"Glowing" ex manifold on a 2.5L S-10

jeffcoslacker wrote:
> I don't know about you guys, but on my planet a rich mixture burns
> cooler....and extreme lean condition is what causes manifold
> overheating, as the unburnt, air deprived mix in the cylinder tries to
> continue burning into the manifold on exhaust stroke....
>
> I'd be looking for a throttle position sensor fault, blown FPR,
> something that would cause excessive lean condition....if he were rich
> he'd be blowing sheets of soot out the exhaust...
>
> It's very possible the Cat is stopped up totally too, that'd explain
> why it won't rev...
>
>
> --
> jeffcoslacker
It's very possible we are not on the same planet as you.

I dropped the exhaust pipe from the manifold and it didn't change
anything. Regarding the lean vs. rich issue; you can definitely smell
the slobbering. I suspect it's detonation/burn in the manifold. I'll
look into the TPS too!

wrote:
>
> I dropped the exhaust pipe from the manifold and it didn't change
> anything. Regarding the lean vs. rich issue; you can definitely smell
> the slobbering. I suspect it's detonation/burn in the manifold. I'll
> look into the TPS too!

It isn't the fuel mixture. If the fuel can't burn in the cylinders it is
going to burn in the exhaust manifold unless there is something causing
it to burn there like late ignition timing or late valve timing or both.

-jim

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You could be describing a loose intake or exhaust or both manifold.

It is either running lean which heats things and/or it is burning the
excess gas the computer via the O2 is dumping in, in the exhaust
manifold.

If you spray carb cleaner or even WD40 along the manifolds' gaskets and
the engine 'sees' it with a reaction, you have it figured.

Just my guess....

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Canadian Off Road Trips Photos: Non members can still view!
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wrote:
>
> I dropped the exhaust pipe from the manifold and it didn't change
> anything. Regarding the lean vs. rich issue; you can definitely smell
> the slobbering. I suspect it's detonation/burn in the manifold. I'll
> look into the TPS too!

On 3 Jul 2006 09:28:44 -0700, wrote:

>I will try to check the timing, but I don't think I can get the engine
>to produce enough RPM

A very low idle is best for checking the timing. Put a timing light
on it before you do anything else

Don
www.donsautomotive.com


>... it's idle is REALLY marginal.
>
>One thing I failed to mention was that the engine gradually began[over
>weeks] to sound like there was a hole or crack in the header pipe. I
>expected to see a hole or sever crack somewere BUT I DIDN'T. That
>STILL baffels me. Could severely retarted timing cause detonation in
>such a way to cause this.
>
>
>
>> Sounds like it could be retarded timing like the other poster
>> said. To me it sounds like first of all you are running real rich or
>> are not burning fuel completely in combustion chamber. That is why
>> exhaust manifold is cherry red , fuel is burning when coming out of
>> exhaust port, either because rich mixture not burning completely or
>> retarded timing would not burn all gas in chamber either. I would
>> pull the sparkplugs and look at the tips, if real white insulator
>> running lean, if a little brown or grey running good, if dry black
>> insulator, running rich and could be shorting out spark, and if wet
>> black could be oil control problem and also shorting out spark
>> sometimes. Is there any black smoke coming out of tailpipe, then
>> running rich, can you smell excessive gas smell after engine warmup
>> (since engine will run rich if computer thinks it is cold through
>> coolant temperature sensor)
>> The good thing with TBI is you can remove air cleaner and look at
>> fuel injectors squirting while engine running,(running without air
>> cleaner OK for short periods of time), dont forget to plug any vacuum
>> or exhaust lines to air cleaner. throttle body injectors have
>> regulators that have low pressures that don't change since they squirt
>> into atmosperic pressure unlike port fuel injectors. You could check
>> fuel pressure anyway. You could check ignition timing also with a
>> timing light and if way retarded could be timing belt or gear or chain
>> problem, try adjusting ignition timing to see if run better than could
>> be gear or chain or belt.

On 2 Jul 2006 18:11:10 -0700, wrote:

>weeks] until it would hardly move. Any throttle movement would stall
>the engine. And the exhaust manifold was red hot before I chose not to
>drive it!
>
>Towed it home ... checked for a leaking TBI - NO CHANGE. Dropped the
>exhaust pipe - NO CHAGE. EGR's OK .. MAP appears OK related tubing
>and connectors OK ... where do I look next? Should I tear into the
>distributor? .. what should I look for?

Late ignition timing.

--
-john
wide-open at throttle dot info

On Mon, 3 Jul 2006 09:26:01 -0700, jeffcoslacker
> wrote:

>if he were rich
>he'd be blowing sheets of soot out the exhaust...
>
>It's very possible the Cat is stopped up totally too, that'd explain
>why it won't rev...

A slightly rich mixtire won't blow soot, but that, combined with
retarded timing, will heat teh exhaust manifold to dull red.

ALso, severely retarded timing keeps the enginine from ever being
able to rev to redline. Retarded in teh range of 45 to 90 degrees.
Engine runs, but poorly, lacks power, poor acceleration, hot
exhaust manifold.

It's not valve timing if compression checks OK.

--
-john
wide-open at throttle dot info

On Mon, 3 Jul 2006 09:26:01 -0700, jeffcoslacker
> wrote:

>I don't know about you guys, but on my planet a rich mixture burns
>cooler....and extreme lean condition is what causes manifold
>overheating, as the unburnt, air deprived mix in the cylinder tries to
>continue burning into the manifold on exhaust stroke....

It's already burnt. A rich mixture finishes burning in the exhaust
manifold, because of air injection (smog pump [or gulping valve on
many 4 cyls]). The unburned HC and H2 + CO burns there.
Lean mixtures tend to leevae excess O2 and H20, with the balance C02.
Try and get THAT mixture to burn by adding air at high temps. :-)
--
-john
wide-open at throttle dot info

"jim" > wrote in message
...
>
>
> wrote:
>>
>> I dropped the exhaust pipe from the manifold and it didn't change
>> anything. Regarding the lean vs. rich issue; you can definitely smell
>> the slobbering. I suspect it's detonation/burn in the manifold. I'll
>> look into the TPS too!
>
> It isn't the fuel mixture. If the fuel can't burn in the cylinders it is
> going to burn in the exhaust manifold unless there is something causing
> it to burn there like late ignition timing or late valve timing or both.

Advanced valve timing, not late valve timing, can cause fuel to burn in the
manifold, i.e. the exhaust valve opens early while the mixture is still well
alight in the cylinder. Late valve timing would have the opposite effect.
--
Dave Baker
www.pumaracing.co.uk
Usenet - a collection of people who only open their mouth to change feet.

On Tue, 4 Jul 2006 16:57:07 +0100, "Dave Baker"
> wrote:

>Advanced valve timing, not late valve timing, can cause fuel to burn in the
>manifold,

Bull****.

It would ping, and maybe pop back through the carburetor.

--
-john
wide-open at throttle dot info