I am having an issue with my car after installing some upgrades. I get a large stumble/hesitation when I give the car some gas and the car jerks and makes a popping sound. I just installed a INTENSE Racing Stage 4 PCM, 2.8" MPS, NGK 1 step colder copper plugs gapped to .035, 60# injectors, Caspers's harness, and GM Stage 2 belt for my 07' Cobalt SS/SC LSJ. Everything installed perfectly fine this past weekend. The motor started right up and there was no additional problems at the time. At the first startup the check engine light was on, but I thought nothing of it since a CASE Learn was needed to be done because of the PCM replacement. Everything was fine and I took the car for a few high speed test runs and everything felt great. I am now (after about 2 days installed) however having a problem while driving. Often, the car will "hiccup" badly causing the car to shake and shudder as if the clutch has slipped or something. The clutch however is not the problem as the car has about 5000 miles on it, and the clutch is perfectly fine. This problem happens when trying to give the car more gas and still occurs even if the gas is eased on ever soo slightly. I could understand a small hesitation if the pedal was mashed to the floor, but this is occuring with a light gas transitions. This problem seems to occur more often when the car is first being driven, and seems to occur less often as it warms up, although it will still happen at any time. What is odd, is the fact that the car can sometimes go through a WOT burst and be totally fine, and then sometimes just the lightest touch causes this problem. I am not sure as to what the problem could be. I will tell you, I have not yet had time to make a service appointment and complete the CASE Learn for the PCM, although people say that this type of problem is definately not caused by a lack of CASE Learn. I took the car to Advance Auto and borrowed the OBDII scanner, and the car had 3 codes tripped. Two of the codes were for the CASE Learn and a third code was something for an improper air metering problem (I should have written down the code!). I cleared the codes and it cleared the third code, but the CASE Learn codes remained (obviously). I am running premium fuel in the car, so I do not believe it to be detonation or anything like that causing this problem. After clearing the codes, the car seemed to run a little better and seemed to actually be making boost in 1st gear, which it didnt seem to before.

There is still however this terrible stumble. This problem makes a loud "popping" sound almost like that of a backfire, and the whole car shudders and jerks as if a rough shift had been made. Is there anything that anyone might suggest for this type of problem? I know a lot of people are probably gonna say that canned tunes are garbage, but this is all I can get for right now until I find someone around Pittsburgh, PA to do something better. The one guy from INTENSE (Brian I think) was nice enough to call me yesterday and attempt to help me. His thought that the problem was some sort of vacuum leak cause by a bad gasket or something. He offered to take a look at some HPTuners data if I could not figure it out, although I don't have access to anyone with that software. Last night I disassembled the stock intake and reconnected it all back up, and I also cleaned the MAF sensor. This did not help either. The only think I have done to the intake is the airbox mod, and I have never had an issue with it in 5000 miles. If anyone could make any suggestions, I would greatly appreciate it. I have already read all of the posts on different CELs for lean/rich/air problems and nothing seemed to help. This weekend I will take the blower back off and check everything else out, but I am hoping this may have happened to someone else before, and they might offer some insight.

Thank you very much,

Cory

 

Take out and clean your air flow sensor... and oh yeah you should get tuned right away because canned tunes SUCK!

 

After I put my 2.8 pulley on my car was having a problem that sounds similar to yours. I dropped in some NGK 1 step colder plugs and they helped but didn't fix it (gap was .040 iirc). I spent about a week playing around with spark plug gap between .040 and .030 and at .033 the car runs almost perfect. My problem was that the car would knock retard very bad everytime I hit the gas, more so when the intake temps were hotter. After sitting in traffic, idling, or high speed runs was when it was the worst. I can still see knock retard in HPT when I first hit the gas but it's much less then it was before and you can hardly feel it at all.

My suggestion would be to try messing with your spark plug gap, it's a lot easier then pulling the charger .

 

Thanks for the input guys, however I have already tried both of those solutions... I have NGK BKR7E's at .035 in there right now. Originally the NGKs were gapped to .040, and I redid them... And i fully disassembled the stock intake system and cleaned the MAF with MAF cleaner... Neither of these fixed the problem.

The only thing I can figure it to be is some sort of vacuum or gasket leak? Maybe something with the fuel injector seals? I will be taking it back apart at some time to install my ZZP dual pass plate, but I really need to get it running properly now... Any additional feedback is extremely appreciated! Thanks!

 

Try running meth.

 

some people have problems with the stage kits from intense. One of my friends ordered the stage 4 kit from them and then he sent his pcm in and never touched it to run with the stage 4 and then he got it back and found his car was spitting and sputtering over 3500 to 4000 rpms, so we started checking over the injectors and wasnt spraying gas out of every whole in each injector

 

I highlighted the problem for you.
also might want to consider some cooling mods for that 2.8" pulley if you havent already done so.

 

Intense racing is a great company to purchase from and they know what they are doing. I have their stage 3 tune and it is awesome. I have been to their shop a few times and talked to them about their tunes and other products. They are very professional and everyone I know personally that has installed their products loves them. People blow up cars NOT Intense

 

Again, I really appreciate all of the feedback I have been getting from everyone here! Thanks! One question..? Doesn't anyone seriously think that it is likely an issue with some sorta air/vacuum/gasket/seal/hose leak/MAF sensor problem? Everyone wants to blame INTENSE tunes.

If it is an issue with an INTENSE tune, then what is technically causing the problem? Is it a timing issue? Is it an A/F issue? Is it knock? Is 93 octane with octane booster not good enough for a mild setup with a 2.8"? I am having this problem right off idle sometimes! I'm not gonna sit here and try to act like a mechanic because I am not, nor am I a master of the Ecotec LSJ and I am humble... but I have built a 1969 Chevelle SS (Including body, suspension, full engine and some trans work) and dicked around with enough other cars to think that this is some sort of an issue with an air/vacuum/gasket leak... Especially when the car tripped a code for un-metered air....

As an FYI though, I just OBDII scanned the car again at Advance Auto on my lunch break, and the only 2 codes present were for the CASE Learn, meaning that the um-metered air code had not come back on... The car however is still intermittently having this problem. What confuses me more is the fact that I was able to take the car from a 0 to ~135 rip right after installing the parts and they performed flawlessly. Then the next day I put it hard through some twisty back roads with my friend (to show off to his stock SRT4 drivin' ass! hahaha) and everything was fine. Then the next couple days while leisurely driving to work I noticed this problem start...

I have checked over the induction system up to the Throttle Body, and a visual inspection does not show any issues with other components. I cleaned and re-gapped my NKG plugs (they were kinda burned and brownish in appearance) to .035 like people had suggested. This problem only seems to appear when the engine is under load, only at boost (i think), and almost always if its lugged. I'm almost beginning to think that maybe the belt is weirdly slipping? Or a gasket got crushed when installing? Or something with the boost bypass into the intake is messed up? I really do not know...

Ohh yea, and as far as cooling mods for the 2.8" pulley, I'm putting on a ZZP dual pass setup this weekend... I also plan to have a CX Racing H/E within a month... Meth is very possibly down the road if needed.

Any other remarks are greatly appreciated! Thanks!

 

did you say you put octane boost in your tank? I wouldn't trust that **** one bit, thats cause for a bad tank of gas. Also, usually its the last thing you touched before the problem started happening, unmetered air would cause part of what you're talking about probably, any bad connections in the intake tubing maybe (happened to me, but it was with stage 2 tune)

 

Yes, I ran a bottle of STP octane booster in the tank when I installed everything. I had a little bit of 87 in the car when I filled up with 93 a day before I did the installs. Since then I have put in more 93. Is it possible this whole thing is just bad gas..? If soo could knock and timing retard cause this big of a problem? As far as what I touched, I did the install of an INTENSE Stage 4 kit with a 2.8"... Soo many of the sensors and connectors were played with. I have checked everything I could think of though, and I figure a bigger problem would be evident if it were an issue such as a connection or sensor. The only thing I can think of is it being is some sorta problem with the boost bypass of blower to intake gaskets, or possibly even a fuel injector to head o-ring problem. Thanks for the feedback...

 

i would take everything apart and start again honestly....sounds like you forgot something somewhere

 

i would make sure the tank is run dry of that crap and filled up with 93 octane with no booster whatsoever and if it still does the problem then start trying to figure it out. Running octane booster is almost ALWAYS not going to help anything. i'd rather run pure 87 in my car than any octane boost.

 

OK guys, here is the current status... I took the car out tonight after work to run some errands... The car still felt like ****... I stopped at Sunoco and put $20 of 93 in it... Afterwards I went to the mall. On the way home I babied it almost till I was home, then I got on it hard, and WOW! the car actually ran right... I did a few other runs with it just to be sure, and everything felt fine. I did some 2nd gear roll-ons full boost shifting at redline and it felt great. I also did some runs from a stop and everything was fine... Soo I'm crossing my fingers and hoping that everything is fine... Could this entire problem really be caused by shitty fuel? I totally never would have thought those symptoms of the sputtering could be ping? Any ideas?

 

I am sorry for your luck but that is your only problem.

 

wow you are ignorant

 

OK, I lied... I've driven the car some more and it still feels like ****... I got on it a few times, and had mixed results. Sometimes it boosts and accelerates nicely and other times it falls on its face... It seems to run better at night? Maybe because of the colder temps? Anyways, I'm basically at a loss right now. I guess I'll just wait till Saturday until I put on my ZPP dual pass and get it all back together. Maybe things will change then. I checked the tuning forum, and couldn't seem to find anyone near me who had HPTuners. Anybody know of anybody or any shops around Greensburg, PA or Pittsburgh, PA that tune? Worst case scenario, I might give in and buy HPTuners myself. Quick question with that... With the initial credits they give you, is it possible to tune your car (same PCM, same VIN) an unlimited ammount of times? You just need more credits to do other cars, right? Thanks for the info guys...

 

I was having a problem in my car due to higher temperatures.

Maybe the car is pulling timing or something when really hot?

 

yes you can tune any car you have a license for unlimited times. only thing that costs credits is licensing another vin or model year.

I have HPTuners but I'm up near Sharon, PA. and i dont have the 2007 unlocked for tuning. only all 2006 ss/sc

 

wow, I think you are if you think any canned tune is good.

I had a friend who had to rebuild his engine last year because of an Intense Tune. By the time we got to know him and scan his engine and make the changes, it was already too late.

 

no i think it is ignorant to think that the Intense tune is the reason his car is running so poorly.

 

The ignorant thing to do would be ignoring all past experiences with the intense tunes or any "stage tunes" and assume they were good.

 

Lets just drop it. i dont like to argue

 

Intense tunes have ALWAYS been terrible (along with their "revised" diffs). I've seen their customers' cars and even their own cars blow up in-person. I've never seen a ZZP customer have any major issues right off the bat. Not to bash, but I'm just throwing that out there. Search ClubGP.com and you'll understand where I'm coming from.

 

I respect your opinion.....I had Brian at intense go over my tune and make sure everything looked good so maybe thats why I am so happy with it