trouble diagnosing misfire
Thread Starter
|
Three Wheeling
Joined: Oct 2011
Posts: 83
Likes: 0
trouble diagnosing misfire
I recently experienced a check engine light that would flash intermittently (p0305). About twp days ago it has start flashing none stop until 2500 rpms then it stays lit. My trucks at 123000 miles so i thought let me do a basic tune up, used kingsbourne wires, plat +4 plugs, and even changed out the coil pack that corresponds with that cylinder. None of that helped, i thought maybe a bad plug wire so i swapped 5 and 6 and i still have the same misfire. Ive also replaced o2 sensors (upstream) and cleaned maf. Has anyone experienced anything like this? I dont even wanna drive the truck right now because it idles so rough. Any help would be greatly appreciated
Super Moderator
Joined: Jan 2011
Posts: 16,322
Likes: 88
From: Savannah Georgia
From the Bosch guide to the ECU and codes it makes:
In the case of misfire monitoring two levels of misfire are checked:
Emission relevant misfire is monitored over 1000 engine revolutions and 2 drive cycles.
Catalyst damage misfire is monitored over 200 engine revolutions. If the threshold is exceeded in any 200 engine revolutions segment the MIL is immediately flashed to signal the driver to reduce engine load. When the misfire decreases below the catalyst damage threshold or ceases altogether the MIL is permanently illuminated
In this case MIL = engine light.
Any coolant loss? Antifreeze sliping into cylinder would take a little while to burn off... New plugs in that cylinder look good?
Clean IACV and throttle body?
Emission relevant misfire is monitored over 1000 engine revolutions and 2 drive cycles.
Catalyst damage misfire is monitored over 200 engine revolutions. If the threshold is exceeded in any 200 engine revolutions segment the MIL is immediately flashed to signal the driver to reduce engine load. When the misfire decreases below the catalyst damage threshold or ceases altogether the MIL is permanently illuminated
In this case MIL = engine light.
Any coolant loss? Antifreeze sliping into cylinder would take a little while to burn off... New plugs in that cylinder look good?
Clean IACV and throttle body?
Thread Starter
|
Three Wheeling
Joined: Oct 2011
Posts: 83
Likes: 0
Very slight loss of coolant but it appears to be coming out of the breather tube on my expansion tank. It's as though my coolant is being over pressurized or getting too hot and bubbling out. The coolant stays in the middle of my tank or else it'll just boil over. My plugs are crispy black and white in the center
Administrator
Joined: Apr 2006
Posts: 25,707
Likes: 107
From: Denver, Colorado
I would first do a coolant pressure test to see if you have a head gasket leaking into #5, if that is OK then a compression test and if need be a leaking down test to determine if you have a valve related issue. Do them in the order given to not waste time.
Let us know what you find.
Let us know what you find.
Thread
Thread Starter
Forum
Replies
Last Post
iceray111
General Tech Help
1
May 15, 2010 02:40 PM
