2005 GTP Sputter

[NAiLs]

Argh! My GTP has been giving me one hell of a time lately. I've got this nasty sputter when boost starts to come into play. I swear some days it's mostly fine and will go like a bat out of hell, but it has been getting progressively worse, sputtering when you put boost into the equation. I've had this problem for a while, so I changed the plugs with some E3's (and new Bosch wires), though the problem didn't exactly go away, but it wasn't very bad. Now, almost always, when at highway speeds and I need to accelerate quicker, she just sputters like mad. This is not limited to highway speeds either, it's even at low speeds with boost applied. I thought maybe a slipping belt since it's only under boost, but I do plan on checking out the plugs to make sure they're fine.

The only other random thing that I notice that doesn't happen on all days, that could be unrelated, is sometimes the car takes a while to shift from 1-2, indicating a vacuum leak... or that's my first thought. I am confident that if I put it into manual mode, it will shift right away, but I haven't tested that more than once on a day it was being a pain.

I know I've read some stuff on ICM's and coil packs that can cause this, but I'm not 100% certain if this is necessarily my case? I might have some old coil packs and a spare ICM from my old '00 GTP, but I don't know if these are interchangeable with my '05.

Other little facts and recap about the car....


86,000 miles
No idea if belts have been changed. They look old, but not cracked or any real obvious signs of damage.
Trans fluid looks and smells great. I think it was changed when I bought the car.
Plugs and wires are new. Plugs are E3's and wires are Bosch. I changed these about 4,000 miles ago.
Coolant looks old. It's starting to look a little cloudy, but not brown like there is oil in it... it's just not as translucent as new stuff. The reservoir looks like it's overfilled as well.
I recently changed the EVAP Solenoid as it had a huge crack. I thought this was my supposed vacuum leak.



Charlie, or anyone else, do you have any suggestions for me before I throw money at this car? I prefer to not just replace everything, even though I'd love to!

Thank you again for your input!!

-Brian

[Slizzo]

How's the MAF look? Cleaned recently? The added request for air may be throwing it off, or at least I know I had issues on my '99 GTP with sputtering when my MAF was going bad/went completely.

EDIT: Also I want to say the coil packs may not work, being it's a different engine designation L67 vs L32. Could be wrong there as well though.

[NAiLs]

I will definitely take a look at the MAF this weekend and clean if needed. I honestly can't say I looked at it. I did slap on my Wizaired intake within 24 hours of buying the car. LOL! I had it on my 04 without issue and I never re-oiled the filter.

Thank you for the tip and I will post my result on Sunday!

[roman1978]

Brian, i have the same problem with 05 GTP with 100k its driving me crazy did the same thing you did replaced plug vires its on and off does not happen all the time like you said sometimes it takes off sometimes it sluggish. Have you connected to a scanner? Mine was showing missfire before i changed plugs and vires.

[WickedMom]

I wonder if your bypass actuators are worn...

[GRRRR8]

I would not have put E3 plugs in it and Bosch wires are not that good, but since they are new you have a coil pack issue as long as it feels like a cylinder cutting on and off. Fuel pump= a smooth hesitation and loss of power. MAF= hesitation going from cruise to load or idle to cruise. Have someone check the misfire counters with a diagnostic scan tool and then you will know which coil to replace.

[GT Drew]

L67 & L32 have the FPR boost referenced. If the vacuum line is cracked or leaking, it will buck and knock. My L67 had the line come off below the blower snout. No signal to the MAP or FPR. Lets just say with no more vac leak and signal to the sensor and FPR is ran much better. ZZP sells a good universal kit. Silicone tubing and brass tee fittings. the nylon tubing was fine but the rubber tee's all cracked and were loose from heat and age. Good call Wicked, the bypass is also on the same vac line.

[GT Drew]

As for plugs NGK TR6ix FTW. What pulley are you running? I still have my Autotap and Palm M130 for scanning.

[NAiLs]

I would not have put E3 plugs in it and Bosch wires are not that good, but since they are new you have a coil pack issue as long as it feels like a cylinder cutting on and off. Fuel pump= a smooth hesitation and loss of power. MAF= hesitation going from cruise to load or idle to cruise. Have someone check the misfire counters with a diagnostic scan tool and then you will know which coil to replace.

What's wrong with the E3's? I always read that they're supposed to be great.. but I trust the word of you. I do plan on pulling them to see how they're running. I will check out NGK's as Drew suggested, if need be. Aren't those what are stock anyway? Is there a big difference between Iridium and Platinum? Wire wise, I couldn't bust out the cash for AC Delco wires, and one of my buddies did a resistance test on several sets of wires, Bosch coming out towards the top of his tests. Is there anything else that you'd recommend that isn't terribly expensive? It's just a daily driver... minimal mods.

To the coil pack issue.... any idea if the L67 coils are compatible with the L32? Visually they look the same to me, but I'm uncertain.

The hesitation is pretty heavy. To me it does honestly sound like a misfire, as it sounds like (I'm quoting another person who stated this as their issue) a machine gun. Acceleration is smooth as long as I'm out of high load (boost). I can watch the factory boost gauge, and if it's only 1 bar or lower, it's fine... and that's probably like half a pound of boost.




L67 & L32 have the FPR boost referenced. If the vacuum line is cracked or leaking, it will buck and knock. My L67 had the line come off below the blower snout. No signal to the MAP or FPR. Lets just say with no more vac leak and signal to the sensor and FPR is ran much better. ZZP sells a good universal kit. Silicone tubing and brass tee fittings. the nylon tubing was fine but the rubber tee's all cracked and were loose from heat and age. Good call Wicked, the bypass is also on the same vac line.

As far as the BBV, what can I look for visually on this? Any testing for the FPR? I do have a gauge to test fuel pressure as well. I'll check out the lines themselves to everything... see if I can't find any cracks.




As for plugs NGK TR6ix FTW. What pulley are you running? I still have my Autotap and Palm M130 for scanning.

Are you in Milwaukee? If so, where at? I'm on the north side... Fox Point to be exact. I used to have an LS1M back in the day, and also an HP Tuner when I was in the mod scene. Also, I just have a stock 3.8 on here. I had a Trasher MPS, but had to leave the hub on the old GTP as the darn backing plate came way too late (took 4 weeks to receive).


**Edit. Bah, I found you on the other forum, and you're in Toronto.

[NAiLs]

Alright, I'm leaning more and more towards a misfire as well.... I wholeheartedly agree with Charlie. I went out to grab dinner, and just actually paying attention to everything for a change... here are a couple observations:


Sitting at idle, I see the RPM's dip roughly 100 RPM's every couple seconds
Very light acceleration, maybe 10-15% throttle, I could feel a very minor hesitation in there
Acceleration after a stop, I could feel a minor hesitation at the go, then normal acceleration. Aforementioned symptom in #2 does persist if very light throttle.
If I'm not mistaken, when in park and listening to the exhaust, I can hear a little "puff" occasionally, which is a misfire, no?


I hope this info helps if there is something else that is being missed!

-B

[Slizzo]

Vac problems as Drew stated are common on the supercharged GM 3.8s. Check all those lines, and they're cheap to replace if one is bad.

TR6s are also the plug of choice for many owners, I remember seeing them recommended a lot. I want to say I also remember the Autolite 104s? 106s? being recommended as well, but others in the know would be better off verifying.

I had put MSD 8.5mm wires on my car at some point in time, they worked out well for me while I had them, but I am not positive on their quality.

[GRRRR8]

Sounds like a coil to me. It is fairly easy to see all the vac lines to inspect them to make sure you do not have a lean misfire.

[GT Drew]

TR6 ix are two ranges colder than stock. If you are still runnings the stock 3.8" pulley TR55ix. Bad coils are common too, same from 1996 to 2005. Di-electric grease is your best friend for these FI motors

[NAiLs]

I went to pick up some plugs today and plan to install them tomorrow. I know for sure it's a misfire now... Going up a long, somewhat steep hill, told me everything I needed to know. It would misfire on occasion while going up the hill, and you could feel it really well. I was going to buy the TR6's, but I don't have a plug gaper for iridium plugs. I ended up getting the TR55ix's because they're gaped at 0.059 and the TR6's were at 0.039, plus the dude told me they're the same heat range as stock. I don't plan on going wild with this car at this point, so I decided I don't need to go all out. That's what the G8 is for! lol

I have a friend who said he has access to a scanner, so I will hopefully get together with him today or tomorrow, to scan these misfires.

My last question is, if I have a coil or two at my parent's house, will a coil from an '00 Grand Prix fit onto an '05? Are they identical? If I'm not mistaken, they are... but I'm not 100% certain. My guess is strictly based on physical appearance.


Thank you for your help and input, guys!! I really do appreciate it! :thumbsup:

[NAiLs]

Alright, well, I felt very ambitious and swapped my plugs with the TR55ix's. I must be a pro at changing them on this car, as it took a whopping 35-45 minutes. lol I took the car out for a spin, and I think my problem is gone... :surprise: I must say, these E3's look like shit after 4,000 miles.... I'll keep my eyes on it for about a week and return with my results. So far, I think it may have just been the plugs. Man, those E3's were highly praised, but I'm in the boat of thinking they're absolute TRASH. NGK TR55ix for the win!

Thank you again for your help, guys!

-Brian

P.S. Here is a picture of what they looked like:


http://grandprix.gameagon.com/DSC_8237-1.jpg

Click For Bigger Image (http://grandprix.gameagon.com/DSC_8237-1-3.jpg) 1.74 MB

[GRRRR8]

Good to hear. I have never installed E3s, but I sure have taken a lot of them out! :)

[GRRRR8]

Yes the coils are the same.

[NAiLs]

Good to hear. I have never installed E3s, but I sure have taken a lot of them out! :)

LOL.... and I can clearly tell why they all come out, never to go back in again!

My plugs in particular, is this just corrosion and crappy plugs, or is this signs of a lean cylinder? Won't it be more white if it were lean? I'm mainly curious. I just hope what these have, aren't signs of something else to come.

[Struggle]

E-3s are people trying to re-invent the wheel=fail.

[roman1978]

After changing plugs mine felt better but still feel that miss sometimes scan your car Brian

[GT Drew]

The more hype and commercials you see on TV the more likely the claims of being better are BS. #6 has some dark marks near the shell. Are any of them cracked? The 55ix are a great all around plug, you won't have to touch them for years.
If you do swap coils, use the di-electric grease on the bottom and towers.

[NAiLs]

That could just be dirt from grabbing it, or something else as you suspect. None of them are cracked from what I can see, which did cross my mind once or twice as the culprit.

Thank you for the heads up on the grease. I couldn't remember if you should on the underside or not. So far she's feeling really strong. I gave it hell twice and also did some nice slow uphill acceleration, and I didn't feel one misfire. She feels nice and strong at this point! :brock:

[NAiLs]

It has been more than a week, obviously, and so far no audible or felt misfires. I gave her a hard time a couple times and no problem. I'm glad it was simply just the spark plugs. E3 plugs will never see my vehicles again!!

Thank you again for everyone's advise!!

-Brian