Low Turbo Boost

vtbullmoose · 04-30-2005, 06:10 PM

Hi all. I have recently finished replacing the head gasket on my 1990 Toyota supra with the 7MGTE engine. The motor idles ok, with the boost gauge reading –4. The motor also runs fine, except for when I try to accelerate. There seems to be a huge lack of power, and my boost gauge will barely get above the 0 mark. I heard that when you blow a head gasket it could kill the turbo as well. Therefore I replaced the turbo with a rebuilt one, and have gotten the exact same results. There is a white smoke coming out of the car when it is first started, but that quickly disappears. I did hook up a vacuum gauge, and that will drop to 0 with just a light push on the gas pedal. Usually that will stay around 15 or so. I have not checked the intercooler pipes, but plan to do so soon after reading other responses. Also I just had the clutch replaced about 2 years ago, so I don’t think that could be the culprit. If anyone has any ideas please let me know, I’m up for checking anything at this point. Thanks!

[Damnit] · 05-05-2005, 06:03 PM

did u try to replace ur head gasket?

monkihead · 05-05-2005, 08:16 PM

are you seeing large bursts of white or is it only after the car sits or idles for a while? it sounds like a cracked head.

vtbullmoose · 05-10-2005, 02:22 PM

NO, The head gasket was replaced, and when I had the head off. I took my head into a machine shop where they water, and pressure tested it along with milling it down so it laid flat back on the engine block. I guess aluminum heads are known for warping.

monkihead · 05-11-2005, 01:27 AM

i'd check the compressed air tubing and the compression for each cylinder. it might just be that your getting mad blow by under boost.

suprra_girl · 05-18-2005, 12:47 PM

you don't have a bhg, i would say ur rings are fine

just a boost leak like ur original idea

what is ur vacuum at idle?

normalish is between 18-20inhg

vtbullmoose · 05-22-2005, 12:02 AM

Thanks for all the suggestions, I finally discovered that the dam pre-converter is blocked. I have looked to try to replace it and no one, including toyota can get it for me. It's the exhaust pipe from the Turbo to the catalitic converter. Anyone have any ideas where I can get one, or can I just go to a down pipe since it still has the catalitic converter?

monkihead · 05-22-2005, 03:49 AM

heres a start....
http://www.suprastore.com/exhaustsection.html

suprra_girl · 05-22-2005, 11:13 AM

go to your local exhaust shop and get a new cat fitted
fixed

is it just ur cat? or has ur whole downpipe rotted out?
there's a megamouth thing on ebay for sale a few times... look pretty nice too and cheep

Black 5spd · 05-25-2005, 02:54 AM

i am a noob to supras but a turbo is a turbo, soi say just get a new down pipe and throw your cat in the trash.
p.s. catalytic converters suck, cats are cool. B)

05-05-2005, 08:16 PM	#3
monkihead SP58GT Join Date: Mar 2005 Location: San Antonio texas Posts: 646	are you seeing large bursts of white or is it only after the car sits or idles for a while? it sounds like a cracked head. __________________ ....all you need is a small taste of success and you will find it suits you.... monique- better off dead

05-11-2005, 01:27 AM	#5
monkihead SP58GT Join Date: Mar 2005 Location: San Antonio texas Posts: 646	i'd check the compressed air tubing and the compression for each cylinder. it might just be that your getting mad blow by under boost. __________________ ....all you need is a small taste of success and you will find it suits you.... monique- better off dead

05-18-2005, 12:47 PM	#6
suprra_girl 7M POWAH! ;) Join Date: Jun 2004 Location: New Zealand Posts: 2,312	you don't have a bhg, i would say ur rings are fine just a boost leak like ur original idea what is ur vacuum at idle? normalish is between 18-20inhg __________________ Please use the forum to ask your questions as they will get replied to much faster than pming me Pics of my build. "Good girls are just bad girls that don't get caught" Do a diagnostic first!

05-22-2005, 03:49 AM	#8
monkihead SP58GT Join Date: Mar 2005 Location: San Antonio texas Posts: 646	heres a start.... http://www.suprastore.com/exhaustsection.html __________________ ....all you need is a small taste of success and you will find it suits you.... monique- better off dead

05-22-2005, 11:13 AM	#9
suprra_girl 7M POWAH! ;) Join Date: Jun 2004 Location: New Zealand Posts: 2,312	go to your local exhaust shop and get a new cat fitted fixed is it just ur cat? or has ur whole downpipe rotted out? there's a megamouth thing on ebay for sale a few times... look pretty nice too and cheep __________________ Please use the forum to ask your questions as they will get replied to much faster than pming me Pics of my build. "Good girls are just bad girls that don't get caught" Do a diagnostic first!

04-30-2005, 06:10 PM	#1
vtbullmoose Stock Join Date: Apr 2005 Posts: 3	Hi all. I have recently finished replacing the head gasket on my 1990 Toyota supra with the 7MGTE engine. The motor idles ok, with the boost gauge reading –4. The motor also runs fine, except for when I try to accelerate. There seems to be a huge lack of power, and my boost gauge will barely get above the 0 mark. I heard that when you blow a head gasket it could kill the turbo as well. Therefore I replaced the turbo with a rebuilt one, and have gotten the exact same results. There is a white smoke coming out of the car when it is first started, but that quickly disappears. I did hook up a vacuum gauge, and that will drop to 0 with just a light push on the gas pedal. Usually that will stay around 15 or so. I have not checked the intercooler pipes, but plan to do so soon after reading other responses. Also I just had the clutch replaced about 2 years ago, so I don’t think that could be the culprit. If anyone has any ideas please let me know, I’m up for checking anything at this point. Thanks!

05-05-2005, 06:03 PM	#2
[Damnit] Stock Join Date: May 2005 Posts: 6	did u try to replace ur head gasket?

05-10-2005, 02:22 PM	#4
vtbullmoose Stock Join Date: Apr 2005 Posts: 3	NO, The head gasket was replaced, and when I had the head off. I took my head into a machine shop where they water, and pressure tested it along with milling it down so it laid flat back on the engine block. I guess aluminum heads are known for warping.

05-22-2005, 12:02 AM	#7
vtbullmoose Stock Join Date: Apr 2005 Posts: 3	Thanks for all the suggestions, I finally discovered that the dam pre-converter is blocked. I have looked to try to replace it and no one, including toyota can get it for me. It's the exhaust pipe from the Turbo to the catalitic converter. Anyone have any ideas where I can get one, or can I just go to a down pipe since it still has the catalitic converter?

05-25-2005, 02:54 AM	#10
Black 5spd Stock Join Date: May 2005 Posts: 10	i am a noob to supras but a turbo is a turbo, soi say just get a new down pipe and throw your cat in the trash. p.s. catalytic converters suck, cats are cool. B)

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