Analyse This

A while ago I went to a tuning shop to fit a pfc and boost controller. The garage couldn't get the boost controller to hold boost and so determine that the boost controller is faulty.

I was told that the car was "half tuned" while waiting for a new boost controller to be sent back to me (warranty).

About two months later I received news that the boost controller is fine.

The following happened since after “half tuning”. Before I knew the boost controller is fine.

I noticed high knocking while accelerating in 5th gear and attribute that to tuning problem, however since I have no budget to re-tune, I avoid accelerating at 5th gear for the time being. I checked the engine bay and hear a mild hissing sound under the pod filter. My turbo is low mount (stock GTT turbo) Since the hissing is mild at that time I thought it came from the radiator fan.

Not long after the knocking problem starts again, but this time it’s down to 4th gear, reading as high as 91.At the same time, the engine would shut down on itself without stalling. Just off like that battery light went on and engine light, just like when starting a car. Ignition works fine and the battery gauge still showing 14.4v as car turns on. It happened rarely and so I didn’t think abt it much.

However recently everything went worse, as soon as I slowed down and downshift (2nd to 1st gear abt 20km.hr) or put the car in neutral while slowing down, the engine would rev itself mildly to about 1200rpm. Otherwise the engine just shuts down like the situation above. The shutting down situation only happens when car is travelling at low speed, so thank god nothing bad happened to me yet.

At the same time, the HICAS light went on at low speed turning and when that happens, the steering becomes really heavy, the car was trying to “fix” my cornering by inducing understeer. Mind that this happens at about 25km/hr and a wide radius turn too.

So I realised something is not right and try to determine the problem. I listen to the engine and the mild hissing became louder this time.

Also I noticed greyish smoke came out of the exhaust when I start the engine. No smoke when cruising. And at times after I stop and accelerated, the car would stutter, as though abt to stall but didn’t stall.

My first thought is that there is a small leak in the intake or intercooler somewhere which causes the engine to burn rich. The soot builds up at the spark plug causing bad ignition timing. The leak has gone bigger now and the stalling get more frequent as the air escapes more; the engine tries to protect itself by mildly revving for more air as I slowed down. However I don’t understand the HICAS trying to fix my cornering at very low speed. Are there any other reasons to this? I am in the middle of exam right now, haven’t got the time to fix the car yet but I hope to find the cause.

sry for long essay