Sudden power loss and flat on acceleration

[morbo1980]

Hi guys,

The latest in a long line of issues popped up today. The car has a little bit of a history which I'll mention now in case it has any bearing on the new issue. Car is an 06 build MY07 GTB 6MT sedan with around 125k km and running stock tune. Current mods are TCP turbo back exhaust with a muffler replacing the resonator in the centre section, and a panel filter. I replaced the OCV's a few months back. Straight after that had a cracked oil pickup replaced and had the timing belt service done at the same time. Fuel filter wasn't changed with this service but is about due.

Was towing an empty trailer down the freeway today and started having issues with my car losing power suddenly. Felt a bit like the brakes were being applied. If I changeed down to 5th I'd be able to recover speed but the power delivery wouldn't be smooth. I'd then be able to go back into 6th for a while before I'd get the sudden power loss again. When I pulled over I reckon there was a slight burning smell but I couldn't pinpoint where I was coming from, it may have just been from the brakes from when I pulled over.

I checked the oil, level was on full. Checekd the coolant overflow bottle and it was on the full mark but there were a few bubbles in it (not to sure about this after reading the head gasket discussions recently). I had over an hour to go to my destination so decided not to risk it and turned around and completed my journey with a different car.

Fast forward a few hours later after getting home. I had to run up the street (this time without trailer) so was playing a bit with the throttle. If I gave the car a moderate boot full, the car would accelerate but would suddenly feel very restricted. Almost as if it was struggling for air. As soon as I'd back off a bit it felt there was a sudden jolt of accelaration and the car would feel more normal. It seemed that if you gradually fed the throttle it felt mostly normal.

I'm meant to be getting a Kido tune Thursday night but not sure if I should cancel now. I don't have a Tactrix cable so no way to do any logging.

I didn't have time to properly look over the car (and not sure I would have picked up on anything if I did). Heres a list of possibilities or things I think I should check
Vacuum hose popped off (there was nothing obvious when I popped the bonnet but I didn't do an exhaustive check)
Dirty MAF
Dirty air filter
Dirty fuel filter
Bad fuel (filled up this morning with V-Power from my normal servo)

Is there anything else I should check or does anyone have any ideas?

Thanks,
Ben.

[HighTech RedNeck]

if its feels ok under light load but get severly worse with more power it can be a blocked cat, but i am new to these but did you notice and missing or was it like a complete change the way it felt

[fibble]

Clutch isn't slipping is it?
Not unheard of at 125ks.
I read, towing a trailer in a tall gear + burning smell + loss of power.....

Did (a) the rev's rise but it felt gutless or (b) it didn't want to rev?

[Dropz]

Check your brake lights. It's possible they have blown. If both blow te ecu thinks you're driving with your brakes on and cuts throttle opening to 20%

[Boostaddict]

Check all above but don't cancel your kido tune!! In fact its almost perfect timing that Matt will have a look at it


If there is an issue he can help you with diagnosing it!! If its just a simple error code he can clear it and tune it for you.!!

[OzSTi]

Check your brake lights. It's possible they have blown. If both blow te ecu thinks you're driving with your brakes on and cuts throttle opening to 20%

With regards to above, was it significant you had a trailer attached and some error in the lights connection?

[morbo1980]

Hi guys,

Thanks for the replys.

if its feels ok under light load but get severly worse with more power it can be a blocked cat, but i am new to these but did you notice and missing or was it like a complete change the way it felt

It had been fine until yesterday when I was halfway down the Eastern freeway. Now when I accelerate as soon as you get past say 50% throttle (maybe less) it's like the car suddenly chokes, you can almost feel a jolt. Flat to the floor the revs do continue to slowly rise as does the car speed but it's like there is a big weight hanging off the back of the car. When I ease off there is another little jolt and the car actually accelerates quicker than what it does at full throttle. The car doesn't really sound different when this happens, you can still hear the turbo spooling and it doesn't sound like it's missing or pinging.

Clutch isn't slipping is it?
Not unheard of at 125ks.
I read, towing a trailer in a tall gear + burning smell + loss of power.....

Did (a) the rev's rise but it felt gutless or (b) it didn't want to rev?

I don't think it's clutch slip. The revs weren't flaring when putting the foot down.

Check your brake lights. It's possible they have blown. If both blow te ecu thinks you're driving with your brakes on and cuts throttle opening to 20%

Will check this at lunch time. The guy at the servo didn't mention anything when he checked the trailer lights but doesn't mean it didn't happen after.

Check all above but don't cancel your kido tune!! In fact its almost perfect timing that Matt will have a look at it


If there is an issue he can help you with diagnosing it!! If its just a simple error code he can clear it and tune it for you.!!

I was thinking this too. Just depends on if it's simple or something mechanical.


I had another thought. Could it be the turbo inlet pipe crushing under higher levels of boost? Might explain why it feels ok under light throttle but when you cross a threshold it suddenly feels like it's choking. Not sure how likely this is on a stock car though.


Thanks,
Ben.

[bosc0]

Does sound like a vacuum leak. If you can check the small vac lines near the turbo and then i'd take a look at the intercooler to throttle body joiner, these are apparently prone to failing.

[KiDo_Tuning]

tmp_IMG_1433-1073296064.jpg (64.16 KiB) Viewed 5082 times

TMIC to throttle gasket. As soon as it comes on boost, air measured by the MAF leaks out on boost above 3200rpm and the result is car runs rich with less ignition timing. Easily fixed.

Other one could be the BOV vacuum hose has popped off

[morbo1980]

Ok so did some checks during lunch.

Brake lights are all working so not that (would have been a nice easy fix).

Couldn't see any vacuum pipes popped off anywhere including around the blow off valve. I'm guessing the only way to check the TMIC to throttle body gasket is to take the TMIC out. If I'm going to that I might as well just replace it. Does anyone have a part number?

I did find something though. Looking at the turbo inlet pipe where it attaches to the turbo there is a crack in the "muffin top" (best way I can think to describe it ) before the hose clamp. I tried to get a pic of it on my phone but couldn't get a decent shot of it. I was able to poke my screwdriver into the crack so I reckon this would count as a vacuum leak. Also there was a bit of caked on dirt and oil around the area that I was scraping off with the screwdriver.
Also it looked to me like the "muffin top" was bulging back over the hose clamp at the bottom of the pipe, but I couldn't find a good angle to look and couldn't fit my hand in there to feel. I'm guessing this means new inlet pipe time.

[dr20t]

That's your problem right there

[Boostaddict]

That's your problem right there

Yep, done and dusted!!

Replace with a Perrin, Kobe , PSR etc etc

[bigBADbenny]

TMIC to throttle gasket. As soon as it comes on boost, air measured by the MAF leaks out on boost above 3200rpm and the result is car runs rich with less ignition timing. Easily fixed.

Other one could be the BOV vacuum hose has popped off

Matt, where is that gasket, in relation to e.g. the TMIC to TB hose?

[KiDo_Tuning]

TMIC to throttle gasket. As soon as it comes on boost, air measured by the MAF leaks out on boost above 3200rpm and the result is car runs rich with less ignition timing. Easily fixed.

Other one could be the BOV vacuum hose has popped off

Matt, where is that gasket, in relation to e.g. the TMIC to TB hose?

Throttle body end, it wraps around the stock rubber pipe and blows out under boost

[morbo1980]

I've just got off the phone with Makin & Luby and they're trying to track down which gasket it is so if you have a part number that would be great. Also if anyone is interested the stock turbo inlet pipe is $246.81 inc gst, they don't have any in Aus and it'll take them 3 weeks to get one from Japan, so I'm about to hit the Checkout button on the Pro Speed Racing website.

Matt I'll send you a PM because it's looking pretty likely I'll have to cancel the tune, unless the new inlet pipe magically teleports into my engine bay, or I can convince a mate to spend a few hours in the dark with me to install the new pipe. That's even if it arrives in time.

Thanks,
Ben