I had my MY01 serviced today, & told them it had not been running as smoothly as normal- really noticeable yesterday, but I thought it might be due to the temp being 30C. I also had a Magnex cat back system fitted 10 days ago.

My dealer said I needed a ECU reset following because of this & after 100 miles should all be reset & fine, if not to bring it back in. 100 miles later, still not smooth- nothing too drastic, just not quite as it should be.

Dealer's comments were news to me, & I am interested in hearing some other opinions, please!

Don't read too much into this, but this is my account of what I can only refer to as an almost un-noticeable degrade in performance, followed by an almost miraculous improvement.

Over the last few months I've been religiously using Shell Optimax, and until recently I've been delighted with the results - smoother running and better performance.

A few days ago I realised that the performance was a bit reduced and put it down to the hot weather (which I'm sure some of it was). Did an ECU reset just in case and didn't make any noticeable difference.
Today I had to refill with BP SuperPlus as I was not in range of a Shell station.
After 5-6 miles I noticed that the performance was significantly better again, as in kick in the back at lower revs better, and much more torquey throughout the rev range.
Now bare in mind I had been running 30 miles on Optimax before filling up and the heat of the day and air temp didn't change in that time period, so it's not like I tried the Super on a cold night or something.

I have a theory (you can laugh if you like).
The EVO magazine review of Shell Optimax said that it was good but left a red/orange residue on some engine components, and they thought it was likely to be the RON enhancing ingredients, but didn't add any further comments.
My theory is that over a period of time (about 4 to 5 months in my case) the residue 'soots up' the engine a bit. Putting some Superplus through the engine has for some reason shifted some/all of this residue and whatever negative affect it was having has now been removed and performance restored to normal.

I'm going to run this tank of Super through and then go back to Optimax. If my theory is correct I should notice an improvement in performance with Optimax initially and then over a further few months things will degrade a bit again(when once again I will try a tank of Super and see if it improves things). I will post any further findings on here.

I'd be interested to know what others think about this.
I don't mind if you all want to pour scorn on the theory but please don't say it's down to the ambient temp or me thinking Super would fix it etc as I actually thought performance would degrade further using BP over Shell fuel, and I've already addressed the ambient temperature issue earlier.

Question for you Bexlee, have you been running Optimax for a while? If so do me a favour and try and tank of SuperPlus and let me know how you get on.

Interesting. I have used Optimax religiously since the start of May, & will test your thoughts by using NUL/SUL as soon as I have worked through the 1/2 tank I have left.

Any other theories re. my situation?

Bex

I don't suggest using NUL, too much risk of det (IMHO).
If you could try SuperPlus (BP specifically) it would be a really useful test.
Thanks and hope it sorts your problem.
BTW: My tank was 1/4 full when I put the BP Superplus in and it still seemed to do the trick.

It looks like the Orange deposit problem will only be a problem after quite a few tanks, so assuming my next tank of Optimax makes the car perform better I will swap back to it for maybe 10 tanks then put a tank of Superplus in to 'flush' things out.

One other thing you might want to check is if you have a mesh air filter, see if it's gunged up with dust and dirt. Unfortunately it seems most services skip the cleaning of it as it 'looks' clean, but a quick rinse in your sink will prove it's actually clogged up quite a bit after even a few weeks use. I have a Blitz unit and a few weeks ago I gave it a good clean, seemed to make things a little better.

In this weather though things are usually pretty lethargic with turbo engines. I had the same problems with my Escort Cosworth before the Scooby. Humidity screws up induction big time on turbo cars :-(

Sheepsplitter- I was running an ITG foam panel filter until I swapped back to the OE paper one today- just got paranoid (?) about MAF sensor failure. Both clean however. Will try the BPSuper (if I can find a BP station nearby!) Are you also running an MY01?

I have an STI4 with quite a few mods. That's a 1998 model.
Last dyno run was 348BHP, that was on SuperPlus fuel, but under normal circumstances the Optimax seems to give a bit better performance - at least for a few weeks :-)
My cars done 68K miles now, so it's nicely run in.

Sheepsplitter

348 :D

Will let you know the 'results'.

Well I did spend rather a lot of money, but I think it was worth it :-)
I have played safe as well though and had extra oil cooler and water injection fitted, so hopefully I will get performance and longetivity of engine. Time will tell I guess, but best part of 70K miles isn't exactly a bad start.

Change in fuel did not help (unfotunately, could only find 95 Ron on today's excursion to Whitby [img]images/smilies/mad.gif[/img] )

I will refer to Dealer tomorrow. Meanwhile, all other thoughts much appreciated. Interestingly enough, Doofus' current thread on this forum matches my symptons too.

I'm due another fill up today (1/4 tamk left) .... may try another busier Garage for Optimax or just plain old super.

It's just frustrating when you know it's just not quite running as well as before but to anybody else it would seem fine :(

I'll report back and let you know sometime today.
Doofus.

Dealer is having a look today. Will let you know what happpens, Doofus.

Bexlee

I am having what sounds like a similar problem to you, my UK300 isnt running as it was, definite lack of punch when you floor it.

I too have used Optimax for ages, and have tried SUL to see if that helped the situation ( it didnt !! )

Dealer has reset ECU - no change !

Car is in today - they think it might be the knock sensor - so they are moving it :confused: supposedly its a known problem !??? its too sensitive where it is, and caused ignition retard or something such like !

will be interesting to see what your dealer comes up with. ]

I know there was a few other peeps with very similar problems too.

dunno how they got on / getting on though !

Filled up in busy station this morning with Optimax ... seems to be a wee bit better but I can still detect almost like a pulsing sensation when accelerating hard uphill with WOT .. very slight but I can feel it.

Let me know how you get on.
Doofus.
P.S Have replied in other thread as well for more exposure :)

Sorry to butt in guys...but here is something to try:

I was forced to take my battery out the other day for some work on another part of the car. I put in back in...and I have all sorts of "artifacts" acceleration felt sluggish..and had the "pulsing" you describe...and some hesitancy at lower revs.

And you know what? I undid the battery again, cleaned the terminals....re-greased them with copper grease and BOOM! Car is back to normal.

Seeing as you all seem to have had your battery's disconnected (and the scoobys seem to have TERRIBLE earthing) might be one to try? 5 mins with brillo pad and some copper grease.......

(will be fitting earthing kit soon, methinks)

Thanks for all the feedback. (Turbo_Steve, AFAIK, my battery has never been disconnected)

Yesterday, my Dealer changed my MAF sensor & reset the ECU. Immediate improvement :) and I hadn't really realized how 'poorly' it had been sounding too! However, roads were far too busy around the Dealership, & on the motorway drive home, to test it through the gears & rev range- but it did seem to deteriorate again :( So much so that after 50 miles I rang the Dealers on my hands-free, but they said to persevere a bit more to give the reset chance to sort itself out.

After a bit more driving around home roads it does indeed seem to be cured! :) But I guess time will tell. A run up the A19 today to York should be conclusive- given how hyper-sensitive I will no doubt be in feeling for a 'judder'!

So what caused my problem? Only recent change has been the fitting of a Magnex system. Could that damage the MAF sensor? I have had an ITG filter for the last 4000 miles- could it be the filter/ the fitting of it (it all seemed OK). I have returned to the OE filter since Monday as 1) the Dealer was not keen on them 2) I couldn't notice the difference anyway! My ITG will shortly be featuring in the 'For Sale' forum.

I hope all this is of some use, & only to add that I have felt very similar symptons in the past on two other cars. The first turned out to be a faulty lambda sensor, the other needed new spark plugs.

I will let you know how it turns out today. <fingers crossed>

It seems as if the problem is solved. :D I even let Mrs Bexlee drive to get a 2nd opinion.

Let me know how you get on Sheepsplitter & Doofus.

Guys I have to post an update which is not quite what I was expecting.

I have to retract ALL my comments about Optimax requring an occasional tank of Superplus to 'clear out' any possible orange deposits.
The reason for this is not a legal requirement or some pressure from Shell :-).
It's simply that I am unsure of the findings in the light of having discovered that I had a dry joint on my ECU which was causing occasional boost variation and eventually a number of total engine cutouts (one of which was in the fast lane of the M4). The problem has now been rectified and the car is very much back to full performance, even in hot weather yesterday it seemed to be pulling like a train, so I am well happy.
I will continue to use Optimax and see if I notice any performance drop off as the months wear on.
Sorry for any confussion my earlier postings may have caused, but I had no idea the ECU was playing up until a couple of days ago when it started to cut out.

confussion? ;)