P0300 mystery problem! - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


Chevrolet When starting new posts, please specify YEAR, MAKE, MODEL, ENGINE type, and whatever modifications you have made.

Reply
 
 
 
Thread Tools Search this Thread
Old 11-19-2013, 05:43 PM   #11
Junior Member
Posts like a Ricer Type-R
Thread Starter
 
Join Date: Nov 2013
Posts: 10
Thanks: 0
Thanked 0 Times in 0 Posts
jacklane21 is on a distinguished road
Default

will check compression tomorrow. I'll post then! Thanks.

Scan-tool doesn't show individual, which would be nice, I would be able to tell if a single cylinder is REALLY the problem, and just screwing up fuel trim enough to make the rest misfire.

At this point, I am going to forget about the fact that iut runs fine at any speed other than idle, because you guys seem to be ignoring it, and it may make us overlook something important. It would be crazy if a bad injector caused this. However, what if it is?!? I like to be completely objective in everything I do, so this makes sense to go down this path with this frame of reference.

Also thinking of biting the bullet and buying this: http://www.autel.us/pdf/MaxiSYS_Comparison.pdf
jacklane21 is offline   Reply With Quote
Old 11-19-2013, 06:11 PM   #12
Senior Administrator








Certified Car Nut
 
Mike's Avatar
 
Join Date: Jul 2003
Location: Horseheads, NY
Posts: 15,649
Thanked 1,001 Times in 777 Posts
Mike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond repute
Default

If it was a bad injector, hence we would see a P030? and not a P0300.

Sorry, but when it comes to a 300, its one of the most difficult P-codes to diagnose. And it get'* really difficult because you had the whole top half off. So there is no telling if you left a vac line off or goofed a gasket or who knows.
Mike is offline   Reply With Quote
Old 11-20-2013, 07:06 AM   #13
Senior Member
True Car Nut
 
jwfirebird's Avatar
 
Join Date: Dec 2009
Location: western,ny state
Posts: 9,616
Thanked 563 Times in 481 Posts
jwfirebird has a reputation beyond reputejwfirebird has a reputation beyond reputejwfirebird has a reputation beyond reputejwfirebird has a reputation beyond reputejwfirebird has a reputation beyond reputejwfirebird has a reputation beyond reputejwfirebird has a reputation beyond reputejwfirebird has a reputation beyond reputejwfirebird has a reputation beyond reputejwfirebird has a reputation beyond reputejwfirebird has a reputation beyond repute
Default

as far as the single misfire code, a single wont always set the single code,sometimes the random because other cylinders are affected. the other way seems you can trust if it says it cyl whatever its definitely going to be something with that one.
jwfirebird is offline   Reply With Quote
Old 11-20-2013, 07:32 AM   #14
Senior Member

Posts like a Camaro
 
Join Date: Aug 2013
Location: Northern California
Posts: 1,014
Thanked 164 Times in 130 Posts
75 racer is a splendid one to behold75 racer is a splendid one to behold75 racer is a splendid one to behold75 racer is a splendid one to behold75 racer is a splendid one to behold75 racer is a splendid one to behold75 racer is a splendid one to behold
Default

That is why having a scanner with a missfire bar graph comes in handy. It will show the cylinder with the most missfires giving you a direction to go.
75 racer is offline   Reply With Quote
Old 11-20-2013, 12:40 PM   #15
Junior Member
Posts like a Ricer Type-R
Thread Starter
 
Join Date: Nov 2013
Posts: 10
Thanks: 0
Thanked 0 Times in 0 Posts
jacklane21 is on a distinguished road
Default

Alright, compression test went bad. Cyl 6 is 10. All others are 180-200.

First thing is that I need to see if the valves are floating due to the .020" head milling. Will pull valve covers and relieve pressure and re-check.
jacklane21 is offline   Reply With Quote
Old 11-20-2013, 12:52 PM   #16
Junior Member
Posts like a Ricer Type-R
Thread Starter
 
Join Date: Nov 2013
Posts: 10
Thanks: 0
Thanked 0 Times in 0 Posts
jacklane21 is on a distinguished road
Default

valves are floating very happy about this.

I will fix, autozone carries the shims. Odd that the machine shop can get them, lol!

I will update when I get it fixed and if it is fixed COMPLETELY!
jacklane21 is offline   Reply With Quote
Old 11-20-2013, 01:23 PM   #17
Junior Member
Posts like a Ricer Type-R
Thread Starter
 
Join Date: Nov 2013
Posts: 10
Thanks: 0
Thanked 0 Times in 0 Posts
jacklane21 is on a distinguished road
Default

I thought I saw rocker shims or rocker spacers on the autozone website, yet I cannot find them ANYWHERE. Anyone have a source I can get these from?

I remember when I asked for a head spacer, the guy who milled my heads said they don't make any for this engine. He said they make rocker arm spacers, but he also said to put it together and if you have problems, THEN shim the arms. Otherwise, it is going to be fine.

Well, this was Schmidts automotive in Indy. One of the last engine machine shops around. I remember asking the parts department a while back for a price on the spacers, they said they can't get them. SO now I'm stock... I really don't want to make my own spacers, but unless I can get a source, I may have to!
jacklane21 is offline   Reply With Quote
Old 11-20-2013, 03:40 PM   #18
Senior Member
True Car Nut
 
jwfirebird's Avatar
 
Join Date: Dec 2009
Location: western,ny state
Posts: 9,616
Thanked 563 Times in 481 Posts
jwfirebird has a reputation beyond reputejwfirebird has a reputation beyond reputejwfirebird has a reputation beyond reputejwfirebird has a reputation beyond reputejwfirebird has a reputation beyond reputejwfirebird has a reputation beyond reputejwfirebird has a reputation beyond reputejwfirebird has a reputation beyond reputejwfirebird has a reputation beyond reputejwfirebird has a reputation beyond reputejwfirebird has a reputation beyond repute
Default

never heard of the spacers, but on a sbc if you make a bunch of changes to heads/cam/lifters/whatever you get custom pushrods from summit or something. so i would measure yours and see if they have shorter ones
jwfirebird is offline   Reply With Quote
Old 11-20-2013, 06:45 PM   #19
Senior Administrator








Certified Car Nut
 
Mike's Avatar
 
Join Date: Jul 2003
Location: Horseheads, NY
Posts: 15,649
Thanked 1,001 Times in 777 Posts
Mike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond reputeMike has a reputation beyond repute
Default

If he only removed .020 from the heads, why did it only effect #6 and not the rest of them?
Mike is offline   Reply With Quote
Old 12-05-2013, 01:38 PM   #20
Junior Member
 
Join Date: Dec 2012
Location: Wichita, Kansas
Posts: 7
Thanks: 0
Thanked 0 Times in 0 Posts
ajulius1220 is on a distinguished road
Default

I know that my post is hind sight and may not be useful at this point. I have been down this road quite a few times. Most the time when I get misfires at idle that clear up when on the throttle I find that my problem is in the valve train. I know this is a tough one at times- cause the p0300 is such a general DTC. It can lead you and many different directions. I would say that .020 is way too much on these particular heads. It seems very little but it is just enough to change the geometry of the valve train components. GM Service specs for Cylinder head cleaning and inspection instructs you to replace the head if you have to mill more then .010! It sounds like you did a very thorough job on the car and I am certain that you are going to make your customer happy. I am sure that there are ways you can work around this- but if it were me i'd just replace the heads at this point. =D Good luck and hope that you Git-R-Done.

Aaron
ajulius1220 is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
95 Bonne mystery problem WeaD 1992-1999 16 02-17-2011 12:32 PM
1999 Bonneville mystery problem-HELP! jkramer0306 Pontiac 2 10-20-2010 08:13 AM
Code P0300 and weak cylinder on #6 egladman 1992-1999 14 11-28-2005 11:16 PM
Mystery problem soatari 1992-1999 11 08-15-2005 08:39 AM
DTC P0300 Engine Misfire Detected Wargamer 1992-1999 26 05-01-2005 02:57 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 09:13 PM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.