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Tuning issue or electrical issue?

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blueanchorgtp

New member
Hello everyone, this is my first post on here so bare with me please. My issue is on a 1998 Pontiac grand prix gtp. I found a 2002 gt for sale with a rebuilt motor and tranny but the car was junk, hit by a garbage truck on the street. I decided to drop the cradle of the gt and transplanted it into my gtp. While the motor was out, I top swapped the l36 and installed zzp 1.9 rockers and ls6 springs I believe from intense. I swapped this cradle into my gtp along with sd headers, an intense shift kit, and supporting items like plugs and thermostat. I sent an email to intense about getting my pcm tuned and just decided to pay the core charge and have them give me a tune. The car is all done now practically besides a vacuum leak which I cannot find as I've replaced all the lines on top of the blower and the vac line that zzp offers. The major problem now is the transmission oscillates between fourth and third at cruise and the car is sluggish after shifts then boosts back up after a couple seconds of lag at full throttle. The motor and transmission ran fine in the gt with no problems at cruising speeds. Can this be a tuning issue or electrical issue? Can this be from the shift kit? I have no idea at this point all replies can help, thank you.

 


blueanchorgtp said:
Hello everyone, this is my first post on here so bare with me please. My issue is on a 1998 Pontiac grand prix gtp. I found a 2002 gt for sale with a rebuilt motor and tranny but the car was junk, hit by a garbage truck on the street. I decided to drop the cradle of the gt and transplanted it into my gtp. While the motor was out, I top swapped the l36 and installed zzp 1.9 rockers and ls6 springs I believe from intense. I swapped this cradle into my gtp along with sd headers, an intense shift kit, and supporting items like plugs and thermostat. I sent an email to intense about getting my pcm tuned and just decided to pay the core charge and have them give me a tune. The car is all done now practically besides a vacuum leak which I cannot find as I've replaced all the lines on top of the blower and the vac line that zzp offers. The major problem now is the transmission oscillates between fourth and third at cruise and the car is sluggish after shifts then boosts back up after a couple seconds of lag at full throttle. The motor and transmission ran fine in the gt with no problems at cruising speeds. Can this be a tuning issue or electrical issue? Can this be from the shift kit? I have no idea at this point all replies can help, thank you.
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Bump

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I went through everything trying to find a vac leak because my trims showing a vac leak and couldn’t find it. Did a smoke test and still nothing. My tune way that far off that my trims were that bad so it could very likely be the tune.

Shift kit wouldn’t cause the issue, that could also be the tune. Make sure your trans fluid is at the correct level too.
 
Swiggles said:
I went through everything trying to find a vac leak because my trims showing a vac leak and couldn’t find it. Did a smoke test and still nothing. My tune way that far off that my trims were that bad so it could very likely be the tune.

Shift kit wouldn’t cause the issue, that could also be the tune. Make sure your trans fluid is at the correct level too.
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Fluid level is correct, even drained the system a second time and topped it off. Would I tuner be able to locate these issues within the tune?

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You’d have to drive around and take a scan for them to see the data. But it could be something simple they missed like the didn’t correct the gear ratio change or something.
 


Swiggles said:
You’d have to drive around and take a scan for them to see the data. But it could be something simple they missed like the didn’t correct the gear ratio change or something.
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The gear ratio change could be what's making the car oscillate between third and fourth gear?
 
is this at hwy speed, the coming out of od back to 3 rd? if so thats likely the 4 th gear hub gone bad. the splines wear off and it jumps back and fourth.

if you had the wrong gear ratio it would be shifting really hard. you would know something was wrong right away.

that vac leak, can you hear it? are you watching your fuel trims? guess im asking how you know you have one? if you had a large one the idle would surge by 500 rpm and sound like you got a huge cam. smaller leaks can cause pos trims, if you see a +16 all the time, you got a leak for sure.

you spray the engine down with carb cleaner yet? move the lines when you spray if at first you get nothing. if the idle jumps up when sprayed you found the leak area. evap line is a common hose to split. as well as the T under the snout.
 
I don't have a tuner or anything to see the maps, I used an obd2 scanner to check codes and it claims I have a vac leak. Checked and replaced all vac lines around the blower including that t. The transmission ran fine before the swap, now that it is in this gtp, when I cruise into fourth, it shifts into fourth, then decides to bob between third and fourth like it doesn't know what to do. If I step on the gas it stops but stays in third, then when I cruise again, it goes into fourth and does this all over again.
 
blueanchorgtp said:
And the trans does shift really hard I just assumed it was the shift kit

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id have to think you got the wrong trans ratio in the tune then. id call intense up ask then you check your file to see what gears they loaded up. ppl are only human, mistakes happen. if they screwed up id hope they would make it right.


dont drive the car like this, it can kill the tranny if you do have the wrong ratio installed.

if intense hangs you. if you got a local junk yard handy grab a na pcm for your year car, take your sc belt off, run that pcm, see if the tranny is happy again.

i can tune ya, but im all the way up north NJ 5 miles from the gwb. id not drive it that far. i do have a spare pcm for 01-03 i could sell ya with a tune on it. worst case scenario.
 


Scottydoggs said:
id have to think you got the wrong trans ratio in the tune then. id call intense up ask then you check your file to see what gears they loaded up. ppl are only human, mistakes happen. if they screwed up id hope they would make it right.


dont drive the car like this, it can kill the tranny if you do have the wrong ratio installed.

if intense hangs you. if you got a local junk yard handy grab a na pcm for your year car, take your sc belt off, run that pcm, see if the tranny is happy again.

i can tune ya, but im all the way up north NJ 5 miles from the gwb. id not drive it that far. i do have a spare pcm for 01-03 i could sell ya with a tune on it. worst case scenario.
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I bought the unlimited file from intense so I'll just email that guy John rucker and ask him about the information on the tune. Thank you guys for all your knowledge, I'll keep it posted

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Scottydoggs said:
and sound like you got a huge cam. smaller leaks can cause pos trims, if you see a +16 all the time, you got a leak for sure.
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While is true it’s not always the case. My trims were up in the +16.4 range, did all the tests, carb cleaner, even a smoke test and there was no leak. Dropped my entire maf table down and it lowered my trims. The lq4 maf table I was using, the one zzp has for download, was too much and I needed to tune it anyways.
 
ive seen that before, but hes not modded enough for that. unless they messed with the maf file in the idle range, from all the canned tunes ive seen all they do is up the last few cells in wot.
 
Car is unregistered still so I had been driving around at lower speeds. Yesterday I had the car cruising at 50+ with no problems. Now I'm thinking it's bouncing between second and third. What do y'all think now? I'm so used to my six speed climbing gears, the problem is between like 30-50 mph.

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they lock in 3 rd about 30 mph, od at 45.

if you lost 3 rd it would scream in second all the way to 45 mph then take od at light throttle. how my first tranny died. note first lol
 
It'll jump between second and third staying in each for a second, if I hit the gas it accelerates in second then to od

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hard to say with out being there.

you got all the plugs back on the tranny, theres only two of them other then the few near the shiftier linkage. the fat round one under the cross over and the one near the pass side axle, that one is the speed sensor iirc.
 
Scottydoggs said:
hard to say with out being there.

you got all the plugs back on the tranny, theres only two of them other then the few near the shiftier linkage. the fat round one under the cross over and the one near the pass side axle, that one is the speed sensor iirc.
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99% sure, I could check. Could it be the intense shift kit i put in?

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