Missfire @ Idle in Closed Loop Only
Thread Starter
Drifting
Joined: Nov 1999
Posts: 1,502
Likes: 12
From: Yorktown Heights NY
Missfire @ Idle in Closed Loop Only
99 Corvette Convertible Stock LS-1 with 71,800 miles
Idles fine up to 189F. As soon as water temp gets to 190F it starts missing at idle like crazy.
Initially had Map code and found the Map sensor had come unplugged?? Plugged it back in and it worked fine for about 2 days, then it started missing again. Changed the Map Sensor and it still does it.
Sets the following codes after clearing codes:
10 PCM:
P300H History Missfire
B0RFA:
U1064H History No Signal BCM Body Control Module
U1096H History No Signal IPC Instrument Panel Control
U1016H History No Signal PCM Engine Control Module
No Other Codes
Removed connectors on PCM and BCM and replugged...all clean and tight. PCM connector bolts torqued to specs.
Checked front frame rail ground packs on driver and passenger sides, all clean.
Think it may be an oxygen sensor with an intermittent therfore not setting O2 sensor codes, but I only have a tech 1 for my 95 and am just checking codes via the DIC on this 99.
Any ideas?
Stumped!
Idles fine up to 189F. As soon as water temp gets to 190F it starts missing at idle like crazy.
Initially had Map code and found the Map sensor had come unplugged?? Plugged it back in and it worked fine for about 2 days, then it started missing again. Changed the Map Sensor and it still does it.
Sets the following codes after clearing codes:
10 PCM:
P300H History Missfire
B0RFA:
U1064H History No Signal BCM Body Control Module
U1096H History No Signal IPC Instrument Panel Control
U1016H History No Signal PCM Engine Control Module
No Other Codes
Removed connectors on PCM and BCM and replugged...all clean and tight. PCM connector bolts torqued to specs.
Checked front frame rail ground packs on driver and passenger sides, all clean.
Think it may be an oxygen sensor with an intermittent therfore not setting O2 sensor codes, but I only have a tech 1 for my 95 and am just checking codes via the DIC on this 99.
Any ideas?
Stumped!
Last edited by 95BLKVette; Apr 29, 2009 at 10:56 PM.
Thread Starter
Drifting
Joined: Nov 1999
Posts: 1,502
Likes: 12
From: Yorktown Heights NY
The codes don't appear right away after clearing.
After clearing codes and the car is above 190F coolant temp it will start missing at idle but stop missfiring at about 1,000 rpm. It doesn't always set codes right away.
Never sets codes after clearing when cold.
After clearing codes and the car is above 190F coolant temp it will start missing at idle but stop missfiring at about 1,000 rpm. It doesn't always set codes right away.
Never sets codes after clearing when cold.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
This might sound like a strange idea but,,,,,,,,,,,,,,,,,,,,,,,,,open BOTH doors and shake the hell out of the rubber accordion tubes between both doors. See if you can feel for the TWO bundles of wire in the tube and then shake. NO COMMS tells me that you have a serial data buss issue. Check the two thin gray connectors to the left of the BCM. Pull the top shorting buss bar off the connectors and look for corrosion.
BC
BC
Instructor
Joined: Feb 2005
Posts: 247
Likes: 1
Plugs and wires
My 1999 coupe at 61000 miles started hesitating at highway speed after 55 any slight acceleration would result in a misfire, i ran the car with the tech 2 computer hooked up and it showed the misfires bangin aroun cylinder 2-5-and7 changed plugs and wires and it all ended, when did you replace yours??? If you havent start with that and dont worry about those u1016 and loss of communication codes they set sometimes because of a slow reaction time for info coming back let us know how you make out good luck
Thread Starter
Drifting
Joined: Nov 1999
Posts: 1,502
Likes: 12
From: Yorktown Heights NY
Like minds think alike 
I just ordered new plugs and wires and also just changed my PCV valve too.
Plugs and wires should arrive tomorrow.
I'll have to try the door thing and also the BCM wire short bars tonight
I'll let you know what happens.
Thanks
I just ordered new plugs and wires and also just changed my PCV valve too.
Plugs and wires should arrive tomorrow.
I'll have to try the door thing and also the BCM wire short bars tonight
I'll let you know what happens.
Thanks
Thread Starter
Drifting
Joined: Nov 1999
Posts: 1,502
Likes: 12
From: Yorktown Heights NY
Plugs and wires will be here tomorrow.
However, I purchased a great piece of scanner software called Car Code OBD-II for $136 with one day shipping. It does all the GM data logging including the specialized ones like cylinder missfire.
Well, I found that cylinder #2 is missfiring. BTW, after I cleaned the crap off my MAF resisitors with starter fluid the miss is now much less, and its not throwing any more codes.
I pulled the wire and plug in #2 and both look OK. Going to change all the plugs and wires tomorrow anyway. If that doesn't stop the miss I'll swap #2 and #4 injectors and see if the miss moves over to cylinder #4.
That should be a good starting point.
BTW, no more serial data communication or other codes.
However, I purchased a great piece of scanner software called Car Code OBD-II for $136 with one day shipping. It does all the GM data logging including the specialized ones like cylinder missfire.
Well, I found that cylinder #2 is missfiring. BTW, after I cleaned the crap off my MAF resisitors with starter fluid the miss is now much less, and its not throwing any more codes.
I pulled the wire and plug in #2 and both look OK. Going to change all the plugs and wires tomorrow anyway. If that doesn't stop the miss I'll swap #2 and #4 injectors and see if the miss moves over to cylinder #4.
That should be a good starting point.
BTW, no more serial data communication or other codes.
Last edited by 95BLKVette; May 1, 2009 at 10:17 PM.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
Melting Slicks
Joined: Jul 2005
Posts: 2,586
Likes: 2
From: Bardstown Kentucky
Just throwing this out there but possibly a bad injector. I have seen one or a couple go bad and its not that noticeable until closed loop when the O2 starts throwing fuel to compensate, basically it keeps reading lean and keeps adding fuel.
Have you noticed a fuel smell at all? Also you might check your coils, could possibly have a bad one or some bad wiring. I know these are all things you have probably thought about, just reminding you though.
Keep us posted!
Have you noticed a fuel smell at all? Also you might check your coils, could possibly have a bad one or some bad wiring. I know these are all things you have probably thought about, just reminding you though.
Keep us posted!
Le Mans Master
Joined: Nov 2005
Posts: 6,993
Likes: 25
Just throwing this out there but possibly a bad injector. I have seen one or a couple go bad and its not that noticeable until closed loop when the O2 starts throwing fuel to compensate, basically it keeps reading lean and keeps adding fuel.
Have you noticed a fuel smell at all? Also you might check your coils, could possibly have a bad one or some bad wiring. I know these are all things you have probably thought about, just reminding you though.
Keep us posted!
Have you noticed a fuel smell at all? Also you might check your coils, could possibly have a bad one or some bad wiring. I know these are all things you have probably thought about, just reminding you though.
Keep us posted!
Thread Starter
Drifting
Joined: Nov 1999
Posts: 1,502
Likes: 12
From: Yorktown Heights NY
Plugs and wires will be here tomorrow.
However, I purchased a great piece of scanner software called Car Code OBD-II for $136 with one day shipping. It does all the GM data logging including the specialized ones like cylinder missfire.
Well, I found that cylinder #2 is missfiring. BTW, after I cleaned the crap off my MAF resisitors with starter fluid the miss is now much less, and its not throwing any more codes.
I pulled the wire and plug in #2 and both look OK. Going to change all the plugs and wires tomorrow anyway. If that doesn't stop the miss I'll swap #2 and #4 injectors and see if the miss moves over to cylinder #4.
That should be a good starting point.
BTW, no more serial data communication or other codes.
However, I purchased a great piece of scanner software called Car Code OBD-II for $136 with one day shipping. It does all the GM data logging including the specialized ones like cylinder missfire.
Well, I found that cylinder #2 is missfiring. BTW, after I cleaned the crap off my MAF resisitors with starter fluid the miss is now much less, and its not throwing any more codes.
I pulled the wire and plug in #2 and both look OK. Going to change all the plugs and wires tomorrow anyway. If that doesn't stop the miss I'll swap #2 and #4 injectors and see if the miss moves over to cylinder #4.
That should be a good starting point.
BTW, no more serial data communication or other codes.
Melting Slicks
Joined: Jul 2005
Posts: 2,586
Likes: 2
From: Bardstown Kentucky
Thread Starter
Drifting
Joined: Nov 1999
Posts: 1,502
Likes: 12
From: Yorktown Heights NY
Changed plugs (AC Delco Iridiums 0.040 new revised gap instead of original factory 0.060) and wires AC Delco OEM black 7mm...used plenty of silicone grease on both ends).
Guess what? No more miss codes
In fact, I'm totally code free
Guess what? No more miss codes
In fact, I'm totally code free