Worrying Behaviour In Very Heavy Rain

January 6, 2011

Short background -

Had my pre-facelift 190 for about 4 years now

Powerflow exhaust fitted in the first 6 months by Demon Tweeks (mid/rear/tailpipe)

Not been giving the oil grade proper consideration (always been semi-synth)

Problem -

The car has made some very strange, loud noises during heavy, constant rain. It seems to be coming from underneath the middle section of the car, around the handbreak / gearstick area. Strange, deep vibrations, almost feels like it's choking and can't breath, and I experience a loss of power. It might be my imagination but it seems to happen more around the 3,000rpm mark, going up hills in the rain, and when I give it the beans, again all in heavy rain.

I know when it's about to happen as the usual tone of the car changes, I can sense it's starting to wobble so I know I have to take it *really* easy on the accelerator or else it'll go.

I've had to pull over twice, it's literally gone *klonk* as though the gear box or exhaust has dropped off, and it cuts out, exhaust emissions light comes on and I'm unable to start again for about 10 mins... When this happens if it's still heavy rain I know there's no point driving as it'll just happen again half a mile down the road. I've got out of the car both times and had a look underneath expecting something to be hanging off, but nothing. When the rain stops or slows down the car is drivable again and the light goes off.

It doesn't always pack in though - on a few more occasions it's been heavy rain but not torrential, and this is when I can prevent it from happening - it needs to be kept really steady on the revs and not pushed AT ALL, literally if I go above 55-60mph or 3000 revs I'll start to get the initial wobbles.

It's really bizarre, I've spoken to my local garage (admittedly not a Toyota specialist) and they can't troubleshoot the problem. I've taken it back to Demon Tweeks a few months ago for them to check the welding on the exhaust and they insist everything is as it should be, and they've never heard of any similar problems being caused by the exhaust system, so I need to look elsewhere.

After a wobble a couple of months ago (just the strange noises - managed to save it falling into loss of power/klonk), I checked the air intake under the bonnet, thinking that could have been sucking through water, but the filter seemed bone dry (admittedly I only half-removed the cover but was able to run my ringer across about 3 inches and it wasn't even damp).

The car runs fine in light/normal rain and is perfect in humid, dry and hot conditions. I do very occasionally get a deepish, almost 'crackle' coming from the exhaust at 3000 revs in colder temperatures.

This has only happened maybe 8-10 times since I've had it (of which I've had to pull over twice), but it really does make you panic when on the motorway in the rain and you can feel something's about to go really wrong. It's at it's worse when the rains literally bouncing back up off the ground and there's a lot of surface rain on the road.

Really hope someone recognises the symptoms because it's a great car otherwise.