NO ECU code and has a dead miss??

[CMV]

was driving along and all of the sudden " blah...." like the fuel pump &/or the FP cpu. but it didnt die this time... i was like " uh oh !?!? " it did get me home though.....I'm about to burn this car i think. I cant get any error codes other than 55. which is all good? 55 System OK (1990-1995 Q45 only) this is an 89' door sticker says 10/89. shall i assume that "55" is the same?the car runs rough like a dead miss in 2 or more cycls. will idle barely, runs rough al any rpm. Fuel pressure is good 45-50 lbs and stable<no jittering on the gauge>. injectors all ohm out good. all plugs look same. replaced anyway. its acts like a coil is bad or an ignition pack is bad but all the plugs look the same??? can unplug coils on passenger side while running with little to no effect. driver side seems to be firing well. have also switched sides of the ignition packs to no affect. had pluneum off inspected everything. all seemed ok. with no code what so ever from the ecu its a nightmare@!#%$. CAN ANYONE PLEASE HELP??whats the easiest way to check the coils. i ohmed them out from the connector and all matched so the primary side is good on all..

signed, CMV...broke q45 owner........
Modified by CMV at 4:56 PM 5/10/2007

[Q451990]

Your problem sounds very much like one or more bad fuel injectors. Even an electrically good injector can be clogged. Check out our "USB Consult Adapator Group Buy" thread in the Q45 forum for the best way to test your Q - assuming you have a laptop and another $30 for the OBD Nissan Scantech software. The newly-developed Power Balance test will tell you which cylinder(s) is dead. In the absence of that, I would use a non-contact IR thermometer to see which "leg" of the exhaust manifold is substantially cooler than the others.

In my experience a dead injector (dead miss) will feel like a bounce at idle, and then smooth out at higher RPMs. The corresponding spark plug in my case was always carboned up beyond sparking without a cleaning first - but from what I have heard that's somewhat unique.

If you're having trouble keeping it idling, you may have something more severe going on. Worst case scenario, your timing chain guides have cratered and you are lucky to only have it slip one tooth on that bank. One tooth slippage, and it runs horribly... two and you're bending valves. Typically the failure is on the left bank, but who knows...

The lack of an error code isn't uncommon... OBD I ECUs are kind of dumb...

Oh and 10/89 is a 1990 model.

Good luck!

Heath