mrweekendwrench
New Member
Hello Fellow Lexus Brotheren,
I have an older 1992 SC400 with about 270K miles on it. It has had a
problem that has gradually manifest itself with poor performance and stall outs. My check engine light has come on and I
pulled the computer codes with a bent paperclip and by watching the check engine light blink them out. I got 41 & 12. I believe 12 is Throttle
positionsensor #1 and 41 is the air flow sensor. I have noticed that car
backfiring through the intake intermitently. I naturally thought the car was out of time till I checked the timing marks on the block.
> I just checked the timing marks today, they were ok. History: I also
replaced the Catalytic converters the two right off the engine exhaust
manifolds about a year ago.
> I have never replaced the middle cat. I am under the impression that
the
middle cat is possibly plugged. How do you test them. Is it necessary
to
have three catalytic convertors?
Right now, the car will still run, then it stalls
after about 5 min or less if left to idle.
On a side note: If I bore out the middle catalytic convertor will
the car pass smog, how will it affect performance?? Will this effect the second set of o2 sensors in any way. This car has as many sensors, as I think is possible on any car. It is like working on a robot.
I tested the catalyic converter last night with a vacum blower and I believe the air flow was adequate out of the middle catalytic convertor.
I did some more reading and inspection. To my disbelief I noticed a piece of tubing coming off the back of the intake manifold. It looks like it leads down to the exhaust system. I did some more research on line and am under the impression that the SC400 is equipped with a Ported EGR Valve. Could this be the problem? Could the valve be stuck open? How would I test this while it is still attached to the car, or should I just take the item out for inspection and possible replacement? Any ideas? Thank you in advance.
Mr. Weekend Wrench
I have an older 1992 SC400 with about 270K miles on it. It has had a
problem that has gradually manifest itself with poor performance and stall outs. My check engine light has come on and I
pulled the computer codes with a bent paperclip and by watching the check engine light blink them out. I got 41 & 12. I believe 12 is Throttle
positionsensor #1 and 41 is the air flow sensor. I have noticed that car
backfiring through the intake intermitently. I naturally thought the car was out of time till I checked the timing marks on the block.
> I just checked the timing marks today, they were ok. History: I also
replaced the Catalytic converters the two right off the engine exhaust
manifolds about a year ago.
> I have never replaced the middle cat. I am under the impression that
the
middle cat is possibly plugged. How do you test them. Is it necessary
to
have three catalytic convertors?
Right now, the car will still run, then it stalls
after about 5 min or less if left to idle.
On a side note: If I bore out the middle catalytic convertor will
the car pass smog, how will it affect performance?? Will this effect the second set of o2 sensors in any way. This car has as many sensors, as I think is possible on any car. It is like working on a robot.
I tested the catalyic converter last night with a vacum blower and I believe the air flow was adequate out of the middle catalytic convertor.
I did some more reading and inspection. To my disbelief I noticed a piece of tubing coming off the back of the intake manifold. It looks like it leads down to the exhaust system. I did some more research on line and am under the impression that the SC400 is equipped with a Ported EGR Valve. Could this be the problem? Could the valve be stuck open? How would I test this while it is still attached to the car, or should I just take the item out for inspection and possible replacement? Any ideas? Thank you in advance.
Mr. Weekend Wrench
