Supra Forums banner
1 - 14 of 14 Posts

·
Registered
Joined
·
235 Posts
Discussion Starter · #1 ·
Well in short I am a newb here on SF, but am not new to turbo charged vehicles due to owning a 91 Stealth RT TT and a 93 3000GT VR-4. Here as of lately I have been experiancing some issues with my Supra. When I am accelerating with moderate pressure on the gas pedal, the car will act as if I am trying to pull another vehicle behind me and a few moments later BAM..the boost hits. It kinda also feels like I deployed a parachute behind me and am getting huge resistance when trying to accelerate. Anywho, another issue that has eemed to arise is I have a jumpy idle. Not real high or to low of an idle..just jumpy at times.

I have searched..well lets say tried to search for a procedure on how to pressure test the vacuum lines and all that good jazz. I am hoping I have a small leak somewheres and that will be a cure all for my sysmptoms. The search function here on SF has been kinda iffy as of lately. I did find a post the other day where a soup can was utilized, but since due to search issues have not been able to recover the thread. I have also picked up a CEL which is pointing to the o2's...dont know if that would have a signifigant reason for the car to act like it does, but thought I would throw that out there. It looks like pressure testing on the MKIV's is a little bit more elaborate vs. the 3/S's cars, as to where we can do a vacuum line reduction mod (leaving only 4 lines) and being able to test the entire system to include IC piping in just a few minutes.

I feel reluctant to post this thread, Iam sure this issue has been beat to death over the years, but if I can t utilize the search function I'm kinda at a stand still. I have today off and would like to use it to narrow down these issues with my Supra.

How do you pressure test a MKIV TT BPU, utilizing the stock twins? (Pictures would be very helpful)

1994 MKIV TT (Auto)
Greddy EBC, Greddy turbo timer, DP, HKS SD exhaust, FCC, stock SMIC.

Thanks for your help in advance for your help, I look forward to your input. :bowdown:
 

·
Registered
Joined
·
967 Posts
There are multiple threads with various techniques on how to do a boost leak test. Also, are you running it in sequential or TTC? I assume with those mods you have a boost gauge (or at least should) so what is it doing on the boost gauge?
 

·
Registered
Joined
·
235 Posts
Discussion Starter · #3 ·
Yeah..
I have a guess-o-meter boost gauge. The boost is set to 14-15psi. The gauge will go to about 8psi and then the reistance will start, boost will hover then BAM, here comes the extra boost, taking me to 14-15psi. I am running sequential at this time.
 

·
Registered
Joined
·
952 Posts
from what you describe, it sounds normal. First turbo will boost to 8 psi and then when both turbo kicks in, you get that sudden jump and boost will go up. :)
 

·
Registered
Joined
·
235 Posts
Discussion Starter · #5 ·
crazysupratt said:
from what you describe, it sounds normal. First turbo will boost to 8 psi and then when both turbo kicks in, you get that sudden jump and boost will go up. :)
Nah...I dont think its normal....The car would run like a raped ape back in the day. :bowdown: Hellbringer found a vacuum line had popped off the pressure tank when I first bought the car. After that inital fix the car was absolutley amazing...I was very impressed with the MKIV platform at BPU level :sadance: ...kinda sad to say my 3/S's needed alot of mods to get to that level. Over time the car has become slower and less responsive in regards to boosting. :rolleyes:

I need to do a pressure test when I find info or a link is provided....
 

·
Registered
Joined
·
3,658 Posts
I have also picked up a CEL which is pointing to the o2's...dont know if that would have a signifigant reason for the car to act like it does,
You need to do a pressure test & Replace your primary o2 sensor. If you are getting a CEL for your primary o2, that will have a large impact on performance. All of your long and short term fuel trims will be way off. Get that fixed ASAP.
 

·
I love sequentials!
Joined
·
2,578 Posts
I'll try and post a picture of what I used to pressure test mine, it's very simplistic and works awesome. I found that the tool who owned the car before me had crimped something inbetween the intake manifolds and it had a major leak there.
 

·
teh DJ
Joined
·
413 Posts
interesting....sometimes I get that feeling on my MKIV Supra too....but I don't get it everytime, maybe once every 2 weeks or so...guess I need to check my lines also...
 

·
Fat Guy in a Little Coat
Joined
·
281 Posts
I would first put the car in TTC mode to make sure it is not a turbo issue. When I had the twins I had an unexplained boost leak. I just put it in TTC and ended up leaving it. After a while I got used to it. Only down side is slight more lag.
 

·
Registered
Joined
·
235 Posts
Discussion Starter · #12 ·
Well get this guys. I went to pressure test the MKIV and I noticed that my piping where the MAF is secured had a nice gash in it. I figured right away that this could be the reason for my issues. I went ahead and removed the MAF and repostioned the remaining intake piping so I could slid my can of corn up in there. Low and behold I noticed that the pipe had a huge gash in it going have way around the accordian section. I was like WTF! :wtflol: Anywho i didnt get a chance to pressure test and am thinking this is the issue Im more than like ly having due to unmetered air getting in there. I am looking for replacements now and will post more when I get the pressure test completed. :bigthumb:
 

·
Registered
Joined
·
307 Posts
My car has been suffering from this symptom since I did a conversion from stock to the HKS EVC EZ. After reading a bit I "guessed"it was that during the mod I may have changed from Seq to TTC. It definitively feels like TTC since the first seems to be some Turbo Lag and then "BAM" just like you mentioned. Still in the process of figuring this out.

I still need to go further since I have not run my car for a while due to some mods/corrections/improvements being done.

thanks for posting this, since I will keep looking into this thread and the one already attached to keep researching.
 

·
I love sequentials!
Joined
·
2,578 Posts
Ok, the way this picture works is this


You have a valve, a piece of 1/8th inch NPT male/male pipe and a 3" pvc plug/cap.

I ground down the outter threads on the pvc plug/cap, then took a drill, drilled a hole in the pvc plug/cap, tapped it for the 1/8th" NPT. After I threaded the rod and valve to it, it's ready to go.

All in all, this cost me $12 with tax at home depot, and $7 of it went to the valve that can be eliminated if you wanted. You can also make this same basic idea with pvc reducers/couples, which I've also done. It isn't as compact and costs a little more, but eliminates the 1/8th inch tap. That is the kind I have for my Lexus, and it also works well.

See the attached pictures and let me know what you think or if this helps anyone!
 
1 - 14 of 14 Posts
Top