New Injectors, Loss of Power

Discussion in 'SN95 4.6L Mustang Tech' started by bbayne35, Feb 15, 2012.

  1. 2000 GT with 150000 miles, daily driver. I installed some new fuel injectors and spark plugs last weekend. The old injectors were stock (19 lbs./hr), and I replaced them with Accel injectors of the same rate. While accelerating, I notice a loss of power, particularly at around 3000 rpms. It feels like the car is hesitating momentarily. I did not have any misfire DTCs. However, I did get a P0171 and P0174 (Too lean in Bank 1 and Bank2) at one point. I thought that may have had to do with a vacuum leak that I may have created during the injector install because I did disconnect and reconnect a bunch of vacuum related components. I checked all of the connections. I actually replaced two hoses that may have been a little suspect and I was able to tighten the EGR tube slightly. I drove the car about 10 miles after that, and I did not see any DTCs, but the loss of power issue was still there.

    Any suggestions as to what to try next? I am thinking that I should reinstall the old injectors to see if the power loss still exists. During removal, a small piece of plastic broke off of one injector near the tip. I assume that one should not be reused. I could purchase one new injector from Ford, but they seem to be pricey. Any help is appreciated!
  2. You can get a pintle and 0-ring kit from your favorite parts store if you'd like to try reinstalling the old injectors.

    As for the spark plugs... Did you replace them with OEM and gap them all? Is your firing order corect? What shape is the rest of your ignition system in?
  3. My vote is there is still a vacuum leak somewhere.

    Did you use new O-rings on the injectors? Did you lube them before installation?

    What about the PVC value?

    If you still wish to re-use the old injectors, consider an injector cleaning/flow test service such as Once cleaned/repaired/flow tested, they are as good as new. Cheaper than new.
  4. I was not aware the pintle was part of the o-ring kit. I will give that a try. Thanks.

    I replaced the spark plugs with Autolite 764's which is what I have always used. They were all gapped to .054". I am not aware of any way to change the firing order, so I assume that is correct. One spark plug cylinder (above the plug) was rusty. The COP boot was rusty as well. I cleaned the boot as well as I could. Another spark plug cylinder had a small amount of oil on the COP side of the plug. I do remember spilling oil on the engine during a refill, so I have a feeling some oil leaked in then. Some of the COP boots were cracking at the end. The electrodes of all plugs looked normal to me. All of that being said, those same conditions existed before I changed the plugs, and it seemed to be running better before. That is why I was focusing more on the injectors.
  5. wmburns,
    What is your recommended method of finding a vacuum leak? I did use new o-rings, and I lubed them with oil. The PCV valve is relatively new, so I have not checked it. It was removed and reinstalled, but that is it. What is the best way to check it? Shake to ensure a rattle sound and remove it with engine running to see if it is pulling vacuum?

    I have seen you mention injectorrx before. I may consider them. However, since my old injectors seem to perform better than the brand new ones, I feel like the old ones may not need service! I guess it could not hurt other than the wait and the $150+shipping.
  6. I noticed that the Accel injectors do not have a pintle cap like the stock injectors. The Accel injector is shown here. The stock injector is shown at the top of the page here. It appears that the o-ring to o-ring distance is longer on the Accels. I wonder if that would cause any issues (like the bottom o-ring not seating properly within the intake manifold). I will have to take some measurements.