I installed my headers about a week and a half ago, since then I have only got around 100 miles on half a tank. I usually get around 140 on the same driving. During the install I unpluged the passenger side spark plug wires for room and the boots seperated on all three of them. I cleaned them up with a file and clamped them all back together. They seemed alright but now I'm questioning them. I have a small shake at idle that wasn't there before the install but I've never had headers on any of my rigs so I'm not sure what to expect. I didn't unplug any of my vacuum lines I just worked around them so I didn't mess those up. When I had the cross over made I had them disconnect the battery so it shouldn't have any bad sensor readings from runing open headers for a day. The truck seems to have more power but it takes a little longer to start now. Where it would take a second before it now takes two. Not too much but it is noticable to me. I'm probably going to order some new wires but wanted to hear any other suggestions people might have first. Thanks in advance.

 

im stepping out on a limb, but im sure someone will chime in, but other than the plugs and wires that you mentioned, did you bolt the headers on tight enough or is there an exhaust leak? not sure, but is there a gasket that goes inbetween the header and the block, and is that on right? also, though im sure the symptoms would be more pronounced, did you put the wires back on the right plugs? im sure you did and if not im sure it would run alot rougher, but what the heck, its a thought.

 

And how's the O2 sensor? (I'm not sure if you have one or two on yours, but it's the front one if you have two)

 

I torqued the headers on pretty tight. I might go back over them shortly just to check them after some use but I can't hear any leaks from them.
I just have an OBD I, but I did have the shop cut the O2 bung out of the old pipe and weld it on the new one. Maybe it didn't like the cutting torch. Does any one know the procedure for testing the O2 sensor before I go digging for it?
Thanks for the replies.

 

You torqued them on tight, but did you cross torque them? That is the question.

Sounds like exhaust is getting by "unsniffed" somewhere.

 

I was very carefull about that. I reused the old studs to lessen the chances even more. After the horror stories I heard I knew I didn't want to have to take them off and put them back on again for striped out threads. But it is always a possability so I'll see if I can feel any flow from them. Would a small header leak make my milage take that much of a crap and longer starts?

 

Headers can actually reduce mileage due to better exhaust scavenging characteristics and reduced head temperatures. But I dont know about that much.

I know when I got my headers on, I was punching it everywhere to see if things were better. Are you?

If I were you, I might focus on the plug wires like you mentioned. Another option is to check your plugs. Their condition and coloration will tell you a lot about whether or not you are burning lean or rich, and what's going on in there.

So what's up with the plug wires? Tell us more...

 

When I was running open headers and for the first day with the full exhaust I was stomping around but I filled up after that. The truck really didn't like open headers with no signal to the O2 sensor. I ran threw a 1/4 tank in less then 30 miles.
When I pulled the boot of the plug the metal connector stayed on the spark plug but the wire came off. This has happened on one before when I changed the plugs and it seems to work fine after. I pulled the metal part off the plug and reconnected it to the wire. I used emery cloth on the metal parts to help the connection then clamped them back together.
I found this in another thread.
I'm going to check it out and see what I get. Although it would seem that my CEL would trigger if I had problems with it.

 

a tip: use an analog voltmeter to look at the o2 sensor reading, so you can see the needle bounce. A DMM won't respond fast enough.

 

I threw a new set of wires on last weekend and the truck seems to be running better. All of the old wires seemed fine except one, it pulled apart again taking it off. It doesn't shake at idle like it used to and is getting better milage. On the first tank I got 100 miles in the first half then the second half saw a lot of freeway miles so I ended up getting 14 mpg. I usually get 17 and change without all the freeway driving. The starts aren't as long but are a little longer then before. Again I've never had headers before to know what to expect. The long start is nothing noticable to an average person just to a gear head that listens to all of the little crap. If I can find an analog meter around sometime I'll check the O2 for s**** and giggles. Thanks for the help and ideas guys.

 

the best way to check an o2 reading is with a ocillascope and make sure it switching from rich to poor i mean lean

 

Didn't know that! Thanks.

Getting 14 mpg. Sounds like the EFI is running "open-loop" and is speed sensing rather than taking queues from the oxygen sensor.

Could disconnect the battery for a few minutes and allow the ECM to dump it's temp memory. Re-connect the battery and drive it for a few minutes and see if there is a difference.