How I fixed overboost and surge problem 1.8T

-Joe · 16th January 2023, 20:59

I had two causes for my 18T 75s poor performance.

Problem 1 Overboost caused total power loss during overtaking and full throttle acceleration.

I removed all three small pipes from the turbo, cleaned them and made new good air tight connections with small lengths of new rubber pipe. I poked the holes clean with a cocktail stick.

I cleaned all the big air pipes and made sure they all sealed well.

I tapped the waste gate arm carefully with a hammer to free it and then levered it to make sure it wasn't stuck closed. It won't move much due to a heavy spring in the actuator.

I took the valve on the air box and cleaned it with WD, tested it on a car battery, hear the thing click and blew through it with 12v power on and off. I refitted it and made sure the air pipes had a good seal.

Problem 2 The car still had a lesser surge problem.

I replaced the HT leads and coil packs with new ones. The turbo needs a super good spark when high boosting. So HT ignition needs to be perfect for smooth acceleration.

Car is now fixed!

tony g · 17th January 2023, 14:25

sounds like a plan for my 1.8T Joe, mine just looses all power for a second at nearly 4000rpm and then kicks back in under hard acceleration. ive re-gapped the plugs 0.70mm and fitted new coil packs and leads made no difference. just far too cold and wet right now

16th January 2023, 20:59	#1
-Joe Avid contributor Rover 75 Classic SE 1.8T Join Date: Dec 2008 Location: wink Posts: 135 Thanks: 0 Thanked 20 Times in 15 Posts	How I fixed overboost and surge problem 1.8T I had two causes for my 18T 75s poor performance. Problem 1 Overboost caused total power loss during overtaking and full throttle acceleration. I removed all three small pipes from the turbo, cleaned them and made new good air tight connections with small lengths of new rubber pipe. I poked the holes clean with a cocktail stick. I cleaned all the big air pipes and made sure they all sealed well. I tapped the waste gate arm carefully with a hammer to free it and then levered it to make sure it wasn't stuck closed. It won't move much due to a heavy spring in the actuator. I took the valve on the air box and cleaned it with WD, tested it on a car battery, hear the thing click and blew through it with 12v power on and off. I refitted it and made sure the air pipes had a good seal. Problem 2 The car still had a lesser surge problem. I replaced the HT leads and coil packs with new ones. The turbo needs a super good spark when high boosting. So HT ignition needs to be perfect for smooth acceleration. Car is now fixed!

17th January 2023, 14:25	#2
tony g Posted a thing or two MG ZT Join Date: Dec 2006 Location: cumbria Posts: 1,238 Thanks: 8 Thanked 43 Times in 24 Posts	sounds like a plan for my 1.8T Joe, mine just looses all power for a second at nearly 4000rpm and then kicks back in under hard acceleration. ive re-gapped the plugs 0.70mm and fitted new coil packs and leads made no difference. just far too cold and wet right now