Red Hot Exhaust Manifold On 99 Camry

[sabbates]

All-

The exhaust manifold on my 99 Camry gets red hot- I can see it glow at night.

I replaced the intake hose and sprayed carb cleaner to check for intake air leaks, did not find any.

Also, I've got P0171 system too lean. I've replaced the air/fuel ratio sensor several times on this car over the years, but not lately. I've had the P0171 code off an on for years.

Could the timing belt be advanced by a tooth? Could the injectors be clogged, bad fuel pressure?

I get about 22 mpg, which seems a bit low.

What do you guys recommend I look into?

Thanks

[Chris Crash]

Sounds like a bad cat to me...

[Silent Runner]

^+1
I saw the exhaust manifold on my Mazda 626 glowing red hot several times, but that was a turbo engine. Makes sense, a gummed up cat. converter will cause excessive backpressure and heat in the exhaust system. Downstream, the O2 sensors would try to lean out the mixture because of incomplete cylinder scavenging, and unburnt fuel mixture emerging in the exhaust. Hopefully someone with a good knowledge of OBD2 will pipe in and add some useful diagnostic ideas.

[fenixus]

^+2

exactly, that's what happens if catalytic converter goes bad...

[ghettosled]

the only other symptom of a bad cat ive run into (aside from a hot exhaust manifold) is engine stumble/bogging down at high RPMs as there is a lot of exhaust trying to exit and there is a blockage.

if it smoothly revs up to 5-6k RPMs (and being you have a lean code) i would put my money on a bad air:fuel sensor. wait, where did you spray the carb cleaner when checking for leaks? around the throttle body intake or around the intake manifold? a leak like this would be post throttlebody by the intake manifold and associated rubber vacuum lines.

what controls the air:fuel information? primary oxygen sensor? do you have a multimeter? i would check that out first. also check the spark to make sure you are getting a good spark. a poor spark wont fully burn the fuel, which can also lead to unspent fuel igniting in the exhaust manifold and poor fuel economy - similar results to a bad o2 sensor.

having the timing belt off by a tooth would cause the engine to run horribly, if even at all.

[fenixus]

^ makes sense.

Since P0171 is the only confirmed problem, then it must be corrected before assuming anything else (or will confirm something else in process of checking).

Here is the trouble area for P0171 (5s-fe):
-Air intake (hose loose)
-Fuel line pressure
-Injector blockage
-Heated oxygen sensor (bank 1 sensor 1)
-Manifold absolute pressure sensor
-Engine coolant temp. sensor

check each and all of them.

This is the description of P0171 (System Too Lean):
"When air–fuel ratio feedback is stable after engine warming up, fuel trim is considerably in error on RICH side (2 trip detection logic)"

HINTS:
-When the DTC P0171 is recorded, the actual air–fuel ratio is on the LEAN side. When DTC P0172 is
recorded, the actual air–fuel ratio is on the RICH side.
-If the vehicle runs out of fuel, the air–fuel ratio is LEAN and DTC P0171 is recorded. The MIL then
comes on.
-If the total of the short–term fuel trim value and long–term fuel trim value is within ± 38 %, the system
is functioning normally.
-The heated oxygen sensor (bank 1 sensor 1) output voltage and the short–term fuel trim value can
be read using the OBD II scan tool or TOYOTA hand–held tester.

[sabbates]

I'm in California, so the upstream O2 sensor is called an air/fuel ratio sensor, and apparently it operates on a different voltage as a standard O2 sensor.

I've replaced it several times over the years, and the P0171 clears for a month or so, then comes back.

I had the injectors cleaned, too, and it came back.

As for the cat, aren't there two cats on a California car?

See picture.

Any ideas on which cat is bad, or how to check them?

Thanks

[fenixus]

if it's a bad cat then it would be the upstream (unmonitored) one as the downstream is monitored by ECU with a post-cat oxygen sensor.

check the rest of things listed. which AFR sensor brand and model are you using, Denso, NGK, something else?

Have yu checked MAP and ECT for EFI sensors?

[chronoti]

Originally Posted by fenixus

^ makes sense.

Since P0171 is the only confirmed problem, then it must be corrected before assuming anything else (or will confirm something else in process of checking).

Here is the trouble area for P0171 (5s-fe):
-Air intake (hose loose)
-Fuel line pressure
-Injector blockage
-Heated oxygen sensor (bank 1 sensor 1)
-Manifold absolute pressure sensor
-Engine coolant temp. sensor

check each and all of them.

This is the description of P0171 (System Too Lean):
"When air–fuel ratio feedback is stable after engine warming up, fuel trim is considerably in error on RICH side (2 trip detection logic)"

HINTS:
-When the DTC P0171 is recorded, the actual air–fuel ratio is on the LEAN side. When DTC P0172 is
recorded, the actual air–fuel ratio is on the RICH side.
-If the vehicle runs out of fuel, the air–fuel ratio is LEAN and DTC P0171 is recorded. The MIL then
comes on.
-If the total of the short–term fuel trim value and long–term fuel trim value is within ± 38 %, the system
is functioning normally.
-The heated oxygen sensor (bank 1 sensor 1) output voltage and the short–term fuel trim value can
be read using the OBD II scan tool or TOYOTA hand–held tester.

good advice

you know what i covered this a few weeks back

i'm gonna search for the answer i posted

Glowing Exhaust Manifold - 99 Camry

also check for lower and upper intake manifold leaks not just vacuum hoses also if the egr is sticking open

[sabbates]

I replaced the exhaust manifold / upper cat this weekend with a used part from Ebay, and the manifold still glows at night.

There was some exhaust leakage downstream of the old cat (see photo), but it didn't look clogged.



After removing the manifold, I could see what I assume are the valves? Are they supposed to be white like that?



I guess I better check the MAP and ECT. Is the ECT the thing that plugs into the bottom of the radiator?

Thanks a lot.

[fenixus]

ECT for EFI is located at/around water outlet (close to thermostat).
it's a 2-wire sensor, there should be another right by it (1-wire) which is a dash gauge sender.

[carsrus]

Dont drive that thing to much. Those white valves indicated the engine is running extremely lean, and therfore getting really really hot.

Check for vacuum leaks. I dont think sensor failure will cause that much of a lean mix. Run a whole can of seafoam into the gas tank to clean the injectors and change fuel filter.

How bad does it run?

[sabbates]

It runs pretty good. Sometimes at start up when it's cold it may die.

I replaced the intake hose, and the vacuum hoses I could easily reach. I also sprayed carb cleaner everywhere, but couldn't find any vacuum leaks.

I'll change the fuel filter. Maybe that's clogged and restricting fuel intake?

Thanks.

[fenixus]

dang, those valves are white. very lean mixture (hence the code)...

check both MAP and ECT, really. MAP rarely goes bad though, and usually causes car to run really rough, almost stalling at idle.

can you connect obd2 live scanner to see what is the real coolant temperature when car is hot and idling (right before fans kick in)?
if you have a droid smartphone, there are cheap BlueTooth OBD2 interfaces at $20 shipped on Hong Kong ebay. they work fine with Torque app from Android Market.

my wife's 5s-fe tends to stay on leaner side, not much, only a few % positive trim at idle, but the engine/coolant temperature reaches 210-214F (at ECT for EFI) easily before the rad fans kick in (based on switch in bottom of rad) when car is idling in parking lot after driving.

also check your IAC valve, it may be sticky.

I would also drop 2 small 12oz bottles of techron concentrate into tank to clean the fuel system. usually either Autozone or Advance have those on sale buy 1 get 1 free.

one or two of your fuel injectors may be clogged partially causing the high positive fuel trims overall.

make sure that vacuum routing is correct and there is absolutely no leaks anywhere. if your idle speed (at fully warmed up car) at idle in Neutral gear (all accessories off) is at 700+/-50rpm then it's fine. other than that there is a problem somewhere.

I would also consider replacing the upstream oxygen/AFR sensor. it might be misreporting because of age.

replacing the fuel filter is always a good idea.

[EEngineer]

ah....white valve...too much red meat.

full tune up needed