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

It's a 91 2.5L TBI ... the rig became progressively sluggish [over
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?

wrote:
> It's a 91 2.5L TBI ... the rig became progressively sluggish [over
> 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?
>

Check cam timing. I had an Olds v-8 that did the exact same thing.
Turned out to be a very stretched timing chain.

--
Steve Walker
(remove wallet to reply)

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

>It's a 91 2.5L TBI ... the rig became progressively sluggish [over
>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?

You have described perfectly the symptoms of grossly retarded ignition
timing. Distributor is a likely culprit.

Don
www.donsaustomotive.com

Steve ... No timing belt or chair ... gear to gear on this. It's
possible I guess but I looking for something not quite that drastic.
BUT you could be right??

Steve Walker wrote:

>
> Check cam timing. I had an Olds v-8 that did the exact same thing.
> Turned out to be a very stretched timing chain.
>
> --
> Steve Walker
> (remove wallet to reply)

Don any suggestion on what to look for? I'll run through the factory
fault tree ... but where should I look first? rotor, ESC module,
etc.??

Don wrote:

> You have described perfectly the symptoms of grossly retarded ignition
> timing. Distributor is a likely culprit.
>
> Don
> www.donsaustomotive.com

wrote:
> It's a 91 2.5L TBI ... the rig became progressively sluggish [over
> 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?
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.

"Don" > wrote in message
...

> You have described perfectly the symptoms of grossly retarded ignition
> timing. Distributor is a likely culprit.
>
> Don
> www.donsaustomotive.com

It does indeed. I have heard these exact symptoms before, and am trying to
remember what was found.

Seems that some of the issues were due to a loose wire or bad connection of
some type, perhaps around the distributor area, but the details evade me at
the
moment.

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
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Don ... I'm going to check the wiring to the distributor from the ECM
and look for anything unusual. One thing I failed to mention was that
the engine begin 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.
>
> It does indeed. I have heard these exact symptoms before, and am trying to
> remember what was found.
>
> Seems that some of the issues were due to a loose wire or bad connection of
> some type, perhaps around the distributor area, but the details evade me at
> the
> moment.

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