'98 xj with 175k 4.0 & auto, stock exhaust manifold cracked at the flange & literally fell into pieces. While replacing manifold with a header, i replaced the intake & (original?) fuel injectors. Started right up, runs like a champ EXCEPT the header is glowing cherry red.
Really wouldn't feel safe 4 wheeling like that....nor driving to work. Any ideas or suggestions?

 

Clogged catalytic converter? I dont think most XJ headers get that hot... What header is it? Is it a Chinese cheapie made from recycled pie plates?

 

The only times I've ever heard of a exhaust header glowing red is with high horsepower engines at high RPM, hot rodded turbocharged diesels and snowplowing.

Of course the odd story of farmers running tractors with the governors cranked way up comes in once and a while too

What did you replace the injectors with? OEM replacements?

 

Lean = heat = glowing

 

Maybe it's running too lean because of an intake leak? You sure you got everything seated properly?

 

That's my guess.

Op. Take some water and slowly pour it over the runners on the intake where it meets the block. When the idle changes you have found where your manifold is leaking. I had to do that with mine and it was just a simple as tightening it a little more.

 

I replaced the rear ccv on the valve cover, along with a piece of hose to replace the cracked ccv & too-short factory line.
I sprayed carb cleaner on ALL vacuum lines to manifold & wherever it originated including brake booster & anything else. Absolutely no difference in idle anywhere.
However, i'm guessing the ccv may have been the culprit? The truck immediately idled at 800 rpm's, no pop through manifold & headers dont appear to glow red anymore. As soon as it gets dark out i'm gonna double check-way too bright today, but i think i'm good.
So far only issue i've noticed, during 1 quick 55mph run for a mile or 2, was rpm's at 2200 when they used to be 1700 or thereabouts. An issue? Gremlin? My imagination?

 

definitely keep an eye on it, as glowing red like others said is either lean or something clogged downstream. The lean condition could be from lots of things.