I got into my car the other day and got the dreaded check engine light. The car runs rough at idle and when i did the self diag on the PCM using the red/grn lights i got error 51, fuel injector signal circuit fault.
what exactly does that mean? bad injector? bad connector? or something else wrong with the FI circuit? Any and all help would be really appreciated.
Thanks
You probably have a bad injector. I had the same error code when one of mine failed. One had failed completely, and another was acting flaky, so I replaced all 6.
To determine which one it is, you can do several things. One is to take a piece of hose, or maybe a funnel, and put one end in your ear, and the other down near each injector (with the car running). If they are working properly, you'll hear a pfft-pfft-pfft sound. The bad one will be silent.
Another test is to put an ohm meter across the 2 leads on each injector (with the car off). The bad one will have a wildly different reading than the working ones. My bad one was ohming infinity, and the flaky one was about 100 ohms. I can't remember what the good ones read, but they were all about the same (13 or 14 ohms, maybe).
A third way is to remove the lead on each injector with the car running. If it stays the same roughness, you've found the bad one. But, I don't recommend this method. When you pull the lead off a running injector, the car will only be running on 4 cylinders, and will likely stall.
I replaced all 6 injectors myself. It was my first major engine work, but I did not find it to be very difficult at all. I had both a Haynes and a Chiltons manual, and it was very straight forward. DO NOT attempt this repair without a manual. The only hard part was removing and installing the injectors into the fuel rail. They are snug, and you don't want to damage them. It has run perfect ever since.
Total cost of repair was about $700. That was 6 new Nissan injectors, plus a few mainfold gaskets. You will also need some gasket removal goo to get the old ones off neatly and completely. And you will need a torque wrench. I had to buy 2 because of the wide range of torque settings. I use the big torque now all the time, but the little one was only used on this job. You can just replace the one bad one, but I figured I was in there anyway. If you have a mechanic do it, expect to pay about $450+ just in labor, no matter how many injectors you replace. You can run this car on 5 cylinders until you make up your mind on what to do. The engine is very well balanced, and won't suffer any damage. It will run rough as all get out, but it will run.
Bill G '91 SE Auto
166,000 miles
You probably have a bad injector. I had the same error code when one of mine failed. One had failed completely, and another was acting flaky, so I replaced all 6.
To determine which one it is, you can do several things. One is to take a piece of hose, or maybe a funnel, and put one end in your ear, and the other down near each injector (with the car running). If they are working properly, you'll hear a pfft-pfft-pfft sound. The bad one will be silent.
Another test is to put an ohm meter across the 2 leads on each injector (with the car off). The bad one will have a wildly different reading than the working ones. My bad one was ohming infinity, and the flaky one was about 100 ohms. I can't remember what the good ones read, but they were all about the same (13 or 14 ohms, maybe).
A third way is to remove the lead on each injector with the car running. If it stays the same roughness, you've found the bad one. But, I don't recommend this method. When you pull the lead off a running injector, the car will only be running on 4 cylinders, and will likely stall.
I replaced all 6 injectors myself. It was my first major engine work, but I did not find it to be very difficult at all. I had both a Haynes and a Chiltons manual, and it was very straight forward. DO NOT attempt this repair without a manual. The only hard part was removing and installing the injectors into the fuel rail. They are snug, and you don't want to damage them. It has run perfect ever since.
Total cost of repair was about $700. That was 6 new Nissan injectors, plus a few mainfold gaskets. You will also need some gasket removal goo to get the old ones off neatly and completely. And you will need a torque wrench. I had to buy 2 because of the wide range of torque settings. I use the big torque now all the time, but the little one was only used on this job. You can just replace the one bad one, but I figured I was in there anyway. If you have a mechanic do it, expect to pay about $450+ just in labor, no matter how many injectors you replace. You can run this car on 5 cylinders until you make up your mind on what to do. The engine is very well balanced, and won't suffer any damage. It will run rough as all get out, but it will run.
Bill G '91 SE Auto
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