Hi all, New to the forum and just bought myself a Mk4 Golf GTI last week and as luck would have it I'm having issues already. its a 2001 1.8Turbo and I think it's boosting isn't quite right. Y reg, AUM engine, 5 speed 150bhp (Standard). A friend thinks who works for a VW specialist has told me it will be a KO3S turbo on my car. It's been modded in the past and i've noticed a few pipes have been cut off....look like breathers to me. The mods are as followed; Remapped Turbo wound up (boosting at roughly 18psi) Decat Silicon hoses Forge dump valve fitted Induction kit Coilovers (now seized ) I think that's about it. So here's the issue. When the engine is first started I give it a minute or 2 to warm up so the turbo isn't put under any stupid load and heat straight away but it only boosts at roughly 4psi with a huge lack of power but as soon as i turn the key off then on it comes back full power? If I'm cruising along on an A road/Dual carriageway/main road and holding the throttle it will start surging if it's holding boost....(roughly holds at about 8-10psi) but doesn't surge if I'm full throttle. When full throttle it will hit 18psi and stay there until i release. However SOMETIMES the pressure drops once it peaks and keeps going down. I haven't had a chance to check the turbo for any play yet but I cannot see any split pipes, my intercooler looks okay and everything seems to be okay. I'm also concerned it may run lean when overboosting as I don't want to destroy my pistons if it is running lean with that sort of pressure. I have no idea where to start and would like to exhaust every avenue before removing my turbo and potentially getting an exchange unit which i was quoted 320 plus vat for the exchange unit with a new housing included too. Thanks Dave!
Welcome to the forum! Dave, Can you perform a scan check for codes and let us know what you found? This would give an idea if the root cause is hardware or if it is the engine calibration thresholds. Thanks
Thanks, I did do a code read and the only one that meant anything when I originally read the codes and cleared them was a boost leak between turbo and throttle body. I cleared the codes and it took a couple days but my EML light is back on. I should be able to get the codes read Friday to see what codes are present atm. I couldn't see a boost leak though but I am praying I have a split pipe. I'll see if I can put it on a reader today and let you know. Thanks
