I've recently had some trouble with my Q after replacing my fuel pump & filter. Lack of power/misfiring mainly. The car seems to run fine when cold, but after it's warm it will begin missing and at its worst the car is not driveable. I checked the codes and have 21- Ignition Signal Circuit, and 34 for knock sensors. Looking into it, 21 appears to mean my Ignition Control Modules are bad? Are there any test procedures to confirm/deny this? I do not want to spend $800 for a new pair if not absolutely necessary to install in a $900 car.

Thanks.

I've gotten a code 21 before and I think it was because I turned the car on with something unplugged. If you wanted to get a new set of ignition control modules (sometimes called ignitor packs), a set of used ones would be a really good bet.. I'm sure there's a VH45 hoarder out there that'd sell you a pair for $50. That said, they rarely fail, so while it's possible one or both are bad, I'd look at other things.

Was the fuel pump you replaced with new?

I'd also be looking at injectors and MAF.

the easiest way to check to see if one of your coil packs is the problem is just unplug the coil pack on any given cylinder, if you unplug the pack and the engine starts to idle rough then you know that the coil pack is working but if you unplug the coil pack and there is no change in engine idle you may have a bad coil pack and you notice I said you may have a bad coil pack because you have to check the fuel injector as well because either one could be the problem do the same for the fuel injector and just unplug it and look for the same results as the coil pack unplugging, you don't want to change a coil pack to find out it was a faulty fuel injector, when my 95 Infiniti Q45 started backfiring and had lack of power it ended up being a bad mass airflow sensor, So would probably make sure your mass airflow sensor is working properly, the location is between the air filter and throttle body you cant miss it,

mac, always keep in mind - a retrieved code ,which translates to a specific part, does NOT ALWAYS mean that part bad.Above is a knock code and an Ignition code ,part of the overall "Ignition System" portion of the car (ECM portion dedicated to ign.). I had temp sensor, Left O2 , and knock codes - first two were phantom codes due to the INTRERELATIONSHIP between ignition componants - KNOCK SENSOR SOLE CULPRIT. I found a DEAL on one ,bought it due to their BAD reputation - kept it for that "rainy -day ! Also keep in mind the individual componants have very good test procedures in the Nissan/INFINITI manuals ....what ? No more access to manuals ?

macgiver wrote: ↑

Sun Apr 22, 2018 8:46 pm

No more access to manuals ?

Nissan wants you to buy them... Not our call.