Red hot manifold -- question

[kpfoten]

Heh... Checking my exhaust for burning grease, I noticed a red glow to my exhaust manifolds... Is this normal?

Thanks

[Jim Sims]

No; it's not normal. Were all of them glowing red? This is usually a sign of an ignition miss and gas burning downstream of the cylinder(s) in the exhaust manifold. Jim

[kpfoten]

Wow! I was looking at where the (three) came together. It was glowing at this point... Now I'm nervous... Any suggestions?

[Jim Sims]

Probably only one of the three on that side is missing. The raw fuel burns when it contacts the hot exhuast gases from the functioning cylinders. Is the other side of the engine showing a similar red glow on the exhaust manifold? On the side with the glow you likely have a fouled plug or a bad or even just plain disconnected spark plug wire. Jim

[kpfoten]

Jim,

Probably a mistake on my end -- Both sides were glowing ever so slightly. I remember before I installed a new WUR that I pulled the plubs and 3 or so plugs were fairly black. (coming random from both sides) the other 3 were clean. Being a 911 newbie, I assumed the plugs would be ok (They were brand new, but I ran the engine a little bit when it was running poorly due to the WUR).

Another clue might be that it seems to miss a little around 3500rpms on the highway...

Coil, cap, rotor, plugs, wires (magnacore), etc are new. Checked timing, etc.

I hadn't done a CIS tuneup, and I don't have a Gunson... Is there an easy way to clean the soot off the plugs?

Thanks

[ttweed]

Check your mixture and timing. Lean mixture and/or retarded timing can slow combustion in the cylinders so that it is still occurring as the exhaust valve opens, superheating the ports and header pipes.

TT

[kpfoten]

I'll check again, thanks!

I pulled the plugs on the right bank of cyls and they look clean. They must've de-carboned themselves...

[Erakad]

Had this problem on a toyota celica I owned, was a plugged catalytic converter.

just my 2 cents

[kpfoten]

I meant to say that the previous owner capped the tube exiting the EGR valve as well. I'm assuming this will cause it to be hot as well...

[john70t]

A Raytek lazer thermometer(~$85) is a great tool to have. The after-cat temps should be 100deg or double what was before(not sure which) to check a clogged cat. A over-hot air-cooled magnesium case is kind of scary because of the rebuild costs.
After the other basics are done, the injector seals have been known to harden and create a lean condition, also while they're out you can put the injectors in a glas jar and check the spray pattern.

Checked the thermo on the headers on the 70T and found # 2 and 3 running about 450deg instead of about 375 on the others. Mixture adjust didn't help so it will be valve adjust time soon (and probably chains and and and later).

BTW, anybody know the standard header temperature ranges?

[kpfoten]

I don't have a cat. I ordered a gunson today, hopefully that will help with my CIS tuning...

My current theory is that the PO disconnected the EGR and didn't compensate the fuel mixture... Could possibly be running lean.