I've been trying to resolve a problem with my 99 SD 5.4 for several weeks now and I just can't figure it out, so I'm hear to ask the experts... I hope someone can help me.

When I bought my truck, someone had cut the wires from the O2 sensor upstream to the wiring harness on my truck and down stream past the pigtail to the sensor itself. I don't know why, but they did. So now I have a new 02 sensor with wires up to the pigtail, and a new pigtail adapter with wires up to the harness behind the truck. The problem is that the new O2 sensor's wires are all white. The wires from the pigtail up to the harness are (2 grey and 2 white). The wires way up in the harness are all different colors!

Had the wires in the harness behind the engine been the same color as the wires on the pigtail, I wouldn't have an issue, but because they aren't I don't have a clue.

So I went to the local dealer for advice (they solde me the O2 and the pigtail, etc...) and they didn't know either, so a guy there looked at a 2000 F150 to see what the colors should match up to and wrote them down for me. I followed the hand drawn schematic but something still isn't right.

I don't have an engine light on (may be blown) but my truck misses out driving down the road, its not constant but it is noticable. It happens more when I'm hualing a trailer or I'm under heavy acceleration (up hill, etc...). It also happens more often when its raining, or there's moisture in the air.

Could it be my plugs? can I just bypass the O2 and forget it?

Can anyone help me?

Thanks!

 

Did it do the same thing before you hooked them back up?

 

Hey 99 FordGuy,

Yeah, its missing out just like it did before I hooked it back up. I disconnected the pigtail last night, and it didn't act any different, hooked it back afterwards. I'm afraid I'm going to burn something up if its running to lean. So I'm thinking either I haven't hooked it up right, or its not my problem.

I've talked to other guys that just bypassed their o2's completely, and they aren't having any problems.

 

Why would anyone disconnect the o2? Its not gonna run right without it.
Sounds like you have a coil issue they get old and the boots crack and short out. You may have to pull them and look at them real well...

 

THe chk engine light should be on ! the bulb must be removed or burnt out.
The truck will not run right at all with out O2's the fuel trims will go open loop to save the engine from melt down(lean) becauuse the pcm sees o2 failureyou may have already melted the tip of a sparkplug off! don't drive it till its fixed.
you should have 3 o2's 1 for each bank and one downstream,
Tell us which ones are missing and what wire colors you have back up past the pigtails an i can help with the colors.
Rich

 

Thanks for the info guys, I really appreciate your help on this.

I'll check on the color of the wires tomorrow. So you think I should replace my plugs after this is all done?

I thought about the coil too, I know allot of people have been having problems with them. I had my truck scanned and all it said was O2, etc...