Big Cams cause to low of vacuum?
12-12-2003, 05:57 PM
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Big Cams cause to low of vacuum? I just had installed a TSP 231/237 with PP heads and now im getting the P0121 code (throttle position sensor circuit insuffiecent ac).
The shop that installed it says that its because the cam is to big and causes to low of vacuum.
I am having problems with it upshifting to early at WOT and also the TCS light comes on and wont let me turn it off or on. ive read some post of other people having the same code and having problems with the tranny shifting to hard and hard starts with some bad idling. which have also
if anybody knows what i need to do to fix this problem, PLEASE let me know
The shop that installed it says that its because the cam is to big and causes to low of vacuum.
I am having problems with it upshifting to early at WOT and also the TCS light comes on and wont let me turn it off or on. ive read some post of other people having the same code and having problems with the tranny shifting to hard and hard starts with some bad idling. which have also
if anybody knows what i need to do to fix this problem, PLEASE let me know
12-12-2003, 06:29 PM
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I get the same conditions on my 98 with a 238/240 cam 
Haven't really done much to solve it yet though, but I'll keep my eye on this thread in case someone else has tackled it..
Haven't really done much to solve it yet though, but I'll keep my eye on this thread in case someone else has tackled it.. 
12-12-2003, 08:01 PM
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Our 98 Z28 had set that code with a bigger camshaft. I don't remember what exactly we did to fix it but it only really had problems at the track IIRC. The other weird thing about that 98 car was the Theft Deterent would activate before the 1-2 shift and shut off fuel, I think we disabled the VATS in LS1-edit to eliminate that.
Jason @ TSP did the tuning, so I'll ask him if he remembers what he did to get rid of the code.
The cam we had at the time was bigger than Brains cam - in stock CID too.
Jason @ TSP did the tuning, so I'll ask him if he remembers what he did to get rid of the code.
The cam we had at the time was bigger than Brains cam - in stock CID too.
12-12-2003, 08:10 PM
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And I thought I was tripping about my ASR light coming on now and then and not being able to shut it off or turn back on rather. The WOT no problem, but PT, it does act wierd with the trans, makes it shift quick into OD, or D, and sometimes like it is slipping, but not...dunno. I am wanting to know about this as well. My idle is only 700rpm, but would like to have it at 850 or 900. Too many stalls.
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12-12-2003, 08:12 PM
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I haven't completely fixed mine yet, but I'm getting closer... The car idles perfectly at 800 RPM, but I've since bumped it to 900 to make driving a little easier as well as pick up a little vacuum (72'ish kPa --> 65'ish kPa). I have a SPEC Stage 4 clutch with the solid hub, and the 100 extra RPM makes a big difference in taking off smoothly from a stoplight 
Some of the idle lope I love so much has gone away though, especially when I added a couple degrees of timing down low.. With the exhaust capped up it sounds more like a 228'ish cam than a 238 .. With the cutout open it sounds nice and healthy though! 
The car idles perfectly at 800 RPM, but I've since bumped it to 900 to make driving a little easier as well as pick up a little vacuum (72'ish kPa --> 65'ish kPa). I have a SPEC Stage 4 clutch with the solid hub, and the 100 extra RPM makes a big difference in taking off smoothly from a stoplight Some of the idle lope I love so much has gone away though, especially when I added a couple degrees of timing down low.. With the exhaust capped up it sounds more like a 228'ish cam than a 238 .. With the cutout open it sounds nice and healthy though!
12-13-2003, 12:10 AM
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I just saw that version 1.3 of LS1 edit has something that you can tune the MAP perameters for this code.
has anybody done this yet? i dont have 1.3 yet, but it looks like ill have to order it now. if you have used this to fix it, what did you change on the table
has anybody done this yet? i dont have 1.3 yet, but it looks like ill have to order it now. if you have used this to fix it, what did you change on the table
12-13-2003, 12:13 PM
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Didn't follow any guide for idle tuning, just went through and spent the time looking for what this particular setup wanted. I had the car idling BETTER at 800 truth be told, because I've been chasing an off-idle stumble problem (only shows up between idle and 2500, and only above about 20% throttle angle).
12-13-2003, 09:11 PM
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Originally Posted by -Joseph-
Our 98 Z28 had set that code with a bigger camshaft. I don't remember what exactly we did to fix it but it only really had problems at the track IIRC. The other weird thing about that 98 car was the Theft Deterent would activate before the 1-2 shift and shut off fuel, I think we disabled the VATS in LS1-edit to eliminate that.
Jason @ TSP did the tuning, so I'll ask him if he remembers what he did to get rid of the code.
The cam we had at the time was bigger than Brains cam - in stock CID too.
Jason @ TSP did the tuning, so I'll ask him if he remembers what he did to get rid of the code.
The cam we had at the time was bigger than Brains cam - in stock CID too.
Please let me know Joseph. today i went to the 1/4 track and had to manually shift my A4. my times sucked but i finally hit the 11's.
12-13-2003, 09:55 PM
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Brian, lemme know when you trace down that stumble, be interesting to solve mine as well, but I wont have my edit cable to well into next week.
Thanks,
Charlie
Thanks,
Charlie
12-14-2003, 11:07 AM
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I looked at my A-Tap logs of before and after the cam and the before MAP numbers when regular driving where in the 40's mostly, there is alot of readings lower and some higher and at WOT in the 90's.
but now after the cam, my regular driving is putting it between 55-65 alot. there is still some lower and at WOT its in the 90's and some 100-105 or so.
i think maybe im suppose to make thet 55-65 MAP window smaller or maybe raise it, but i wonder if this is going to fix the problems or if its just going to make the light not come on
but now after the cam, my regular driving is putting it between 55-65 alot. there is still some lower and at WOT its in the 90's and some 100-105 or so.
i think maybe im suppose to make thet 55-65 MAP window smaller or maybe raise it, but i wonder if this is going to fix the problems or if its just going to make the light not come on
