P0300 Random/Multiple Cylinder Misfire Detected
05-18-2006, 11:57 AM
#11
Launching!
Thread Starter
iTrader: (5)
Join Date: Nov 2004
Location: Melrose NY
Posts: 286
Likes: 0
Received 0 Likes
on
0 Posts
So open loop is when the computer is reverting back to the VE to control fuel deleivery, where in closed loop it is using the O2's to control fuel. Open loop is during WOT and initial startup when the O2's are'nt warmed up yet. If I still am getting a code then my VE must be off!!!, what about the PE chart? Thanks for all the help guys, still getting the hang of this program.
Andy
Andy
05-19-2006, 12:44 AM
#12
A number of other problems can cause misfires. Running rich *can* be a cause but is not the only possible cause. It's just something to look into. Without a wideband logger you can tell if it's rich by "reading" your spark plugs.
The PE chart is a divisor. For example, it your VE tables are right on the money, every cell should net 14.7:1 AFR for each given RPM and MAP. The PE value is what is used to divide that 14.7 AFR by. For example, 14.7 / a PE value of 1.20 = 12.25:1 AFR. If your VE tables are not right this end result can get really screwed up fast. Say your VE is really getting you 13:1 AFR for that cell and you have 1.20 PE set, that would be 10.83:1 AFR which is probably rich enough to throw a code. It doesn't take much skew in the VE table to mess everything up.
The PE chart is a divisor. For example, it your VE tables are right on the money, every cell should net 14.7:1 AFR for each given RPM and MAP. The PE value is what is used to divide that 14.7 AFR by. For example, 14.7 / a PE value of 1.20 = 12.25:1 AFR. If your VE tables are not right this end result can get really screwed up fast. Say your VE is really getting you 13:1 AFR for that cell and you have 1.20 PE set, that would be 10.83:1 AFR which is probably rich enough to throw a code. It doesn't take much skew in the VE table to mess everything up.
05-19-2006, 01:21 AM
#13
TECH Addict
iTrader: (25)
Join Date: Dec 2004
Location: southern california
Posts: 2,913
Likes: 0
Received 0 Likes
on
0 Posts
have been having the same code thrown, i just replaced my plugs and wires . so i will see if that helps. if thats not it , its got to be in the tunning somewhere,i'll get it figured out .
05-19-2006, 01:45 AM
#14
Are you guys using your Long Term Fuel Trims to dial in VE?
It's slow but has been effective for me over time. I have a suggestion for getting some LTrim data for high throttle positions.
- First, fill up with the highest octane non-oxygenated unleaded fuel you can get.
- Disable PE by setting PE Enable temp to something off the scale of reality. You can instead increase the TPS values to something off scale for PE enable.
- Retard timing in the upper RPM temorarily by 10 degrees or more so you can safely run WOT without detonation.
Log LTrim Bank 1 and 2, MAP, RPM and capture some logs. Use the LTrim % to increase or decrese your VE for that RPM x MAP cell.
It works and will get you enough data to get your VE tables right on, but it takes patience.
It's slow but has been effective for me over time. I have a suggestion for getting some LTrim data for high throttle positions.
- First, fill up with the highest octane non-oxygenated unleaded fuel you can get.
- Disable PE by setting PE Enable temp to something off the scale of reality. You can instead increase the TPS values to something off scale for PE enable.
- Retard timing in the upper RPM temorarily by 10 degrees or more so you can safely run WOT without detonation.
Log LTrim Bank 1 and 2, MAP, RPM and capture some logs. Use the LTrim % to increase or decrese your VE for that RPM x MAP cell.
It works and will get you enough data to get your VE tables right on, but it takes patience.
05-19-2006, 05:48 PM
#15
Originally Posted by SBChvy
So open loop is when the computer is reverting back to the VE to control fuel deleivery, where in closed loop it is using the O2's to control fuel. Open loop is during WOT and initial startup when the O2's are'nt warmed up yet. If I still am getting a code then my VE must be off!!!, what about the PE chart? Thanks for all the help guys, still getting the hang of this program.
Andy
Andy
If your misfire code popped up immediately after resuming MAF operation, and you haven't modified the MAF Frequency calibration and/or Injector Flow Rate table, then I would suspect that your VE was/is lean in the upper load areas (where PE kicks in) and PE divisor is high enough to bring you in line. Now that MAF is enabled, it is delivering a truer airflow measurement and your PE is over-richening.
What do your front O2 sensors read at WOT?
05-19-2006, 06:04 PM
#16
I am aware of the "Ltrim tip into" pe but after 4K isn't it all maf not VE dc? With that being the case, usually this would create a leaner scenario if the maf table is untouched, (showing less air than what's really there). Granted I agree under 4k his scenario could be more fuel than he wants due to maf+ve. Considering his mods I'd guess his maf isn't to far off, regarless of ve tuning. Just a K&N. I always say the same thing...wanna play and mod, a WB kicks ***!
05-25-2006, 11:41 AM
#19
Launching!
Thread Starter
iTrader: (5)
Join Date: Nov 2004
Location: Melrose NY
Posts: 286
Likes: 0
Received 0 Likes
on
0 Posts
Sorry I havent been around in a while, I preformed the crank re-learn and havent had any codes in 300 miles. I also went back and checked the VE again-It was dead on and smooth. So I guess we figured it out, now I just have to keep going. Thanks a lot for the help guys.
