boost problem
 

for a while now I have had an intermittent boost problem. this has happened on my old standard ECU and my current chipped one (1.1 Bar)so it's not the ECU that is at fault.

Sometimes when I have been sitting in traffic for a while or a short blast on a hot day, my boost seems to limit itself to 0.4 bar. once it's cooled down, I get the full 1.1 bar again.

I have changed the boost solenoid and the problem has not changed so its not a sticky solenoid.
any ideas ?

Also, a separate problem that may be related. When I go down hill and off the gas for a while, the engine check light comes on and wqill only disappear when I dip the clutch and let the engine idle for a few seconds. Only error code I get is for the IACV have adjusted the TPS sensor correctly as the JGM site. I have cleaned it and I have replaced the IACV it. Not sure if this is related to the boost problem.

MAP sensor maybe....?

How confident are you that the 0.4 figure you quoted is accurate, as that sounds BELOW minimum actuator pressure, implying that something is leaking maybe.

its accurate. same reading on two gauges. doubt it's a leak as it's always exactly the same pressure when the problem occurs and boost comepletly normaly up till it hits 0.4 bar. Also when things have cooled down I get full boost again so a leak is unlikely.

I do have a spare map sensor that I can try but not sure it will work. the connectros for the early and late classic map sensors are different. still 3 wire but I have a spare round connector one while the one on the car is mroe of a flat 3-wire one and the sensor is much smaller on the car than the spare I had.

seems to me like it is pulling the boost through a detonation issue or something.

also might be worth checking the actuator isn't sticking. can you read any diagnostics codes that may give you a clue?

only code I get is for IACV which I have cleaned and replaced. I have also adjusted the TPS

no codes for knock sensor plus it's been happing for a few years intermitantly so if it was a detonation issue, I would have expected the engine to have gone by now.

Can the actuator be manipulated by hand? or is it to tough? i'll have a look at the actuator at the weekend

actualy, juts had a thought. When I first got the car, I could hear the wastegate rattle in the turbo on idle. there was free play in teh wastegate actuator rod, so I adjusted it just enough to put slight pressue on keeping it closed on idle to stop the rattle.
On doing some netsurfing on this problem, I discovered there is supposed to be a certain amount of preload on the wastegate, which I gather is what I did, although probably not enough.
I couldnt find anything on the net about how to correctly set up a TD05 waste gate actuator. ANyone on here know the correct proceedure to do so just so I can eliminate it as a problem while I am checking the actuator out ?

it 'may' simply be the car is so hot it wont run correctly until cool again............


basically with the actuator rod removed and the w/gate penny held closed you should have only 1/2 of the hole visible and have to stretch it slightly to drop home

thanks, actuator is deffinately set wrong so I will sort that.
had a play with the throttle on the way home and I am beginning to think Si may be right and it's the ignition being retarded to avoid detonation or whatever.
I usualy run on 95ron + octane booster as it's mapped for 97 ron fuel so when I fill up Friday, I am going to try some 99 ron as this should help alleviate the problem if it is detonation

While your adjusting the actuator (as per Alyn's post, half hole lined up then tug to pre-tension), make sure the wastegate flap moves freely then plumb the turbo outlet nipple direct to the turbo bypassing the boost solenoid.
This should get you boosting to around 0.5-0.6bar.

If you boost to this, which is going to run with the actuator wide open, this should then prove that your boost restriction down to 0.4bar is not solenoid, wastegate or actuator related.

Have you checked the turbo to intercooler pipe for split/cracks ? If it's running a plastic hard pipe these can split and it may be expanding when hot.

Are you sure your DV is closing and not bleeding boost off ?

Swapping early and late MAP sensors will not work as the early one (with round connector) only runs upto about 2.2bar atmospheric pressure and the later is a 3bar sensor running a different scaling.

I will try what you said about bypassing the solenoid, however I have tried 2 and the symptoms remain the same so I doubt it's the solenoid. I have wondered if it is the actuator so fingers crossed.

I willl check the Y-pipe but I have had it off in the past and it was fine then and I was experiencing the intermittent problems before that.

I am on an aftermarket DV now, but the symptoms were there with the OE DV before so again, I doubt it's that.

Noted what you said about the map sensor. I wont bother trying it.

Reverse what I said above.
1. Plumb the actuator first then see if this runs 0.4bar. This will confirm if boost control is active when you see your fault condition.
2. Then adjust the actuator and do it again and record the boost level.
Revert back to normal boost plumbing, then 'IF' the problem occurs again record the level to confirm if it is the same recorded at point 2 above.

If it is then the ECU is potentially detecting something and switching boost control off.
On the MY93-96 I did experience on a number of occasions MAF failure that exhibited limited boost, but not CEL. Cleaning the MAF in some cases cured it, in others only another MAF cured it.
The MY97-98 runs a similar MAF design, although I am not sue if the ECU applies the same control/fault logic. But it could well do.......

thanks, I also have a spare green maf somewhere so I could try that

didn't even need to replumb the actuator, the actuator is the problem.
I could move it by hand but it wasn't exactly smooth. I think when it gets hot, metal expands and the slight roughness in the actuator movement is causing it to stick.
As I still have the heat shield on, when I have been moving for a bit, the airflow cools it down and it works normal again.
When I get paid, looks like i'll get a new actuator off ebay.

One final question though, now that I correctly adjusted the actuator rod, I am boosting slightly more. I am now getting a momentary spike at 1.2bar, then dropping to 1.15 bar. There is no fuel cut and the AFR gauge still says "rich" when this happens so I assume the 1.2 bar spike is ok ?

And looking on ebay, would this be ok? and does it need to be 1.2 bar as that is what I am boosting to ? :-
http://www.ebay.co.uk/itm/Turbocharg...item1e785adc94