Intermittent boost...what to check

[willg54]

just been for a drive and have an update

after the drive, i pulled the codes and got 2224 - Maximum charge air pressure exceeded

so according to s2central could be

• Intake air leak after turbocharger
• Wastegate frequency valve (N75) faulty
• Vacuum tube from inlet manifold and J220 has leak or is disconnected
• MAP sensor in J220 is faulty

I'll add a check to the wastegate and MAF to this too...

wish i could do it now but it's all far too hot!

heres a video of it too - 3rd gear pull from about 2000rpm to 4500rpm. at about 10 seconds you'll see the boost needle drop then come straight back up.



this only happens i think when the ecu uses it's magic overboost function.

[willg54]

wastegate diaphragm looks fine...my fingers are a little burnt though haha

found the other end of the wastegate to n75 was loose...must have been one of those ones you miss! other than that, i cant seen anything that looks like it might be leaking (i know this isnt the best method lol) all joints are tight and i've done the markH mod so not the o-ring.

I've cleaned the MAF and connector

I might change the vac hose to ECU tomorrow as that is the only original one left.

[Drummer87]

Yeah check the ecu for splits. least you'll have it sorted tomorrow

[newsh]

If you have a leak in the hose from turbo to wastegate then you will exceed mapped boost pressure and the ecu will shut the boost down

[martinws]

If you exceed max boost pressure do you not get a boost cut? I had a hole in the lower waste-gate chamber and it would boost cut and nearly make me go through the windscreen.

[willg54]

If you have a leak in the hose from turbo to wastegate then you will exceed mapped boost pressure and the ecu will shut the boost down

well hopefully sealing that up will have sorted it then. i had missed the pipe clip off it



@ martinws yes, i was getting a boost cut. Dropping out then coming back...watch the vid!

[willg54]

ps...thanks for all you help!

[willg54]

Still not fixed...it's only when the overboost function is used.

Tomorrow I'll try changing the maf, n75 and changing the ecu boost line. One of those will hopefully fix it as I leave at 9pm for the ferry!

Sent from my GT-I9300 using Tapatalk 2

[willg54]

I had a good look over things today, and on inspection the n75 fell apart!! Changed and the boost cut seemed to have disappeared.

Think I might still have a small boost leak somewhere as the revs hold when you declutch and coming up to a stop the revs drop very low. Could be isv too I think?

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[UrS4boy]

...Think I might still have a small boost leak somewhere as the revs hold when you declutch and coming up to a stop the revs drop very low. Could be isv too I think?

Revs holding on declutching = stiff throttle poteniometer, and/or dashpot too far out?

Revs dropping too low = ISV (probably)

Links to info: (click on the labels) http://members.shaw.ca/speedtek/UrS%...ice%20Map.html

Photo of AAN showing dashpot and ISV