Another LT1 misfire thread - but this time its fixed!
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Joined: Sep 2002
Posts: 470
From: Gwinnet County, GA
Another LT1 misfire thread - but this time its fixed!
I'm starting this thread because I haven't really had much help in terms of help from searches on this board, so hopefully this will help atleast SOMEONE.
It appears that after much fighting i have finally fixed the problem(s) with misfiring on my car. At first yes, it was the optispark and yes, it was the fact that the bearings were completely screwed. But even after that, I still had a pretty bad misfire, so I diagnosed it as such.
I threw three codes (one of which i knew i was already throwing, but that's a different story) and they are as follows:
p0300 (of course)
p0171 (fuel system bank 1 too lean)
p0160 (piece of crap bank 2 sensor 2 heated oxygen sensor little/no activity)
Checked resistance on each of my Northstar coil towers - checked out OK.
Replaced optispark and found the bearings to be pretty much shot; replaced the optispark with the following three items and it ran worlds better, but still had a miss.
1. Replaced plugs with Bosch Plats (i know people say they suck but for me they work just fine!)
2. Replaced Plug wires with a universal kit from Napa ($22 for 8mm wires, can't beat that!)
3. Put heat sleeves on the spark plug wires (napa federal mogul stuff - looks pretty good).
...Checked fuel pressure - off by a bit, but was within reason (~40 lbs at startup, dropped to 35lbs after a little bit).
So finally I checked all around my headers for any burnt material: plastics, wire material etc. Anything that looked out of the ordinary. Came across the front driver side o2 sensor harness extension which i ***THOUGHT*** was okay since i routed it very well.... it had the living CRAP burned out of it. This is the third time I have replaced this harness extension, it was clear that atleast one of the wires was burned all the way through and probably arcing over to other wires (which I imagine were burned through too).
Sure enough, I just removed the o2 sensor harness connection on the driver side and the car does not miss - it doesn't run PERFECTLY, but it doesn't miss at all. I noticed an instant power increase.... was like night and day.
Most all of these problems can be traced in some way back to the exhaust; be it headers or my catback. I have a SLP Loudmouth catback which rattled bolts loose on the optispark causing it to rattle and vibrate thus destroying the bearings (or so i've concluded). Furthermore, my exhaust headers (SLP midlengths) have burned various oxygen sensor harnesses, spark plug wires etc. All causing misfires, rich conditions etc, but this is also partially the fault of my exhaust leak. I knew that I'd done something wrong, and I'm only now starting to rectify my mistakes, and learning from them.
just a reminder ... double, triple and quadruple check your connections, bolts etc. Also, if your car rattles or anything like that - you WILL have problems. Its not a question of if but when....
It appears that after much fighting i have finally fixed the problem(s) with misfiring on my car. At first yes, it was the optispark and yes, it was the fact that the bearings were completely screwed. But even after that, I still had a pretty bad misfire, so I diagnosed it as such.
I threw three codes (one of which i knew i was already throwing, but that's a different story) and they are as follows:
p0300 (of course)
p0171 (fuel system bank 1 too lean)
p0160 (piece of crap bank 2 sensor 2 heated oxygen sensor little/no activity)
Checked resistance on each of my Northstar coil towers - checked out OK.
Replaced optispark and found the bearings to be pretty much shot; replaced the optispark with the following three items and it ran worlds better, but still had a miss.
1. Replaced plugs with Bosch Plats (i know people say they suck but for me they work just fine!)
2. Replaced Plug wires with a universal kit from Napa ($22 for 8mm wires, can't beat that!)
3. Put heat sleeves on the spark plug wires (napa federal mogul stuff - looks pretty good).
...Checked fuel pressure - off by a bit, but was within reason (~40 lbs at startup, dropped to 35lbs after a little bit).
So finally I checked all around my headers for any burnt material: plastics, wire material etc. Anything that looked out of the ordinary. Came across the front driver side o2 sensor harness extension which i ***THOUGHT*** was okay since i routed it very well.... it had the living CRAP burned out of it. This is the third time I have replaced this harness extension, it was clear that atleast one of the wires was burned all the way through and probably arcing over to other wires (which I imagine were burned through too).
Sure enough, I just removed the o2 sensor harness connection on the driver side and the car does not miss - it doesn't run PERFECTLY, but it doesn't miss at all. I noticed an instant power increase.... was like night and day.
Most all of these problems can be traced in some way back to the exhaust; be it headers or my catback. I have a SLP Loudmouth catback which rattled bolts loose on the optispark causing it to rattle and vibrate thus destroying the bearings (or so i've concluded). Furthermore, my exhaust headers (SLP midlengths) have burned various oxygen sensor harnesses, spark plug wires etc. All causing misfires, rich conditions etc, but this is also partially the fault of my exhaust leak. I knew that I'd done something wrong, and I'm only now starting to rectify my mistakes, and learning from them.
just a reminder ... double, triple and quadruple check your connections, bolts etc. Also, if your car rattles or anything like that - you WILL have problems. Its not a question of if but when....
Registered User
Joined: Apr 2003
Posts: 892
From: Dallas/Fort Worth
Re: Another LT1 misfire thread - but this time its fixed!
If you burned through the o2 wires check the fuse under the hood for "heater/actuator", as that pre-heats the o2's and will blow if there is a short.
-James
-James
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