Automotive Forums .com - the leading automotive community online! Automotive Forums .com - the leading automotive community online!
Automotive Forums .com - the leading automotive community online! 
-
Latest | 0 Rplys
Go Back   Automotive Forums .com Car Chat > Pontiac > 6000
Reply Show Printable Version Show Printable Version | Email this Page Email this Page | Subscription Subscribe to this Thread
 
Thread Tools
Old 08-31-2010, 06:55 AM   #1
Electric_mouse
AF Newbie
 
Join Date: May 2008
Location: Regina
Posts: 76
Thanks: 6
Thanked 2 Times in 2 Posts
Engine missing at high idle & above 35 mph

Pontiac 6000, 2.8 V6. Enigne wasn't running when purchased due to faulty crankshaft sensor (posted previously). Now that the car is driveable I find it misses (like bad ign wires) when driving; also very noticeable at high idle speeds, I'm guessing in range of 1200 to 1500 rpm. Tried different set of wires and examined front plugs. Wires didn't change anything and the plugs look decent so I'm ruling these out as the cause at this time. I experienced a similar problem on a Lumina 3.1 but that unit ran rough at low idle and driving. That problem was traced to two bad injectors. This car runs smooth at low idle but rough at higher speeds. Shorting out plug wires individually doesn't point to any one cylinder as a likely culprit.

(for the Lumina I built a simple gadget which goes inline with the ignition wires and allows me to short to ground the spark to any plug of choice. I find this home made tool quite handy and would post a picture if I knew how. lol)

Anyone experience similar problems? Would defective injector(s) work decently at low idle yet cause problems at higher speeds unlike the Lumina which was at all rpm's?

Thanks
Electric_mouse is offline   Reply With Quote
Old 08-31-2010, 07:28 AM   #2
TRINI55
AF Newbie
 
Join Date: Jul 2010
Location: BRAMPTON
Posts: 15
Thanks: 0
Thanked 0 Times in 0 Posts
Re: Engine missing at high idle & above 35 mph

check the coil pack, could be breaking down under load
TRINI55 is offline   Reply With Quote
Old 08-31-2010, 10:00 PM   #3
Electric_mouse
AF Newbie
Thread starter
 
Join Date: May 2008
Location: Regina
Posts: 76
Thanks: 6
Thanked 2 Times in 2 Posts
Re: Engine missing at high idle & above 35 mph

Quote:
Originally Posted by TRINI55 View Post
check the coil pack, could be breaking down under load
Before replacing the coil pack I thought I would check the resistance of the injectors. I thought they should be accessable from the ECM rather than remove the plenum.

Well not so fast. No 1 and No 6 injectors are accessable at the top of the engine, no problem. But I notice from the drawing:
http://www.autozone.com/autozone/repairinfo/repairguide/repairGuideContent.jsp?pageId=0996b43f8039380f
that they group the injectors front and rear.

Silly question. It would seem to me that all three injectors would receive signal simultaneously. Shouldn't only one cylinder receive a pulse? Why inject fuel into the other two cylinders since they won't be at the correct position to fire?
Electric_mouse is offline   Reply With Quote
Old 08-31-2010, 10:13 PM   #4
danielsatur
AF Enthusiast
 
Join Date: Mar 2008
Location: garner, North Carolina
Posts: 3,579
Thanks: 86
Thanked 100 Times in 100 Posts
Re: Engine missing at high idle & above 35 mph

Are you getting consistant misfires on same cylinders, or is the misfires random?

I have seen a plugged catalytic converter on one bank, causing random misfires on the same bank.
danielsatur is offline   Reply With Quote
Old 08-31-2010, 10:28 PM   #5
Electric_mouse
AF Newbie
Thread starter
 
Join Date: May 2008
Location: Regina
Posts: 76
Thanks: 6
Thanked 2 Times in 2 Posts
Re: Engine missing at high idle & above 35 mph

Quote:
Originally Posted by danielsatur View Post
Are you getting consistant misfires on same cylinders, or is the misfires random?

I have seen a plugged catalytic converter on one bank, causing random misfires on the same bank.

They are random misfires. I wasn't able to detect any weak cylinders (using my device). The engine tone and rpm changes approx equal for each cylinder when the plug wire is shorted.

"catalytic converter on one bank". ???
The converter is further back on the exhaust after the two banks have been joined.
Electric_mouse is offline   Reply With Quote
Old 09-01-2010, 12:25 PM   #6
TRINI55
AF Newbie
 
Join Date: Jul 2010
Location: BRAMPTON
Posts: 15
Thanks: 0
Thanked 0 Times in 0 Posts
Re: Engine missing at high idle & above 35 mph

" random misfire " can also be cured by flushing injectors.
TRINI55 is offline   Reply With Quote
Old 09-01-2010, 02:06 PM   #7
danielsatur
AF Enthusiast
 
Join Date: Mar 2008
Location: garner, North Carolina
Posts: 3,579
Thanks: 86
Thanked 100 Times in 100 Posts
Re: Engine missing at high idle & above 35 mph

The best way to clean Injector's is out of the car, and them to a diesel shop, were they can micro bath, blowout, and the flow rate tested.

Don't forget the new fuel filter!
danielsatur is offline   Reply With Quote
Old 09-02-2010, 09:33 PM   #8
Electric_mouse
AF Newbie
Thread starter
 
Join Date: May 2008
Location: Regina
Posts: 76
Thanks: 6
Thanked 2 Times in 2 Posts
Re: Engine missing at high idle & above 35 mph

Thanks for the tip about taking the injectors to a diesel shop. I wondered about that possibility.

Update:

Installed a good set of plugs and wires salvaged from wrecker. ($10. OK so I'm cheap. lol). That improved it somewhat but still not good enough. So decided to pull the plenum and checked the resistance of each injector individually. It is possible to pull one injector wires off on each bank and then read the resistance of the two remaining in that bank. Being that the injectors are connected in parrallel the reading should be about 6 ohms. The resistance was a little low I thought. After I got it apart I found no. 5 injector reading 9.7 ohms so I replaced it with another used one that tested just over 12 ohms. The car runs beautifully now. Lots of power and smooth.
Electric_mouse is offline   Reply With Quote
Old 10-16-2010, 10:06 PM   #9
3100
Banned
 
Join Date: Nov 2008
Location: chicago, Illinois
Posts: 1,034
Thanks: 0
Thanked 2 Times in 2 Posts
Re: Engine missing at high idle & above 35 mph

If you are noticing small vibration in gas pedal when accelerating between 1200-1300 rpm try different alternator believe it or not.
3100 is offline   Reply With Quote
Old 10-16-2010, 10:09 PM   #10
3100
Banned
 
Join Date: Nov 2008
Location: chicago, Illinois
Posts: 1,034
Thanks: 0
Thanked 2 Times in 2 Posts
Re: Engine missing at high idle & above 35 mph

or just remove serpentine belt for a minute or two and test drive around the block to eliminate mechanical vibrations
3100 is offline   Reply With Quote
 
Reply

POST REPLY TO THIS THREAD

Go Back   Automotive Forums .com Car Chat > Pontiac > 6000

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -5. The time now is 01:58 AM.

Community Participation Guidelines | How to use your User Control Panel

Powered by: vBulletin | Copyright Jelsoft Enterprises Ltd.
 
 
no new posts