Bad misfire
Bad misfire My car has had an intermittent miss for over a year now. I just finally bought HP tuners VCM suite. I logged the misfire data and #2 is missing alot. Over 200 counts a few times. Pulled the plug and it is a nice light brown color. Visually inspected and appears to have no cracks or carbon tracking. I swapped the coils with #4. Still missing on #2. I put a couple of bottles of Techron in the tank and went out and beat the snout out of her a few times. Still miss on #2. Last night I swapped the injectors between #4 and #2. Drove it today. Still bad miss on #2. It is mostly right after I take off from a stop. It mostly comes out of it once I get the rpm's up. But it comes right back after I slow down. I tried the CASE learn as some have said that fixed misfire issues. Still misses. My next step is to replace the plug and possibly swap the plug wires. It has fairly new MSD wires and it does not have any external damage to the wire. Any other suggestions? I don't believe it is a wiring issue due to the way it acts and comes out of it when the rpm's are increased. Any help would be greatly appreciated.
Scott.
Scott.
TECH Senior Member
Joined: Apr 2002
Posts: 6,080
Likes: 17
From: So.Cal.
Also, pull the pushrods and check for any being bent...
I still think you may have a minor coolant leak into #2... when you did the coolant pressure test, how long was pressure maintained and how slowly did it drop (did it maintain the same pressure for at least 30 minutes)...?
I still think you may have a minor coolant leak into #2... when you did the coolant pressure test, how long was pressure maintained and how slowly did it drop (did it maintain the same pressure for at least 30 minutes)...?
It held pressure for over an hour. Only lost maybe 1/2 psi. Also I would think I would see signs of coolant leaking on the spark plug and it appeared to be OK. I suppose it could be a slight coolant leak that would burn off. I will pressure check it again. Also, the coolant level has not dropped at all in the 3 years I have owned the car.
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I did the block test and no combustion gases in the coolant. Pushrods are OK. I went to change the O2 sensors as I had a few slow response codes for the right bank. I ordered new Denso's from Rock Auto as they were on a smoking sell!! I removed the old one from the right bank. I thought I had extensions. Nope. They are a different sensor with a 4ft harness on them. Not sure what brand. I googled all of the numbers on them and came up with nothing. I wonder if they are even the right ones? The harness is covered in a thick, red sleeve. Looks like some of the Bosch ones I have seen. The following info is on the sensor:
0 258 005 740
8811831 12v 982
That's it. Any ideas on what these are and if they are even the right ones? Attached are a couple of pics.
0 258 005 740
8811831 12v 982
That's it. Any ideas on what these are and if they are even the right ones? Attached are a couple of pics.
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o2 sensor will not cause single cylinder misfire, your following the right path, if a sparkplug, wire swap does not move the misfire check that that coil is getting signal from the PCM, along with power and ground could just be an open wire but thoose should throw a coil code
