[Tom F]

installed new motor. Old motor blew smoke but ran the same way. Put all new sensors, computer module, 02 sensors, thermostats, coils, plugs and cat converters. Runs rough when in drive or reverse after warm up. Very little mid range power until I get it to down shift. When I give it a good amount of gas there is a mild vibration until it hits the next gear. Any ideas

 

[rogoman]

If you purchased a new ECM (engine control module) from a Nissan dealership, the dealership will flash (program) the ECM to the VIN number of your vehicle and all of the specs. However, if you purchased an aftermarket ECM, you also will need to have it flashed to match your VIN number of your vehicle and all of the specs.

 

[VStar650CL]

you also will need to have it flashed to match your VIN number of your vehicle and all of the specs

Yep, it may not have the right firmware off the shelf, and it will definitely need an IAVL (Idle Air Volume Learn) even if it has the correct program. Without IAVL, the ECM can't read the MAF correctly and all sorts of performance problems can result. Your engine takes in roughly 9,000 gallons of air for every gallon of gasoline, so it's easy to see why even a small mis-calibration of the Mass Airflow can cause large issues, hesitation/poor idle if it reads lower than actual or poor gas mileage if it reads higher.

 

[Tom F]

If you purchased a new ECM (engine control module) from a Nissan dealership, the dealership will flash (program) the ECM to the VIN number of your vehicle and all of the specs. However, if you purchased an aftermarket ECM, you also will need to have it flashed to match your VIN number of your vehicle and all of the specs.

Sent the old one in to get fixed and they said they couldn't fix it so they gave me another cloned from my old one. Vin and security all done by them. Also forgot to mention new motor mounts

 

[Tom F]

Sent the old one in to get fixed and they said they couldn't fix it so they gave me another cloned from my old one. Vin and security all done by them. Also forgot to mention new motor mounts

It seems like there are a lot of posts with the same problem I have but very little on a specific fix. I know that it could be a lot of different things just odd so many people have the same problem. Also the sensors I bought where Nissan parts not aftermarket.

 

[rogoman]

It seems like there are a lot of posts with the same problem I have but very little on a specific fix. I know that it could be a lot of different things just odd so many people have the same problem. Also the sensors I bought where Nissan parts not aftermarket.

In this day and age with specialized ECUs, IDPMs, BCMs and various internal registration IDs to fit particular engine combinations, it's become difficult to just swap engines and matching their associated electronics. A typical shade tree mechanic/enthusiast gets lost with this new technology. Gone are the old days of a carb, one distributor with a set of points, one coil and the vehicles that have them are disappearing and parts are hard to find if at all.

Look what's ahead for us. Driverless cars and all electric cars; full of new crazy electronics. "Welcome to the brave new world"

 

[Tom F]

Yep, it may not have the right firmware off the shelf, and it will definitely need an IAVL (Idle Air Volume Learn) even if it has the correct program. Without IAVL, the ECM can't read the MAF correctly and all sorts of performance problems can result. Your engine takes in roughly 9,000 gallons of air for every gallon of gasoline, so it's easy to see why even a small mis-calibration of the Mass Airflow can cause large issues, hesitation/poor idle if it reads lower than actual or poor gas mileage if it reads higher.

Bought all new sensors when new motor installed. Still had problems, had four different mechanics look at it and couldn't find the problem. Last one said I should try all nissan brand sensors so I tried that, still same. Also new injectors same result. cleaned and put old injectors back in, same, Tried swapping back and fourth with sensors and coils still same thing. Did all the throttle and peddle relearn and still the same. Pulling what little hair I have out trying to figure this out

 

[rogoman]

Bought all new sensors when new motor installed. Still had problems, had four different mechanics look at it and couldn't find the problem. Last one said I should try all nissan brand sensors so I tried that, still same. Also new injectors same result. cleaned and put old injectors back in, same, Tried swapping back and fourth with sensors and coils still same thing. Did all the throttle and peddle relearn and still the same. Pulling what little hair I have out trying to figure this out

Have you ever performed an ECU fault code readout using a DTC scan tool? If not, do a scan to see if any fault codes are set. Post any code found to the forum so that we can help you more.

 

[Tom F]

Have you ever performed an ECU fault code readout using a DTC scan tool? If not, do a scan to see if any fault codes are set. Post any code found to the forum so that we can help you more.

Engine light off and it doesn't show any fault codes with scan tool

 

[VStar650CL]

Well, on a mechanically-healthy engine, there are only three systems that can "lie" to the ECM without producing a fault code, exhaust pressure, fuel pressure, and the intake system. Fuel pressure is straightforward to check with a gauge. A restricted exhaust can also be checked using a vacuum gauge, you'll have normal vacuum readings at idle that "go away" when the pedal is applied. Exhaust restrictions also produce a characteristic deep, "moaning" sound when accelerating. Intake problems can comprise either unmetered air (a vacuum leak) or the MAF (obstructed or mis-reading). With no codes, it pretty much has to be one of those.