I was hoping someone may have an idea here, but my 98 4.0 OHV Sport (60,000 miles) had a misfire code for the #2 cylinder. Anyways, after replacing plugs and wires several times, I realized it was likely the injector. After replacing the injector on the #2 cylinder it ran great again, for about a day, then it would start idling high, stumbling again and threw a P0171 (Bank 1, Lean) code......

Ideas? I checked all the vacuum lines and they are good, no other codes.

 

Go back to the injector, check that the O ring is intact and that connector is plugged in securely.... Philip

 

On some of the other Ford car forums I've read of quite a few issues with the injector connector not staying securely attached once they've been "tampered with" after several years in the hot engine compartment. You might try unplugging the injector, using some dielectric grease in the connector, then using a cable tie to make sure the electrical connector remains firmly connected to the injector.

-Rod

 

Thank you all for the ideas!

I went back and pulled the codes again after letting it go for a bit. Now I am getting the Right bank and Left Bank lean, as well as getting the Cylinder #2 misfire AGAIN and a Cylinder #3 misfire. Talk about a mess!

When I replaced the #2 injector, I bought all new O-rings for the other injectors as well and put new ones on all around. Of course all new gaskets too for the intake.

I am getting 16.2 mpg when I used to get 19.4 now.

Here is a question.. I can not remember, but is it recommended that when you replace one injector, you replace them all? I know that goes with plugs and wires (which by th way were replaced several times all recently with this).

Any more ideas would be great!

 

There is no need to replace the injectors as a set.....They are individually pulsed (fueled as required)..

With the work performed and the codes being set, did you install the required Silicone (peanut sized) at all junctures between heads, block and intake manifold??? .... Philip

 

There was no need to use any silicone or sealer as the lower intake was not removed from the heads or block. I have an OHV 4.0, with a two piece intake manifold, upper and lower. The upper is removed, then the fuel rail/bar can be removed.

What I found interesting is that the fuel rail is one big card with intake holes punched in it and placed over the lower intake manifold, then the upper is stacked on top. I did replace all the gaskets including the spacer with brand new ones and torqued to spec. The O-rings were replaced on all the injectors (manifold side and rail side of the injector). Codes were deleted afterwards. A day later and 30 miles down the road, new codes pop up.