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boost only when cold

izup69

izup69

Destroys cars
Ok so I have had this problem for a while now the car only gives me full boost while It is cold. Once the car warms up it no longer gives me boost. Im just about ready to have the computer relearn factory settings. I have not messed with the pcm the previous owner did.

Car dont shift when it is suposed to and other stuff has lead me to beleave this. Just take a look at these logs and see if you can tell anything outa whack. If you need more info just let me know and ill log more data points. These where taken with torq I have highlighted the areas where I run into boost.

Download data log.csv for free on uploading.com I think that link works. But I'm at work so it wont work for me. Thanks for all the help
 


I'm guessing this is on the '97 GTP?

Have you checked for vacuum leaks?

Any SES lights?

BBV moving correctly?
 
I have checked everything possible. no vac leaks bbv works fine it opens all they way up when I hammer on it. no ses lights the car is in perfect shape except for this one problem.
 
I have a thought, maybe the car isnt getting enough air or maybe its just not dense enough. Check ya exhaust back pressure too, that should be no higher than 1 1/2-2psi at WOT or at least 4k-5krpm. Maybe your not getting enough air in and enough air out. That air flow restriction could disrupt the boost psi.

It works in the morning while the engine is cold but dosent work correcty once at operating temp. Possibly the air flow at diff temps or your car may only be operating off of open loop correctly(cold start until engine reaches operating temp) and once in closed loop(operating temp), something may be off affecting the boost

Hope this helps, Dee!!!
 
I have open cone k&n and a full magniflow exhaust. I dont think it is the air in/out. But I will check. What is the best way to check? Im guessing its something to do with open/closed loop. I never had this problem when I got the car. But it was in the fall and air temps were cooler. And this problem only started when it got hot out. So with that in mind might be the air is not dense enough and the car has something changed in the computer that kills boost when its in closed loop.

Would a computer re-learn fix this problem ?
I have a spair 97 computer but I think it is fried. When I hook it up to the car it wont even start. So I might just get that one re-programed and see if I can use it since this car is my dd at the moment. And I don't have the time to put it in the shop.
 
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See I think it has the orig cat on it. Not positive tho. I'm half tempted to cut a hole in front of the cat and see if that makes a diffrence then I can just weld the hole shut with some spair steel if that is not the problem. It has ben sugested that it was the problem. But it sure dont seem like its cloged.
 
izup69 said:
See I think it has the orig cat on it. Not positive tho. I'm half tempted to cut a hole in front of the cat and see if that makes a diffrence then I can just weld the hole shut with some spair steel if that is not the problem. It has ben sugested that it was the problem. But it sure dont seem like its cloged.
Click to expand...

Let the cat idle and warm up try it from cold as well. But rev it and see if it hesitates, i believe the rev limiter on gtps is 4000? But if it hesitates at all its time to cut a whole in it or take it out
 
Yup, the cat being part of the way ya car breathes could definately be causing some air flow issues. In the case of that not being the issue, trying to let the PCM re-learn itself may work. if not for this issue, it may very well fix another or prevent one from happening.

To do a back pressure test, just put a PSI guage into the O2 sensor location. S1(upstream O2 sensor) port will tell u the psi b4 the cat and S2(downstream O2 sensor) will basically tell u the PSI after the cat(for the mufflers and pretty much the rest of the system). So use S1 port to check the CAT

Shouldnt be no more than 2psi at WOT and really not even that much, should be a lil less than 2psi especially with u having it modded a lil(should be breathing pretty good unless it is clogged somewhere)

Let us know............
 
That. ^^

Should be 0-1 psi of back pressure.

Hell just take the upper o2 out and drive it around the block, it'll sound like a tractor, but if you dont have a pressure gauge, its another way of doing it.
 
Yeh Ill try that guys. I have some time off at work comeing up here so I should be able to get to it this weekend. If it is the cat I got some spair exhaust pipe laying around I will just delete the dam thing. Thanks for all the input. I might even be able to get to it today after work. Will have to see what the wife wants me to do around the house :/
 


Ok so I tryed to work on my car over the weekend. Didnt work out to well but I did manage to find a exhaust leak I was looking for. It is right after the cat. I do Not a s1 o2 port only s2 If i have a s1 I cannot find/see it on my dp to remove it. Didnt have the time to drill a hole in my dp and then re-weld it (it started to rain and as most of us know water plus high voltage don't mix) I don't have the cash yet to have the pcm re-learn at the garage. So for now I will just have to live with the problem. (saves me money on new tires)
 
sorry couldnt see it. Ill rip it out tonight if the rain stops. If it is my cat will be a good time to fix the masive exhaust leak that makes the car sound like a pos. EDIT: I tryed getting it off but to no avail. Absolutly not enuf room to turn a wrench in there. Hopefully I can make it to my parents house this weekend and ill just cut the dam cat out once and for all.
 
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