Thread: Any Newbie to GTP tuning tips, as far as what NOT to do??

Originally Posted by dsmuts

Vacuum leak

Originally Posted by 98ctd

Check all the vacuum "t's" around the LIM and base of the blower I had to replace them on my 99

Thanks for the quick replies guys!
I will be doing some vacuum leak checking today.

Newbie to these cars, so forgive me...
What is "LIM"? Is that Lower Intake Manifold??

The blower had been replaced prior to us buying the car, so that's a definite possibility.

Lim is lower intake manifold

Still sounds lean. When I had a vacuum leak I used starting fluid and sprayed it around all the hoses and where the Supercharger meets the lower intake manifold (especially under the throttle body). If you spray the starting fluid into a leak the idle will change so it's pretty easy to hear.

Originally Posted by Reptile

Any type of leak, no matter how small will make the car show lean. That looks like it's still thinking that it's lean, did you try to reset your fuel trims with the HPTuners?
This thing doesn't have any type of valve cover breather on it does it?

Yeah, that is sure what it seems like, but I do not understand why when FIRST STARTED and warmed up, that it was acting "normal", with both the O2's and STFT's moving/fluctuating at idle like they should? The O2's were going between .100 and .900v (with rear one always being a little lower), which is correct and functioning, and the STFT's were also changing at idle and when raised slightly above idle....then they seemed to stop moving and sort of "lockup" for no reason whatsoever??? Is that when it is/was doing that stupid CAT TEST maybe?

No, to both questions.
Was using my scanner here at work, so no way to reset trims, but as I have always understood it, the STFT's will and should change whenever the car is running, regardless of any "memory" saved by the LTFT's? I wasn't even watching LTFT's because I have not seen them change yet, no matter whether I am using scanner here at work, or HPTuners. I have always disabled LTFT's in the past, but have not touched anything in this tune, aside from a mild fan setting and disabling SES light on the P0171 and P0420.

Originally Posted by JoRoW99

Still sounds lean. When I had a vacuum leak I used starting fluid and sprayed it around all the hoses and where the Supercharger meets the lower intake manifold (especially under the throttle body). If you spray the starting fluid into a leak the idle will change so it's pretty easy to hear.

I am going to try that this weekend. All I had here was Brakleen and MAF sensor cleaner, and neither really made a noticeable difference in idle speed or sound.

I am also going to get an HPTuner scan and post it here if I am able to. Maybe if one of you guys looks at it, you'll see whatever it is that I am missing...

Thanks for the replies so far.

You have the p0171 for a reason. Usually a vacuum leak. Don't disable it

move the vac lines while spraying them.

the evap hose off the tb top, the fat one, it cracked on my car in the bend the line makes, and if i moved it a bit the engine started to surge like it had a huge ass cam.

kids, i tell ya... lol

this is the fat vac line i changed, the closest one you see. used a fat one, then stuffed a thinner one inside the fat one then to the factory line to the evap sensor.

Originally Posted by Scottydoggs

kids, i tell ya... lol

this is the fat vac line i changed, the closest one you see. used a fat one, then stuffed a thinner one inside the fat one then to the factory line to the evap sensor.

The hose I replaced, is shown by the yellow arrows, because it was cracked & dry rotted looking, just like yours looks to be.
The larger one I circled, was missing the clamp.

I will double check the one you replaced tomorrow. Thanks again.

I'll post up what I do or don't find tomorrow.

yeah it looks cracked, but its still solid. in time im sure that one will need to be replaced. its the last line that needs to be replaced, i changed all of them, and the T's when i did my lim job.

well....my 2001 does NOT have that hose you show in the picture?

I tried to attach a copy of tune and scan here, but it says "INVALID FILE", but I do have a copy of each uploaded at HPTuners site:
2001 Grand Prix Supercharged GTP with recurring P0420 and P0171

I cannot find any vacuum leaks, and with MIL/SES light turned off, but still active, as suggested elsewhere on this site, it comes up as 1 I/M monitor INCONCLUSIVE, which will not pass emissions test.

As the scan shows, it is full rich (STFTs), and O2 sensor is less than .100 volt unless I rev it up off idle, then it works fine...

any ideas or help is greatly appreciated...

Do yourself a huge favor. Don't even look at 02 voltage... Get a wideband 02!

You said your running very lean...
What are your ltft's?

The O2 voltages are fine for monitoring what I need to see....right now.

Not trying to be a knucklehead, and I appreciate all the replies and people trying to help me, but whatever is going on here, basically stops the O2 sensors (both) from moving at all. A WB isn't going to tell me anything different, except an actual a/f ratio which is not what I need to know. I need to figure out what the cause of the O2 stagnation is.

I am not doing any tuning, yet. I'm just trying to figure out what is happening here, and why it is happening. Both the STFTs and LTFTs are pegged full rich when the O2's stop moving. I see +20.3% on the STFTs (which can't go any higher), and I cannot remember what the LTFTs are at the moment. Unfortunately, I cannot view the HPT scan from work PC.

Starting to get aggravated at this POS...

Our 2001 GTP does NOT have the hose shown above in the picture.

I have the codes (P0171 and P0420) set to "No error reported", just to try and get this this load through the stupid emission test, but now it has one I/M test INCOMPLETE so they won't even test it...

7 READY
1 INCOMPLETE

Says..."EVAP SYSTEM" test INCOMPLETE...

The picture attached... I have circled the hose that this 2001 GTP does NOT have...is that what's going on today with this car? Should that EVAP hose be there somewhere??

is there a open tube off tb?

look on the back sc for the evap solenoid, it should have 2 vac hose to it. make sure they are not cracked. maybe just change the sensor? set the code back to normal, and see if that makes it read for the test.


should be set up like this.