emergency help please

[wbudna12]

hello all i have been working on my 91 q45 slowly. i change the spark plugsreplace two knock sensor with used ones in good shape. the old knock had huge cracks in them. hook everthing back up and started the car and it did but after 10 min runing rough i hear cracking noise from under the car i took a look and the exhaust was RED HOT. what could be the problem here, i got nervouse and turn it off and never touch it again. If any body have a idea what i could do about this problem. please help i need it.

[DAEDALUS]

I can't imagine what it could be. Is the coolant level good? How was it running before the work you did?

[Q451990]

Could it be runnig so rich that it's dumping fuel into the exhaust? Clogged cats? That's a new one to me...

Heath

[DAEDALUS]

The clogged cat makes sense, except nothing was done that could cause that. Was the fuel rail or injectors touched at all? Was there a lot of smoke billowing out the exhaust? Did the exhaust smell rich like fuel?

[kmeter]

check to make sure fuel pressure regulators have vacuum lines hooked up; high fuel pressure internal fuel leaks and timing are some basics to start with

[wbudna12]

the car was running good except for one injector. i change four injector and the knock sensor. there was no white smoke coming from the exhaust, i will check for the fuel smell and the fuel pressure.thanks for the replys

[wbudna12]

no fuel smell from the exhaust and the fuel pressure seems fine any other things i should check for. neeeed help herethanks

[JedCoop]

Could a really bad O2 sensor cause the ECU to make the mixture to be way too rich?

Or maybe if O2 is wayyyy too high, the ECU retards timing causing fuel to burn late?

So the backyard mechanic question is if you put back the original O2 sensor (assuming it didn't get wrecked) does it work right again?

[DAEDALUS]

A really bad O2 sensor would be no worse than a cold brand new sensor when the car is first started. Rich, yes, but nothing like that. Same for O2 being way high (same thing as not working, isn't it?) and timing shouldn't be out of whack with what was done (don't think O2 affects timing). I'd be certain it was a pinched seal except there aren't any other symptoms. Maybe it is indeed a clogged cat. Do a vacuum check on the engine.

[Q45tech]

Coolant temp sensor shares same harness with knock sensors [check engine light codes]?

[PoorManQ45]

Hmm.. Red Hot exhaust manifolds? Was it both exhaust manifolds, or just one?

Hmm.. The only time I've ever heard of an exhaust becoming redhot was when a turbo charger was used, but that's not the case here.

Maybe one of the coolant passages in the block is clogged?

What plugs did you use? OEM? Did you use hotter then OEM plugs?

Would pre-detonation cause the exhaust to heat up like that?

[Q451990]

Did you lube the injector o-rings? I suspect it's something to do with a leaking lower o-ring or rings.

Heath