Okay, I'll try to make this brief. Over the past few weeks I have had a few isolated occurances with my car...I have GMS-1 and a newly inserted K&N drop in.

First problem happened a few weeks ago when I went WOT up a hill (with a few people in the car), second gear, and maybe around 4500rpm it seemed as though the wastegate randomly opened up. I never let off the gas but there was a definite blow off, loss of power, and then everything resumed as if I had let of the gas myself and got back in it.

Second problem happened this past friday, getting on the highway, third gear felt sluggish as did 5th. I thought nothing of it, until it felt like the car was shaking as if I were on a poorly surfaced road. I attempted to accelerate in 5th gear at around 65mph and the car didn't build any boost and started chugging as if I were out of gas. I had plenty of gas by the way. I was in and out of the throttle trying to figure it out, but the boost gauge would read no higher than -3 even at WOT. I pulled it off on the shoulder and revved it a few times to hear loud backfires out of the exhaust. It sounded like it was dumping way too much gas in for no reason and it was all getting burned off in the cats. I checked all the hoses and pipes to find everything secure. I turned it off, turned it back on, and everything was fine...drove home with no issues.

This morning on the way to work, cruising along the car would go from -3 and jump to +3lbs as if I tapped the gas...but I didn't. It did this a few times as well as building more boost than normal in light acceleration during upshifts and regular cruising at highway speeds. I would give it a little bit of gas and boost would build a lot more than it normally does as if it has a mind of its own.

My only guess to these weird happenings is that the ecu is screwed up or reading things wrong. Anyone have any other ideas? Another note: CEL never came on during any of this. Although it did come on a while back for a bad MAP (i think) but went away.

 

You may be having misfiring and/or an issue with an air/pressure metering sensor. That would explain the loss of power mid-pull, the popping, and the inability to make reliable boost. Some of what you describe can also happen due to a boost leak or boost solenoid issue.

I've had MAPs go out before and the car will still run okay though. The boost and AFRs will fluctuate with quick throttle changes, but it has the ability to continue operating while ignoring MAP input.

I would check your charge piping for leaks first. It's free, somewhat common, and usually easily fixable. Make sure your IC is not cracked and losing metered air. I'd then check the sparkplugs as they may be causing misfiring. I'd then try to remember what the MAP code was you got and look into popping on a new MAP sensor. If it threw a code, then there's a possibility that something's still up with it. The boost solenoid should throw a code, so I'd throw out that possiblity for now.

Just some ideas to get you started. Some of these things should throw a code, so it's a bit of a shot in the dark.

 

The first problem you described is something that occured on my car from when I got it with 7 miles til about 6-8k miles. Under WOT the car would surge, it would rise 75HP then lose 50HP then rise another 75hp and lose another 50hp and so on (no codes). I took the car to the stealership multiple times, and everyone just told me nothing was wrong. It came to the lemon law point, and we took it in to the director, and it preformed fine, and has been fine ever since, except for one day about 6 months later it did it. But noone has ever been able to tell me what happened, so if you make any discoveries feel free to let me know, and good luck.

 

similar to what is happening to me and a couple others on here as well. But no CELs so the shops wont look at it. However last night during a WOT run I did get it to mess up so bad that the CEL started flashing at me for about 30 seconds. Going to see if they can pull that code today.

 

flashing CEL is typicaly a misfire.

 

Im having similar issues, refer to "what do these codes mean" thread in the same section, might help you out and i just just dropped my car off at the dealer today to see if they can fix it this time.

 

It was a mis-fire and had nothing to to with the surging issue I am experiencing.

 

You could try disconnecting the electrical connection to your evap purge solenoid - it's very quick and easy to do.



There's a line from the fuel tank, and an electrical connection, on the part highlighted in the photo - just unclip the electrical connection and see if it makes a difference. My car was stumbling and hesitating before I did this, and is running much better now. You'll get a check engine light eventually, but it's nothing to worry about in the short-term, and it will tell you if this part is causing a problem.

 

see, the crappy thing is, is that it's not happening all the time. These are just weird, random occurances and they're usually different in nature. I'm not sure how a misfire could have that much of an effect on my car. I will have them check the MAP when I take it in. Is there anything specific that they would look at to tell if it's bad? Oh and I definitely checked all the piping and everything else pretty well and it all seems to be okay. Like I said, it's running fine now as if nothing ever happened.

 

A few people with the GMS1 tune are having similar, if not the same problem. It is random, with constant accelerator pedal pressure in vacuum the car becomes irradic and the needle on the boost guage bounces around in vacuum and mine has even gone into boost by a few pounds before, where it never did that before. Sometimes my car makes 20 lbs of boost just fine and sometimes it will only make 5 lbs in WOT with NO CEL.

 

If the TMAP in the Cold Air Side of the Intercooler pipe, if the wiring is rubbing on the AC Compressor or one of the butt wire connectors are loose, you can loose boost mid acceleration without setting a code. Try tie wrapping the ires back and check the stage 1 butt connectors to make sure they are tite.

 

I will check on that and see if there's anything going on with the wires. And davidcroft, that is pretty much exactly what was happening yesterday. You put it into better words than I did. I've never seen that sort of problem on here, maybe I'm not looking in the right places.

 

A ton of stage 1 cars having issues right now. Check your wiring especially the lower T-MAP on the coldpipe. If no issue is found, you could also try having the dealer try reflashng the stage 1 tune into the car again. I had had zero issues with my stage 1 sensors and tune in my car but I did all the install myself. I do not like others working on my car.

 

Reflashing the stage 1 won't do anything. Your software and calibration doesn't get corrupted. You can reset you block learns by doing a battery disconnect for 30 seconds.

 

Some mine feels fast and pulls like a raped ape, and other times it can't get out of it's own way.

 

Do you have the GMPP Stage Kit? If so check the TMAP wires and make sure they are not touching the AC compressor. If they are tape them up and tie wrap them back. Also check the butt connectors and make sure the connection is solid.

 

Well I checked all the wiring and everything seems snug. It's all run through plastic tubing so it doesn't rub on anything. None of the wires are exposed except for where they were spliced but the seal looks really good on them. I double checked all the intake and charge piping and everything looks fine...now what?

 

Check the intercooler pipe (cold air side) to see if the PCV line nipple is not cracked and still connected to the tube.

If you intercooler is production parts, not aftermarket, you could take it to the dealer with the low power complaint and have them perform a leak test, the test uses smoke and looks and can detect any leak.

 

Yes I do have the stage 1 kit.

 

Bump anyone have any luck figuring out this issue.

 

I'm curious if you would see the bouncing boost gauge if it were an actual mechanical boost gauge.

 

okay so I have been in, out, around, and under my car and I can't find anything. Nothing seems to be cracked or leaking, hoses are intact, wires are good, everything's snug. The only thing that could possibly be an issue is the TMAP on the cold side charge piping is slightly flexible, whereas the other one mounted on the motor is not. I think that just has to do with the fact that it's mounted on plastic and not metal. I tried getting down there to tighten it up but that's pretty much impossible. I look like a cutter now after trying to get a rachet in there last night. I'm also limited on tools so I might just schedule an appt. with the dealer. 3rd gear was a little choppy again yesterday; it would still boost to 20+ but it just isn't very smooth.

 

does anyone have anymore information on this, i am having a weird problem, second gear is fine, and if i NLS into third my car runs fine, but if i start in third it boosts like 25 (my tune is set to 21) and feels like there is no "real put you in your seat type of pull", til the boost drops down to 21 again..... i'm pretty sure it is just the clutch (getting spec stage 3+ shortly) but i was wondering if this sounded similar to a problem anyone else is having cause i don't think (even tho it feels like it is) it's the clutch for one reason.... why would i boost too high when (if) the clutch is spinning?

 

My car is hit or miss power wise as well..... Some times second and third gear pulls like a mother ****** and other times it feels real sluggish....I'm gonna attempt to do a boost leak test this Weekend.

I too noticed that the lower tmap is a little sloppy. I might even throw a zip tie around it to see if it helps.

 

The TMAP should not be "slightly flexible", it should feel very secure. Maybe the o-ring is broken causing a leak. or they did not trim the sensor or tube and is is caught on the anti-rotation fin on the tube.