Hey all,

I have a 92 300zx TT that is misfiring and I think the issue has to do with cylinders 5 and 6. For those that dont know... this is the cylinder numbering (according to alldata)

(view from above, rear of engine)
56
34
12

Heres a bit of the background story -
#1 March 2011 blew the passenger side turbo
#2 Sept 2011 replaced both stock T22 turbos with 2 T25 turbos
#3 This is where the misfire started, it felt like it was about 80% as fast as before the turbo blew, and over the next couple of days degraded to more like 50-60%. It was especially slower in the low end.

I had a diagnostic done at this point and was told cylinder 6 was reporting as a dead hole so I have since replaced all 6 spark plugs (it has a z1 ecu upgrade and 555cc injectors so I got the spark plugs they recommend after that upgrade) and the #6 coil pack.

While the car is idling, I can unplug the coil pack connector on cylinder 1, 2, 3, and 4 and the RPM's drop a bit and come back up when I reconnect it. Cylinders 5 and 6 though cause no change in the RPM's when disconnected/reconnected.

The engine had to be pulled when the turbos were replaced so I'm not sure if maybe something was not hooked back up right or not. There are 2 wires that are not connected to anything (from the wiring harness). Here are a couple pictures of them attached, if someone could help me identify what they are and where they should go I would greatly appreciate it.

I have replaced all plastic 6 coil pack connector also tried disconnecting the coil pack wire from cylinder 3 and connecting it to cylinder 5, the RPM's drop but do not come up when it is plugged into #5. The RPM's also do not come up when coil pack connector 5 is connected to cylinder 3. This may be normal behavior, I dont know enough about cars to tell though.

I also tried taking the coil pack from cylinder 3 and putting it into cylinder 5, same results.

I have done multiple compression tests and all cylinders are in the correct range.

I really want to get my car going again, I havent been able to drive it for about a year because of the turbos and the misfire melting the new cats I put on it.

Thanks in advance for any advice!

PS> Pictures 1 and 3 are of the 1 disconnected wire on the driver side, picture 2 is the disconnected wire on the passenger side

 

Give me some Numbers.. I'd like to know what the Compression Actually is..

All Plugs out.. throttle Wide Open.. Spin till max Number.. All Cylinders..

Do you have a Wideband Mixture Gauge.. Can you get one?.


With the Car running, ( Idling ) Use a Spray brake Cleaner with a 'Snout', and Squirt around the Injectors of Cylinder 5/6.. and at the Intake Plenum Seam .. looking for leaks.. if it's leaking, the RPM will jump up..

Cap

 

Hey Cap, thank you for the response and suggestions.

I didnt record the exact numbers but they were between 140-150 psi on each.

I dont have a wideband mixture gauge, I wont be able to get one for a couple weeks. I'm assuming it would be running lean since 2 cylinders arent firing..

I will do another compression check and record each cylinder. I will also try what you suggested with the brake cleaner and post the results.