery for a bit and seeing if that resets things. Worth a shot?

[ukflyboy]

Thanks for the help so far folks, keep it coming I'm not the worlds most mechanical person so it is all very much appreciated! I have a good fault code reader among all the bits and pieces that Mark gave me so will have to spend the weekend figuring out how to use it and trying to suss this showstopper out. I kinda want it to be rubbish weather now, just so I don't feel like I'm missing out!

The irony is that the 61 plate day runner I bought the week before is also currently crippled so I'm reliant on my 15 year old 306 that I was planning on selling! Looks like I best keep hold of it a few weeks yet...

[ukflyboy]

Ok, thanks folks, I'll have a play around with the distributor and see if that sorts things, might not get a chance to do so properly until the weekend though.

By way of clarfication, it seems to die at exactly 2500 rpm every time and relatively quickly runs down to a stop without really a chance to catch and fire again. It may sound a tiny bit rough running, but I've only ever heard it running twice, so don't have a great frame of reference! It is almost as though it just loses ignition at 2500 rpm so the courses of action above sound like a great start point.

Edited by ukflyboy on Wednesday 15th April 13:51

[ukflyboy]

So while I am studiously reading up all the manuals (and Mark kindly gave me several, including the SH bible) about distributors and fault code readers, here is a link to a video I took of it tonight (please excuse quality, its just from my phone).

https://www.youtube.com/watch?v=XM56rpYGVr4

Now I'll reiterate that I've only ever driven a TVR once but what I notice is that the battery light (or "Ignition Warning Light" according to the manual) stays on until a split second before the engine cuts out (I understand it is normal to stay on quite late in a 2.9i?). Is this maybe a sign that there is a problem in the handover from battery to alternator as in the alternator says "right, I've got things from here" but isn't actually supplying sufficient energy for the ignitors so it just cuts out? The battery light comes straight back on afterwards but the engine cuts so quickly that it can't take over and spark things up again...

Edited by ukflyboy on Wednesday 15th April 22:06

[ukflyboy]

Thanks for the replies folks, feeling pretty positive that we are heading in the right direction and will check all things alternator related over the weekend, removing it completely if necessary to isolate the problem. Sod's law says it wont be something as easy as a dodgy earth, but fingers crossed!

I'll let you know how I get on sometime over the weekend.

[ukflyboy]

Well it only took me 45 minutes after work to have the alternator off and everything tied safely out of the way for a very quick diagnostic test run in the garage and it fired up and went past 3000 rpm no problems; looks like with all your help we may have found the guilty barsteward! The voltage regulator bushes look quite worn but rather than just replace that and hope for the best I'll probably take the whole unit into a pro that the guy at work highly recommends and have it tested.

Fingers crossed I'll be back up and running again in no time!

[ukflyboy]

Bugger, back to the drawing board... the alternator guy in Burghfield just called back and said that he has tested it and it seems to working ok. Bearings are a little noisy and voltage regulator a bit worn so I'm going to get it rebuilt while it is off, but looks like I'll have to do a bit more digging when I have it back later in the week!

[ukflyboy]

Having the alternator refurbed certainly won't have done the car any harm and I'm optimistcally hopeful that in the process of messing around with wires and stuff that I may accidentally have sorted things. But I really won't know until it is refitted, probably Wednesday night.

Removing it has still been a very worthwhile step in diagnosing the issue and there are a few options for isolating where the problem might be...

[ukflyboy]

The alternator is with a pro in Burghfield who comes highly recommended and only deals with starters and alternators, so I'd hope his testing and repairs will cover any diode problems. I'll mention it specifically when I hear from him tomorrow though. And yes, he is gonna replace the regulator, the bearings and anything else that looks like it might need sorted when he strips it completely apart. To answer a few earlier questions, yes I've tested all the blade fuses (no idea how to test the big clusters or what on earth they are though!), nope, I've not touched a thing between parking it up after my delivery and trying it again the other night when I discovered the problem. Not had anything in the cigarette lighter.
Ticked it over again tonight for 20 seconds without the alternator in to make sure my previous fault isolation wasn't a fluke and it started and ran above 3000 rpm effortlessly (sounded great too!). I'll stick the alternator back in, hopefully Wednesday and see how I get on. If the fault is still there the alternator repair guy suggested running a jumper lead off the alternator earth to the battery so I'll discuss that with him in more detail when I pick it up.

How many and where are the main earths on a late S3?

[ukflyboy]

Well I am happy to report that after sticking the as-new alternator on this evening the S fired up and ran beautifully on a 45 minute jolly around the countryside tonight! I assume it was the alty that did the trick but I cleaned all the earths etc while it was off too, so I'll never really know.

But the important thing is that it is up and running again and I couldnt have done it without all your help, so many thanks!! Have to say, the guy at Burghfield did a cracking job on the alternator too, really good service and highly recommended.