# What should i do if my engine wont go higher than 1500RPM?



## paripa_andrey (Oct 10, 2007)

I have a 2002 Nisan Sentra SER spec-v. I got this car with missing ECU and Wiring Harness. I got ithe other ecu and installed everything like it should be. The problem that i have is that i get these codes P1122, P0328, P0102, P0223, P0123, P1126, P0113.
Also i got a Air Mass Flow Meter from a 03 Altima i am not sure if thats the case why it wont give out more than 1500RPM at a full throttle down to the floor.
thats what the code reader is saying:
P1122 - manufacturer control fuel air metering.
P0328 - knock sensor 1 circut high input bank 1 or sensor 1
P0102 - MAF or VAF A circut low input
P0223 - TPS/Pedal position sensor/switch B circut high input
P0123 - TPS/Pedal position sensor A circut high input
P1126 - manufacturer control fuel air metering
P0113 - IAT sensor 1 circut high input
Basically what my questions: 
Which sensors should i replace?
What should i do to the ECU to reset it?
Where is the knock sensor located?
What do these codes actually mean?


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## BeyondBiscuits2 (Jan 18, 2006)

Its your MAF... the ECU itself can handle from around 1500-2000 rpms depending on the engine, and the MAF takes over after that. Sounds like you have a bad MAF and it is affecting your other systems. I assume you got the ECU and harness out of a 2.5 litre Altima rather than the V-6; believe it or not but people have made similar mistakes to that. You might want to have the ECU tested and make sure everything is working properly. Also, take your car (after you get a new MAF) to a car parts store and have them clear the ECU codes. That should tell you after you replace your MAF if it is just that, or if you have a more serious problem.


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## xbrandonx (Mar 27, 2004)

When the b15 detects severe problems it goes into "limp mode" to prevent any further damage. It does sound like you got a bad maf. However, If you didn't disconnect the battery before you unplugged your maf that has been known to trip the limp mode. Disconnect your battery, unplug the MAF and plug it back in, then hook your battery back up. See if that helps anything.


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## paripa_andrey (Oct 10, 2007)

And also what about the KNOCK SENSOR how does it affect the engine throttle?


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## BeyondBiscuits2 (Jan 18, 2006)

It shouldn't. If you trigger your knock sensor, it should shut your engine down completely (that's what it does on earlier Nissan engines at least). Since Nissan now incorporates a good deal of Renault engine sensors and such, I am not quite sure on the newer engines on how to knock sensor reacts overall. All the knock sensor should do is detect knocks in your crankcase, and that should not affect your idle; it would basically allow your engine to crank and upon hearing a knock (or a phantom knock) would kill your engine.


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## paripa_andrey (Oct 10, 2007)

i heard that some people takeout their knock sensor and stick it somewhere on the chassis that lets the car rpm go even higher and it is not bothered by any knocking. Also my engine has this little knocking sound around 2000rpm i checked oil,it was full and light. Or could that be becouse of the fuel grade? im suggested to have 91 but i put 87 in it.


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## BeyondBiscuits2 (Jan 18, 2006)

Any time a manufacturer suggests you use a higher octane fuel, USE it. Its like putting 87 octane in a Jaguar or a Mercedes; just don't do it. User a poorer grade of fuel can cause some serious problems in terms of sensors, and can ruin your engine altogether. Yes, it is more expensive per gallon, but if it allows your engine to run and last over 300,000 miles in the long run, I think it is worth it. I used to work at a Jaguar car dealership, and I cannot tell you how many salesmen we had to let go because they would test drive the cars and fill them up on crap grade fuel (trying to save the dealership money). In the end, the Jaguars ran like crap and had to have almost all their sensors replaced. That alone could be a major problem on why your car is running terribly.

Also, if you hear a knock around 2000 rpms, that can be a serious problem. How many miles are on the engine, and how frequently was it maintenanced and maintained? Has it had an oil change, new plugs, etc.? You might want to have your bottom-end inspected, because it could very well be a bad rod bearing. Especially, if the engine was ever drag-raced or run hard with low oil or no maintenance.


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## xbrandonx (Mar 27, 2004)

paripa_andrey said:


> i heard that some people takeout their knock sensor and stick it somewhere on the chassis that lets the car rpm go even higher and it is not bothered by any knocking. Also my engine has this little knocking sound around 2000rpm i checked oil,it was full and light. Or could that be becouse of the fuel grade? im suggested to have 91 but i put 87 in it.


First off BeyondBiscuits2, the Knock Sensor just pulls timing, it doesn't kill the engine. I guess maybe if it was really bad knock it may though.

You can relocate your knock sensor, however that doesn't remove the rev limiter. However it will make the knock sensor not retard timing, but you're still not going above 6250 rpms.

Trust me, I still hit the rev limiter from time to time.

And yes putting 87 octane in your car to save money is no smarter then putting in a quart LESS oil to save money. Suck it up or buy a different car.


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## paripa_andrey (Oct 10, 2007)

Yeah defenately, i always put 91 in my its just this one time. My car has only 23000 miles and its a 02 i worked on it for a long time and payed it off. I am just getting my ASE certificate. i maintained it very well used only mobil 1 i just dont get what is it with this car. Its very picky.


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## xbrandonx (Mar 27, 2004)

the knock sensor on the 02 is especially very picky, I'd say your engine was probably detecting knock and its not happy.


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