Misfire and turbo issues: yet another thread
08-07-2015, 11:24 AM
#1
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Thread Starter
Join Date: 08-07-2015
Location: NC
Posts: 62
Misfire and turbo issues: yet another thread
I am new to this forum and cars
My name is Giancarlo from NC
I am sorry to start yet another topic about turbo, misfire and GMTU issues. I have read many forum pages looking for an answer and I am starting to get an idea, but I need some help
THE CAR:
-2010 HHR SS manual, multi function display in the dash
-Bought on Feb 2015 with 36K miles
-After a month I found out it had the GMTU kit installed (Bosch sensors, sticker in the engine bay.... the Chevy dealer didn't know about it)
-Car ran fine for 3 months, breaks traction in 1st and second, lots of torque steering, turbo boost always around 18PSI, pure fine
-It had a K&N air filter installed by previous owner
-Only issue after a week: turbo down to 14-15psi max after I washed the engine bay. Searching I assumed it was the crimps on the T-map sensors. Yes, they are crimped and not soldered. Run like that for 3-4 days, and they the power and boost were back
THE SYMPTOMS:
-MISFIRE: after 3 months running fire, CEL came up with a cylinder4 misfire code. Cleared the code and it came back again. Swapped coils (#4 with #3) and swapped spark plugs (#4 with #2) and still got misfire on cylinder4, so it's not the coils themselves or the spark plugs (which I changed recently, all 4)
-Driving the car normally, I wouldn't get the misfire (sometimes I DO hear the exhaust popping)... but banging through gears, it comes up
-Reading around I found out about carbon build up issues or fuel injectors.
-Run Seafoam in the tank (and also injector cleaner and top lubrificant from Lucas) and Seafoam in the intake through the small vacuum line in the center of it. Let it sit for 20 minutes and after a lot of smoke and banging through gears the misfire was gone
-This lead to issue #2
-LACK/NOT FULL BOOST: full boost comes and goes. It doesn't change only under acceleration or braking (so I guess the lower t-map sensor is not hitting the AC compressor I believe. The connector is facing the back of the car anyway). One day I would get full boost (up to 20psi, that I never reached in the 3 months the car had no issues), another I would get MAX 15-16psi
-When I don't get full boost, the car drives OK and it's quick, even though I feel not all the power is there. Reaching 4500-5000 RPM no misfire codes pop up
-When I do get full boost and bang through gears, cylinder4 misfire code pops up. I think when I go more than 16-17psi of boost.
I happens the most on 5th gear, rolling up from 60-65mph and then WOT.
-The CEL blinks for a few seconds and then stays on for a few more seconds. When this happens boost is max 10-12psi and I feel the car sputtering while keeping the foot on the pedal. CEL goes away and after a few more seconds, full boost is back, almost feeling like a ON/OFF switch
-I swapped top and bottom T-MAP sensors, no change. Top had the thicker blue o-ring, bottom had the thinner green one. Lower sensor (on plastic pipe) felt to fit not as tight as the top one (on intake). When swapped, lower felt better because of the thicker o-ring
-I run a turbo leak test, by myself building a PVC elbow fitting to plug on the turbo rubber hose on the back of the engine. First time I do this (not familiar with turbos). I could listen to the air in the system, so a little hard to pinpoint if there is a leak. BUT... if I grabbed the lower turbo pipe where the TMAP sensor is and wiggled some wires down there, I could hear the sound of the air changing, louder.
-CONSIDERATIONS: based on the symptoms and reading multiple boards and topics
-Crimped wires on T-MAP sensors: could be part of the problem, but I never got a T-map sensor error code
-Leak on turbo: not sure how it comes and goes. It should always be there, not randomly autofix
-Cylinder4 crud on valves: shouldn't I get the misfire code, even with less boost at the same high RPMs?
-Misfire code come up always in the same cylinder and above a certain boost PSI
-Could cylinder4 injector be bad, not delivering enough fuel when requested by the turbo?
I have the TORQUE app (and a couple more) and an OBDII reader. Got one freeze frame, but doesn't tells ME much
Now the car has 43.500 miles, 4 new spark plugs gapped 0.035 in (0.90 mm), Mobil1 fresh oil change (after Seafoam) and ACDelco air filter.
Sorry for the super long post, but I tried to answer questions you may have in advance
THANKS!!
My name is Giancarlo from NC
I am sorry to start yet another topic about turbo, misfire and GMTU issues. I have read many forum pages looking for an answer and I am starting to get an idea, but I need some help
THE CAR:
-2010 HHR SS manual, multi function display in the dash
-Bought on Feb 2015 with 36K miles
-After a month I found out it had the GMTU kit installed (Bosch sensors, sticker in the engine bay.... the Chevy dealer didn't know about it)
-Car ran fine for 3 months, breaks traction in 1st and second, lots of torque steering, turbo boost always around 18PSI, pure fine
-It had a K&N air filter installed by previous owner
-Only issue after a week: turbo down to 14-15psi max after I washed the engine bay. Searching I assumed it was the crimps on the T-map sensors. Yes, they are crimped and not soldered. Run like that for 3-4 days, and they the power and boost were back
THE SYMPTOMS:
-MISFIRE: after 3 months running fire, CEL came up with a cylinder4 misfire code. Cleared the code and it came back again. Swapped coils (#4 with #3) and swapped spark plugs (#4 with #2) and still got misfire on cylinder4, so it's not the coils themselves or the spark plugs (which I changed recently, all 4)
-Driving the car normally, I wouldn't get the misfire (sometimes I DO hear the exhaust popping)... but banging through gears, it comes up
-Reading around I found out about carbon build up issues or fuel injectors.
-Run Seafoam in the tank (and also injector cleaner and top lubrificant from Lucas) and Seafoam in the intake through the small vacuum line in the center of it. Let it sit for 20 minutes and after a lot of smoke and banging through gears the misfire was gone
-This lead to issue #2
-LACK/NOT FULL BOOST: full boost comes and goes. It doesn't change only under acceleration or braking (so I guess the lower t-map sensor is not hitting the AC compressor I believe. The connector is facing the back of the car anyway). One day I would get full boost (up to 20psi, that I never reached in the 3 months the car had no issues), another I would get MAX 15-16psi
-When I don't get full boost, the car drives OK and it's quick, even though I feel not all the power is there. Reaching 4500-5000 RPM no misfire codes pop up
-When I do get full boost and bang through gears, cylinder4 misfire code pops up. I think when I go more than 16-17psi of boost.
I happens the most on 5th gear, rolling up from 60-65mph and then WOT.
-The CEL blinks for a few seconds and then stays on for a few more seconds. When this happens boost is max 10-12psi and I feel the car sputtering while keeping the foot on the pedal. CEL goes away and after a few more seconds, full boost is back, almost feeling like a ON/OFF switch
-I swapped top and bottom T-MAP sensors, no change. Top had the thicker blue o-ring, bottom had the thinner green one. Lower sensor (on plastic pipe) felt to fit not as tight as the top one (on intake). When swapped, lower felt better because of the thicker o-ring
-I run a turbo leak test, by myself building a PVC elbow fitting to plug on the turbo rubber hose on the back of the engine. First time I do this (not familiar with turbos). I could listen to the air in the system, so a little hard to pinpoint if there is a leak. BUT... if I grabbed the lower turbo pipe where the TMAP sensor is and wiggled some wires down there, I could hear the sound of the air changing, louder.
-CONSIDERATIONS: based on the symptoms and reading multiple boards and topics
-Crimped wires on T-MAP sensors: could be part of the problem, but I never got a T-map sensor error code
-Leak on turbo: not sure how it comes and goes. It should always be there, not randomly autofix
-Cylinder4 crud on valves: shouldn't I get the misfire code, even with less boost at the same high RPMs?
-Misfire code come up always in the same cylinder and above a certain boost PSI
-Could cylinder4 injector be bad, not delivering enough fuel when requested by the turbo?
I have the TORQUE app (and a couple more) and an OBDII reader. Got one freeze frame, but doesn't tells ME much
Now the car has 43.500 miles, 4 new spark plugs gapped 0.035 in (0.90 mm), Mobil1 fresh oil change (after Seafoam) and ACDelco air filter.
Sorry for the super long post, but I tried to answer questions you may have in advance
THANKS!!
08-07-2015, 12:57 PM
#3
Senior Member
Join Date: 09-07-2008
Location: Mebane, NC
Posts: 1,016
Good question about the plugs Oldblue
I had the some of the same issues. 1st showed up after driving the car in the rain, which I generally don't do. Then it would show up randomly. I got one of the 1st stages kits available (Lived in the North of Detroit, work with GM power train engineers...) at the time the crimp fittings were all that were offered, this was late 2008, beginning of 2009... if memory serves me right.
I never got a misfire, boost was limited to~ 5 at best. Soldered the connections, used adhesive heat shrink problem fixed.
If you have the stage kit you should be boosting more than what you are seeing, you should be in the 21 - 23 PSI range. Look for a loose hose or a cracked tube.
Little bit of history here.. The big deal at the time was whether HPT was going to be able to read the stage tune or not because we were told it may not. With the NEW stage tune the learn down feature was removed. In reality since this is a torque based system, it is a learn down feature. What they did was raise some of the values so increase performance of the bolt on mods wasn't negated over time. Long story... Once us tuners figured out and understood what the various tables did we also learned that the stage tune inherently had some nanny issues that the original file didn't at which point we changed the cal information for the new sensors and modified the non-stage factory tune.
I had the some of the same issues. 1st showed up after driving the car in the rain, which I generally don't do. Then it would show up randomly. I got one of the 1st stages kits available (Lived in the North of Detroit, work with GM power train engineers...) at the time the crimp fittings were all that were offered, this was late 2008, beginning of 2009... if memory serves me right.
I never got a misfire, boost was limited to~ 5 at best. Soldered the connections, used adhesive heat shrink problem fixed.
If you have the stage kit you should be boosting more than what you are seeing, you should be in the 21 - 23 PSI range. Look for a loose hose or a cracked tube.
Little bit of history here.. The big deal at the time was whether HPT was going to be able to read the stage tune or not because we were told it may not. With the NEW stage tune the learn down feature was removed. In reality since this is a torque based system, it is a learn down feature. What they did was raise some of the values so increase performance of the bolt on mods wasn't negated over time. Long story... Once us tuners figured out and understood what the various tables did we also learned that the stage tune inherently had some nanny issues that the original file didn't at which point we changed the cal information for the new sensors and modified the non-stage factory tune.
08-07-2015, 02:43 PM
#4
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Join Date: 12-06-2009
Location: Alabama
Posts: 11,090
[QUOTE=DrLoch
"If you have the stage kit you should be boosting more than what you are seeing, you should be in the 21 - 23 PSI range. Look for a loose hose or a cracked tube."
Uh, not exactly correct. Don't need to let the OP think something is wrong because his doesn't peak at 21-23. Mine hit's at best 19-20 with the GMTU. And yes, everything on mine is working correctly and hitting the power numbers it should be. I have the plug/play harness on mine. No crimps/solder.
"If you have the stage kit you should be boosting more than what you are seeing, you should be in the 21 - 23 PSI range. Look for a loose hose or a cracked tube."
Uh, not exactly correct. Don't need to let the OP think something is wrong because his doesn't peak at 21-23. Mine hit's at best 19-20 with the GMTU. And yes, everything on mine is working correctly and hitting the power numbers it should be. I have the plug/play harness on mine. No crimps/solder.
08-07-2015, 03:54 PM
#5
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Thread Starter
Join Date: 08-07-2015
Location: NC
Posts: 62
You got me there... I thought I wrote everything!
Plugs are ACDelco 12620540. The car had the same plugs
Compression test done, because I know some cars had the heads replaced:
Cyl1 152
Cyl2 142
Cyl3 150
Cyl4 145
And yes, always code P0304.
19-20 PSI is good enough for me as long as everything works
Just weird that with the car running fine I got max 18-19, and only lately I got a little over 20psi.
I will solder the wires at some point. If there is a problem with them, would the Tmap sensor throw a code?
Another thing I thought about is the harness between the coil and the main harness.
And thanks for the welcome!
08-07-2015, 04:35 PM
#7
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Join Date: 08-07-2015
Location: NC
Posts: 62
Tell you the truth, I am used to 30 year old harleys and as long as compression numbers are within 10%, I'm good. So I checked for overall numbers and eyeballed the finer numbers
Maybe on a modern engine numbers need to be tighter.. so my bad
08-07-2015, 04:44 PM
#8
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Join Date: 01-23-2009
Location: Fredericksburg, Virginia
Posts: 24,680
If it's ALWAYS and ONLY P0304, then cylinder #4 is producing enough misfires for the computer to flag it. Injector or spark if your pressure readings are correct.
The sensors have their own codes, but sometimes cause odd behavior in other systems when marginal.
The sensors have their own codes, but sometimes cause odd behavior in other systems when marginal.
08-07-2015, 09:35 PM
#10
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Join Date: 10-13-2011
Location: Welland,Ont Canada
Posts: 36,488
A code P0304 may mean that one or more of the following has happened: Faulty spark plug or wire Faulty coil (pack) Faulty oxygen sensor(s) Faulty fuel injector Burned exhaust valve Faulty catalytic converter(s) Running out of fuel Poor compression Defective computer
Read more at: OBD-II Trouble Code: P0304 Cylinder 4 Four Misfire Detected
Copyright OBD-Codes.com
Read more at: OBD-II Trouble Code: P0304 Cylinder 4 Four Misfire Detected
Copyright OBD-Codes.com