Thread: Cylinder misfire after L67 to L67 swap

I've just finished doing a swap from one L67 to another. Had cracked heads in the original motor and possibly a bad block (not tested) on my old motor (1997 GTP, ~250K miles) and so I got a pulled motor that was compression checked and has a 6 month, unlimited mile warranty on it (from a 2002 GTP with ~130K miles). Last weekend with help I figured out what was preventing me from actually starting the car and now that I've got it started I'm getting a misfire in cylinder 4 that I'm trying to diagnose - the clincher is, is that I have to travel from my university every weekend to work on it, (about 90 miles one way) and so working on it for an hour at a time isn't quite possible so I'm hoping for a few ideas that I can check at once as soon as I get there.

What it's doing:

• When starting the car, the car will run for about 3-5 seconds before developing a misfire in the 4th cylinder
• I get a very wispy smoke that starts to come from around both of the valve covers.
• My scan tool will throw two (of the same) codes. P0304 Cylinder 4 Misfire and P0304 Pending.

Additional Information:

• The rear knock sensor was somewhat loose in its metal housing (the area where it goes from plastic to metal).
• I have one new stud on my exhaust flange and so I don't know how solid the connection is (both sides are tightened down as far as possible)
• I'm leaking fuel from the larger of the two fuel lines on the fuel rail as soon as I turn the car to accessory and I hear the fuel pump engage.
• The car is full of water instead of coolant because I'm going to use Prestone's radiator/cooling system flush to get rid of the coolant/oil mix in the cooling system (but the car's never running for more than 30 seconds at a time and isn't heating up).
• The EVAP switch and purge are attached via vacuum but haven't been placed back on their bracket because I'm trying to figure out just how to reattach everything, but they don't look to be in the way of anything are far enough out of the way/not near the exhaust.

What I've done so far:

• The spark plugs are all new Bosch Iridium plugs and there are all new Duralast spark plug wires.
• I swapped plugs and wires around to see if maybe one was bad, but the problem stayed in the same cylinder (number 4, rear middle of engine)
• I tested the compression of cylinder 4 vs cylinder 3 (front middle of engine) and have 40 PSI in the rear and 105 up front. The engine however was tested before I purchased it and compression was fine.
• I removed the fuel rail and pulled all the injectors, replaced their o-rings and swapped injector 4 with a different injector and replaced the fuel rail. It's tough to tell if injector 4 is in all the way. The misfire stayed in the same cylinder.

What I still plan to do:

• Drop some oil into cylinder 4's spark plug cavity and redo the compression test
• Anything that I get told to do here >.>

My guess is that there are probably multiple issues here that together are causing the misfire. I imagine the leaking fuel could be a lot of the problem, but I am in no way very knowledgeable on the subject and am hoping for some insight as to what is going on and what I can do to fix my few remaining issues. Thanks for everything so far! I wouldn't even have the engine in if not for the forums :-) Any help would be greatly appreciated and I'll be starting on the car tomorrow evening again.

Thanks!
Zae

First off you need to fix that fuel leak, or you won't have to worry about the misfire long, lol... The wispy smoke from the covers could just be old oil burning off from the install.

You really need to check the compression again. That is a huge difference. Heck, just for grins double check that you have the spark plug tight in the head. Could just be that simple.

If you want to check to see if the injectors are sealing you could spray some carb cleaner around all the injectors where they go into the head and see if the motor changes tone. If so, then that's a vac leak.

Any recommendations for removing and installing the rear knock sensor without separating engine/tranny? 22mm shallow just barely isn't deep enough and the electrical connector stops it and I don't have enough clearance for a crow's foot to get in there either... Replacing the fuel line makes the knock much less noticeable but the code still throws so I think I'm finally close. When I swap wires the misfire stays.

Originally Posted by scottydoggs

i've never changed one but i would think a deep socket a extension long enough to be under the pans. and a long pair or needle nose pliers for the plug should get it out.

In order to get the old one out, I broke off the electrical connector and that was fine, shallow socket on an extension got it just fine. Getting the new one torqued is going to be the hard part; I have it hand tight in there but the electrical connector gets in the way of the shallow socket and the socket is too wide to get into the opening and so my deep sockets haven't worked.

Originally Posted by BillBoost37

Crows foot?

I can't get the extension on the crow's foot and still be able to grab the sensor. I'll keep thinking about it throughout the week as well and see if I can't think of something.

Just read BillBoost's post where he says to swap #1 & #4 at the coil. I did that and never got a code so can you tell me where to go next? I have replaced the plugs and the wires