Topic: Random misfires (P0300) - variable cam timing ??

[Chemist]

Okay, folks,

My car has been with a local garage for two weeks trying to pin down the source of a persistent Random Misfire condition in my Stage II S/C '06 Sol. Plugs have been changed, injectors replaced, coils check as good. Misfires remain.

When they shut off the variable cam timing, the misfires disappear; turn it back on, misfires are back.

Any ideas I can take them on Monday?

Thanks,

Chemist

[1LILNDN]

Sounds like the timing has jumped , or maybe one of the timing resistors is fouling . seems odd with it turned off theres no miss. Have they put a Meter on them to see if there putting out the proper amount of power ?  Garage not open on saturdays. Thats a Bummer.

[GaryH]

I also had a p0300 misfire code on my wife's stage II S/C.  It was caused by a plugged cat.  Do you have a boost gauge?  Are you showing more boost than usual? 

[Chemist]

Thanks, Guys. They pulled the cam cover and looked at the timing chain. The marks are aligned, so it would appear base timing is good.

My boost shows normal for my elevation @ about 5.25# WOT.

I'll know more on Monday, Lord willing.

[Jackknife]

Thanks, Guys. They pulled the cam cover and looked at the timing chain. The marks are aligned, so it would appear base timing is good.

My boost shows normal for my elevation @ about 5.25# WOT.

I'll know more on Monday, Lord willing.

Chemist, I get 8-9PSI on my Stage II...and, I'm no "higher" than you.

[Divingsolo (formely Randy@DDM)]

Chemist,

Got your email last night.  sounds like maybe you cam phasing actuators are going bad.  They do have a history of going south.  if they shut off VVT and the problem goes away, then that sounds like the issue. 

[Chemist]

Chemist,

Got your email last night.  sounds like maybe you cam phasing actuators are going bad.  They do have a history of going south.  if they shut off VVT and the problem goes away, then that sounds like the issue. 

Thanks, Randy. I'll pass that on to the folks at the garage.

--Byron

[Critterman]

Byron,  5 lbs is a stage I boost.  Stage II should be in the 8-9 lbs range.  For what it is worth I agree with Randy on the cam actuators.  I really believe you have to have a free flowing exhaust on the SC kappa, back pressure can't be good for the engine.

[GaryH]

Chemist, I get 8-9PSI on my Stage II...and, I'm no "higher" than you.

I'm at sea level and boost around 10, maybe 12 on a real cool day.  I hit 14 with the plugged cat. 

[Critterman]

I am at 33 ft at home, so you might as well say sea level, I used to get about the same maybe a little less

[Chemist]

I've never seen more than 6.5 on my DashHawk. (??)

[Critterman]

Do you have a stock cat?

[Chemist]

Do you have a stock cat?

I have the DDMWorks long tube headers, high flow cat, and exhaust (in addition to the Stage II S/C). All were installed at once two years ago in South Carolina.

[Graywolf]

Your timing chain can also be strechted out like mine which set off that code. Chain needs to be replaced if that is the case

[Chemist]

Your timing chain can also be strechted out like mine which set off that code. Chain needs to be replaced if that is the case

Thanks for that idea. I'll pass it all along.

I really appreciate the input from everyone.

[Chemist]

Your timing chain can also be strechted out like mine which set off that code. Chain needs to be replaced if that is the case

The garage owner and #1 tech are on the car now (have been for the last 2-3 days, I hear). They are thinking chain tensioner, will know more this afternoon.

Thanks again to all for the input/support.

[Chemist]

Well, it would appear that physical causes have been eliminated and we're looking at software issues now. Fun times.

[Jackknife]

Well, it would appear that physical causes have been eliminated and we're looking at software issues now. Fun times.

Have you checked the wiring bundle where it passes near the supercharger?  I remember someone having erratic electrical problems caused by tightly stretched wires rubbing.

[Chemist]

Have you checked the wiring bundle where it passes near the supercharger?  I remember someone having erratic electrical problems caused by tightly stretched wires rubbing.

I'll have them look. Thanks for that reminder!

[1KULSOL]

I'll have them look. Thanks for that reminder!

that was me ... sometimes the wiring harness is a little short ... sometimes moisture gets into the connectors ... Randy/Dave told me to disconnect the harness and check/clean the contacts ... that seemed to work for a while but they ended up giving me a whole new harness.

[Chemist]

bump for more input. Still no joy in Lubbock.

[spider]

Misfire with No Apparent Cause

 

This information applies to:

 

2004-07 ION Redline

2005-07 Cobalt SS

with 2.0L Supercharged Engine (RPO LSJ).

 

2007-09 Solstice GXP and SKY Redline

2008-10 Cobalt SS and HHR SS

with 2.0L Turbocharged Engine (RPO LNF).

 

A vehicle may illuminate a MIL with DTCs P0300, P0301, P0302 or P0304. The root cause typically cannot be determined. The misfire condition usually occurs with extended idling and may be reduced or eliminated by raising the RPM slightly or inducing an engine load (such as the A/C).

 

Engineering has determined that aftermarket parts (such as a light-weight aluminum flywheel or accessory belt drive pulleys) can contribute to this issue. Whenever any portion of the rotating assembly is changed to an aftermarket component, there is a potential for this condition. When diagnosing a misfire DTC and no condition can be found following SI procedures, inspect for installed aftermarket components.

 
found here------------ http://www.sandyblogs.com/cgi-bin/mt/mt-search.cgi?search=lnf&IncludeBlogs=10&limit=20

[Chemist]

Thanks, spider. I had just found that link this morning.

[Arabas]

Chemist, do you have an aftermarket flywheel?

[Critterman]

He has a DDM supercharger which puts a little load on the engine