Jump to content


Toggle shoutbox Shoutbox Open the Shoutbox in a popup

@  ejguillot : (21 September 2018 - 03:03 PM)

Agreed. I'd rather pay money to keep this site going than be on Facebook and having everything on there be used to make a buck for Zuck and company.

@  Vicious6 : (20 September 2018 - 01:48 PM)

We need to get this place moving again! Post link to this site on every social media site you know! Been around too long and we can't let it go down..........

@  Vicious6 : (20 September 2018 - 01:08 PM)

Seems everyone is too stressed to be online and worried about where their next meal is coming from! Rough times right now!

@  ejguillot : (14 September 2018 - 01:15 AM)

Still dead in here. Get off Facebook!

@  tpivette : (02 August 2018 - 01:08 AM)

Crazy, huh? I remember when I first got my GS in 2010 this place was a lot more active

@  Marchi1 : (30 July 2018 - 06:24 PM)

wow two weeks with no input

@  buck531 : (17 July 2018 - 01:15 AM)

ded

@  ejguillot : (12 July 2018 - 04:47 PM)

It is dead in here. Everyone on facebook?

@  M_Dogg : (03 July 2018 - 11:40 PM)

hello!!
echo
..echo
....echo

@  buck531 : (28 June 2018 - 01:37 PM)

this place is dead :(

@  keithr182 : (03 June 2018 - 07:13 PM)

Hey everyone. Just posted some parts for sale including a S2 IC if anyone is interested!

@  wq : (02 June 2018 - 04:46 PM)

p0171

@  jmaechtlen : (26 May 2018 - 04:34 AM)

fun, fun, fun

@  jmaechtlen : (26 May 2018 - 04:34 AM)

Still prepping the L67 for my Corvair project - cranks but no fuel pump

@  NKmssin3 : (07 May 2018 - 09:38 PM)

Hey Folks, I have a move happening and I have a sealed 5-gallon can of Renegade Pro 1 Methanol that I cannot take with me. Is anyone near the Orlando area interested?

@  phcdsqu : (06 May 2018 - 11:13 PM)

Wow, been a while since I logged in here...

@  ejguillot : (19 March 2018 - 02:10 AM)

Checking in here, because I will never use Facebook. :ph34r:

@  marcleach75 : (01 March 2018 - 06:13 AM)

Pinch hitting for Pedro Borbon, Manny Mota.

@  WildGS : (01 March 2018 - 03:56 AM)

echo....echo...echo.....

@  marcleach75 : (13 February 2018 - 05:08 AM)

Listening to PUTS, miss these dudes/


Photo
- - - - -

Can't get rid of No.4 Misfire at idle......


  • Please log in to reply
30 replies to this topic

#1 WaterDog

WaterDog

    Member

  • Members
  • PipPipPip
  • 206 posts
  • LocationVirginia Beach, VA

Posted 02 June 2016 - 11:41 PM

Replaced wires with ACDelco, regapped AL-605's to .055, moved and replaced coils, swapped wire terminals, cleaned crank sensor, cleaned all sensors, I.A.C., etc. swapped evap, cleaned PVC, checked for vacuum leaks spraying carb cleaner, spritzed wires checking for arcs, cleaned MAF, swapped MAF with other used MAF, cleaned and heat sink compound the ICM, swapped ICM with used one, cleaned ICM connectors with contact cleaner, ....

 

Checked and cleaned battery ground and ICM ground under bracket, checked injector resistance, swapped injector, put new O-rings on injectors, checked fuel pressure with existing gauge on billet fuel rails, pulled PCM and checked and cleaned the connectors, checked for broken or suspect wires, O2 sensor was replaced in 2009, (not sure on this one yet)  otherwise....no change.   

 

Aeroforce gauge shows 70-100 misfires, then drops to 20-40, then 0, back up to 80-100 misfires on #4

cylinder.  Then light is popped, Aeroforce shows PO300, random misfire, but all on No. 4 cylinder.

 

Dig up HP Tuners, (haven't used it in years) and run scan.  Looks like everything working but I've forgotten most of what I learned, as the car always ran great after the original final tune with it.   It does show a PO102 code with the PO300, which is a "MAF Sensor Circuit Low Frequency (Immature)" so I swapped the MAF's again and recheck the wires. No Change.  Swapped back to original MAF and then it went away...?   Reload Calibration to PCM, no change. 

 

I also notice in the DTC box, lower right, in the "Once per trip Tests" it showed the Oxygen Sensor and Heater as "Incomplete" in red. Now it just lists the O2 sensor "Incomplete" Is this saying the o2 sensor is dead?   I'm seeing activity on the scan...? 

 

I'm at my wits end on this and open to any suggestions! 

 

 

 

 

Ok, scan now loaded, 6-3-2016......

Attached Files


Edited by WaterDog, 05 June 2016 - 12:03 PM.

  • 0

#2 Murphinator

Murphinator

    Yeah, I rule.

  • Forum Moderator
  • 9,385 posts
  • LocationMaine
  • First Name:
    Keith

Posted 03 June 2016 - 12:07 AM

Charles , did you swap the ICM since we spoke on the phone ? I thought  you hadn't done that .

 

Have you swapped the spark plug , wire , and coil pack  with another cylinder to see if the problem moves with the parts ?

 

The noise you said you had was it on cold start ? if it makes that noise at a predictable time (cold start etc...) use a stethoscope ( tubing/pipe) to figure out if that sound is coming from the same cyl/area

 

get a borescope from auto zone etc... and have a looksee in that cylinder ???

 

sorry I had to be brief on the phone.



#3 WaterDog

WaterDog

    Member

  • Members
  • PipPipPip
  • 206 posts
  • LocationVirginia Beach, VA

Posted 03 June 2016 - 12:26 AM

No problem, appreciate the help.

 

Yep, did all the above...... the minor tick is hard to pin down.   Any thoughts on the PO102 randomly popping up?  Also burning rich now but can't find any vacuum leaks...


Edited by WaterDog, 05 June 2016 - 12:06 PM.

  • 0

#4 WaterDog

WaterDog

    Member

  • Members
  • PipPipPip
  • 206 posts
  • LocationVirginia Beach, VA

Posted 03 June 2016 - 03:41 PM

Scan now loaded.  Looks like o2 sensor is acting up...?  When I compare it to a scan from 2012, the o2 sensor is steady

at mid 400's while idling.  This one is all over the place.  Am I reading this right?

 

 

Attached Files


  • 0

#5 WaterDog

WaterDog

    Member

  • Members
  • PipPipPip
  • 206 posts
  • LocationVirginia Beach, VA

Posted 05 June 2016 - 09:53 PM

Double checked the Compression and they read:

 

Cylinder #

 

#3 - 180

#5 - 178

#1 - 175

#2 - 170

#4 - 170

#6 - 180

 

Not great but not real bad for 237,000 miles I suppose.  2 and 4 are the low ones in the back.  Are these low enough to

be causing a misfire? 

 

 


  • 0

#6 Jobu

Jobu

    Member

  • Members
  • PipPipPip
  • 145 posts
  • LocationMichigan
  • First Name:
    Chris

Posted 06 June 2016 - 05:01 PM

O2's should bounce all over at idle. Your car have the stock cam?
  • 0

#7 WaterDog

WaterDog

    Member

  • Members
  • PipPipPip
  • 206 posts
  • LocationVirginia Beach, VA

Posted 06 June 2016 - 06:30 PM

Thanks for the reply.

 

Yes, it has the stock cam.  That's good that it is acting normal.  Does showing "incomplete" in the DTC mean anything? 

I ordered a new MAF since the one I swapped with was a used Cardone MAF, chances are its not a good one.

The Delphi reman. that was in there, might have been the original problem.  I'll know tomorrow when the new one comes in.


Edited by WaterDog, 07 June 2016 - 12:55 PM.

  • 0

#8 WildGS

WildGS

    Fastest FWD GS in the PNW

  • Administrator
  • 4,428 posts
  • LocationChehalis, WA
  • First Name:
    David

Posted 07 June 2016 - 01:00 AM

Bad injector?



#9 WaterDog

WaterDog

    Member

  • Members
  • PipPipPip
  • 206 posts
  • LocationVirginia Beach, VA

Posted 07 June 2016 - 12:51 PM

Good thought.

 

Don't believe so, as I swapped with my original injector and back again with no change.  Resistance was good on all of them (12.6) and I replaced the O-rings. Pressure looks goods on the fuel rails too. 


  • 0

#10 WaterDog

WaterDog

    Member

  • Members
  • PipPipPip
  • 206 posts
  • LocationVirginia Beach, VA

Posted 07 June 2016 - 10:47 PM

New MAF didn't work.  Still misfiring on #4.....


  • 0

#11 WaterDog

WaterDog

    Member

  • Members
  • PipPipPip
  • 206 posts
  • LocationVirginia Beach, VA

Posted 14 June 2016 - 08:33 PM

Swapped Ignition Control Module with brand new AC Delco one, and cleaned bolt connections under the raised ICM.  Checked for vacuum leaks again and wiggled wires looking for breaks.

 

No change at all.  Still misfiring on No.4 and running rich.   Any suggestions?


  • 0

#12 DWS'00GS

DWS'00GS

    Wheres the Newbie Guide?

  • Members
  • PipPip
  • 86 posts
  • LocationArizona
  • First Name:
    Dave

Posted 16 June 2016 - 04:37 PM

I think at this point, I would want to get a look under that sparkplug and see what the piston looks like. If it looks ok, I hate to say it, buuut, the head likely needs to come off and be checked for any cracks. You have done everything else as far as I can see by your posts. Maybe someone else has a better idea. But it looks like you have exhausted all other possibilities. With the two lower compression readings it makes me suspect the head has a issue. But maybe you could get lucky and it is just a gasket. Since it is running rich and you can't find any vac leaks.....
  • 0

#13 WaterDog

WaterDog

    Member

  • Members
  • PipPipPip
  • 206 posts
  • LocationVirginia Beach, VA

Posted 16 June 2016 - 07:12 PM

Thanks.

Good point and funny you should just post that.  I just went to the muffler shop to hoist it up and see if I was missing any holes in the muffler/resonator, manifolds, plugged up, etc. and found I could hear that tick easier from under a real lift.  Sounds like a valve tick in 4 and I have a slight shake. 

 

Could a spent or broken valve spring be doing that, or more like a burnt valve be causing all this?

I'm not finding any other telltales to a cracked head as of yet, (fingers crossed).

 

I need a borescope and no one rents them around here...


  • 0

#14 DWS'00GS

DWS'00GS

    Wheres the Newbie Guide?

  • Members
  • PipPip
  • 86 posts
  • LocationArizona
  • First Name:
    Dave

Posted 16 June 2016 - 08:55 PM

Have to admit, didn't really consider a valve specific issue. I would think a broken spring would be much more obvious. Worn out spring? Bent valve? Lifter gone bad? Valve guide bad? The thing that lead me to gasket or crack, is side by side low compression. Got a Harbor Freight in your area? Can get camera/scopes fairly cheap there. Hear it better from underneath? I don't even want to go there!
  • 0

#15 WaterDog

WaterDog

    Member

  • Members
  • PipPipPip
  • 206 posts
  • LocationVirginia Beach, VA

Posted 19 June 2016 - 01:22 AM

I'll have to see a youtube video for broken rocker/spring sounds. 

 

So, I got one of those USB Laptop Borescopes for a $20, as everything else is $150 up and no one rents them locally.  Its a pain w/o an articulating camera head, so I improvised one out of a tube and string. The light could have been stronger, but it gave me an idea of how it looked until I can get a real one.

 

I didn't find any chips out of the piston.  I did find some vertical gouges in one side but was surprised to still find crosshatch in the cylinder at 237,000 miles, not bad.  I noticed a shiny spot on the piston, can't tell what it is.  The valves looked like one was very dirty and carbon had built up around the edges and the other valve shiny.  I did find what looked like carbon on one edge of the piston..or could it be a melted piston edge?  See pics.  

 

Now wondering it its worth pulling the rear valve cover to look for damage on #4 rocker/spring assembly...

Attached Files


Edited by WaterDog, 19 June 2016 - 01:23 AM.

  • 0

#16 DugarsGS

DugarsGS

    Wheres the Newbie Guide?

  • Members
  • PipPip
  • 42 posts
  • LocationOrangeburg, South Carolina
  • First Name:
    Terrell

Posted 19 June 2016 - 01:33 AM

I'm having the exact problem. Just replaced my faulty ignition switch. I looked at my misfire data and number 4 is counting off and occasionally number 3
  • 0

#17 Murphinator

Murphinator

    Yeah, I rule.

  • Forum Moderator
  • 9,385 posts
  • LocationMaine
  • First Name:
    Keith

Posted 19 June 2016 - 02:43 AM

I wonder what info is out there on what exactly will register as a misfire , my possible misconception is that it would only report a misfire if there is a non existent or off time ignition event . Don't know that slightly low compression would cause an actual misfire to register , I can see coolant getting on a plug causing a miss where head gasket was mentioned with lowest comp cylinders next to each other.

 

If a vac leak can cause it then I would first look at all the components you added with the ic , its been on there a long time now and not being installed by the general  puts a bullseye on anything modified to me - the best install still adds additional components not rigorously R&D'ed by GM , extra gaskets etc... more places for leaks to occur, have you tried (carefully) something flammable to locate vac leak ? propane , carb cleaner etc... I really don't think a vac leak is the issue but with the piston looking ok. I wouldn't want to pull it apart if I didn't have to but pulling the valve cover and watching it run a minute to look for a rocker/pushrod type issue would be minimally intrusive. Have you tried stethoscope type items long screwdriver on the valve cover with your ear to it , section of pipe ,etc... just to try to isolate the location of the noise



#18 WaterDog

WaterDog

    Member

  • Members
  • PipPipPip
  • 206 posts
  • LocationVirginia Beach, VA

Posted 19 June 2016 - 03:04 AM

Thanks for the reply.  I'm surprised how well and tight it's been for 7 years, almost OEM in its dependability.. until now

 

Yep, have used carb cleaner heavily looking for vac leaks, nothing that I could find. 

 

Have auto stethesope and can't really pinpoint anything with that either. 

 

I will have to pull the valve cover, being the rear, its more of a bear and harder to run with all the components that come off.

Need to do it to be sure...

 

DugarsGS-  I feel your pain!  Let me know if you figure it out...


  • 0

#19 WaterDog

WaterDog

    Member

  • Members
  • PipPipPip
  • 206 posts
  • LocationVirginia Beach, VA

Posted 30 June 2016 - 10:22 PM

Pulled the valve cover and checked for broken springs/rockers, bent rods.  Ran the engine and all looked like it was operating as it should.  Couldn't find any telltale signs of being off.  Buttoned it all up and still don't have a clue

about what the hell is going on...

 

 

Attached Files


  • 0

#20 ticketmagnet

ticketmagnet

    Been There. Done That.

  • Members
  • PipPipPipPipPip
  • 818 posts
  • LocationMI
  • First Name:
    Luke

Posted 11 July 2016 - 02:41 AM

Are they all oiling?  You said there was a sound - which is kind of ominous.  But if it's just an exhaust leak or something....  What about the crank position sensor?  The PCM logs misfires from engine speed changing in ways it shouldn't.  If you damaged a tooth on the wheel or something it could show a problem in the same engine position each time, but you would think that would also log on the opposite cylinder (is that #1?).  Is it misfiring at idle or under load or both?


  • 0




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users

BoHeGeHa Dark Blue 2.1.1 © Thomas Yugar (Chemical Chaos)
Official upgrade for IPB 2.3.x © Michael ( Dev Fuse )
3.X © Upgrade by Dumbledore ( Tppskinning )