Have had a few problems which have started today. 5th Gear on the motorway at around 75, put my foot down and boost goes through the roof, before dropping, picking up, dropping etc. Seems to fluctuate badly under acceleration. Anyway, got off the motorway, and it seemed to disappear.
The car was then rolling roaded (pointof being on the motorway was to get there, and ran a fantastic 260bhp with which I was very happy. However, on the drive home, it started again.
At first it was only in 5th, but it has since moved to third and fourth as well. However, in third and fourth it seems to go over the 17psi cut-off, then stabilise out at around 10-12psi.
Car is a MY99 UK with a full H+S de-cat, a forge VTA d.v. and an AE801ecu. The downpipe was only installed around two weeks ago, and the ecu was reset at the time. Car is always run on Optimax, oil levels are fine, water is ok and there are no dodgy noises. Fuel consumption is ok and the car ran all the way home at a restrained 70mph without any fault lights or notices.
I am totally at a loss for it, all the hoses seem fine and I don't have a dawes or anything similar before anyone asks!

Any possible explanations welcome! Anyone offering to help fix it around S.Wales is even better!! Thanks guys.

 

Come on guys, I want to fix it tomorrow!!

 

a tek2 remap?
Seriously, i would consider the above to sort your problem out

Tony

 

Not an unknown problem on some full de-cat cars?
Would it be possible to stick the original centre section back in and see what happens?
As JB says, a re-map to optimize your set-up would be sensible and safer.
JohnD

 

It is a common problem on de-cat cars then is it?
I was looking at a tek2, but I am also considering a unichip as they have been recommended to me by a few people. Is it also worth investing in a dawes to act as a restrictor to prevent my boost from going over 1 bar? I intend to go for more boost eventually, but I am taking my time to make sure all the engine is as efficiant as possible before I concern myself with boost levels.
The only thing is, if it is a common problem with de-cat cars, why was it seemingly getting progressively worse over the day?

 

Check for oil in the solenoid etc.

Also look up my old thread on restrictor valve replacing restrictor.

Sorry won't be around to give more info on crappy 30000bps dodgy connection in the sticks.

 

Thanks John, will do.
Any advice on how to get at the solenoid to check it anyone?

 

Well, this is what the search facility turned up (hint hint )

http://www.scoobynet.co.uk/bbs/thread.asp?ThreadID=95387

A few others too, but this one had pictures!

Good luck.

 

Cheers mate.
Will have a go at it this afternoon.
I am also re-setting the ECU to see if that will help stabilise it out, if not then I will be calling some people tomorrow for some more advice, to see if it can be solved by a simple re-map or not.

Any other ideas as to the cause?

 

Well, ECU reset seems to have temporarily sorted the problem out. All the same, I will be assessing re-map options tomorrow. Any ideas on the best version, tek 2 or unichip etc??

 

Prob best option is link from BR then you can mod till your hearts content. I just had a tek3 from Bob Rawle it is most satisfactory! But should realy have linked

 

Have just spoken to TSL, who think it is not overboost, but the spark plugs not being set-up properly, along with the fual pump not getting enough fuel to the engine. I have a boost guage fitted and it has been going up to around 17psi in fifth gear, but not sure if it went that high in third or fourth when it has seemingly 'cut-off'. this would seem to sound possible, but I'm not sure. Would this seem like a possile explanation? Only does it under initial acceleration, after which it seemed to stabilise itself, which is what made me suspect overboost. Now, however, i'm not so sure. Have also spoken to Jw and g-force, who both said it was overboost due to the de-cat.
It may be worth mentioning that it is not a savage slow down when it cuts, more like an 'on-off' switch for the turbo.

 

twigster, how are you enjoying D/P?? you wouldnt believe what it cost me to have mine fitted mate, certainly spins through the revs a bit faster, just in process off fitting knocklink & boost gauge then a remap is order, when ive saved up

 

Well so far it is a mixed thing mate.
I was all singing it's praises until I started getting this problem, so now I'm not so sure. Still, if it is sorted out as something simple then I will be happy.
Bttt while I'm here though.

 

up we go!!

 

Bttt for a worried m8

 

Not so worried any more mate
Car is going for a diagnostic check-up on Thursday, inc checks on the solenoid and the actuator, and if they come up clear, it looks like it is going for a further check on saturday, which may include the addition of a boost controller to prevent it from spiking so early, instead giving me a controlled limit of 1 bar.
I know it can go higher safely, but for now I am happy to run at 1 bar, until I can get a re-map for the fuelling to compensate for higher pressures.
So by Sat. Afternoon, it should all be fixed and running ok!

 

At 17psi you aren't all that far from the fuel cut limiter, however, if the thing is surging up and down before this point, in my (limited) experience, it is usually either (as JB says) an oil coated solenoid or a leak in the system. You say you've checked all the hoses, so that rules that out. You've got a forge VTA DV, has the problem occured since fitting that or was it ok initially? If the spring in the DV is too weak I can imagine it will be leaking air on boost, causing that oscillation.

These things are often a process of elimination.

 

twigster, group buy on re-maps!! you never know

 

lmfao @ Andy!
The last one was enough of a pain to set-up mate! Not going through all that again! If someone else wants to have a go though, i will be tempted!
Anyway, like I said, it has been creeping around 17psi, but not always hitting it, so the car is going to a garage for a full diagnostic, including a clean of the solenoid tomorrow. Seems to be running ok at the moment anyway, so I'm not over concerned any more. I also found a slight leak in the exhaust which I have now fixed, and I'm sure this would not have been any help.
Will report back when I find out what the problem was. Thanks fellas, and if anyone can name anything else to try then it would be more than welcome!