okay, so i figured out my no spark, figured out my vacuum leaks, and now a new problem. if i give the car half throttle, i can run up to redline no problems, and boost will go to around 5lbs. now at full throttle no matter what gear the boost jumps to anywhere between 9 and 12 lbs the car goes no where and it starts backfiring like crazy like its hitting a rev limiter. first thing i thought was boost leak, but i built a tester and couldn't find any leaks. the car is a stock gte swap with 3in turbo back exhaust and k&n pop charger. i've replaced all vacuum lines, plugs wires, plugs and timing belt. i'm at a loss. i also just cleaned and checked the cps.
please help...new issue
- Thread starter 7mslider
- Start date
Check the cps wires at the connector. They are bad to burn into. I dont know what the symptoms are for fuel cut because I have never hit it but they say around 12 psi with stock afm is where fuel cut is. Try lowering your boost around 8 psi and see what happens. I also read if you are hitting fuel cut that your check engine light will flash.
i cant really change my boost, because the motor is stock. no boost controller or anything. i doubt its the cps, because when i pull a plug wire, i'm getting spark well. i don't know if this helps, but i can hear the turbo start spooing around 1500rpm which seems a bit early to be spooling so hard. if i remember correctly before i had this problem the turbo didn't spool that hard till around 3000rpm. from everything i have read on this forum, it sounds like fuel cut due to a boost leak, but when i tested i didn't hear any. i did get alot of noise from the air going in when i did it though. it also seems like the motor is running hotter than usual, could this cause the problem
---------- Post added at 09:14 PM ---------- Previous post was at 09:13 PM ----------
i forgot to mention, i have no codes either
---------- Post added at 09:14 PM ---------- Previous post was at 09:13 PM ----------
i forgot to mention, i have no codes either
Check the hose going from the actuator to the wastegate on the turbo. If it has a hole in it or if it has came off the turbo will keep building boost. It will hit fuel cut. If it is stock it should not go over 8 psi.
hard to hit fuel-cut with stock everything including boost. But I would definitely check that wastegate vacuum line. A manual boost controller is inexpensive and you can easily set it and forget it, and not have to worry about overboosting. Also you said you had no codes. If you did overboost, you would have a code....which is # 34. BTW my turbo is slightly audible at low rpm too.
thanks for the help guys....after i looked at the wastegate it does look like the vacuum line may be binded a bit. i'll replace it later today and report back.
89supracrazy;1543458 said:
with my experience boost cut hits around 15psi and ya the check engine light will come on for like 5 seconds then quickly go away...you may be hitting boost cut but 6psi is stock boost and if all you have is an exhaust it shouldnt really go past 8... make sure there are no shims on that wastgate from the previous owner
7mLove;1543716 said:
I shimmed my actuator myself. I have the lexus afm and 550s. I have the factory bypass screw so I would have to run alot of boost to hit fuel cut. I hopefully will never get to the point.
okay, so i replaced the vacuum line going to the actuator, not my problem. i doubt the actuator is shimmed because i did not have this problem when it was colder weather and if i'm not mistaken the more dense air would have made me hit fuel cut earlier. when i get a chance i'll check to see that the wastegate is opening correctly. should i be able to hear an audible difference in the exhaust when the wastegate opens? i have a tms downpipe with integrated elbow test pipe and blitz nur spec.
If the actuator is shimmed it will have washers between the turbo and the actuator itself. Real easy to see. There should be no washers . When you replaced the timing belt did you put it in time correctly. You have to set the timing with the jumper between te1 and e1. If you dont you are fighting the computer.
just checked, no shims on the wastegate. one thing i did notice though, i am missing some clamps on the pcv lines. i know when i ran the boost leak test i had to cap off the lines so air wouldn't come through. if the lines aren't clamped and not air tight, could this cause my problems. i guess what i'm asking is, could bad pcv lines cause a boost leak?
7mslider;1543784 said:
7mslider;1543468 said:
you are not testing for boost leaks properly, back to square one
if you hear air rushing in during the boost leak test dont you think that that air must be going somewhere (ie escaping somewhere)?
the pcv lines have nothing to do with the pressure circuit. so they should not need to be blocked off (no need to pressurize the accordion tube).
listening for leaks is obviously not a good way to find a leak.
I usually test right from the Turbo discharge in.
(I unbolt the intake cam so I can test right up to the head this is how I found my intake gasket leak)
(I unbolt the intake cam so I can test right up to the head this is how I found my intake gasket leak)
I believe I would check the hose coming out of the turbo to the intercooler. The pipe has a coupling about half way before it gets to the intercooler. I would get the car up on ramps and check all the connections going from turbo to intercooler and out of the intercooler to the intake. Even the rubber boot before the TB on the 3000 pipe.
i replaced all the clamps on the intercooler piping, still the same problem. when i did my test for a boost leak i did it two different ways 1. i disconnected the accordian and blew straight through the turbo with the pcv lines capped 2. blowing through the same way but i disconnected the charge pipe and capped right before the 3000 pipe. should i disconnect the intercooler piping from the turbo and just put my air in through there? i just figured that i should have the air passing through the turbo incase the housing was some how cracked. so when i run the air through, i shouldn't hear any air moving at all once pressurized?
If your turbo compressor housing is somehow cracked then you have a problem, no need to perform a test to bypass an obvious issue. You should be able to figure out where the air is going, and if it is supposed to go there.7mslider;1543921 said:
Good f'ing call my friend. this would be the best test as long as you cap off various ports that are supposed to leak boost (ie pcv, egr, evap, possibly others)IJ.;1543864 said:
With all of this said, a boost leak may not be your problem, but since a "unconfirmed problem" caused you to replace all of the clamps on your piping tells me that you are grasping at straws, and not willing to properly diagnose the problem. Some actual results, to a well performed test is needed to move on with diagnosis.